A heterogeneous method of coupled multiscale strength model is presented in this paper for calculating the strength of medical polyesters such as polylactide (PLA), polyglycolide (PGA) and their copolymers during degradation by bulk erosion. The macroscopic device is discretized into an array of mesoscopic cells. A polymer chain is assumed to stay in one cell. With the polymer chain scission, it is found that the molecular weight, chain recrystallization induced by polymer chain scissions, and the cavities formation due to polymer cell collapse play different roles in the composition of mechanical strength of the polymer. Therefore, three types of strength phases were proposed to display the heterogeneous strength structures and to represent different strength contribution to polymers, which are amorphous phase, crystallinity phase and strength vacancy phase, respectively. The strength of the amorphous phase is related to the molecular weight; strength of the crystallinity phase is related to molecular weight and degree of crystallization; and the strength vacancy phase has negligible strength. The vacancy strength phase includes not only the cells with cavity status but also those with an amorphous status, but a molecular weight value below a threshold molecular weight. This heterogeneous strength model is coupled with micro chain scission, chain recrystallization and a macro oligomer diffusion equation to form a multiscale strength model which can simulate the strength phase evolution, cells status evolution, molecular weight, degree of crystallinity, weight loss and device strength during degradation. Different example cases are used to verify this model. The results demonstrate a good fit to experimental data.

本文提出了一种非均质的多尺度耦合强度模型方法，用于计算医用聚酯（如聚丙交酯（PLA），聚乙交酯（PGA）及其共聚物）在整体腐蚀降解过程中的强度。宏观装置被离散成介观单元的阵列。假定聚合物链保留在一个单元中。通过聚合物断链，发现分子量，由聚合物链断裂引起的链重结晶以及由于聚合物单元塌陷而形成的空腔在聚合物的机械强度组成中起不同的作用。因此，提出了三种类型的强度相，以显示非均质强度结构并代表不同的强度对聚合物的贡献，即非晶相，结晶度阶段和强度空缺阶段。无定形相的强度与分子量有关。结晶相的强度与分子量和结晶度有关。强度空缺阶段的强度可以忽略不计。空位强度相不仅包括具有空洞状态的细胞，还包括具有无定形状态的细胞，还包括低于阈值分子量的分子量值。该异质强度模型与微链断裂，链重结晶和宏观低聚物扩散方程相结合，形成了多尺度强度模型，该模型可以模拟强度相演化，细胞状态演化，分子量，结晶度，失重和器件强度。降解。使用不同的示例案例来验证此模型。结果表明非常适合实验数据。