THE INFLUENCE OF THERMOPLASTIC FILM INTERLEAVING ON THE INTERLAMINAR SHEAR-STRENGTH AND MODE-I FRACTURE OF LAMINATED COMPOSITES

Results are presented on the interlaminar shear strength (ILSS) and Mo de I fracture toughness (G(1C)) of glass/epoxy laminates interleaved w ith thermoplastic polyester films using four-point bending and double cantilever beam tests, respectively. The ILSS equation Stem classical beam theory was modified to account for the increased film thickness. Is was found that the ultimate failure lend and ILSS could be doubled if a thermoplastic film of high ductility but low glass transition tem perature is used Good film/composite ply adhesion is necessary. Mode I fracture toughness is influenced by film thickness and interleaving w ith a 0.2 mm thick film increased the G(1C) by 40 percent. Interleavin g with a thinner film (0.1 mm), however, resulted in adhesive failure and reduced fibre bridging.