Three-dimensional braided composite materials have been widely applied to engineering structure manufacturing. It is of a great importance to characterize the impact damage of the three-dimensional braided composite under various temperatures for optimizing the engineering structure. Here we conducted transverse impact deformation and damage of three-dimensional braided composite beams with different braiding angles at room and elevated temperatures. A split Hopkinson pressure bar with a heating device combined with high-speed camera was employed to test multiple transverse impact behaviors and to record the impact deformation developments. The results indicated that failure load, initial modulus, and energy absorption decreased with the increase of temperature, whereas the deformation increased slightly with elevated temperatures. We found that the impact brittle damages occurred earlier and the local adiabatic temperature raised higher when the temperature is lower than the glass transition temperature (Tg) of epoxy resin. While above the Tg, the impact ductile damages occurred later and the local temperature raised lower. The thermal stress distribution along the braiding yarn leads to cracks propagation in yarn direction. Part of the impact energy absorptions converted into thermal energy. In addition, the beam with larger braiding angle has high damage tolerance and crack propagation resistance.

中文翻译：

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3D编织复合梁在室温和高温下的多重横向冲击损伤行为

三维编织复合材料已广泛应用于工程结构制造。表征三维编织复合材料在不同温度下的冲击损伤对优化工程结构具有重要意义。在这里，我们对不同编织角度的三维编织复合梁在室温和高温下进行横向冲击变形和破坏。采用带加热装置的分体式霍普金森压力棒结合高速摄像机来测试多种横向冲击行为并记录冲击变形的发展。结果表明，破坏载荷、初始模量和能量吸收随着温度的升高而降低，而变形随着温度的升高而略有增加。我们发现当温度低于环氧树脂的玻璃化转变温度（Tg）时，冲击脆性破坏发生得更早，局部绝热温度升高得更高。高于Tg时，冲击韧性破坏发生较晚，局部温度升高较低。沿编织纱线的热应力分布导致裂纹沿纱线方向传播。部分冲击能量吸收转化为热能。此外，编织角较大的梁具有较高的损伤容限和抗裂纹扩展能力。冲击韧性破坏发生较晚，局部温度升高较低。沿编织纱线的热应力分布导致裂纹沿纱线方向传播。部分冲击能量吸收转化为热能。此外，编织角较大的梁具有较高的损伤容限和抗裂纹扩展能力。冲击韧性破坏发生较晚，局部温度升高较低。沿编织纱线的热应力分布导致裂纹沿纱线方向传播。部分冲击能量吸收转化为热能。此外，编织角较大的梁具有较高的损伤容限和抗裂纹扩展能力。