Experimental investigation on the formation of resin-rich zones in composites processing

Abstract

Resin-rich zones are a common phenomenon in liquid composite moulding processes. These resin-rich zones need to be studied in the design of composite structures because they cause unwanted residual stress and deformation, and part-to-part variation. An experimental study on the formation of resin-rich zones in angled composite parts is presented in this paper. Two open-channel mould sets were designed and fabricated. Fibre preforms were loaded into these moulds and the gaps formed were visually inspected with a microscope. Two types of gaps were found in the experiments: at corner radii and beside corner radii. The influences of radius, fibre volume fraction, enclosed angle, and stacking sequence were investigated, and the significant factors affecting gaps were identified with the aid of Design of Experiments (DOE). It can be concluded from the experimental results that: 1) Fibre volume fraction is the most significant factor affecting the gaps at corner radii. Gap thickness decreases with increasing fibre volume fraction; 2) Gap thickness decreases with increasing radius; 3) The gap thickness of unidirectional preforms is larger than that of the cross-ply preforms.