MODEL RESIN PERMEATION OF FIBER REINFORCEMENTS AFTER SHEAR DEFORMATION

In liquid composite molding processes such as resin transfer molding a nd structural reaction injection molding, fiber reinforcements are for med with automated processes to conform to the complex shape of the mo ld cavity. Deformation of the fiber reinforcement during the forming o peration can be characterized by factors such as the local surface cur vature of the mold and the type of reinforcement. For bidirectional fi ber fabrics, simple shear is the major deformation mode in the forming process. Deformation of the fiber reinforcement after being formed to the mold cavity shape results in variations of local fiber content. I n addition, the network structure of the fiber reinforcement is also r earranged. This may cause some significant effects on the fiber permea bility and result in a mold filling pattern quite different from that expected. Therefore, a good understanding and measurement of the perme abilities for the deformed fiber reinforcements is of great importance . In the now simulation of the filling process, the success of the pre diction depends greatly on the correct values of;in-plane permeabiliti es. A change of the in-plane permeability of the fabric after shear de formation must be well understood before an accurate flow simulation c an be obtained. This article investigates the permeability of fiber re inforcements in relation to different shear angles. Several flow exper iments were conducted on bidirectional woven roving fabrics at differe nt shear angles. Two relevant factors-the ratio of principal permeabil ities and the direction of principal axes crith respect to the orienta tion of the fabric-are studied to investigate their variations with re spect to shear deformation of the fiber reinforcements. It is found th at the angle shift of the principal axes increases with the shear angl e. At the same time, the in-plane permeability ratio may decrease with the shear angle.