Damage accumulations before ultimate failure in laminated composites containing an open hole were studied and compared under tensile and compressive loadings. Four laminate layups, [02/± 45]2s, [0/90/ ± 45]2s, [ ± 45]4s, and [ ± 30/ ± 60]2s, were selected for the investigation. Two sets of laminates were prepared with one loaded in tension and another loaded in compression. They were examined using X-ray techniques after being loaded to specific load levels.
Damage accumulated in these laminates before ultimate failure can be correlated to the characteristic lengths used for the prediction of the notched strength. For laminates that the damage accumulations were found similar under different loading conditions, the same characteristic length can be used for the strength prediction under these loading conditions. On the other hand, if the damage mechanisms were different due to different type of loadings, then different characteristic lengths need to be used to predict the notched strength accurately. The experimental study presented in this paper reveals the physical explanation of using the characteristic length as a parameter for the theoretical strength prediction.