Fiber Reinforced Composites

Fiber Reinforced Composites

• Fibers such as glass, carbon, aramid, or natural fibers are used as reinforcement in a matrix

Properties of Fiber-Reinforced Composites

• High strength-to-weight ratio and high specific strength are characteristic

Uses of Fiber-Reinforced Composites

• Applications include aerospace, automotive, sporting goods, construction, and various industries

Classification Based on Fiber Orientation

• Continuous (aligned) fibers: anisotropic properties, highest strength and reinforcement in the longitudinal direction, but low in the transverse direction, leading to potential fractures

Discontinuous Fiber Composites

• Classified based on fiber orientation
• Discontinuous and aligned fiber composites: made of discontinuous fibers with preferential orientation, but lower reinforcement efficiency than continuous aligned composites

Discontinuous and Random Composites

• Isotropic mechanical properties
• Capable of withstanding multidirectional stress

Aramid Fiber Reinforced Composites (AFRCs)

• Fiber type: Aramid fibers like Kevlar, known for high strength, low weight, impact and heat resistance
• Properties: Offer exceptional impact resistance, light weight, and high strength, making them ideal for high-stress environments
• Applications: Used in military, aerospace, sports, and automotive sectors, such as bulletproof jackets, helmets, protective gear, and tire reinforcement

Glass Fiber Reinforced Composites (GFRCs)

• Fiber type: Glass fibers such as E-glass, S-glass, and AR-glass
• Properties: Known for corrosion resistance, high tensile strength, impact resistance, lighter than metals, offering a balance between strength and weight
• Applications: Used in automotive, aerospace, marine, and industrial sectors, such as car bodies, aircraft components, boat hulls, pipes, and flooring

Carbon Fiber Reinforced Composites (CFRCs)

• Fiber type: Carbon fibers including graphite, graphene, and carbon nanotubes, are dispersed in a polymer matrix
• Properties: Extremely high strength-to-weight ratio, low coefficient of thermal expansion, resistance to corrosion, chemicals, and high temperatures
• Applications: Used in aerospace, sports equipment, automotive, and wind turbine blades, and medical devices due to their lightweight and durable properties

Laminar Composites

• Composed of alternating layers of same or different materials bonded, providing high strength
• Two-dimensional sheets or panels with a preferred high-strength direction stacked and cemented, where the orientation of high strength varies with layer

Advantages of Laminar Composites

• Lamination enhances resistance to impact, shock, and pressure, increasing overall durability of the product
• Examples: Plywood, copper bottom steel articles, speedboat hulls, snow skis

Plywood

• Several fused layers of thin wood veneers bonded with adhesive, resulting in a strong, durable panel
• The cross-grain structure, with wood veneers in alternating directions, adds strength to withstand multidirectional stress

Biocomposites

• Matrix (resin) and natural fiber reinforcement composite materials
• Designed to reduce environmental impact by replacing petroleum-based, non-renewable composites

Components of Biocomposites: Matrix Phase

• Formed by polymers from renewable (e.g., biopolymers like PLA, PVA) and nonrenewable sources
• Protects fibers from degradation, holds them together, and transfers mechanical loads

Components of Biocomposites: Reinforcement

• Natural fibers (e.g., cotton, hemp, flax, jute, kenaf) or wood particles/fibers from renewable sources (recycled wood, waste paper, or crop byproducts) are used

Advantages of Biocomposites

• Renewable, biodegradable, and recyclable, providing environmental sustainability over synthetic fibers (glass, carbon, Kevlar)
• Cost-effective, as natural fibers and bio-based matrices are often less expensive than synthetic fibers
• Environmentally friendly, biodegradable, recyclable components reduce ecological impact

Applications of Biocomposites

• Partial biodegradable: Automotive interior panels (e.g., Jute/Epoxy), construction insulation (e.g., Jute/Epoxy), consumer goods packaging, sports equipment like bicycle frames (e.g., Carbon Fiber/PLA)
• Completely biodegradable: Packaging (e.g., Starch Plastics), plant pots (e.g., Cellulose-based plastics), medical sutures (e.g., Soy Plastics)
• Hybrid: Automotive structural parts (e.g., Wood/Non-Wood Fiber composites), construction panels (e.g., Wood/Non-Wood Fiber composites), eco-friendly packaging (e.g., Wood composites), furniture and decking

Classification of Bio-Composites

• Partial Biodegradable Biocomposites contain at least one component from natural resources, combine traditional/synthetic polymers with natural fibers, fillers, or biopolymers
• Jute/Epoxy composites and Carbon Fiber/PLA (Polylactic acid) composites are examples of partial biodegradable composites

Completely Biodegradable Biocomposites

• These biocomposites are made from bio-fibers and matrices composed of biodegradable polymers, which are either renewable or petro-based

Biopolymer Matrices

• Cellulose-based plastics (e.g., cellulose acetate, ethyl cellulose, cellulose sulfate) are biodegradable, serving as replacements for petroleum-based plastics
• Soy plastics made from soybeans are renewable, biodegradable, sustainable alternatives to fossil fuel-based plastics.
• Starch plastics (TPS): Biodegradable plastics made from natural starch polymer

Hybrid Biocomposites

• Two or more fibers or polymer blends are combined in a single matrix to overcome the limitations of natural fibers or matrices
• Key features include combining natural fibers with other materials, a mix of wood, non-wood fibers and polymer matrices, and enhancing properties while overcoming limitations of single material systems

Materials Used in Hybrid Biocomposites

• Wood fibers: Hardwood and softwood (e.g., cellulose and lignin)
• Non-wood fibers: (Hemp, sugarcane, rice straw, jute, banana, pineapple, oil palm, sisal, flax)

Common Polymers Used in Hybrid Biocomposites

• Polyethylene (PE), Polypropylene (PP) and Polyvinyl chloride (PVC)