纤维增强复合材料激光烧蚀效应的数值模拟

考虑材料的热解、氧化、相变及辐射和内外对流换热等物理过程,给出了激光烧蚀纤维增强复合材料的物理模型及数学模型。以碳纤维/环氧树脂复合材料为例,编程计算了材料的激光烧蚀过程,计算结果与实验结果符合得较好。计算结果表明：考虑复合材料的内对流时得到的结果更准确;较强功率密度激光辐照时,氧化对烧蚀的贡献可以忽略;功率密度一定时,烧蚀质量随时间近似为线性变化,功率密度越高,烧蚀效率越高。以辐照结束时背表面温度及烧蚀质量为目标物理量,对烧蚀过程做了参数敏感性分析,结果表明：热容及热导率对背表面温度的影响较大;树脂含量对烧蚀质量的影响较大,但其相对敏感度随激光功率密度增加而下降;激光功率密度超过1 kW/cm2时,辐射系数对烧蚀质量影响较大,但其相对敏感度随激光功率密度增加而下降。

Numerical simulation of laser ablation of fiber-reinforced composite materials

The paper presents the physics and the math models of laser ablation for fiber-reinforced composite materials in consideration of the physical processes including pyrogenation, oxidation, radiation, phase transi- tion, both inner and outer convections. By taking carbon/epoxy composites for examples, the laser ablation process is simulated, and the results agree well with the experimental results. The numerical results indicate that the inner convection plays an important role in the ablation process; the oxidation effect can be ignored during high intense laser irradiation; the ablation mass is nearly linear to laser irradiation time when the laser power density is a constant and the ablation efficiency increases with increasing power density. The parameter sensitivity is analyzed with the loss mass and the rear surface temperature at the end of laser irradiation as the object. The analysis results show that the thermal capacity and thermal conductivity have more influences on the bear surface temperature; the epoxy volume fraction has much influence on ablation mass, but its relative sensitivity decreases with increasing laser power density. Moreover, the radiation coefficient is an important factor when the laser power density is more than 1 kW/cm2 , but its relative sensitivity decreases with increas- ing laser power density.