Thermo-mechanical modelling of FRP cross-ply composite laminates drilling: Delamination damage analysis

Abstract

Among other factors, thrust force, feed rate, twist drill bit chisel edge and point angle are the principal factors responsible for delamination drilling-induced damage during thermomechanical deformation. Hence, in this paper, an analytical thermo-mechanical model is proposed to predict critical feed rate and critical thrust force at the onset of delamination crack on CFRP composite cross-ply laminates, using the principle of linear elastic fracture mechanics (LEFM), laminated classical plate theory, cutting mechanics and energy conservation theory. The delamination zone (crack opening Mode I) is modelled as an elliptical plate. The advantages of this proposed model over the existing models in literature are that the influence of drill geometry (chisel edge and point angle) on push-out delamination are incorporated, and mixed loads condition are considered. The forces on chisel edges and cutting lips are modelled as a concentrated (point) and uniformly distributed loads, resulting into a better prediction. The model is validated with models in the literature and the results obtained show the flexibility of the proposed model to imitate the results of existing models.

A new analytical critical thrust force model for delamination analysis of laminated composites during drilling operation

“…Consequently, this important observation assists in reconciling the disparity between concentrated and distributed load critical thrust force models in the literature [3][4][5] as the total thrust force can now be adequately represented by the sum of the applied force on the cutting lips and chisel edge, respectively, as reported in [22]. In this regard, a new critical force model which accounts for the effects of the point angle was recently proposed in [53].…”

“…For the quasi-isotropic case, the critical thrust force is computed based on CLPT assumptions for Zhang and Guraja models [4 & 5] and the critical thrust force is computed for the new model based on assumption of FSDT. For the cross-ply case with mixed loading, the critical thrust force is computed for the model proposed in [53] derived based on CLPT and the new model derived based on FSDT. The relative critical thrust forces for different number of uncut plies are then computed for the two cases considered to demonstrate the effect of shear deformation on the critical thrust force.…”

“…A special case of cross-ply laminate as described in [53] without thermal effects is herein considered where the extensional and bending stiffness matrices are uncoupled so that the resultant moments, according to classical Kirchhoff's assumption, neglecting the in-plane displacement, are expressed as:…”

“…Following the procedure described in [53], the strain energy and external work due to bending can be expressed as:…”

Challenges on machining characteristics of natural fiber-reinforced composites – A review

“…The drill is pressed against the work piece and rotated at hundreds to thousands of revolutions per minutes.This forces the cutting edge against the work piece , cutting off chip from the hole as it drilled. 99 . It is a more profitable process than other processing processes.…”