Drilling Damage of GFRP and Residual Mechanical Behavior - Part I: Drilling Damage Generation

The drilling of composite laminates generates several kinds of damage that can be detrimental to the mechanical behavior around the hole. The present work is the first part of a study that investigates the effect of the drilling on the residual mechanical behavior of glass fiber reinforced plastic (GFRP) laminates when the hole is subjected to bearing load. In the first part, the influence of drilling parameters on the type and extension of the damage is analyzed. The damage is described at the macro level (delaminated area) and at the micro level (cracks, fiber-matrix debonding, etc.). The Design of Experiments and Analysis of Variance techniques are used in order to determine the statistical influence of the drilling parameters on the delamination area. Moreover, the effects of drilling with or without a support beneath the specimens are analyzed and discussed. Results indicate that the degree of peel-up delamination depends on the feed rate and on the helix angle of the twist drill. Push-down delamination is mainly affected by the feed rate, by the presence of support beneath the specimen, and by the twist drill temperature.