Mechanical Testing of 3D Fabric Composites and Their Matrix Material SC-15

Abstract : The U.S. Army is actively investigating advanced light-weight structural materials for protective applications in combat vehicles. One such class of materials is Fiber Reinforced Polymer Composites (FRPC). FRPC are a class of materials that consist of a polymeric matrix that is reinforced through the inclusion of long fibers that are bundled together in a structure known as a fiber tow. Traditional FRPC structures generally contain stacks of individual layered fabrics (lamina) oriented in a particular fiber orientations. This traditional FRPC has anisotropic architectures that lead to the development of large interlaminar shear stresses between adjacent layers. The built up of shear stress would ultimately delaminate the composite. To counter the delamination failure, a new class of FRPC has been developed by weaving fiber tows together. The weaving technique eliminates or reduces much of the shear stresses accumulation between the adjacent layers at large angles. Despite this, delamination may still occur. In an effort to further reduce the delamination mode of failure, researchers have proposed the addition of through the thickness reinforcement. The proposed methods such as z-pinning and stitching; however, can often damage fiber tows and result in large losses in plane stiffness. Another through the thickness method is 3D weaving. It involves the use of an additional yarn, which integrally binds the fabric layers together. The addition of the through thickness yarn can suppress and even eliminate the delamination mode of failure altogether. While much is known about the mechanical performance of woven composites, little has been done to understand how the 3D weaving architecture affects the mechanical performance. The effect of architectural weaves on the progression of failure in both quasi-static tension and compression are examined.