Compression‐after‐impact properties of carbon fiber composites with interlays of Aramid pulp micro‐/nanofibers

Abstract

AbstractThe inherent resin‐rich ply interfaces in laminar carbon fiber reinforced polymer (CFRP) composites are toughened by ultrathin interlays formed by Aramid pulp (AP) micro‐/nanofibers, to show that stronger and more impact‐resistant CFRP can be manufactured with minimum disruption to the current composite forming process. Flexible nonwoven AP micro‐/nano‐fibers, less than 1 mm in length, can conveniently fit in the uneven surface profiles or microresin‐rich areas between carbon fiber plies and form in situ quasi‐Z‐directional fiber‐bridging across the ply interfaces. CFRPs with multiple interfacial AP interlays estimated to be around 3 and 6 g/m2 were tested before and after low energy impact. Ultrathin resin‐rich ply‐interface layers in plain CFRP were transformed into ultrathin “Short Aramid Fiber Epoxy” layers by the AP interlays (20–50 μm in thickness), leading to enhanced compressive energy absorption and up to 86.7% increase in Compression‐After‐Impact Strength. Keeping the interlay thin (around 30 μm or thinner if possible), even the compressive strength (without impact) is not compromised, and the energy absorption under compressive loading (without impact) is 130% higher. The distinctly different compressive failure mechanisms, delamination failure of the plain CFRP was transformed into matrix shear failure in AP‐toughened CFRP, as identified by nondestructive X‐ray microcomputed tomography scans. Scanning electron microscopy was performed on the failure surface to inspect the microscopic toughening mechanisms.