Morphology and compression-after-impact strength relationship in interleaved toughened composites

Morphology and compression after impact (CAI) strength relationships in interleaved toughened high performance composites are investigated using a quantitative two-dimensional image analysis approach. A group of six quasi-isotropic carbon fiber-epoxy composites with identical compositions, but having variations in CAI strengths, were analyzed to study how the interleaf particle size, particle size distribution, and location of particles in the interlaminar region affect the CAI strength values and the corresponding damage mechanisms. It is found that the CAI strength of interleaved-toughened composites is significantly affected by the size and size distribution of toughener particles in the interlaminar regions of the composite. In general, high CAI strength composites exhibit more uniform particle size distribution throughout the interlaminar regions. Whereas, for low CAI strength composites, the interleaf particles tend to cluster together and have varied size distribution.