Effect of polycarbonate film surface morphology and oxygen plasma treatment on mode I and II fracture toughness of interleaved composite laminates

Polycarbonate (PC) offers excellent impact resistance, high elongation at break and high glass transition temperature making it a candidate for toughening composite laminates. Therefore, PC films were selected to interleave bi-directional glass fiber (GF)/epoxy composites to study mode I and mode II interlaminar fracture toughness. PC films with smooth and textured surface finishes and oxygen plasma treatment were used to examine their effect on composite toughening using double cantilever beam and end notched flexure tests for mode I and II interlaminar fracture toughness characterization, respectively. Oxygen plasma functionalization improved wetting and adhesive bonding of PC film with epoxy. Increase up to 71% in mode I and 42% in mode II interlaminar fracture toughness for interleaved composites was measured. The microscopic observations of fractured surfaces indicate that improved toughness in the case of PC interleaves is related to promoting cohesive-adhesive failure of the film, providing additional energy dissipating mechanisms during delamination propagation. Dynamic mechanical analysis revealed that PC films are able to preserve high operational temperature of composite.