Damage behavior evaluation of thermoplastic resin based CF/PA6 laminate composites with fiber discontinuity

The tensile tests of the unidirectional CFRP laminate composites (CF/PA6) with fiber discontinuity were performed, and mechanical properties were obtained. The laminate stacking sequence of the specimens is [024], and the specimens have fiber discontinuity of 6, 12 and 18 layers. And, the damage growth behaviors were investigated by microscopic observation and acoustic emission (AE) monitoring. Furthermore, the delamination onset stresses were predicted by the simple analysis model. As a result, the stress-strain curves showed nonlinear behavior, and nonlinear starting points became early with increase of the fiber discontinuity layers. It is found that the initial damage of the specimen was the crack between fiber discontinuity end/resin interface by microscopic observation and AE monitoring. And, the delamination between continuous/discontinuous ply around the resin occurred. After that, the resin at the fiber discontinuity was broken at the time of maximum applied stress, then the delamination grew extensively in the specimen, finally the specimens was broken. In addition, the delamination onset stresses were predicted by analysis model using energy release rate, and these stresses were almost agree with experimental values. ©2016 The Society of Materials Science.