Investigation of tensile property and strain distribution of drilled carbon fiber reinforced polyetheretherkrtone composites

Abstract

Tool geometry can significantly influence hole quality during drilling of CFRP laminates, which has impact on mechanical properties. In this paper, drilling experiments with different drill bit geometries (twist, brad and dagger drill) are carried out on carbon fiber reinforced polyetheretherketone (CF/PEEK) composites. The influence of tool geometry on drilling temperature, thrust force, and hole-making quality are analyzed. The effect of machining-induced damage on the tensile properties of CF/PEEK composites with machined hole are investigated. The strain distributions around the holes were measured using digital image correlation (DIC). The results indicate that PEEK is softened by heat, the matrix is plastically deformed, and the edge burrs of the hole are curled and agglomerated. The best hole-making quality is obtained by brad drill. Compared to the tensile strength of undrilled laminates, the tensile strength of the laminates drilled with brad, dagger and twist drills decreases by 51.47%, 53.99% and 56.09%, respectively. The strain distribution of open-hole laminates with different machining-induced damage shows obvious difference. The fracture mode of matrix cracking, fiber splitting, delamination, fiber pull-out and debonding are mainly observed. The research results in this paper can provide reference for the optimization of CF/PEEK composites drilling process.