A Comparison between Forming Behaviours of Two Pre-Consolidated Woven Thermoplastic Composites

Abstract

This paper presents the results of an investigation on stretch forming behaviour of two consolidated woven thermoplastic composites: a self-reinforced polypropylene (SRPP) and a glass-fibre reinforced polypropylene (GRPP) composite. A custom-built press with a hemispherical punch was employed to deform composites' specimens possessing different aspect ratios into an open die. The induced strains on the outer surface of specimens were measured continuously through two high speed, high resolution CCD cameras by employing a Digital Image Correlation (DIC) technique. The strain paths at three different locations on the surface of specimens were compared to elucidate the effect of fibre and matrix on the formability of a woven composite. The fractured surface of specimens was investigated to reveal the effect of fibre mechanical properties on failure morphologies in woven composites. It was found out that the main mode of failure in GRPP is fibre fracture while observed failure morphologies in SRPP were a complex combination of different failure mechanisms. It was revealed that the combination of applied boundary conditions and specimen's width determines the effective forming mechanisms.

Investigating the forming limits of a flax fibre-reinforced polypropylene composite in different water treatment conditions

“…Therefore, it is hypothesized that the fibre strain should be used as the key parameter in predicting the onset of failure for this class of material system, instead of principal strains. The current study proposes a new FLC which uses [17] fibre strain and strain ratio. Fibre strain represents the amount of strain acting on the flax fibres, and it requires tracking of the evolution of fibre movement, especially when fibres trellis under shear deformation.…”