Some aspects of interlaminar toughening: reactively terminated thermoplastic particles in thermoset composites

Abstract

Novel, reactively terminated, polysulphone thermoplastics have been used as particulate interlaminar toughening agents in epoxy, bismaleimide, and cyanate ester resin based composites. These particles dissolved completely into each thermoset resin matrix during cure, resulting in two separate toughening mechanisms. A crack front pinning type toughening was observed at low particle areal densities in the interlaminar regions (<3 × 10 3 particles cm −2), whilst a toughened film interleaf effect was produced at high particle areal densities (>6 × 10 3 particles cm −2). The fracture toughness, G 1c, of one epoxy composite was improved from 0.51 ± 0.07 kJ m −2 to 0.77 ± 0.10 kJ m −2, with no drop in interlaminar shear strength. Compression after impact testing of the cyanate ester composite at 6.67 × 10 3 J m −1 revealed a decrease in delamination area from 28.2 ± 3.0 cm 2 to 11.6 ± 1.5 cm 2 with interlaminar toughening. Compression resistance rose accordingly from 223.4 ± 0.7 MPa to 268.9 ± 15.9 MPa. This was achieved for a laminate weight increase of only 1.1%.