Vacuum-bagged composite laminate forming processes: Predicting thickness deviation in complex shapes

This paper focuses on the manufacturing of composite laminates using vacuum-bag processes. When forming complex shapes, such as corners, the laminate thickness may deviate from the nominal thickness obtained for flat plates. This is due to two phenomena that occur in corners: (i) because of the geometry, the available consolidation pressure differs from the expected pressure; and (ii) friction may prevent adequate conformation of the laminate to the mould. The thickness deviation is associated with defects (porosity, dry or resin-rich areas or fibre wrinkling). We propose an analytical model to describe these two phenomena, which relies only on two geometric ratio: radius to flange length and thickness to radius, and two material properties: bulk factor and inter ply friction coefficient. The model estimation was compared to an extensive experimental database including a variety of configurations: male or female tools and various flange lengths, weavings and corner radii.