Thermal stress induced composite laminate delamination analysis and experiment verification

To solve thermal stress induced delamination in composite laminates that used in flying vehicles, experimental tests and numerical analysis were carried out. Bilinear controlled cohesive elements were adopted to simulate the delamination in laminates, quadratic failure criterion was used to predict the initiation of stiffness softening process, and power law criterion was applied to determine the delamination propagation under mix-mode fractures. The mechanical and thermal expansion properties of lamina applied in those numerical models were tested at high temperature (70℃), room temperature (23℃) and low temperature (-50℃) respectively. The delamination experiments were carried out by use of apparatus DIL-402C. Each composite laminate experienced a same temperature changes, and the maximum temperature difference was 120℃. After experiments, the laminates in given plies were found that delamination appeared in their mid-ply in both ends. Comparisons were made between experimental results and numerical analysis. Compared results show that the predicted delamination zone was well according with the experimental results, which would certify the rightness and reliability of this analysis method.