随机多尺度短切碳纤维复合结构模型中RVE尺寸效应和方向模量的均一化响应

RVE Size Effect and Homogenizing Response of Directional Modulus in Stochastic Multi-scale Chopped Carbon Fiber Composite Structure Model

采用一种新型的多尺度短切纤维填充树脂均匀化方法,目的在于探寻随机短切纤维离散角度对复合结构方向模量的均一化响应,同时研究卷曲短切碳纤维(CCF)单元在具有代表体积元(RVE)结构中随机分布所引起的复合材料结构性能变化。在均一化方法中使用一种基于高斯定理的RVE结构子域后处理方案,用于提取三维结构的平均应变和应力。利用X射线计算机断层扫描方法确定2阶张量取向角和剪切纤维长度在测试样品中的概率分布信息,设计比较3种尺寸的RVE模型,通过实验和计算研究CCF多尺度复合模型应力影响区衰减长度的影响因素和该均匀化方法引起的带有旋转角度的RVE方向模量均匀化响应。研究结果表明,复合结构的剪切模量比正轴模量相对旋转角度更为敏感,衰减长度与RVE尺寸、单胞结构和纤维扭曲度等因素相关。因此,研究随机短纤维的离散性对宏观复合结构方向模量的设计,铺层角度的优化等领域具有十分重要的应用。

A new homogenization method of multi-scale chopped fiber filling resin matrix was adopted with the purpose of exploring the effect of the discrete angle of stochastic chopped fiber on the homogenizing response of directional modulus of the composite structure.We also studied the changes of composite structure performance caused by the random distribution of the crimp chopped carbon fiber(CCF)unit in the representative volume element(RVE)structure.In the homogenization method,a RVE subdomain post-processing scheme based on Gauss theorem was used to extract the average strain and stress of the three-dimensional structure.In addition,X-ray computed tomography(CT)was employed to determine the second-order tensor orientation angle and the probability distribution information of chopped fiber length in the test sample.The RVE models of three dimensions were designed and compared.The influencing factors of attenuation length in stress-affected zone of multiscale CCF composite model and the homogenizing response of RVE directional modulus with rotation angle caused by this homogenization method were studied by experiments and calculations.The results showed that the shear modulus of the composite structure is more sensitive to rotation angle than the positive axial modulus,and that the attenuation length is related to RVE size,unit cell(UC)structure and fiber tortuosity.Therefore,it is of practical significane to study the discreteness of stochastic chopped carbon fiber for the design of directional modulus of macroscopic composite structures and the optimization of layering angle.