Mechanical Characterization and Damage Analysis of Carbon/Flax Hybrid Laminates with Holes Machined by Abrasive Water Jet

Abstract

ABSTRACT This paper experimentally examines the influence of abrasive water jet (AWJ) machined holes on the mechanical performance and damage evolution of flax/epoxy and carbon/flax/epoxy hybrid composites. The specimens were made of unidirectional flax fiber (F) and woven carbon fiber (C) in four configurations: unidirectional flax [0 F]16 (UD-F), unidirectional hybrid [0–90C2/0 F6]S (UD-CF), cross-ply [0–90C2/(0/90)F6]S (CF [0/90]), and angle-ply [0–90C2/(45)F6]S (CF [±45]). The specimens were subjected to static and quasi-static load-unload tensile tests until failure and the damage evolution and plastic strain were monitored. Results revealed severe delamination induced by AWJ at the entry and the exit of the hole in UD-CF and CF [±45] samples, and no delamination was evident in the flax/epoxy plies. The specimens with holes showed pronounced stiffness degradation compared to hole-free specimens. A similar trend was observed in their permanent plastic strain. The cross-ply hybrids showed the lowest increase in damage. While all hybrids exhibited failure by carbon fiber breakage and delamination at the carbon–flax interface, only the laminates with unidirectional flax plies failed by fiber splitting around the hole.