Formation Mechanisms and Suppression Strategies of Delamination Defects in Drilling of Carbon Fiber Composite Materials

Abstract

The delamination defects in the drilling of carbon fiber composite materials are the key problem restricting the hole-making quality of these materials. Systematically studied on the geometric characteristics, formation mechanism and suppression strategy for delamination defects. In terms of geometric characteristics, established a morphological classification system and characteristic parameter description method of delamination defects; revealed the spatiotemporal evolution laws of delamination defect during the drilling process; clarified the dominance of ply structure and material anisotropy in delamination morphology. In terms of formation mechanism, found out the axial force was the main driving force of interlaminar crack initiation, correlated the interlaminar stress field distribution with crack propagation path, built a prediction model of delamination critical conditions based on linear elastic fracture mechanics. In terms of suppression strategy, gave suppression approach from three aspects: process parameters' optimization, cutting tool's geometric structure design, and assisted machining technologies. It indicates that the delamination morphology is mainly decided by the stiffness distribution of the laminated layers, the exit delamination size is related to the relative relationship between the peak axial force and the critical value, and can effectively suppress delamination defects by controlling axial force under the threshold combined with assisted machining methods.