MICROMECHANICS AND ACOUSTIC-EMISSION ANALYSIS OF THE FAILURE PROCESS OF THERMOPLASTIC COMPOSITES

The finite element method (FEM) and acoustic emission technique (AE) were applied to the micromechanics analysis of the failure process of composites with thermoplastic matrix materials. FEM calculations to local stress-strain distribution and the influence of very different intermediate layer properties are interpreted with regard to microscopic failure mechanisms in composite materials. The strongly differing AE behaviour of both chalk-filled polyvinylchloride and high density polyethylene and short-glass-fibre reinforced polypropylene, polyamide, PBTP, SAN and ABS in tensile test experiments is demonstrated. Representative loading limits are derived from the nature and extent of the dominating failure mechanisms by comparison of theoretical and experimental results. The influence of critical strain, shear strength and fracture toughness properties of the modified matrix as well as the composite morphology and phase adhesion on significant deformation and failure stages is discussed. Finally some conclusions are drawn about a possible critical long-term strain of composites.