Influence of preforming on the quality of curved composite parts manufactured by flexible injection

Flexible Injection is a new processing technique for the manufacture of advanced composites made of continuous reinforcing fibers and thermosetting polymer matrix. The primary objective of this new process is to provide faster and less expensive manufacturing than traditional methods like autoclave processing or Resin Transfer Molding. The present paper investigates the effectiveness of the proposed method to produce composite structures possessing sharp corners. A specially devised setup is used to manufacture out of glass fibers and vinyl ester resin a series of Z-shaped parts with small radii. The quality of the fabricated parts is assessed to detect possible defects induced by the manufacturing process. Each stage of the production cycle is analyzed thoroughly to develop a simplified finite element model reproducing the fiber bed behavior during processing. Parametric studies are conducted to evaluate the impact of processing conditions on the quality of final products. The combination of numerical simulations and experimental observations demonstrates clearly the importance of the preforming stage. At the same time, it provides useful insights on the physical phenomena occurring during Flexible Injection.