Preform permeability variation with porosity of fiberglass and carbon mats

An experimental investigation on fiber bed permeability variation with porosity for three types of reinforcement mats is performed. The reinforcements consist of plain-weave carbon, plain-weave fiberglass, and chopped fiberglass mats. Resin flow experiments are performed in a rectangular cavity with different fiber volume fractions. RL 440 epoxy resin is used as the working fluid in the experiments. Several layers of mats are laid inside the mold in each experiment and resin is injected at a constant pressure. The effects of reinforcement type and porosity on fiber bed permeability are investigated. Fiber mat permeability of woven mats show large degrees of anisotropy. Resin flow in chopped fiberglass mats is circular, suggesting an isotropic permeability tensor. In all the three cases, preform permeability increases with fiber bed porosity in a non-linear fashion. The results of this investigation could be employed in optimization of liquid composite molding manufacturing processes.