Finite-element analysis of a polymer composite subjected to ball indentation

The finite-element (FE) contact technique presented in this paper is applied to the problem of steel-bail indentation of a composite material consisting of unidirectional continuous carbon fibres in a poly(ether ether ketone) matrix. Indentation was carried out with fibre orientations either normal (N) or parallel (P) to the contact surface at a fibre volume fraction of 0.44. The FE contact analysis involves both an anisotropic (homogeneous) macro- and (inhomogeneous) micro-contact analysis, following an approximate displacement coupling technique. The FE contact-stress analysis of a fibre/matrix micro-structure has a major limitation. If the FE micro-model is used, only a very small (for example 0.1 mm x 0.1 mm x 0.1 mm) 3D segment can be modelled. If an anisotropic model is used, there is no similar size limitation but the results cannot describe the stress and strain states of a real fibre/matrix micro-structure. The FE contact results show the location and the distribution of the sub-surface stresses and strains. For N fibre orientation there is a high shear stress region below the surface, from where the fibre/matrix interfacial failure initiates before propagating to the surface. In the case of P fibre orientation the matrix is subjected to local plastic deformation while the characteristic deformation of the fibre is bending. (C) 1999 Elsevier Science Ltd. All rights reserved.