碳/酚醛复合材料烧蚀过程热应力分析

Thermal stress analysis of carbon/phenolic composites during ablation process

为了评价防热材料的烧蚀性能,利用有限元软件ANSYS对碳/酚醛复合材料烧蚀过程中热应力的分布与演化规律进行了数值模拟.计算了恒定热流边界条件下材料的瞬态温度场和热应力场,采用蔡-希尔准则对材料热解区进行了破坏分析.数值计算结果与试验测试及图像分析结果的比较表明,随烧蚀过程的进行,材料热影响深度逐渐增大,温度梯度减小;材料热解区存在因热膨胀引起的热应力峰值,并随烧蚀过程逐渐后移,热应力是导致材料裂纹产生并扩展的主要原因.

For evaluating the ablative properties of thermal protective materials, the thermal stress distribution and evolution of carbon/phenolic composites during the ablation process were numerically simulated by FE software ANSYS. Both the transient temperature field and the thermal stress field under steady heat flux were computed. The criterion of Tsai-Hill was adopted to analyze the failure of composites in the pyrolysis region. Furthermore, the computed results were compared to experimental data and graphical analysis results. Thermal influential depth increased gradually with the ablative process, while the temperature gradient decreased. Thermal stress in the pyrolysis region caused by thermal expansion achieved a peak value, which moved gradually rearward from the ablative surface. Thermal stress was the main reason leading to the crack initiation and expansion.