Role of conventional drilling and abrasive water jet induced damage on the mechanical response of flax/epoxy laminates with holes

Abstract

Many engineering applications using composite materials require an assembly of components which can be accomplished using adhesives, welding, or fasteners. The last requires the machining of holes, which are usually done via conventional drilling or abrasive water jet process. The choice of the machining process is important because it has a direct impact on the surface quality of the machined holes, and, consequently, on the performance of the composite structure. Although most studies on the effect of machining methods were focused on conventional composites, little is known about the effect of conventional drilling (CD) and Abrasive water jet (AWJ) machining methods on the mechanical behaviour of flax composites with holes. This study is the first to experimentally investigate the influence of the machining process in pure flax/epoxy composites with three different layups, namely, unidirectional (F[0]), cross-ply (F[0/90]) and angle-ply (F[±45]). A delamination factor was employed to evaluate the degree of delamination damage around the surface of the hole. The lowest delamination factor at the exit of the hole was observed for F[0]-AWJ with a value of 0.777 and the highest was observed for the F[±45]-AWJ with a value of 1.484. Damage analyses of the layups under a quasi-static loading condition showed that the average final stiffness damage for F[0]-CD was 13% greater than that of F[0]-AWJ, and for F[0/90]-AWJ and F[±45]-AWJ were respectively 25% and 27% greater than their counterpart samples machined by CD method. The damage results correlate well with the delamination factor.