Composite materials are emerging as revolutionary engineering materials due to their excellent properties such as high strength-to-weight ratio, resistance to corrosion and durability. Polymer matrix composites (PMCs) are composite materials consisting of a polymer matrix reinforced with fibres. The fibres are usually glass fibres, carbon fibres or Kevlar and provide strength, while the polymer matrix holds them together, transfers load and protects the fibres from environmental damages. Due to their lightweight yet durable properties, PMCs are finding widespread applications in industries ranging from aerospace to automotive to infrastructure.
What are Polymer Matrix Composites?
A polymer matrix composite consists of a polymer matrix combined with reinforcements in the form of fibres, particles or flakes. The matrix binds the reinforcement and protects it from environmental damages and absorption of moisture. Common matrix materials include thermosetting polymers like epoxy, vinyl ester and polyester, as well as thermoplastic polymers like polycarbonate, nylon and polypropylene. The reinforcements are usually continuous filaments or chopped fibres. Glass fibres are the most commonly used reinforcements, although carbon fibres, Kevlar and boron fibres are also used where high strength is required.
Properties of PMCs
Compared to unreinforced polymers or conventional metallic materials, PMCs exhibit significantly improved properties that make them ideal for structural applications. Some key properties of PMCs include:
– High specific strength and stiffness: PMCs have strength and stiffness close to some metals but with much lower density, resulting in high specific properties. This makes them an excellent lightweight material.
– Enhanced corrosion resistance: The polymer matrix protects the fibres and prevents galvanic corrosion. PMCs can withstand corrosive environments where metals get corroded.
– Design flexibility: PMC parts can be easily molded to near-net shapes, allowing complexity and integration of features.
– Fatigue and creep resistance: properly made Polymer Matrix Composites withstand cycles of recurring loads and stresses without failure. Thestiff fibres impart excellent resistance against creep.
– Impact resistance: though fibres like carbon/Kevlar absorb energy well, short glass fibres in epoxy increase energy absorption capacity of the composite.
Manufacturing of PMCs
The main manufacturing techniques used for PMCs are:
– Hand lay-up/Spray-up method: Reinforcements are impregnated with resin by roller or squeegee on a mold surface. Multiple rolls are stacked to obtain thickness and then cured. Most common method.
– Filament winding: Continuous filaments (glass/carbon) are wetted with resin and wrap over a rotating mandrel according to programmed patterns. Used in high-pressure vessels.
– Pultrusion process: Continuous reinforcements are pulled through a resin bath and into a heated die to form shaped profiles like tubes.
– Compression molding: Precut stacks of dry reinforcements and resin films are placed in a heated mold and compressed to necessary thickness and shape.
– Injection molding: For thermoplastic composites, reinforced pellets or powders are injection molded into final parts.
Applications of PMCs
Some major application areas of polymer matrix composites:
Automotive: Body panels, chassis, bumpers to reduce weight and provide dent/rust resistance.
Aerospace: Aircraft components (fan cowls, blades), satellite panels. Carbon fiber composites are used extensively here.
Marine: For boat hulls, decks, etc. due to corrosion resistance and strength-to-density properties.
Infrastructure: Bridge decks, railings to withstand environmental factors. High strength pipes transport corrosive fluids.
Electrical/Electronics: Substrates, circuit boards, housings for electronic devices needing strength, low weight and dimensional stability.
Sports and Leisure: Bicycle frames, rackets, golf clubs where lightweight strength is key.
Wind Energy: Blades in wind turbines gain advantage from lower weight and better stiffness-to-weight ratios.
With their superior mechanical, thermal and environmental resistance properties achieved at lower weight compared to metals, polymer matrix composites have emerged as engineering materials of the future. Although initial costs are still higher, overall lifetime costs are lower due to weight reductions, decreased maintenance needs etc. Continued R&D focus on matrix enhancements, fiber development and high rate manufacturing is expanding the PMC horizon to new frontiers. Their increasing usage will have significant impact on the eco-friendliness and sustainability of numerous industries.