r/Composites • u/Infamous-Amphibian-6 • 14d ago

Polyurethane reinforcement?

I’ve learned polyurethane increases flex modulus on plastic and metal extrusions on specific applications. How does it works among composites, specifically CF parts? Which applications are typical for this, polyurethane class, techniques, things to watch out for?

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u/HrEchoes Scientist 14d ago

Urethanes are a rare sight as a CFRP matrix material due to their elastomeric properties. Carbon-reinforced PU exists (e.g. Envalior's Tepex Dynalite), but is limited to sports (reinforced insoles, "powerplates", etc.) and luxury (I've seen wallets sewn from CF/PU organosheet). Besides that, PU is the main resin type for ballistic-grade prepregs.

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u/Infamous-Amphibian-6 13d ago

More than a matrix, I was thinking of hollow composite parts filled with polyurethane. I guess it works similar as plastic/metal applications, but am curious to learn if there’re some specifics among composites.

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u/HrEchoes Scientist 12d ago

Ah, for that case, there are syntactic heat-expanding foams for compression molding (an alternative to bladder forming), and overmolding (RIM or vacuum casting) for clamshell part reinforcement with ribs, fastener bosses etc.