by Introduction to Carbon Prepreg
Carbon Prepreg, commonly known as prepreg, is a fiber reinforced composite material that consists of fiber reinforcement such as carbon fiber woven cloth or unidirectional tapes that is pre-impregnated with a partially cured thermoset resin. The ‘pre’ in prepreg refers to the pre-impregnation of the fibers with resin while the ‘preg’ refers to the impregnated state. Prepreg has several advantages compared to dry fibers like uniform distribution of resin and predictable fiber volume fraction.
Composition and Properties of Carbon Prepreg
A typical Carbon Prepreg consists of 60-65% by volume carbon fibers embedded in 35-40% by weight epoxy or phenolic resin. The resin acts as a binding agent transferring loads to fibers while protecting them from environmental damages. Carbon fibers in prepreg provide high strength-to-weight ratio making prepreg very durable and stiff. Depending on the fiber orientation, carbon prepregs have tensile strength ranging from 500-5000MPa and tensile modulus around 150-800GPa. They also have low thermal expansion, high corrosion resistance and electrical conductivity. However, prepregs are usually costly compared to normal composites due to intensive manufacturing process.
Manufacturing Process of Carbon Prepreg
The manufacturing process of Carbon Prepreg can be divided into three main steps:
– Fiber Placement: Continuous tow carbon fibers or woven fiber mats are placed onto a release film using an automated machine. The fibers can be unidirectional or multiaxial based on end product requirements.
– Resin Impregnation: The resin, usually a thermosetting epoxy or phenolic, is applied onto the fibers using a controlled method like solvent dip, roller coating etc. Roller pressure helps achieve required fiber-resin volume fraction.
– Partial Cure: The resin-wetted fibers undergo a partial curing process using heat and pressure to gel the resin. This helps preserve the tack and drape properties of prepreg for storage and future processing.
The above process ensures uniform distribution of resin and predictable properties. Prepregs are then cut, packaged and stored at low temperatures for shelf life.
Applications of Carbon Prepreg
Due to their high strength-to-weight ratio and customizability, Carbon Prepregs find applications in:
– Aerospace: Widely used in primary structure parts like wings, fuselage panels, floor beams etc of commercial and military aircraft for their light weight and durability.
– Automotive: Demand is growing for use in supercars, race cars and electric vehicles to reduce weight and enhance performance. Components include wheels, chassis etc.
– Sports Equipment: Manufacturing of tennis rackets, hockey sticks, bicycle frames etc to achieve optimal stiffness-to-weight balance.
– Wind Turbines: Prepregs are replacing metals in turbine blades to handle high stresses and reduce weight for improved efficiency.
– Marine: Components of yachts, sailboats, racing shells benefit from prepregs’ mechanical properties and corrosion resistance.
– Infrastructure: Emerging fields include bridge girders, tunnels etc by enabling larger spans and sizes.
To conclude, Carbon Prepreg has gained popularity in high-performance applications due to advantages like predictable properties, design flexibility and lightweight. Continuous innovations aim to reduce manufacturing costs and develop novel resin systems for broader market penetration. With the focus shifting towards sustainable technologies, carbon prepregs will play a bigger role in transportation and renewable energy industries.
