Experimental and numerical investigations of the damages induced while drilling flax/epoxy composite

Abstract

The influence of the drilling parameters and the stacking sequence of flax/epoxy composite laminate on the cutting force and the damage induced were studied experimentally and numerically. Drilling tests were carried out based on full experimental design and the delamination at the entry and exit of the hole were quantified using an optical microscopy. Moreover, the damages at the wall of the hole were analyzed using scanning electron microscopy. Based on the experimental results, it was observed that the drilling forces and the machining quality are influenced on the one side by the spindle speed and feed and on the other side by the stacking sequence composite plate. In fact, the cutting forces recorded when drilling a composite plate with [90/0/90/0]2s is 30% higher to the one recorded when drilling a composite made with quasi-isotropic stacking sequence. A numerical model was developed in ABAQUS/Explicit using Hashin’s failure criteria in order to predict the cutting forces and the defects induced by the interaction of the drill and composite as a function of the machining parameters. The developed model has been validated at the macro-scale (thrust force) and the meso-scale (delamination at the entry and exit of the hole).

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

“…Several damages such as fiber pullout, matrix degradation, and delamination were observed during the machining processes. 10 These undesirable machining-induced damages result in decreased strength and stiffness, which can be extremely detrimental to the performance of NFRC structures. Hence, the use of open-hole flax laminates in structural applications requires an in-depth understanding of machining-induced damages on the hole surface and their effect on the mechanical behaviour of flax laminates.…”

The Effect of Fiber Waviness on the Residual Stress State and Its Prediction by the Hole Drilling Method in Fiber Metal Laminates: A Global-Local Finite Element Analysis

“…Information about damages and delamination around the borehole, as well as the borehole quality itself can be predicted by this approach [19,20]. Several material combinations like CFRP [21], glass fiber aluminum reinforced epoxy (GLARE) [22] or CFRP/titan hybrids [23] were numerically investigated by varying process parameters. The results of these investigations cannot be directly transferred to the hole drilling method used in the presented work, as different drilling speed, feed rate, diameter and geometry of drill bit influence the released strains and the evaluated residual stresses [24,25].…”