Drilling analytical model of composite material with pilot hole

Pierre Rahme,Robert Piquet,Yann Landon,Pierre Lagarrigue,Frederic Lachaud

doi:10.1051/meca/2015110

Abstract

The use of composite materials machining is increasing more and more in aeronautical. Drilling process is in particular the most used process in the assembly of aeronautical structures. When drilling thick composite laminates, delamination occurs at the exit of the hole. These defects are assumed to be the major defects. They diminish the strength of the structure to failure. To minimize delamination, drilling process with pilot hole is used. In this paper, analytical model for drilling thick composite structures with pilot hole using a twist drill is proposed. This model predicts the critical thrust force at delamination. Different hypotheses of boundary conditions and external loading are proposed. Numerical model is also developed in order to validate the proposed analytical model. Punching tests with twist drill are then realized in order to select the corresponding hypothesis of boundary conditions and external loading. These results may be used to optimize the cutting conditions when drilling thick composite plates with pilot hole.

Highlights

Modern aeronautical structures require typically the use of composite materials
Drilling process with pilot hole minimizes the delamination at exit
This paper focuses on the drilling with pilot hole of thick composite structures using a twist drill in order to minimize the defects at the exit of the hole

Summary

Introduction

Modern aeronautical structures require typically the use of composite materials. The assembly of composite parts requires knowledge in drilling of composite materials. Rahme et al [8] showed the effect of the chisel edge on the critical thrust force at delamination when drilling thick composite material with a twist drill. An analytical model for predicting the critical thrust force at delamination is developed when drilling with pilot hole composite laminates using a twist drill. This model is based on fracture mechanics. A new concept of modelling the exit of the hole, when drilling with pilot hole a composite material, is used in this paper In this model, three new hypotheses of boundary conditions and external loadings are proposed.

Analytical model

Experimental part

Results and discussion