Assessing the properties of Poly(dicyclopentadiene) reinforced with discontinuous carbon fibers

Ring-opening metathesis polymers (ROMPs) have remarkable toughness usually failing in a ductile rather than brittle manner. Despite these advantages, these resins have rarely been evaluated in composite materials. We investigated composites of milled carbon fiber and poly(dicyclopentadiene) (pDCPD), a common and inexpensive ROMP polymer. We observed that 10 wt% fibers gave significant increases in tensile modulus (137%), compressive modulus (34%), and fracture toughness (54%) with significant decreases in tensile (42%) and flexural yield strength (46%). Compressive yield strength, ultimate tensile strength, and flexural modulus remained about the same as the unfilled resin. The increases in modulus were well fit by the rule of mixtures for randomly distributed fibers even though microcomputed tomography data showed local regions of anisotropy due to stress applied during sample fabrication. Decreases in tensile and flexural yield were possibly due to weak interfacial strength arising from a lack of surface treatment on the carbon fiber.