External compaction pressure over vacuum-bagged composite parts: Effect on the quality of flax fiber/epoxy laminates

Abstract

Vacuum bagging allows the removal of trapped air between fabrics layers, extraction of moisture and volatiles, andoptimization of the fiber-to-resin ratio. However, during vacuum bagging the compaction pressure is limited to atmosphericpressure, preventing the composite reaching higher fiber volumetric contents and also allows surface porosity toarise, affecting the esthetical appearance of the composite and also its mechanical performance. While the autoclaveprocess has shown to solve these problems, the cost of the equipment is too high for many applications. In the presentwork, a series of experiments are carried out by compressing unidirectional flax/epoxy vacuum-bagged laminates in ahydraulic press at different pressures. The quality of the laminates is analyzed in terms of surface finish, internal voidcontent, and mechanical properties. The additional compaction from hydraulic pressure is shown to be very effective inimproving considerably the overall quality of the composites.