Effects of stitch yarns on interlaminar shear behavior of three-dimensional stitched carbon fiber epoxy composites at room temperature and high temperature

Effects of four kinds of stitch yarns (carbon fiber (CF), aramid fiber, PBO fiber, and silk fiber (SF)) on interlaminar shear strength (ILSS) and failure behavior of the three-dimensional stitched composites (3DSCs) were investigated by double-notch shear test at room temperature (RT) and 100 ℃. The failure process was recorded by the high-speed camera system. The interfacial strength of stitch yarns/resin at 100 ℃ was quantitatively measured for the first time. The results revealed that the mechanical properties of stitch yarns play a dominant role in determining the ILSS of composites at RT, and 3DSCs stitched with PBO stitch yarn show the best ILSS at RT, which can reach about 82.6 MPa. At 100 ℃, the stitch yarns/resin interface performance is the decisive factor to the ILSS of composites, 3DSCs stitched with CF stitch yarn show the best interlaminar shear performance, and the ILSS is about 52.4 MPa. Moreover, the improvement of the ILSS by stitching was more obviously at 100 ℃, increasing by at least 42%. The low-cost SF has a great advantage in replacing CF at RT on the premise of guaranteeing mechanical properties. Graphical abstract: The effects of four kinds of stitch yarns on interlaminar shear damage law and failure mechanism of the 3DSCs were revealed at room temperature and 100 ℃. [Figure not available: see fulltext.]