Development of Novel Thin-Ply Technology for Carbon Fibre Composite Materials

Abstract

The increasing popularity of carbon fibre reinforced polymers means that enhancement of material properties is of high commercial value. Thin-ply technology is one area of research focussed on achieving this goal. The aim of this work was to investigate the use of thin-ply technology by studying the effect of ply thickness on the physical and mechanical properties of carbon fibre composite materials, after exposure to various environmental conditions. A review of mechanical properties at ambient conditions and after exposure to both high temperature and moisture was conducted. Quasi-isotropic thin-ply carbon fibre composites were found to have enhanced mechanical properties, compared to thicker ply materials comprising the same resin and matrix, under various loading conditions. One of the main mechanisms for this is thought to be the lower interfacial stresses seen with thin-ply materials, as demonstrated through the use of high-speed camera video recording and digital image correlation. An investigation into the effect of ply thickness on moisture absorption and diffusion rate was also conducted. For the material under investigation, diffusion rates remained constant with changes to ply thickness, whereas moisture absorption was greater for the thinner ply material. In addition, the effect of ply thickness on viscoelastic properties was also studied. The use of dynamic mechanical analysis suggested that the material under investigation tended to a two-phase state. This is thought to be the result of phase-separation of the epoxy resin matrix and poly-ether-sulfone (PES) toughening particles. Ply thickness was shown to have some effect on the phase separation of epoxy and PES.