A Review of Flow and Compaction Modelling Relevant to Thermoset Matrix Laminate Processing

Abstract

Cost-effective manufacturing has become the primary objective for many industries using composite materials in primary structures. To realize this objective, the trial and error method, expert system control and process modelling have been used to help understand the interaction between the parameters affecting product quality. Among the multitude of phenomena occurring during composites processing, resin flow is a critical issue. It affects the fiber volume fraction distribution, the mechanical properties of the laminate and the final dimensions of the part. Flow of composites during cure can be separated into two major mechanisms: percolation flow and shear flow. For percolation flow, applying pressure to the laminate is similar to squeezing a sponge that causes the fluid to bleed out. In this case, the pressure gradient causes resin flow relative to the fibers and the flow has to be coupled with the fiber bed compaction behaviour to obtain the final shape of the laminate. For shear flow, the composite behaves as a very viscous fluid filled with inextensible fibers. In this case the resin and fibers move together and the driving force is the deviatoric component of the stress applied to the laminate. Typically, the percolation flow approach is used to model the flow and compaction of thermoset matrix composites and the shear flow approach is applied to thermoplastic matrix composites. The flow and compaction behaviour of thermoset matrix laminates of simple shape is well covered in the literature, but there is much less on the behaviour of complex shapes, or the interaction between the two mechanisms in high viscosity or complex geometry situations. This paper presents a comprehensive review of the literature relevant to flow and compaction modelling of thermoset matrix laminates during cure, covering the literature up to November 1996.