三维C/C复合材料烧/剥蚀行为的机械剥蚀细观模型

Mesoscopic modeling of mechanical erosion for the ablation-erosion behavior of 3D C/C composites

热化学烧蚀和机械剥蚀是碳/碳(C/C)复合材料在热防护系统中面临的常见问题.本文建立了一个细观机械剥蚀模型用于分析三维C/C复合材料的烧/剥蚀行为.首先,建立了一个描述C/C复合材料反应和扩散现象的细观热化学烧蚀模型,并通过数值模拟方法获得了烧蚀的形貌;然后,获得的瞬态烧蚀形貌被作为机械剥蚀分析的几何模型.对于机械剥蚀,采用渐近损伤方法对复合材料在机械剥蚀作用下的损伤和失效行为进行分析;接着,提出了一个策略用于探讨C/C复合材料的烧/剥蚀行为,该策略将机械剥蚀引入到烧蚀的数值计算中.本文通过数值的方法计算了气流剪切力与表面粗糙度之间的关系,该关系可以被当作机械剥蚀判据引入到烧蚀的数值计算中;还探讨了反应/扩散比、组分反应性差异和气流剪切的临界压力对复合材料烧/剥蚀的质量损失率和机械剥蚀因子的影响.结果表明:本文提出的机械剥蚀细观模型能够较好地分析C/C复合材料的机械剥蚀损伤和失效行为及表征其烧/剥蚀性能;本文对热防护系统材料的评价和设计具有一定的指导意义.

Thermochemical ablation and mechanical erosion are common issues faced by carbon/carbon(C/C)composites in thermal protection systems.A mesoscopic mechanical erosion model is established to analyze the ablation-erosion behavior of 3D C/C composites.Firstly,a mesoscopic thermochemical ablation model describing the reaction and diffusion phenomenon of C/C composites is built and solved through numerical methods to obtain ablation morphologies.Then,the transient ablation morphologies are used as the geometric models for mechanical erosion analysis.Progressive damage method is employed for the damage and failure analysis of composites under mechanical erosion.A strategy introducing the mechanical erosion into numerical ablation calculation is proposed to investigate the ablation-erosion behavior.Moreover,the relationship between airflow shear and surface roughness is numerically calculated,which can be treated as a mechanical erosion criterion introduced into numerical ablation calculation.The effects of the reaction-diffusion ratio,component reactivity ratio,and critical pressure,on the surface recession,mass loss rate,and mechanical erosion factor are investigated.The results show that the mesoscopic mechanical erosion model can analyze the damage and failure behavior of erosion,and the ablation-erosion performance can well be characterized.This paper is beneficial to the evaluation and design of thermal protection system materials.