Void Reduction in Composite Processing: Mechanisms, Processes and Predictive Modeling

During manufacturing of composite materials, the goal is to ensure that the resin occupies all the empty spaces between the fibers preventing formation of micro and macrovoids. Microvoids are caused due to presence of moisture, air or volatiles in the resin while macrovoids are dry fiber regions caused by failure of resin to infiltrate the empty spaces between the fibers.

In this presentation, the mechanism of void formation in processes such as Liquid Composite Molding, Autoclave and Out of Autoclave processing, thermoplastic tape placement and adhesive bonding will be discussed. Models to predict void formation, growth and transport will be introduced. The role of material and process parameters will be highlighted and the coupling between macro scale and microscale void formation will be addressed. Effect of individual parameters on the models will be investigated, factors that cause their variability and influence of transient variations will be described. Formulations that include coupling of meso- and micro- scale development in the macro-scale model will be described. Finally, some strategies to suppress or prevent voids during processing based on the understanding of resin flow and void formation, growth and transport will be presented along with examples in various composite manufacturing processes.