编织复合材料绝热温升路径与局域剪切破坏的细观结构机制

Braided composite materials are used to manufacture blades in solid rocket motor and the cone of missile. 3D multi-way adiabatic shear bands could be formed by localized plastic instability combined with the shear deformation at fiber/matrix interfaces under impulsive loading. This would lead to intricate inhomogeneous temperature distribution and localized damages. However, adiabatic heating paths and localized damage mechanism in braided composite materials under impulsive loading have not been sufficiently studied so far. In this project, thermo-mechanical coupling constitutive relation will be proposed based on mechanical parameters obtained from quasi-static and dynamic experiments. The constitutive relation will include strain-rate effect, adiabatic softening effect, ductile and shear damage criterions. Transient temperature rise and localized damages in yarns, yarns/matrix interfaces and matrix will be calculated by the meso-structural finite element analysis. Evolution paths of the adiabatic heating and the localized damages will be established. Their distribution and evolution processes will be deduced from the meso-structural level. And a high-speed infrared thermography technique will be applied to capture the transient temperature rise of composite specimens under impulsive loadings. Compared with 2D laminated composites, the 3D multi-way adiabatic shear mechanism of braided composite material will be revealed by considering the synergistic effect of the localized softening and yarns’ cross-insertion. It is expected that such an effort could explore the meso-structural mechanism of adiabatic shear failure in braided composites. Results would be extended to optimize structural design of 3D braided composite materials to ensure their shear damage tolerance in significant regions under intensive dynamic loadings.

编织复合材料用于制备固体火箭发动机叶片和导弹头锥，在高速冲击载荷下会因为局域塑性失稳和纤维束/基体界面剪切，形成三维多向绝热剪切带，引起复杂非均匀温升分布和局域破坏。目前编织复合材料在冲击加载下的瞬态温升路径与局域破坏机理尚未得到足够确认。项目将在材料动静态力学测试基础上，提出计及纤维束和基体力学性质应变率效应、绝热温升软化效应、延性/剪切失效准则的热力耦合本构关系；以有限元计算实现非均匀细观结构模型中纤维束、纤维束/基体界面、基体的瞬态温升与局域破坏；解析绝热温升路径、局域剪切破坏路径，从细观层面剖析两者的分布和演化过程；结合冲击加载下的瞬态红外热成像分析，与二维层压复合材料对比，揭示三维编织复合材料局域温升软化与纤维束多向穿插协同作用所致的绝热剪切机理。项目研究价值在于探索编织复合材料绝热剪切破坏的细观结构机制，并为结构强化设计提供依据和启发，确保材料关键区域在强动载作用下的剪切阻抗。

三维编织复合材料具有优良的冲击分层阻抗，但也会因此造成独特的绝热温升路径和复杂的局域剪切破坏，从而影响结构件整体刚度、强度及可靠性。本项目通过动静态力学测试、有限元计算和红外热成像技术解析多种三维编织复合材料结构的绝热剪切路径、温升分布和局域热力耦合破坏。主要研究内容：（1）三维编织复材试件冲击压缩下的渐进破坏、瞬态温升、局域热力耦合失效机理；（2）三维编织复材板件冲塞剪切、圆管冲击压溃的绝热剪切带局域数据分析；（3）三维双轴向经编复材冲击压缩下的绝热温升过程和局部纤维束扭结作用机制；（4）环形编织复材短梁低速冲击响应及冲击损伤与内部构型对冲后压缩失效模式的协同效应；（5）三维机织复材面内偏轴压缩失效过程中捆绑纱的面外拉伸和面内剪切阻抗；（6）环形编织复材管件低速冲击下的局域温升行为和热力耦合失效机理。研究发现：（一）动载作用下编织复材的局域温升是损伤失效的有效指示，其温度可达到甚至超过聚合物基体的玻璃化转变温度，从而在绝热剪切带、基体软化、材料失效之间建立关联性；（二）各阶段出现的时间先后为序分别是峰值力、绝热剪切变形、加速温升、峰值温度和绝热剪切失效，且绝热剪切带内部的塑性变形呈现非均匀状态；（三）纤维束屈曲处容易积聚温度且在绝热剪切带上形成温度波动，纤维束扭结过程中的屈曲折叠效应可进一步吸收冲击能量从而阻碍绝热剪切带发展，同时也可引发面内裂纹从扭结处向远端扩展；（四）环形编织复材短梁冲后压缩过程中的温度分布并不均匀，温升集中于编织层并与局部折叠、屈曲、弯曲、撕裂、张开和分离损伤相对应；（五）三维织物复材厚度方向捆绑纱可有效抵抗面内偏轴冲击压缩失效过程中经纬纱面外拉伸和面内剪切作用；（六）绝热温升效应通过降低局部基体刚度影响环形编织复材横向冲击失效模式、回弹性和层内裂纹扩展。本项目研究成果对于优化编织结构设计、提高编织复合材料关键区域冲击损伤容限具有参考意义。