Numerical modeling offers considerable promise to reduce costs associated with trial-and-error process in the manufacturing industry. In laser cutting of fiber-reinforced composites, the developed thermal stress in the cut region has considerable influence on the application of the machined composite and the end product quality. Nevertheless, measurement of the thermal stress is quite challenging in practice. Here, an uncoupled thermo-mechanical finite element model is developed to accurately predict formation of heat-affected zone, kerf width, thermal field, and thermal residual stress of an anisotropic carbon/Kevlar fiber reinforced composite during multi-pass laser cutting process. A novel approach of element deletion incorporating temperature-dependent Hashin failure criteria and VUMAT subroutine is proposed. The study is carried out using Abaqus interlinked with Fortran compiler to define laser Gaussian beam (DFLUX subroutine) and material removal (VUMAT subroutine) for determining the temperature gradient and cut characteristics, respectively. The numerical results agree well with the experimental scanning electron micrographs of heat-affected zone and kerf width. In addition, residual temperature after subsequent pass results in greater temperature distribution and heat accumulation. It has also been established that the strength of composite gradually decays with the increase of temperature due to stiffness (elastic moduli) degradation in the area of the cutting zone, accelerating damage initiation in both fibers and matrix.

中文翻译：

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碳/凯夫拉尔混合复合材料的多道激光切割：通过热机械建模预测热应力、热影响区和切口宽度

数值建模为降低与制造业中试错过程相关的成本提供了巨大的希望。在纤维增强复合材料的激光切割中，切割区域产生的热应力对加工复合材料的应用和最终产品质量有相当大的影响。然而，热应力的测量在实践中非常具有挑战性。在这里，开发了一种非耦合热机械有限元模型，以准确预测多道次激光切割过程中各向异性碳/凯夫拉纤维增强复合材料的热影响区、切口宽度、热场和热残余应力的形成。提出了一种结合温度相关的 Hashin 失效准则和 VUMAT 子程序的单元删除新方法。该研究使用与 Fortran 编译器互连的 Abaqus 进行，以定义激光高斯光束（DFLUX 子程序）和材料去除（VUMAT 子程序），分别用于确定温度梯度和切割特性。数值结果与热影响区和切口宽度的实验扫描电子显微照片非常吻合。此外，后续道次后的残余温度导致更大的温度分布和热量积累。还已经确定，由于切割区区域的刚度（弹性模量）退化，复合材料的强度随着温度的升高而逐渐衰减，加速了纤维和基体的损伤开始。