A void or a pore is three-dimensional region that remains unfilled with polymer and fibers in a composite material.
[5] Among other factors that can influence the quantity and location of voids are pre-preg impregnation, surface morphology, curing parameters, compaction pressure, fiber bridging, excessive resin bleed, and the thickness of layup .
It is difficult for a resin or matrix with a high viscosity to penetrate the original void spaces between adjacent fibers.
Traditionally, using vacuum bagging system and autoclave under pressure and heat will minimize or prevent voids from forming.
The vacuum bagging system combined with autoclave is a common method used in industrial processes to achieve a low void content for thermoset composites.