经编织物气囊蒙皮梯形撕裂行为及破坏机制

Trapezoid tearing behavior and damage mechanism of warp-knitted envelope fabrics

为研究气囊蒙皮梯形撕裂行为及其破坏机制,针对典型经编织物气囊蒙皮膜材,考虑其纱线细观结构及材料非线性,建立系列参数下膜材梯形撕裂数值模型。首先,将得到的数值结果与试验数据进行对比,验证了数值模拟方法的有效性。其次,通过数值模拟结果分析了梯形撕裂的破坏形态及典型偏轴角度下的撕裂破坏历程。然后,探讨了膜材梯形撕裂力学行为及与破坏强度受切缝长度及纱线偏转等关键参数的影响机制。最后,纳入剪切影响因素,提出了梯形偏轴撕裂破坏强度预测理论。结果表明:裂缝邻域内应力集中翼型区域形状、范围的变化对撕裂扩展方向、撕裂抗力起控制作用,而切缝长度及纱线偏轴是影响应力集中翼型区形状演变的主因;缘于裂缝长度可干扰膜面外变形、裂纹前端区域形态及其纱线应力水平,随裂缝长度增加,断裂位移下降明显,而在轴初始撕裂抗力非减反增;纱线偏转可对翼型区及纱线受载水平施加复杂效应,纱线偏转角度的增加导致撕裂强度呈倒“V”型规律。所得结论及研究方法可为经编织物气囊蒙皮裂纹止裂分析及气囊结构安全性评估提供有益参考。

The trapezoid tearing behavior and damage mechanism of envelope materials were investigated.Numerical simulation studies were conducted on a typical warp-knitted envelope fabric under a series of parameters,considering the microscopic structure of the yarns and the nonlinear characteristics of the envelope material.First,the numerical simulation method was verified by comparing the obtained results with experimental data.Then,the damage morphology and tearing damage process under typical bias angles were analyzed by the numerical simulation results.Next,the effects of the slit length and bias angle on the mechanical behavior and tearing strength of the envelope material were discussed in detail.Finally,the shearing effect was introduced and the prediction theory of off-axis trapezoid tearing strength of envelope material was proposed.Results show that the shape and extent of the airfoil-shaped stress concentration zone in the vicinity of the slit were vital factors influencing the propagation direction and tearing strength of slit.The evolution of the airfoil-shaped zone of stress concentration was obviously affected by the slit length and initial bias angle of yarns.Slit length could interfere with the out-of-plane deformation of envelope surface,the shape of slit tip,and the stress level of yarns.As the slit length increased,the fracture displacement decreased significantly,whereas the on-axis tearing strength increased.Since the yarn direction could exert complex effects on the airfoil-shaped zone and the stress level of the yarn,an inverted“V”-shaped relationship was presented between tearing strength and yarn bias angle.The research findings can provide reference for the slit arrest analysis and safety assessment of pneumatic membrane structures.