Ply-Slip During the Forming of Thermoplastic Composite Parts

Abstract

A model for the ply-slip deformation behavior of a laminate composite is presented which allows prediction of the stresses, displacements, and strains developed during the forming process. The model takes into account the viscous nature of the matrix and the stress relaxation achievable via ply slippage. The stress response is inherently time dependent and is strongly affected by the forming rate. Results calculated for the isother mal three point bending of a unidirectional lay-up agree well with previous experimental data. An important parameter, the maximum system time constant, is identified and related to the material properties and part geometry. Comparisons with experiments and simulation results for nonisothermal forming are also discussed.