Mode II delamination and damage resistance of carbon/epoxy composite laminates interleaved with thermoplastic particles

In order to evaluate thermoplastic particle interlayer toughening effect on compression strength after impact (CAI) and damage resistance under quasi-static concentrated force, both non-interleaved and interleaved specimens of three types of carbon-fiber epoxy composites, HT7/5228, HT3/NY9200G, and HT3/5224, are fabricated. Mode II fracture toughness test and quasi-static indentation (QSI) test are conducted. The experimental results indicate that the interlayer zones formed by particles and matrix can significantly suppress delamination; mode II delamination resistance and damage resistance are significantly enhanced. The interleaved specimen can achieve small damage area at the expense of greater indent depth in local region. The toughening mechanisms are chiefly as follows: geometrical effect of interlayer, crack path deflection, and crack-tip shielding. Furthermore, a large amount of energy is absorbed by ductile deformation and ultimate failure of thermoplastic particles.