In this article, the thermomechanical fracture responses of shape memory polymers (SMPs) under two common stress free- strain recovery and fixed strain- stress recovery loading cycles are investigated. The shape memory properties of cracked SMPs for both single and mixed fracture modes are examined. The effect of phase transformation on the fracture parameters of the material is evaluated by the extended finite element method (XFEM). In addition, the fracture behavior is studied when the crack is created during the thermomechanical process. The results show that the initially cracked SMPs can fully preserve the shape memory property for both stress free- strain recovery and fixed strain- stress recovery cycles. Moreover, as a promising application, SMPs can be well employed in self-healing materials due to complete closure of the crack at the end of the shape recovery cycle. In cases where a crack is created in the midst of the fixed strain- stress recovery thermomechanical process, it is observed that the performance of the structure in providing desired reaction forces is reduced by increase of the crack length. Nevertheless, the presence of compressive forces in the initial steps of the force recovery cycle may potentially contribute to crack healing if additive healing agents are employed.

在本文中，研究了形状记忆聚合物 (SMP) 在两种常见的无应力应变恢复和固定应变应力恢复加载循环下的热机械断裂响应。对单一和混合断裂模式的裂纹 SMP 的形状记忆特性进行了检查。相变对材料断裂参数的影响通过扩展有限元法 (XFEM) 进行评估。此外，研究了在热机械过程中产生裂纹时的断裂行为。结果表明，初始开裂的 SMP 可以充分保留无应力应变恢复和固定应变-应力恢复的形状记忆特性。循环。此外，作为一种有前景的应用，由于在形状恢复周期结束时完全闭合裂纹，SMP 可以很好地用于自修复材料。在固定应变-应力恢复热机械过程中产生裂纹的情况下，观察到结构在提供所需反作用力方面的性能因裂纹长度的增加而降低。然而，如果使用添加剂愈合剂，在力恢复循环的初始步骤中存在的压缩力可能有助于裂纹愈合。