A Subjective-Objective Evaluation Method of Hole Surface Quality in Drilling CFRP-Ti Stacks

Hole surface quality in drilling carbon fiber-reinforced plastics and titanium alloy (CFRP-Ti) stacks is a key factor affecting high-quality assembly and reliable usage of the structure so it need be reasonably evaluated. However, there is no standardized evaluation system of hole surface quality in drilling CFRP-Ti stacks. The existing evaluation indexes cannot meet the evaluation requirements on the surface quality of the hole. This paper proposes a subjective-objective evaluation method to evaluate the surface quality of the hole in drilling CFRP-Ti stacks. Firstly, the evaluation factors are determined by experiments, including CFRP delamination, CFRP hole entrance tears, surface roughness of CFRP and Ti, and the evaluation system is established according to defect characteristics and industry standards. Secondly, the subjective evaluation model is established based on the improved analytic hierarchy process, the objective evaluation model is established based on the entropy weight method and the subjective and objective combination weight calculation method is obtained based on the principle of minimum discriminant information. Finally, the surface quality of the hole is evaluated by subjective, objective, subjective-objective evaluation methods respectively. The result shows that subjective-objective evaluation method is more reasonable and effective.