Modified Exit-ply Delamination Model for Drilling FRPs

Abstract

Delamination has been identified as one of the most deleterious damage processes associated with drilling fiber reinforced plastics (FRPs) due to the resulting drastic reduction of structural strength and stiffness. In recent years, several experimental, numerical, and analytical studies have been conducted aimed at understanding delamination initiation and progression during drilling. In this study, a comprehensive review of existing analytical studies has been presented comparing and contrasting their respective advantages and disadvantages. Special emphasis has been laid upon presenting all assumptions made and the underlying implications thereby. Suggestions at improving the existing models so as to facilitate a more realistic description of the drill process using composite lamination theories have also been included.

Experimental study of surface quality and damage when drilling unidirectional CFRP composites

“…The surface defects observed are consistent with our prior investigations on CFRPs [1,[7][8][9][10]. The data generated in this investigation (experimental data) correlates well between thrust force, delamination, and fiber breakout [2,3,10]. Thus, this correlation can be used as a monitoring parameter in an automated drilling operation.…”

“…Even though the without defeating the advantages of composite strength characteristics, the need exists for improved methods of quality hole production [1]. Drilling induced damages such as spalling, delamination [2,3], edge chipping, fiber pullout, crack formation [1,4], and excessive tool wear [1] are undesirable and may compromise the structural integrity. The inhomogeneity of FRPs caused by the difference in properties of the fiber and the matrix materials will result in a machined surface that is less regular and is usually rougher in comparison with machined metal surfaces [5].…”

Prediction of critical thrust force for exit-ply delamination during drilling composite laminates: thermo-mechanical analysis

“…The Gururaja model (Gururaja and Ramulu, 2009) modified the Zhang model (Zhang et al, 2001) to account for a more realistic representation of the contact forces experienced by the uncut composite laminate during drilling. By considering uniformly distributed load acting on the elliptical anisotropic plate allowing for bending-extension coupling, a good agreement was observed between predicted thrust force and the experimental data.…”

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

“…These properties account for manufacturing of structural parts with FRP composites in the aircraft and spacecraft industries, where drilling of the structural parts is frequently encountered for manufacturing either riveted assemblies or structural repairs [3,4]. Due to inherent anisotropy and structural inhomogeneity in the FRP composite laminates [1], drilling operation may cause delamination in the structural parts which in turn reduces the bearing strength and stiffness of the structure [5,6]. This consequently impairs the load bearing capacity of the structure.…”

“…The Classical Laminate Plate Theory (CLPT) approach which is a 3-parameter shell theory with classical displacement formulation and an equivalent single layer description combined with assumption of linear elastic fracture mechanics (LEFM) mode I has been employed to analyse the laminate structure during drilling operation to determine the amount of work required to initiate and cause propagation of delamination drilling-induced damage in the composite laminates [3][4][5][22][23][24][25][26][27]. Classical laminate plate theory provides reasonable results for thin laminates as it ignores the effect of out-of-plane shear deformation.…”