Drilling Damage of GFRP and Residual Mechanical Behavior - Part II: Static and Cyclic Bearing Loads

The damage generated during the drilling of Glass Fiber Reinforced Plastics (GFRP) laminates can be detrimental for the mechanical behavior of the material around the hole, especially when the hole surface is subjected to a bearing load. The present work is the second part of a study aiming to investigate the effect of drilling conditions on the residual mechanical behavior of GFRP laminates subjected to a bearing load. To address this aim, holes drilled in different conditions were tested with static and cyclic bearing loads. The results of these tests were characterized through quantitative parameters and through microscopic observations of hole sections. Results indicate that for the range of the experimental conditions investigated, the main cause of mechanical failure is the micro damage generated at the inner part of the hole surface, while delamination plays a minor role. Therefore, despite the general attention paid during drilling to reduce delamination, the optimal drilling conditions should avoid the onset of microcracks distributed in the inner part of the hole.