Three-dimensionally woven glass fiber composite struts: characterization and mechanical response in tension and compression

Abstract

Three-dimensionally woven E- and S2-glass fiber textiles have been used in the past to create delamination-resistant corrugated core sandwich panels. During subsequent out-of-plane loading, the E-glass composite core struts and S2-glass composite faces are subjected to either compressive or tension loads. This study has investigated the relationships between the three-dimensional fiber architecture, fiber properties and the mechanical response of representative samples of the core and faces. Using X-ray computed tomography and optical microscopy to characterize the three-dimensional fiber architectures, it is found that the in-plane warp and weft fibers suffer significant off-axis displacement (waviness) due to their interaction with through thickness z-fiber tows. The consequence of this fiber waviness on the relationships of the in-plane tensile and compressive mechanical properties, along with fiber type, fiber volume fraction, and strut aspect ratio are experimentally investigated. The large initial misalignment angle of the warp and weft fiber tows results in a strut compressive strength that is substantially lower than its tensile strength due to compressive failure by either elastic or localized fiber microbuckling. Simple micromechanical models are used to relate the compressive strength of the three-dimensional woven composite struts to strut aspect ratio, fiber volume fractions in the three directions and the three-dimensional fiber architecture.