Investigation on delamination morphology during drilling composite laminates

Drilling-induced delamination of composite materials is a key factor that affects the quality of subsequent machining. To investigate the developing process of delamination, experiments with different drilling depth are conducted. In order to observe the delamination of different cross-sections in radial direction of the hole, the grinding method is adopted. Three-dimensional morphology of delamination at the exit of hole is obtained. The regularity of delamination with the change of drilling depth is analyzed, and the existence of “hidden delamination zone” is obtained finally. Due to the rebound effect of hole diameter and the inverted cone of drill guide section, the “hidden delamination zone” will be generated under the condition that the edge of delamination area is compressed tightly again. The critical thrust force of delamination is also studied, and it is proved to be correct.