Post fatigue and fatigue fracture behavior of stitchbonded biaxial carbon epoxy composites

Fatigue, post fatigue and fatigue fracture onset life behavior of a type of stitchbonded biaxial carbon epoxy composite is presented. Effects of stacking sequence [0/90]s and [90/0]s on initial static properties and damage evolution in the composite laminates are investigated. The stress and strain levels where damage at macro-scale initiates were determined. The tensile-tensile fatigue capacity of the composite with different stacking sequence at these levels was determined. The post fatigue residual tensile properties were determined to study the influences of damage evolution due to fatigue on mechanical properties of the composite laminates. The fatigue onset life experiment was conducted to determine the threshold energy release rate for stitchbonded composites. No significant influence of the layer stacking sequence on the initial stiffness of the material was reported; however, a large influence was found on the evolution of damage during the fatigue test particularly on [90/0]s composite laminate.