Tensile behaviors of layer-to-layer 2.5D angle-interlock woven composites with/without a center hole at various temperatures

The temperature-dependent mechanical behaviors of open-hole composite plates are essential for composite design and structures. Here, tensile experiments of shallow straight-link-shaped 2.5D woven composites (abbr. 2.5DWC) with/without a center hole are first conducted at different temperatures (20 °C, 180 °C and 240 °C). Failure modes are examined by scanning electron microscope (SEM). Thermal property of QY8911-IV resin is investigated by DMA analysis. It is noted for samples without the center hole that with the increase of temperature, the tensile stress–strain curves exhibit a linear response until that a slight nonlinearity at the end stage. The strength retention rates at 180 °C and 240 °C are totally equal. For the open-hole samples, it is interestingly found that the strength retention rates are higher than that of samples without the hole at 180 °C, resulting from the stress concentration accommodation and fiber-dominated failure mode. Even at 240 °C, there is no necking phenomenon for all the failed samples, but more broom-like damage extent is observed in the cross-section. Due to the primary load-bearing warp yarns and hole-edge stress concentration, obvious pull-out warp yarns emerge near the hole edge.