Mode II interlaminar shear behavior of needled/tufted interlocking composites

The needled/tufted interlocking fabric is a new fabric structure. At present, the mode II interlaminar shear behavior of needled/tufted interlocking composite has not been clarified. In this work, the needled/tufted interlocking fabrics and reinforced composites were fabricated, and the interlaminar shear behavior of mode II was studied experimentally and numerically, the mechanism of tufting effect on interlaminar shear properties of needled composites was revealed. The study found that the interlaminar shear properties of needled/tufted interlocking composites were greatly improved by tufted fiber bundles. The maximum failure load of the needled/tufted interlocking specimen increased 108.93%, and the interlaminar shear stress of the needled/tufted interlocking specimen improved by 89.39%. The interlaminar shear strength increased linearly with the increase of tufted fiber bundle implantation volume. The implantation pattern of tufted fibers had effected on interlaminar shear property. Under the same implantation volume, the thinner tufted fiber bundles and more implantation points were more beneficial to improve the interlaminar shear performance. The typical shear failure modes included matrix cracking, fibers pullout, and brittle fracture of tufted fiber bundles and needled fiber bundles. Moreover, a numerical simulation model of interlaminar shear behavior based on three cohesive zones (TCZMs) was proposed. The predicted displacement-load curves were highly in accord with the experiments. The error range was controlled within 1.08% - 3.76%. The simulation model could predict the mode II shear behavior of needled and tufted interlocking composites effectively, which was helpful to the early manufacturing process design of needled and tufted interlocking fabrics.