Abstract

While fiber reinforced polymer (FRP) composites are widely utilized in structural components due to their favorable mechanical properties, delamination between reinforcing plies remains a major problem, weakening the composite structure and limiting more widespread applications of FRPs. Carbon nanotubes (CNTs) carry the promise of enhancing this poor out-of-plane mechanical performance, although their integration has been challenging. In this work, macroscopic CNT veils with controlled nano-meso structure were drawn from the gas-phase using a semi-industrial process and then integrated into woven carbon fiber/epoxy matrix composites utilizing a facile and scalable approach. Interlaminar fracture toughness (ILFT) of the resulting composites was determined in Mode-I (opening mode) test. Additionally, crack propagation and interlaminar toughening mechanisms were systematically analyzed by means of optical microscope, SEM, and Raman analysis. The results showed that mode I ILFT was improved as much as 60% when interleaving as-received fluffy CNT veils and also revealed that interlaminar crossing between CNT veil/CF interfaces is of paramount importance in toughening mechanism.