As composites continue to be adopted in more industries, fiber-reinforced plastics can be found in products that people interact with every
day, including cars and sporting goods. Fiber-reinforced plastics consist of reinforcing
fibers surrounded by a plastic matrix. There are several types of fibers that can be used including glass, carbon fiber, and aramid which give the material
its high tensile strength. The matrix gives the composite the compressive
strength and, in the case of fiber reinforced plastics, can be made using
thermoset or thermoplastic polymers.
Thermoset polymers are polymers that are cured into a solid
form and cannot be returned to their original uncured form. Composites made
with thermoset matrices are strong and have very good fatigue strength. They
are extremely brittle and have low impact-toughness making. They are commonly used
for high-heat applications because the thermoset matrix doesn’t melt like
thermoplastics. Thermoset composites are generally cheaper and easier to
produce because the liquid resin is very easy to work with. Thermoset
composites are very difficult to recycle because the thermoset cannot be
remolded or reshaped; only the reinforcing fiber used can be reclaimed.
Thermoplastic polymers are polymers that can be molded,
melted, and remolded without altering its physical properties. Thermoplastic
matrix composites are tougher and less brittle than thermosets, with very good
impact resistance and damage tolerance. Since the matrix can be melted the
composite materials are easier to repair and can be remolded and recycled
easily. Thermoplastic composites are less dense than thermosets making them a
viable alternative for weight critical applications. The thermoplastic
composites manufacturing process is more energy intensive due to the high
temperatures and pressures needed to melt the plastic and impregnate fibers
with the matrix. The energy required makes thermoplastic composites more costly
than thermosets.
These two similar materials have such different properties
that both will continue to be used in different applications for very different
reasons and the products of the future will likely be a combination of both.
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