Study of the bending induced gap in fiber preforming of woven fiber mats

In the preforming of an RTM process, the configuration of the fiber mats should deform in order to conform to the mold surface. Several deformation modes may occur during a forming process. It can be characterized by factors such as the local surface curvature of the mold, the loading condition and the type of reinforcement. It has been suggested that fiber deformation modes may include fiber stretching, fiber straightening, shear slip, and buckling. As the fiber is bent at the bending edge in the preforming, a small gap may emerge from the outer side owing to the movement of fiber bundles. Studies on the relation between the channel gap formation and the bending angle together with the effect of the fiber content were investigated in order to establish a useful guide for the design of mold with bending edges. A model with a slip factor was proposed to estimate the bent fiber thickness.