Molds/Tools are the cornerstone of any composite part manufacturing process. The quality of the final part is inherently tied to the quality of the tool used in its creation. Molds/tools precisely define part dimensions, surface finish, tolerances, shape, and overall appearance.

At Ahmedabad Textiles Industry’s Research Association (ATIRA), we are proud to offer specialized tool and part design services tailored to meet the needs of industries working with composite materials.

Our tool design process meticulously considers molding strategy, release strategy, and manufacturing process compatibility. This comprehensive approach ensures optimal performance and seamless integration with your production processes.

Our expertise spans across various composite manufacturing processes, including Vacuum Bagging, Hand Layup, Infusion, and Pultrusion. Additionally, we excel in thermal analysis to ensure optimal tool performance in varying temperature environments.

Our Services:

Composite Design
At ATIRA, we possess extensive experience in various composite component manufacturing techniques. Our expertise enables us to evaluate the pros and cons of each method and recommend the most suitable manufacturing solution for each specific project. Below are some of the common options we offer:

• Hand Lay-Up
• Resin Transfer Molding (RTM)
• Autoclave Molding
• Compression Molding
• Pultrusion

Our tailored approach ensures that we deliver optimal solutions tailored to your unique requirements.

Customized Tool Design: We excel in providing specialized mold design services tailored to the needs of composite part manufacturing. Our expertise ensures that your production processes are efficient, precise, and of the highest quality.

Composite Tooling: The manufacture of composite product and assemblies requires that some kind of accurate repeatable tool surface and be capable of withstanding repeated exposures to the cure cycle environment of high temperature and pressure. One of the most critical parameters in the design of tooling for composites is the difference between the coefficient of thermal expansion (CTE) of the tool being designed and of the composite product being fabricated.

Testing
Our expertise encompasses comprehensive composite testing, ranging from specimen manufacture to Mechanical, thermal, fire retardant, electrical and environmental testing. We ensure that every aspect of the composite material is rigorously evaluated to meet the highest standards of performance and durability.

By collaborating closely with our customers, we gain a comprehensive understanding of their needs, allowing us to assist with component design, material selection, and process definition to achieve optimal results. We provide valuable support in optimizing the design of both prototype and production tooling, ensuring superior quality and efficiency in manufacturing.

Contact : composites-research@atira.in

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According to a recent sanitation report by WHO (World Health Organization) released in October 2023, more than 1.5 billion individuals worldwide still lack access to basic sanitation services, including private toilets. Shockingly, 419 million people continue to practice open defecation, posing severe health risks. Inadequate sanitation is directly linked to the transmission of diseases such as cholera, dysentery, typhoid, intestinal worm infections, and polio. It also contributes to stunting and the alarming spread of antimicrobial resistance. Notably, diarrhoeal diseases remain a leading cause of death, especially among children under 5, despite being largely preventable. Enhancing water, sanitation, and hygiene measures can significantly reduce mortality rates in this vulnerable population. Let us now explore the broad benefits of enhanced sanitation beyond diarrhoea risk reduction

Boosting health and wellbeing: Key benefits of improved sanitation:

• Reducing the spread of intestinal worms, schistosomiasis and trachoma, which are neglected tropical diseases that cause suffering for millions

• Reducing the severity and impact of malnutrition

• Promoting dignity and boosting safety, particularly among women and girls;

• Promoting school attendance: girls’ school attendance is particularly boosted by the provision of separate sanitary facilities

• Reducing the spread of antimicrobial resistance

Redefining sanitation infrastructure with Textile Reinforced Concrete Modular Toilet

Introduction:

Textile Reinforced Concrete (TRC) is a versatile composite material composed of cement enriched with chemicals and reinforced with layers of textiles. Its unique composition allows for easy casting, requiring minimal machinery and labour. This makes TRC a cost-effective and efficient solution for various construction projects. The combination of rich cement and textile reinforcement ensures durability and structural integrity, making TRC suitable for a wide range of applications in the construction industry. The Cement absorbs the compressive load and the textile reinforcement absorbs the tensile and shear stresses. Unlike traditional concrete, TRC boasts low weight, corrosion-resistant reinforcement, and simplified formwork.

Setting up TRC based Toilets in rural areas can improve living conditions and align with government initiatives. These affordable and long-lasting toilets require minimal maintenance, with rapid 4-hour fabrication and modular components for easy installation, reducing setup time significantly.

Key Features of Textile Reinforced Concrete Modular Toilet:

• Installation Time: 4 hrs

• Based on Twin-pit pour-flush design

• Basic Structural Components: Textile Reinforced Concrete (TRC) and Pultruded Composite Frame

• UV resistant

• Fire resistant

• Maintenance free life-long use

Basic building components:

• Toilet Pan

• Water-seal

• Superstructure

• Interconnecting pipe work

• Leach pits

• Light Points

Size of the toilet:

• Width: 914 mm (2.99 ft)

• Breadth: 1219 mm (3.99 ft)

• Height: Front: 2215 mm (7.2 ft)/Back: 1963 mm (6.4 ft)

Installation of Textile Reinforced Concrete based Toilet in just 4 hours

Installation Steps:

Advantages of lightweight TRC panels

• Reduced density

• High compressive strength

• Improved thermal insulation properties

• Purely mineral, recyclable &Lightweight concrete

• Environment friendly, energy efficient technology

• The material has very low water absorbance capacity i.e. 10-15%

• Fire &Termite resistant

• High thermal insulation

• Low cost, light weight and prefabricated premium quality walls

For more information, please connect with us on composites-research@atira.in

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Embracing Sustainability:

Jute, a natural fiber derived from the stems of the jute plant, offers several ecological benefits. It is a renewable resource with a low carbon footprint and requires minimal chemical treatment during processing. By utilizing jute fiber composites for prosthetic sockets, we can contribute to a more sustainable and eco-friendly approach to prosthetics.

Enhanced Comfort and Fit:

One of the key advantages of using jute fiber composites in prosthetic sockets is the enhanced comfort and fit they provide. Jute fibers possess excellent moisture-wicking properties, allowing for better breathability and reduced sweating. The natural flexibility and softness of jute fibers ensure a gentle and comfortable interface between the residual limb and the socket, minimizing the risk of skin irritation or pressure sores.

Customization and Adaptability:

Jute fiber composites offer remarkable adaptability, enabling customization according to individual needs. The inherent flexibility of jute fibers allows for precise shaping and contouring of the socket to match the unique anatomy of the residual limb. This personalized fit ensures optimal weight distribution and stability, resulting in improved balance and mobility for the user.

Manufacturing Considerations:

The manufacturing process for jute fiber composites involves impregnating the jute fibers with a polymer matrix followed by curing. This process can be performed using various techniques, including vacuum infusion or compression molding, depending on the desired properties and complexity of the socket design.

Strength and Durability:

Contrary to common misconceptions about natural fibers, jute fiber composites exhibit impressive strength and durability. When combined with appropriate resin systems, jute fibers provide sufficient structural integrity to withstand the stresses and strains encountered during daily activities. This ensures longevity and reliability in prosthetic sockets, reducing the need for frequent replacements.

Aesthetics and Design:

The socket material plays a crucial role in distributing the forces exerted during locomotion and absorbing impacts. Natural fiber composites, including jute fiber composites, exhibit excellent shock absorption properties, reducing the strain on the residual limb and providing a cushioning effect. This can enhance user comfort and minimize the risk of injuries or discomfort during activities.

Biocompatibility and Skin Health:

Natural fiber composites are known for their biocompatibility, which is crucial for socket materials. Jute fiber composites have a low tendency to cause skin irritation or allergies, making them suitable for individuals with sensitive skin. Additionally, the moisture-wicking properties of jute fibers help maintain a dry and breathable environment, reducing the risk of skin-related issues.

Comparison of Natural fiber composite-based socket over other synthetic and conventional socket materials

The utilization of jute fiber composites in the fabrication of prosthetic leg sockets represents a sustainable and innovative approach in the field of prosthetics. By embracing jute fibers’ inherent properties, such as comfort, customization, and durability, we can revolutionize the design and functionality of prosthetic sockets. The combination of eco-friendliness, enhanced comfort, and aesthetics makes jute fiber composites an exciting material for creating prosthetic leg sockets that cater to both the physical and emotional well-being of users. This remarkable innovation holds promise for a more sustainable and inclusive future in the field of prosthetics.

ATIRA (Ahmedabad Textile Industry’s Research Association) in collaboration with the Blind People’s Association (BPA) and supported by the National Jute Board, is at the forefront of developing natural fiber-based socket materials for prosthetic legs. This groundbreaking initiative aims to revolutionize the field of prosthetics by utilizing sustainable and biocompatible materials, specifically natural fibers like jute.

The partnership between ATIRA, BPA, and the National Jute Board signifies a collective effort towards creating innovative solutions that address the needs of individuals with limb loss. By combining their expertise in textile research, prosthetic design, and support for the physical impaired community, this collaboration holds tremendous potential for transforming the lives of amputees.

Furthermore, the partnership between ATIRA, BPA, and the National Jute Board emphasizes the importance of affordability and accessibility of prosthetics. Natural fibers, like jute, are cost-effective compared to synthetic materials, making prosthetic legs more affordable for a broader population. This inclusivity is critical in ensuring that individuals from all walks of life can benefit from advanced prosthetic technologies.

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Applications of Ladders

Here are some common applications of ladders:

• Industrial applications (Chemical plants, Manufacturing industries, etc.)
• Transportation (Firefighting Vehicles, Marine and Mass transport).
• Water and Sewage Water Treatment plants.
• Electrical substations and Power plants.
• Paper industry and Food processing plants.
• Civil Constructions.
• Household applications.

Comparative Study

Conventionally Aluminum ladders are widely used in various sectors. Aluminum is lighter and easier to transport, making it a better and more commonly used material for straight and full-length extension ladders and even, mobile platform ladders.

As per ground, market research Aluminum ladders are preferred over other types of ladders due to their recyclability. This means once the Aluminum ladder is damaged; it can give a scrap value. Also, Aluminum ladders are durable, corrosion resistant, and light in weight they have a strong adaptability in different professional and nonprofessional sectors.

Why FRP composite ladders?

The whole world is worried about depleting natural and conventional resources. To solve this puzzle, many researchers are ongoing to develop non-conventional engineering materials. And as they say “Researches made worldwide have proved that composite materials exhibit extraordinary properties. Hence most of the world is adopting modern composite materials over conventional engineering materials.”

Fiberglass (FRP) is highly resistant to corrosion from a large variety of chemicals which can corrode Aluminum also. For example, strong alkaline solutions, inorganic acids, and heavy metal salts can be very corrosive to Aluminum. FRP has excellent corrosion resistance to acidic and alkaline environments.

FRP is also unaffected by exposure to water, even in marine environments. This makes fiberglass ladders suitable for many industrial applications.

Fiberglass ladders are open to being manufactured to any height but their weight increases with height, therefore making it difficult to be handled by one person alone. But Strength wise, FRP ladders are stronger and more rigid than Aluminum.

So, FRP ladders found more Pros compared to Aluminium ladders.

Why these FRP ladders are not widely preferred in the market?

The main hindrance due to which the FRP ladder is less popular in the market is Adaptability. In any industry adaptability of any product is very important and is very challenging for ground operations to switch from conventional things to new and advanced things.

Adaptability comes from awareness, a Sense of reliability, and Trust building. Many end users are unaware of FRP ladders and their benefits, Also it is difficult to build trust in these products especially when it comes to human safety.

So firstly to get FRP ladders adapted over conventional Aluminium ladders, it is very important to build trust in this product.

How we can build trust in the product?

The answer to this question is “Testing and analysis of the product”.

To evaluate all Pros of the FRP ladder Different types of testing need to be conducted.

1. Fire retardancy:
   • Vertical or horizontal flammability tests can be carried out to evaluate the burning behavior of the material. To safeguard the FRP ladder in the context of a Fire incident, it is very important that the material should be Fire retardant. UL-94 or IS 6746 are very common standards that can be followed to ensure flame retardancy of FRP Ladders.
   • Spread of the flame test as per ASTM D 635 can also be conducted to understand the spread pattern of fire on FRP ladder material in case of a fire incident.
   • Surface Burning characteristics (Flame spread Index and Smoke Developed Index ) As per ASTM E 84 (Also known as Steiner tunnel test) is a big-scale test carried out in a closed Tunnel. It is very useful to evaluate the actual spread of flame and smoke developed in case of fire incidents.
   • A limiting Oxygen index test is carried out considering the safety point. This test can give an idea about the minimum oxygen concentration required for the burning of material.
2. Electrical Safety
   • To evaluate the Insulative properties of the FRP ladder We can conduct an HV test or Dielectric Strength test As per ASTM D 149 to find out the maximum voltage which an FRP ladder material can sustain.
   • The Insulation Resistance of FRP material can be tested.
   • Antistatic properties of the material can be checked as per ASTM D 257.
3. Thermal properties
   • To compare the difference in Thermal properties of FRP ladders and Aluminium Ladders, we can conduct a Thermal conductivity test and Thermal expansion coefficient test as per ASTM standards or ISO standards.
4. UV protection
   • To evaluate the degradation of FRP material properties when exposed to actual Weather conditions and UV radiations, UV resistance testing as per ASTM G 154/155 can be conducted followed by mechanical, physical, and appearance change tests after UV exposure.
5. Strength
   • To evaluate the Strength of FRP material various Mechanical and Physical Type tests can be conducted as follows
     • Tensile Test to evaluate Strength, Young’s Modules, and elongation as per ASTM D 638/3039
     • Compressive test to evaluate Strength and Modulus as per ASTM D 6641/3410/695
     • Shear Strength test As per ASTM D 2344
     • Flexural and Shear modulus of full section profiles of FRP ladder
     • The hardness of material As per ASTM D 2583
     • Izod Impact strength of FRP material as per ASTM D 256
     • Water Absorption test as per ASTM D 570
     • Specific Gravity /Density As per ASTM D 792
6. Safety
   • As discussed earlier Safety is the most important parameter to be considered while adopting new products. To ensure the best working safety, FRP ladders can be tested for their performance as per EN 131-2.
   • EN131 is a European committee for standardization (CEN) harmonized standard for portable steps and ladders, manufactured from metal and certain other materials such as FRP. It covers minimum safety requirements.
   • AS per EN 131 following practice tests are carried out to ensure maximum working safety
     • The slip resistance of the feet while the ladder is in the position of use. In this test, the ladder is positioned in an actual way and a determined Static load is applied on the 4th rung/step of the ladder.
     • Lateral deflection tests evaluate the bend movement while the ladder is laid on its side. Maximum permissible deflection while the load is applied and after removal of load should not exceed a certain calculated value based on the length of the ladder.
     • Horizontal Deflection/Bend test to evaluate the bending movement and maximum deflection while the ladder is placed horizontally.
     • Torsion test to evaluate the twist movement whilst the ladder is laid on a test rig. In this test, the torsional load is applied to the center of the rung and the deformation is measured. The same test is conducted when the ladder is placed vertically in the position of its use.
     • Strength of Ladder test: In this test, the rung or steps of the ladder are tested to a static load of about 275 Kg. After the removal of the test loads the ladder, stabilizers, and their connections shall remain functional with no fracture or visible cracks.
     • Durability test to evaluate the life of the ladder.

This complete testing and evaluation of Ladders can help us to come to the conclusion that FRP ladders can also be preferred as an option to conventional Aluminum ladders and can overcome the limiting factors in the case of aluminum ladders.

At ATIRA we have a facility for testing composite materials used in various engineering sectors.

For Testing Related queries please contact

Composite Materials Testing Laboratory

Ahmedabad Textile Industry’s Research Association (ATIRA)
P.O. Ambawadi Vistar, Ahmedabad- 380 015
Phone: +091-79-26307921-22-23 (Ext: 382)
Fax : +91-79-26304677, Mobile:9096014577
Email: composites_testing@atira.in
Web: www.atira.in

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Advantages of Sandwich Composites

The sandwich composite structure provides superior mechanical properties compared to the individual components. The face sheets provide strength and stiffness while the core material provides low density and energy absorption capability. The combination of these properties results in a lightweight yet strong structure.

Sandwich composites have several advantages over traditional materials like metals or solid composites. They have a high strength-to-weight ratio, excellent thermal and acoustic insulation properties, and resistance to impact and fatigue. They also have a high resistance to corrosion and are easily repairable.

Design Considerations for Sandwich Composites

The design of sandwich composites requires careful consideration of the core material, face sheet material, and adhesive. The core material should be lightweight, have good compressive strength, and be resistant to crushing. The face sheets should have high strength and stiffness and be resistant to buckling. The adhesive should have good bonding properties and be resistant to moisture and temperature changes.

Core structures are the backbone of various engineering applications, especially in the aerospace and civil engineering fields. Structural panels made from various materials, such as metals, papers, polymers, and ceramics, are commonly used to manufacture these core structures.

Development of Triangular Carbon Fiber-Based Core Material

In recent years, there have been several developments in the field of sandwich composites. One such development is the use of triangular carbon fiber-based core material. This type of core material has a unique triangular shape that provides superior strength and stiffness compared to traditional core materials. The triangular shape allows for better load distribution, resulting in a stronger and stiffer structure.

Triangular carbon fiber-based core materials have several advantages over traditional core materials. They have a higher strength-to-weight ratio, higher compressive strength, and better energy absorption capability. They also have better resistance to crushing and are less prone to delamination.

The use of triangular carbon fiber-based core material has revolutionized the design of sandwich composites. It has allowed for the development of lightweight yet strong structures that are suitable for various engineering applications.

Mechanical Characterization of Sandwich Composites

ATIRA has developed a new core material made from carbon fiber reinforced composite and compared it with sandwich composites made from three different core and skin materials. The aim of this study was to investigate the mechanical characterization of these sandwich composites and find the best-performing material.

After performing the mechanical characterization, it was found that the triangular carbon core with carbon face sheet had the maximum compressive and lap shear strength when compared to the other sandwich composites. This makes it an ideal choice for applications that require high compressive strength.

Table: Sandwich composite composition and designation

In conclusion, sandwich composites are an essential class of materials that have revolutionized the design of lightweight yet strong structures. The use of triangular carbon fiber-based core material has further enhanced the properties of sandwich composites and has allowed for the development of structures that are suitable for various engineering applications. ATIRA has developed the carbon core material for structural application. The method used to manufacture the core structure was simple, cost-effective, and led to improved physical properties in the final product. The sandwich composites were made with different combinations of core and skin materials, and their lap shear strength and compression strength were evaluated. Results showed that sandwich composites with similar core and skin materials exhibited the highest lap shear and compressive strength. This study opens up exciting new possibilities for revolutionizing sandwich panel design and developing even stronger and more lightweight materials for a range of applications. As technology continues to advance, we can expect further developments in the field of sandwich composites.

The patent filed by ATIRA on this technology is a testament to its potential in the field of composite materials. The search for technology transfer partners is ongoing, and it is an exciting time for the composite material industry as a whole.

Reference:

• A. Sharma, T. Gangopdhyay, A. K. Bhuyan, A. Patel, Development of triangular carbon fiber-based core material for sandwich structural panel, In Proceeding of 60th Joint Technological Conference (JTC), held at SITRA, Coimbatore, on 11-12th Nov. 2022.
• H. Xie, H. Fang, W. Cai, L. Wan, R. Huo, D. Hui, Development of an innovative composite sandwich matting with GFRP face sheets and wood core, Rev. Adv. Mater. Sci. 60 (2021) 80–91. https://doi.org/10.1515/rams-2021-0016.
• V.S. Kathavate, K. Amudha, L. Adithya, A. Pandurangan, N.R. Ramesh, K. Gopakumar, Mechanical behavior of composite materials for marine applications-an experimental and computational approach, J. Mech. Behav. Mater. 27 (2018) 1–22. https://doi.org/10.1515/jmbm-2018-0003.
• A.C. Manalo, T. Aravinthan, W. Karunasena, M.M. Islam, Flexural behavior of structural fiber composite sandwich beams in flatwise and edgewise positions, Compos. Struct. 92 (2010) 984–995.
• A. Manalo, T. Aravinthan, A. Fam, B. Benmokrane, State-of-the-Art Review on FRP Sandwich Systems for Lightweight Civil Infrastructure, J. Compos. Constr. 21 (2017) 443–461. https://doi.org/10.1061/(ASCE)CC.1943-5614.0000729.
• D. Regaçon, A. Garay, Development of Composites Sandwich Structures Using a Core Cork, J. Mater. Sci. Eng. A. 8 (2018) 100–107. https://doi.org/10.17265/2161-6213/2018.5-6.003.
• A. Redmann, V. Damodaran, F. Tischer, P. Prabhakar, T.A. Osswald, Evaluation of single-lap and block shear test methods in adhesively bonded composite joints, J. Compos. Sci. 5 (2021). https://doi.org/10.3390/jcs5010027.

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A composite material can be defined as an artificially prepared or natural multiphase that exhibits significant properties of constituent material resulting in a superior and stronger product.

Being formed by the combination of two or more materials that have different characteristics, Composite materials open a wide window for application in various engineering sectors like Aerospace, defense, Automobile, etc.

Applications of composites

➢ Automobiles industries: Automobile parts like components of an engine, spray nozzle, tires, etc.

➢ Aeronautical applications: structural components like wings, body & stabilizer of aircraft, etc.

➢ Marine applications: shaft, hulls, spars, and other parts of ships.

➢ Safety equipment like helmets.

➢ Sports equipment like tennis rackets, golf sticks, other safety equipment.

➢ Communication Industry like preparation of antennae and electronic circuit boards.

Constituents of composites

Two essential constituents of composites are:

• Matrix phase: It is the continuous body constituent (Dispersion phase) which encloses the composite and gives its bulk form. It may be polymer, metal or ceramic material.

• Dispersed phase: It is the Structural constituent (Dispersed phase) which determines internal structure of the composite and gives its bulk form. It may be Fiber, Particulate, Flakes or Whisker.

Types of composites

Depending upon the type of Matrix and Reinforcement, Composite materials are categorized into,

Need of testing and analysis of composite materials

As per Theories, Composite materials are being used from ancient times in direct or indirect ways, either in conventional or non-conventional forms.

Research made worldwide has proved that composite materials exhibit extraordinary properties. Hence most of the world is adopting modern composite materials over conventional engineering materials.

Now the question arises,

“How come it has been proved that Composites are better than Conventional materials”

Answer: “Testing and analysis of composite materials”.

Thorough Testing practices and Standards have helped to evaluate the performance of composite materials. The data derived from composite materials testing and analysis can be used to compare the composite materials against conventional materials.

Composite materials testing plays a vital role across the composite’s supply chain and product life cycle. A range of challenges in regards to safety, quality, process control, regulatory compliance, and performance is encountered. Whether you are a base chemical provider, additive supplier, fibre manufacturer, or end-user, overcoming these challenges can give your business a significant commercial advantage.

Some of the important advantages of composite materials are,

1. Corrosion resistance
2. Life and durability
3. Good mechanical and electrical properties.
4. Ease of manufacturing

Types of composite materials testing and analysis

A. Mechanical testing

The characterization of composites for mechanical properties is very important from a design and analysis as well as a life prediction point of view.

The mechanical and physical testing of polymers and their composites is vital to determine the material properties for use in the design and analysis of the product, quality control, application performance requirements, and production process.

The mechanical and physical testing ensure the material complies with performance requirements.

Mechanical testing of composites includes tensile (tension), flexural, impact, shear, and compression, and physical testing includes water absorption, density, void content, hardness, and scratch resistance.

Besides these, many other standardized bearing strength tests as per ASTM D 5961 and interlaminar fracture toughness tests to ASTM D 5538 are reported as mechanical tests on composites.

Tensile test:  

Tensile testing is a destructive test process that provides information about the tensile strength, yield strength, and ductility of the metallic material. It measures the force required to break a composite or plastic specimen and the extent to which the specimen stretches or elongates to that breaking point.

Tensile testing of composites is generally in the form of basic tension or flat-sandwich tension testing in accordance with standards such as ISO 527-4, ISO 527-5, ASTM D 638, ASTM D 3039, and ASTM C 297.

The test specimen is prepared in accordance with standards applicable for the testing (Specimen shown below in images A and B) and subjected to tensile load with the help of a Universal testing machine. Such tests produce stress-strain diagrams used to determine tensile modulus.

Tensile testing also provides tensile strength (at yield and at break), tensile modulus, tensile strain, elongation, and percent elongation at yield, elongation, and elongation at break in percentage.

Flexural test:

The flexural test measures the force required to bend a beam under three-point loading conditions, and it is generally applicable to both rigid and semi-rigid materials, resins. The data is often used to select materials for parts that will support loads without flexing.

The most common flexural testing of plastics, polymer composites, and large fiber-reinforced plates involves three-point and four-point bend testing as per ISO 178, ASTM D 790, and ASTM D 6272 to ensure suitability under various conditions for better insight into their properties and to ensure that they are suitable for the intended application.

A variety of specimen shapes can be used for this test, but the most commonly used specimen size for ASTM is 3.2 mm 12.7 mm 125 mm Most commonly in the flexural test, the specimen lies on a support span, and the load is applied to the center by the loading nose producing three points bending at a specified rate.

The parameters for this test are the support span, the speed of the loading, and the maximum deflection for the test.

These parameters are based on the test specimen thickness and are defined differently by ASTM and ISO. Flexural testing also gives a semiqualitative idea of the fiber/matrix interfacial strength of a composite.

Flexural properties testing provides editable and raw data on flexural stress at yield, flexural strain at yield, flexural stress at break, flexural strain at break, flexural stress at 3.5% (ISO) or 5.0% (ASTM) deflection, flexural modulus, and stress/strain curves.

Impact test:

The impact test is designed to determine how a specimen of a known material such as polymers, ceramics, and composites will respond to a suddenly applied stress.

The impact test is explicitly used for evaluating the toughness, brittleness, notch sensitivity, and impact strength of engineering materials to resist high-rate loading [8,9].

The ability to quantify the impact property is a great advantage in product liability and safety. Impact test specimen types include notch configurations such as V-notch and U-notch. Impact testing most commonly consists of Charpy and Izod specimen configurations.

The Izod impact test differs from the Charpy impact test in the way that the notch is positioned facing the striker. ASTM D256, ISO 180, and ASTM D  are some of the standards for pendulum impact testing.

In this test, a specimen is machined to a square or round section, with either one, two, or three notches. The Izod impact test consists of a pendulum with a determined weight at the end of its arm swinging down and striking the specimen while it is held securely in a vertical position (Shown in fig C & D).

The impact strength is determined by the loss of energy of the pendulum as determined by precisely measuring the loss of height in the pendulum’s swing. Also, the impact strength is defined as the tendency of polymer composites to endure high-energy impact without breaking or fracturing.

It is being reported that in fiber-reinforced polymer composites and hybrid composites the impact properties are governed by the properties of the individual fibers used for hybridization, interlaminar, and interfacial adhesion between the fiber and the matrix.

Besides the Pendulum Impact test, one more method is used to evaluate the resistance of the material to sudden impacts i.e. Drop Weight Impact test.

In this test, Specimen is hit by an indenter caring a weight or mass from a certain specified height. The energy induced by falling mass on the specimen is recorded and is used to evaluate the impact strength of the material. These tests are carried out as per ASTM D 7136M-05, ASTM D 3763, and ISO 6603.

Compression test:

Composite compression testing methods provide a means of introducing a compressive load into the material while preventing it from buckling.

Compression testing determines the behavior of materials under a crushing load, and the compression and deformation at various loads are recorded to calculate compressive stress and strain. The most common testing standards include ASTM D 695, ASTM D 3410, and ISO 14126.

Interlaminar shear strength test: 

The interlaminar shear strength (ILSS) is another important mechanical test that provides information about the quality of the resin-fiber bond.

The ILSS of unidirectional laminates and carbon fiber reinforced plastics are usually determined through a three-point bending test, where the resistance to interlaminar shear stress is kept parallel to the layers of the laminate and is measured.

Shear test:  

Shear tests are used to determine the attributes such as shear strain, shear stress, shear modulus, and failure mode since the awareness of the “deformable” mechanical properties of plastics and polymer composites is essential to extend their applications.

Shear testing can be used for quality control, comparative testing, and finite element (FE) analysis of new materials.

Shear strength results are important to design a wide variety of materials like adhesives, plastics, films, and sheet products that tend to be subjected to various “shear loads,” or in applications where factors such as crushing.

loads are a risk. Standards for the shear tests include ASTM D3518 and ISO 14129. The ASTM C 273, and ASTM D 2344.

Hardness:

A hardness test is Performed on materials to check resistance to indentation.

Different Hardness testing practices are used on composite materials like:

1. Rockwell hardness
2. Shore hardness
3. Barcol hardness

Apart from the above described mechanical properties, some physical properties are also evaluated to understand the behavior of composite material.

1. Water/moisture absorption test: To evaluate the percentage of moisture or water absorbed by the material. ASTM D 570 is the standard practice for this test.
2. Resin content or fiber content: To evaluate the Percentage of Fiber/Reinforcement or Percentage of Matrix in composite product.
3. Density Measurement: Density and specific gravity of material is evaluated as per ASTM D 792.

B. Electrical testing

The electrical properties of composites are very important to a wide range of industries such as automotive, aerospace, building products, marine, etc.

Electrical tests, in general, are measurements of the resistance, conductivity, or charge storage either on the surface or through the material.

Various factors such as dielectric strength, volume, and surface resistivity are crucial to gauge the nature of the material.

• Dielectric strength:

Dielectric strength, also known as dielectric breakdown strength (DBS), is the maximum electrical potential that a material can resist before the electrical current breaks through the material and the material is no longer an insulator. DBS is tested per ASTM D149 and measured in kV/mm or V/mil.

• Insulation Resistance:

An insulation resistance (IR) test measures the total resistance between any two points separated by electrical insulation. The test, therefore, determines how effective the dielectric (insulation) is in resisting the flow of electrical current. Such tests are useful for checking the quality of insulation, not only when a product is first manufactured but also over time as the product is used.

• Volume resistivity and Surface resistivity:

Surface resistivity is the resistance to leakage current along the surface of insulating material. Volume resistivity is the resistance to leakage current through the body of insulating material. The higher the surface/volume resistivity, the lower the leakage current and the less conductive the material is.

• Dry Arc Resistance

When electric current travels across an insulator’s surface, it can become conductive due to damage, erosion, or other factors. Arc resistance is a measure of the time required to make an insulating surface conductive under a high voltage/ low current arc in carefully controlled laboratory conditions.
In other terms, arc resistance is the ability of the plastic material to resist the action of a high voltage electrical arc and resist the formation of a conducting path along its surface under a given time.

The most generally used standard test to calculate arc resistance is ASTM D495. 

C. Thermal properties testing

Some raw materials used in the manufacture of composite materials can be negatively impacted by the effects of temperature and humidity. It is therefore essential to ensure they are stored within highly controlled environmental conditions prior to use. 

Differential scanning calorimetry (DSC) is one of the common tests used to check the cure and confirm the material’s thermal properties. DSC is one of the most important test types when discussing quality control. DSC can provide information on the physical structure of the material via important thermal transitions such as glass transition temperature (Tg) [link], melting temperature (Tm), crystallization temperatures, percent crystallinity, enthalpy of melting and crystallization, specific heat capacity (Cp) and oxidation induction time (OIT). 

Dynamic mechanical analysis (DMA) is a technique that can be used to provide information on the material’s physical structure via its viscoelastic mechanical properties. The test allows the material’s response to a sinusoidal force during a temperature or frequency sweep to be obtained.  DMA can be used to determine the mechanical properties (mechanical modulus or stiffness and damping) of the composite and important thermal transitions of the adhesive, such as the glass transition temperature and the degree of cure of polymer and composite materials.

Thermogravimetric analysis (TGA) can be used to provide information on the material’s chemical and physical structure via thermal decompositions. TGA provides information on the temperature and rate of decomposition of materials and the number of volatiles and fillers they contain. With advanced analysis software, characteristic temperatures such as melting points and decomposition temperatures can also be evaluated.

Thermal conductivity refers to the intrinsic ability of a material to transfer or conduct heat. It is also defined as the amount of heat per unit time per unit area that can be conducted through a plate of unit thickness of a given material, the faces of the plate differing by one unit of temperature.

D. Heat and flame testing

Flammability Testing:

Flammability test methods measure how easily materials ignite, how quickly they burn, and how they react when burned.

There are several methods for fire resistance or flammability. Depending on the materials and applications of the materials there are different methods or practices for flammability testing like,

– UL 94, UL 94HB, 94V, 94VTM, 94-5V, 94HBF, 94HF or UL 94 V-0, V-1 and V-2
– Limiting oxygen index (LOI)
– Vertical burning test (VC)
– Flammability ASTM D635, ISO 3795

Flammability testing is a critical part of ensuring safe and trustworthy products. Industry applications for flammability test methods include textiles and consumer goods, aerospace and transportation, bedding, and furniture materials.

Vertical and horizontal flammability testing

The materials are placed over a Bunsen burner either vertically or horizontally, depending on the specification. During a vertical flammability test, a material is observed for the duration of time it burns after the igniting flame is removed, how much of the specimen burns, and whether it drips flaming particles.

In contrast, horizontal flammability tests observe if the material continues to burn after the test flame is removed, and then calculate the rate at which the specimen burns.

Limiting oxygen index (LOI)

The limiting oxygen index (LOI) is the minimum concentration of oxygen, expressed as a percentage, that will support the combustion of a material. It is measured by passing a mixture of oxygen and nitrogen over a burning specimen, and reducing the oxygen level until a critical level is reached. The standard test method for evaluating the LOI of composite material is ASTM D 2863.

Toxicity:

Toxicity of products of combustion in terms of small molecular species is evaluated to ensure the safe behavior of materials in case of fire hazard or combustion. Also, combustion characteristics of natural & synthetic materials can be compared using this testing.

NES 713 and NCD 1409 are the common practices for this testing. Around 14 types of effluent gasses can be measured in PPM using these practices.

This testing finds application in products used in mass transport, defense, aerospace, etc.

Smoke density test:

This test is for the Determination of smoke generated by solid materials & assemblies mounted in a vertical orientation within the chamber. This test measures the amount of smoke given off by a material that is burning or smoldering.

Standard Test Methods for this testing include ASTM E 662, ISO 5659, and NFPA 258.

These tests are carried out to ensure the safe behavior of the material. Also, as per ISO 5659 and EN45545, this parameter is evaluated to determine the hazard level of the material.

Cone calorimeter test:

To evaluate the amount of heat released or evolved from the substance this test is carried out. Cone calorimeter Measures Rate of heat release, smoke release rates, time to ignition, Mass loss rates, effective heat of combustion.

The Cone Calorimeter is a fire testing tool based on the principle that the amount of heat released from a burning sample is directly related to the amount of oxygen consumed during the combustion. The amount of heat a material generates is directly aligned with the severity of a fire, such as fire growth rate. To assess a material’s flammability, it is exposed to an external radiant heat source.

A sample is placed below a cone-shaped radiant heater and typically exposed to an external flux from the heater. Once enough pyrolysis products are generated, ignition occurs. The combustion products travel through the Cone heater and through an instrumented exhaust pipe. The values measured/calculated are, the time to ignition, the mass-loss rate during combustion, time to and the value of the maximum amount of heat released during combustion, and the total amount of heat released during the test. The standard Test method for this test is ISO 5660-1:2002.

Smoke opacity:

To Determine the Deterioration of visibility due to smoke produced because of combustion of the material.

In this test, the material is burnt in a closed chamber, and visibility through the smoke generated is evaluated using a Lux meter.

This test is commonly done to evaluate components used in mass transport as per the UIC-564-2 standard.

Spread of flame:

Flame spread tests aim at measuring the tendency of a flame to propagate over a substrate and directly correlate to surface flame propagation in a real fire scenario.

As per the UIC-564-2 standard, it is very important to evaluate the spread of Flame.

In this test, the Critical area of spread of flame and afterglow time is calculated to evaluate the burning behavior and resistance of the material to the spread of flame.

Lift spread of flame:

The Spread of Flame Apparatus is an important test for comparing the performance of essentially flat materials, composites or assemblies, which are used primarily as the exposed surfaces of walls. ISO 5658­2 and ASTM E1321 allow wider use of the test beyond marine applications. The major differences between ISO 5658­2 and the IMO test are that ISO 5658­2 is limited in scope to testing the spread of flame over vertical specimens and does not include the stack for estimating the heat release rate.

Sector wise requirement of testing and analysis of composite materials

As discussed, Composite materials find applications in various engineering sectors and most of the world is adopting modern composite materials replacing conventional materials. Hence a wider scope for testing and analysis of composite materials has been generated.

Depending upon the sectors and application, different properties and characteristics of composite materials are evaluated.

1. Composite materials testing for Structural members.

Composite materials especially Pultruded profiles, find their application as support structures, structural members in industrial or civil applications.

Testing’s carried out:

Mechanical properties like Tensile properties, compressive properties, flexural properties, bearing strength, shear strength, Physical properties as per ASTM, ISO, BS, and IS standards.

Full section bending test, Static loading Test, Full section shear modulus test etc

Flammability test:

UL-94, Spread of flame as per ASTM D 635 and Limiting oxygen index as per ASTM D 2863.

Electrical test:

Dielectric strength, Break down the voltage as per ASTM D 149, Critical trackability index, and Dry Arc Resistance Test.

2. Automobile components:

Testing carried out:

Mechanical properties like Tensile properties, compressive properties, flexural properties, bearing strength, shear strength, Physical properties as per ASTM, ISO, BS, and IS standards.

Flammability test:

UL-94, Spread of flame as per ASTM D 635 and Limiting oxygen index as per ASTM D 2863.

Electrical test:

Dielectric strength, Break down the voltage as per ASTM D 149, Critical trackability index, and Dry Arc Resistance Test.

Heat and flame testing:

Cone calorimeter test as per ISO 5660, EN45545-2.
Fire resistance characteristics as per UIC-564-2.
Smoke density testing as per EN45545-2, ISO 5659.
Toxicity Index testing as per NCD 1409, NES 713.

3. Composite materials for Mass transports, and Aerospace

Testing carried out:

Mechanical properties like Tensile properties, compressive properties, flexural properties, bearing strength, shear strength, Physical properties as per ASTM, ISO, BS, and IS standards.

Flatwise mechanical strength as per ASTM C 297

Flammability test:

UL-94, Spread of flame as per ASTM D 635 and Limiting oxygen index as per ASTM D 2863.

Electrical test:

Dielectric strength, Break down the voltage as per ASTM D 149, Critical trackability index, and Dry Arc Resistance Test.

Heat and flame testing:

Cone calorimeter test as per ISO 5660, EN45545-2.
Fire resistance characteristics as per UIC-564-2.
Smoke density testing as per EN45545-2, ISO 5659.
Toxicity Index testing as per NCD 1409, NES 713.
Toxicity of smoke as per EN 45545-2.
Flooring Radiant Panel Testing for flooring materials.
Lift spread of flame /IMO testing

4. FRP gratings ,Walkways and Cable trays(Civil constructions)

Testing carried out:

Mechanical properties like Tensile properties, compressive properties, flexural properties, bearing strength, shear strength, Physical properties as per ASTM, ISO, BS, and IS standards.

Full section bending test, Static loading Test, etc.

Flammability test:

UL-94, Spread of flame as per ASTM D 635 and Limiting oxygen index as per ASTM D 2863.

UV Resistance test As per ASTM G154

5. Composite materials for Ship Building

Testing carried out:

Mechanical properties like Tensile properties, compressive properties, flexural properties, bearing strength, shear strength, Physical properties as per ASTM, ISO, BS, and IS standards.

Flammability test:

UL-94, Spread of flame as per ASTM D 635 and Limiting oxygen index as per ASTM D 2863.

UV Resistance test As per ASTM G154

6. FRP storage Tanks testing

Testing carried out:

Mechanical properties like Tensile properties, compressive properties, flexural properties, bearing strength, shear strength, Physical properties as per ASTM, ISO, BS, and IS standards.

Flammability test:

UL-94, Spread of flame as per ASTM D 635 and Limiting oxygen index as per ASTM D 2863.

UV Resistance test As per ASTM G154

Ageing test in a hot air oven,

Ageing test by immersion into solvents or desired liquids as per UL-1316.

7. Composite laminates testing

Testing carried out:

Mechanical properties like Tensile properties, compressive properties, flexural properties, bearing strength, shear strength, Physical properties as per ASTM, ISO, BS, and IS standards.

Flammability test:

UL-94, Spread of flame as per ASTM D 635 and Limiting oxygen index as per ASTM D 2863.

UV Resistance test As per ASTM G154

Electrical test:

Dielectric strength, Break down the voltage as per ASTM D 149, Critical trackability index, and Dry Arc Resistance Test.
Insulation Resistance Test.
Heat shock and Heat distortion.
Volume resistivity and surface resistivity.

8. Composite materials for defense applications

Composite materials testing carried out:

Mechanical properties like Tensile properties, compressive properties, flexural properties, bearing strength, shear strength, Physical properties as per ASTM, ISO, BS, and IS standards.

Flatwise mechanical strength as per ASTM C 297

Drop weight Impact testing as per ASTM D 3763.

Flammability test:

UL-94, Spread of flame as per ASTM D 635 and Limiting oxygen index as per ASTM D 2863.

Electrical test:

Dielectric strength, Break down the voltage as per ASTM D 149, Critical trackability index, and Dry Arc Resistance Test.

Heat and flame testing:

Cone calorimeter test as per ISO 5660, EN45545-2.
Fire resistance characteristics as per UIC-564-2.
Smoke density testing as per EN45545-2, ISO 5659.
Toxicity Index testing as per NCD 1409, NES 713.
Toxicity of smoke as per EN 45545-2.
Flooring Radiant Panel Testing for flooring materials.
Lift spread of flame /IMO testing

ATIRA facilities

At ATIRA we have a facility for testing composite materials used in various engineering sectors.

We have a Facility for

1. Mechanical testing
   1. Tensile properties (ASTM D 638, ASTM D 3039, ISO 527, ASTM C 297, BS 4994 & Equivalent Standards)
   2. Compressive properties (ASTM D 695, ASTM D 3410 & Equivalent Standards)
   3. Shear properties (ASTM D 2344, BS 4994, ASTM F 711, EN 2563, ISO 14130 & Equivalent Standards)
   4. Flexural properties (ASTM D 790, EN 2562, ISO 14125 & Equivalent Standards)
   5. Bearing strength (ASTM D 5961 & Equivalent Standards)
   6. Lap shear strength (BS 4994, ASTM D 3163, ASTM D 5868 & Equivalent standards)
   7. Peel strength (BS 4994 & Equivalent Standards)
   8. Impact strength (ASTM D 256, ASTM D 4812, ISO 180 & Equivalent Standards)
   9. Drop weight impact (ASTM D 3763, ISO 6603, ASTM D 7136 & Equivalent Standards)
   10. Full section bending test
   11. Full section shear modulus test
   12. Static loading test
   13. Bending test on FRP full sections like rods and pipes. (ASTM F 711)
   14. Stiffness test
   15. Heat deflection Temperature and VICAT softening temperature. (ISO 75-1)
2. Physical testing
   1. Hardness (Barcol, Rockwell. Shore) (ASTM E 18, ASTM B 254, ASTM D 2583 & Equivalent standards)
   2. Glass content/resin content (ASTM D 3171, ISO 14127 & Equivalent Standards)
   3. Water absorption (ASTM D 570 & Equivalent Standards)
   4. Void content
   5. Specific gravity and Density (AST D 792, ISO 1183 & Equivalent Standards)
   6. Resistance to chemicals
   7. Wicking resistance.
3. Electrical testing
   1. Breakdown voltage testing (ASTM D 149 & Equivalent standards)
   2. Dielectric Strength (ASTM D 149 & Equivalent standards)
   3. Dry arc resistance (ASTM D 495)
   4. Glow wire test
   5. Comparative tracking Index
4. Flammability testing
   1. UL-94
   2. Horizontal flammability as per ASTM D 635
   3. Limiting oxygen Index (ASTM D 2863, ISO 4589, & Equivalent Standards)
   4. Toxicity Testing As per NCD 1409 and NES 713
5. Thermal properties testing
   1. DSC (Differential scanning calorimetry) (ASTM D 3418 & equivalent standards)
   2. DMA (ASTM D 7028)
6. Heat and flame testing
   1. Deterioration of Visibility due to smoke generated (UIC 564-2)
   2. Lateral spread of flame (UIC 564-2)
   3. Lift spread of flame/ IMO
   4. Cone calorimeter test (ISO 5660, EN 45545-2)
   5. Smoke density (ISO 5659, EN 45545-2)
   6. Flooring radiant panel
   7. Single flame source test.
7. Non-destructive testing
   1. Ultrasonic scanner
   2. X-rays
8. Dynamic mechanical analysis of materials and fatigue testing.
9. Immersion ageing of FRP Tanks as per UL-1316.
10.  Ageing test of composite materials.

Composite sectors we serve:

We conduct composite materials testing for,

1. Mass Transport (Railways, Metro-Rails, Bullet trains, Public transport buses etc)
2. Structural applications
3. Aerospace and aviation sectors
4. Ship building
5. Storage tanks for industrial applications (Chemical, Fuels etc)
6. Sewerage plants
7. Cable trays for Electrical installations.
8. Automobile components
9. Wind energy applications
10.  Effluent gas treatment plants
11.  Solar power plants
12.  Defense sector
13. Composite Laminates

Also, We serve,

1. Adhesives manufacturing,
2. Resin or Matrix manufacturing sectors

For composite materials testing, related queries please contact:

Composite Materials Testing Laboratory

Ahmedabad Textile Industry’s Research  Association (ATIRA)
P.O. Ambawadi Vistar, Ahmedabad- 380 015
Phone : +091-79-26307921-22-23 (Ext : 382)
Fax : +91-79-26304677,Mobile:9096014577
Email: composites_testing@atira.in

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Composite material is defined as the material formed by combining two or more different materials/ constituents macroscopically that are distinct in the properties and they do not dissolve into each other.

The combination of different constituents in the composites provides the composite material with unique properties which are different from the individual constituent. 

An example of composites is the mud building bricks used since ancient times, which is formed by combining mud bricks and straws. This allowed the composite to have the strength and resistance of mud bricks and the tensile strength of straw.

In general, the composite material comprises three main components (a) the matrix, the continuous phase; (b) the reinforcements, the continuous or discontinues phase used to strengthen the composite, and (c) the fine interface region. 

For thousands of years, composite materials have played crucial roles in human life, starting with enabling early civilizations to build houses and continuing on to making advances in modern technology possible.

People use composite materials in their day-to-day life, including the ceramic tiling in our bathroom, which help keep us dry.

Composites can indeed be found in the majority of common products, including building and engineering projects, medical applications, energy and transportation, sports, aircraft, automotive, and other fields.

Evolution of Composite Materials

Humans are using composite material for thousands of years. The first composite was found in 1500 BC when mud and straw were used by Egyptians and Mesopotamians to make their houses.

The Mongols developed the first bow using wood, bone, and animal glue. During World War II the civilization of the composite was enhanced and moved from the laboratory into actual production. Also, the development of components from fiber-reinforced polymer composites was adopted by the industries.

By 1945, the use of fiber-reinforced polymer composites started to use primarily in military applications.

In 1946, the first FPR composite boat hull was introduced and by 1947 the automobile body was made from composite material and successfully tested.

Types of composites

Matrix material

The primary function of the matrix material in polymer composite is to act as a binder and transfer the load between constituents of the composites, provide the component its net shape, and determines its surface quality.

Polymer composites uses generally two types of matrix material viz. thermoplastic and thermosetting. Since the dawn of the composite era, both materials have been used for the development of composites.

The characteristic of the thermoplastic and thermosetting are as follows:

	Thermoplastic	Thermosetting
Introduction	Thermoplastics can be heated and softened and then moulded or shaped and upon cooling it hold the desired shape. It has one- or two-dimensional molecular structure and they tend to show an exaggerated melting point at an elevated temperature.	Thermosetting materials endure an irreversible chemical bond reaction bond i.e., crosslinking or curing during process to change the phase from liquid to solid state. The cross linking enables to eradicates the component remelting with application of heat.
Benefits	Can be recycled Remould and reshape capability with the application of heat Easy to manufacture high volumes quickly Chemically retardant and impact resistant Costlier than the thermosets Environment friendly processing adhesive to metal	Cannot be recycled Once cured than cannot be reshaped or remold Better dimensional stability   Cost effective More Resistant against high temperature Hard and Rigid Excellent aesthetics finishes Better mechanical properties
Structure
Types	Some thermoplastic material used in polymer composites: Acrylonitrile Butadiene Styrene (ABS) Poly (methyl methacrylate) (PMMA) (Acrylic) Polybenzimidazole Polyethylene Homopolymer Copolymer Polyurethane Styrene Acrylonitrile Polypropylene (PP)Polyamide (PA)Polycarbonate (PC)Polyether ether ketone (PEEK) Polylactic Acid (PLA)  Polyvinyl chloride (PVC) Teflon	Some thermosetting material used in polymer composites: ResinUnsaturated polyesterVinyl esterPhenolSiliconeCyanate estersMethyl Methacrylate (MMA)Bismaleimide (BMI)Urea FormaldehydeFluoropolymersMelamine

Fiber Reinforcement Composite material

In fiber-reinforced polymer composites, different types of fibers can be used as reinforced material. The selection of the reinforced material is depending on the end application of the component/material. Some common fiber reinforcement is as follows:

Glass fiber

As the name implies the fiber generates from the silica-based or other formulations of the glass by heating at 1675°C. Different types of glass fiber are available based on their properties.

• A-glass (alkali glass): good chemical resistance, but lower electrical properties.
• C-glass (chemical glass): high chemical resistance
• E-glass (electrical glass): excellent insulator and water resistance.
• S-Glass (structural glass): good mechanical properties.
• D-glass (dielectric glass): good electrical properties but poor mechanical properties compared to E & S glass fiber
• E-CR glass fiber (electronic glass fiber): electric resistance, chemical resistance, good mechanical properties, waterproof compared to E-glass
• AR-glass (alkali-resistant glass): specifically used in concrete. It provides strength and flexibility to the concrete in order to prevent the cracks 
• M-Glass Fiber: it consists of beryllium in its composition which provides better elasticity compared to E-glass
• Z-Glass Fiber: Used to produce transparent components, high mechanical, UV, acid, alkali, salt, scratch, wear, and temperature resistance, used in 3d printer filament

Carbon Fibers

Carbon fiber is composed of carbon atoms bonded together to form a long chain. Carbon fibers are extremely stiff, strong and light compared to glass fiber.

The fibers are extremely stiff, strong, low weight to strength ratio, low coefficient of thermal expansion, and have good resistance to chemical and high temperatures.

Carbon fiber was first invented near Cleveland, Ohio, in 1958.

Based on modulus, strength, and final heat treatment temperature, carbon fibers can be classified into the following categories:

Aramid fibers

Kevlar is made from aromatic polyamide (aramid) fibers, which DuPont made publically available in the early 1970s.

The Kevlar fiber possesses high strength, good resistance to abrasion, chemical resistance, non-conductive, low flammability, and good fabric integrity at elevated temperatures. The aramid fiber generally available in yellow color and widely used in the application where high strength and low weight is required.

Due to its good impact resistance, property Kevlar fiber is used in the ballistic application

Based upon the location of chemical bond in the structure of Kevlar fiber is classified into two types:

1. Meta-aramid: The chemical bond of meta-aramid is in a zigzag pattern and the tensile strength of the meta-aramid fiber is lower than the para-aramid. These fibers have good thermal, chemical, and radiation resistance.
2. Para-aramid: In para-aramid fiber, the chemical bond structures are aligned in the long direction of the fiber. This type of fiber possesses hood tensile strength. Such fiber is widely used in the civil engineering structural applications

Natural fiber

Natural fiber-reinforced composites have become extremely popular for many uses in recent years, due to their good characteristics.

Due to government policies and environmental consciousness the use of natural fiber in polymer composite increases.

Natural fibers have low density, high specific strength and provide good thermal and acoustical insulation. The natural fiber is derived either from plants or animals.

These fibers have an edge over synthetic fibers in various sectors such as automobile, construction, and sports industries because of their comparable mechanical properties with glass fiber.

Classification of Natural fiber

Classification based on reinforcement structure

Particle reinforced	Short fiber reinforced
Unidirectional fiber reinforced	Bidirectional reinforced
Laminate composite

Applications of Composite Materials

1. Space: antenna, radar, satellite structures, solar reflectors, etc.
2. Aircraft: aerofoil surfaces, compressor blades, engine bay doors, fan blades, rotor shafts in helicopters, turbine blades, turbine shafts, wing box structures, etc.
3. Automobiles: automobile body, bumper, mudguards, door panels, dashboard, driveshaft, fuel tank, CNG cylinder, chassis, fender, etc.
4. Wind turbine blades: rotor blades, nose cone, nacelle cover, accessories for wind electric generators.
5. Sports: Skis, surfboards, windsurfing, table tennis boards, slats, and gliding wing spar, Tennis, badminton, fishing rods, golf clubs, baseball bats, hockey sticks, pole shaft, Sword, etc.

Centre of Excellence – Composites at ATIRA

ATIRA was declared as “Centre of Excellence in Composites” by the Ministry of Textiles, Government of India in March 2011.

ATIRA has created a Centre of Excellence (CoE) for developing advanced composites applications through an advanced process in order to achieve weight reduction, high mechanical properties, cost competitiveness and to enhance the knowledge base in composites through research, development, and training.

Work done at ATIRA (Composite Materials)

1. Carbon Fibre and Epoxy Resin-based products through vacuum infusion process. Various components for satellite communication systems have been developed. These works have been done for SAC-ISRO Ahmedabad.
2.  Satellite communication systems were also developed using carbon-epoxy prepregs.
3. The carbon core material is under development for making homogeneous sandwich panels for better performance.
4. Natural fibers like jute and cotton-based composites were developed using the compression molding process. These find application in partition, door, and engineering fabrication.
5. Pultrusion based composite profiles developed for diversified applications like building construction, furniture, cooling tower, etc.
6. Compression-molded composites that are based on synthetic reinforcement like Glass fiber, Carbon fiber, Aramid, etc, and natural reinforcement like Cotton fiber, Jute fiber, etc have been developed for diversified applications.
7. Vacuum infusion (VARI) based process used to developed space and aircraft products based on carbon, aramid, and epoxy system. Also, sandwich structure based on an aluminum honeycomb, carbon core and quartz core, etc. also developed.

Fabrication & processing facilities available at ATIRA

If you are interested to get more information, please write to composites-research@atira.in 

References:

• Ngo TD. Introduction to composite materials. Composite and Nanocomposite Materials From Knowledge to Industrial Applications. 2020 Feb 25.
• Dawoud MM, Saleh HM. Introductory chapter: Background on composite materials. characterizations of Some Composite Materials 2018 Nov 5. IntechOpen.
• Priyanka P, Dixit A, Mali HS. High-Strength Hybrid Textile Composites with Carbon, Kevlar, and E-Glass Fibers for Impact-Resistant Structures. A Review. Mechanics of Composite Materials. 2017 Nov;53(5):685-704.
• Bhatt P, Goe A. Carbon fibres: production, properties and potential use. Material Science Research India. 2017 Jun 25;14(1):52-7.
• Ashik KP, Sharma RS. A review on mechanical properties of natural fiber reinforced hybrid polymer composites. Journal of minerals and materials characterization and engineering. 2015;3(05):420.
• Saba N, Jawaid M. Epoxy resin based hybrid polymer composites. InHybrid polymer composite materials 2017 Jan 1 (pp. 57-82). Woodhead Publishing.
• Rajak DK, Pagar DD, Menezes PL, Linul E. Fiber-reinforced polymer composites: Manufacturing, properties, and applications. Polymers. 2019 Oct;11(10):1667.
• Zhang L. The application of composite fiber materials in sports equipment. In2015 International Conference on Education, Management, Information and Medicine 2015 Apr (pp. 450-453). Atlantis Press.
• https://www.addcomposites.com/post/reinforcement-fibers-terminology-types-and-formats
•  https://www.homestratosphere.com/types-of-fiberglass/#6ECRGlassFiber

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