Moderation of thermoplastic composite crystallinity and mechanical properties through in situ manufacturing and post-manufacturing tempering: Part 1 - Mechanical characterisation

Abstract

This study presents an investigation into the sensitivity of CF-PPS thermoplastic composite material to automated fibre placement process parameters: specifically the surface temperature of the layup tool and the addition of simple tempering post-manufacturing. The impact of both are investigated using DSC and mechanical tests, with a thermal analysis of the as-delivered material acting as a reference. Reference material measurements show that secondary crystallinity can be produced by exposing the material to temperatures above the cold (heating) crystallisation temperature. This secondary crystallinity begins to dominate the polymer-inherent crystallinity as the tempering conditions begin to approach the material melting temperature. At the maximum temperature tested (260° C), secondary crystallinity accounts for over 70% of the total. Laminates produced using heated tools show a significant increase in both inter-laminar shear and perpendicular tensile properties with increasing temperature. Additionally, tempering samples is able to increase the polymer tensile strength by up to 32%.