Elastic stiffness analysis of a thermo-formed plain-weave fabric composite. Part I: Geometry

Abstract

The present paper investigates experimentally the influence of thermoforming on the geometry of a plain-weave carbon fibre thermoplastic laminate. Specifically, effects the fabric stretching and simple shear deformation modes on yarn crimp and cross-section geometry are examined. For that purpose, specimens are stretched and sheared in a heat chamber above the melting temperature of the resin. Microscopic geometry analyses are carried out on laminate cross-sections prepared along both yarn directions. It is found that both deformation modes significantly influence yarn crimp and cross-section geometry. The observed deformations are schematised in order to enable stiffness modelling in Part II of this paper. To verify the proposed schematisations, additional laminate cross-sections are cut from thermoformed products which contain several areas with nearly constant shear deformation. Fabric stretching and simple shear occur simultaneously in the products. Observed yarn deformations correspond well with the proposed schematisations.