Limit Analysis of Ductile Fiber-Reinforced Structures

A continuum theory of plastic behavior of fiber-reinforced materials, presented earlier by the writers, is outlined. The theory, valid for general states of stress, is based on a maximum shear stress criterion and accounts for plastic extensibility of the fibers as well as plastic flow of the ductile matrix material. Application of the general theory, stated in terms of appropriate stress resultants, is made to reinforced beams and plates. Yield or interaction surfaces are constructed giving the critical combinations of generalized stresses under which yielding may occur. Significant features of structural behavior, as predicted by the theory, are brought out by studying the characteristics of the interaction surfaces and by considering some simple applications. One outstanding feature is the apparent shear-limited plastic behavior of structures with strong reinforcing fibers. The presence of strong fibers is shown to induce transverse shear failure rather than bending failure in structures composed of isotropic materials.