Many investigations on the mechanical properties of plastics reinforced with glass fibers have hitherto been carried out for practical use. In the theoretical point of view, however, the plan to understanding the mechanical properties of such a composite material as FRP has not yet been developed sufficiently, because of the complicated state of its system involving adhesion to clarify the difference and relation between plastics and glass fibers and so on.
In this study, theoretical calculations have been made of the mechanical reinforcement and anisotropy of glass fibers, with increase and orientation and other changes, by taking the Model A proposed by Whitney and Riley, and the Model B by Halpin and Tsai as a structural unit.
On comparing the calculated results with the experimental data obtained for polyethylene, including various amount of randomly oriented glass fibers at various temperatures, and for polyester reinforced with glass thread, it is concluded that both the structural models mentioned above must be available in order to describe the mechanical reinforcement and anisotropy of FRP.