摘要
建立了基于等效响应比拟技术的三维机织复合材料弹性性能预报模型.首先将三维机织物的结构单元分解为4个子元(经纱、纬纱、填充纱和接结纱),用几何模型去估算这些子元的体积分数.然后依据不同的外载形式,将复合材料的应力-应变关系等效地表达为3组诸子元所组成的三维弹簧网络.根据刚度系数的物理意义,采用不同的弹簧网络连接形式,并按体积平均化方法获得材料总体刚度矩阵中相应的刚度系数,进而计算得到三维机织复合材料的9个弹性系数.该模型考虑了层内交织经纱、层间交织接结纱的弯曲以及材料内部纯树脂区对三维机织复合材料弹性性能的影响.试验结果与模型的理论预测值进行比较,表明这个模型是有效的.
Based on the observation of the yarn's patterns along the longitudinal and transversal directions of the specimens of woven composite for various binding patterns, a geometric model is presented to describe the fibrous architectures of 3D woven preforms. Three assumptions are made for the purpose of the modeling: (1) the cross section of all yarns is of racetrack shape and the packing density and geometry are uniform along yarn's length, (2) yarns of stuffer and filling are in a straight form, and (3) yarns of warp and binder are deflected along their length with sections of straight parts joined by arc ones. A unit cell with its constituent yarn systems called 'sub-unit cells', such as warp, filling, stuffer and binder, is defined and the length and orientation of yarns in each sub-unit cell are estimated. Thus, the volume of the sub-unit cell can be obtained, and the fiber volume fraction of the unit cell can also be calculated out. Following the geometric model of the fibrous architecture, a mechanical model is proposed to approach the elastic properties of 3D woven composites. The stiffness and compliance matrix of sub-unit cells corresponding to each yarn systems within the unit cell are developed. According to different load sharing relations, three multi-dimensional spring networks are used to simulate the stress-strain relationships of 3D woven composites by a method termed as the effective response comparison technique. The volume averaging method is used to approach the corresponding stiffness components in the total stiffness matrix and nine elastic constants of 3D woven composites are thus obtained. In the development of the model several considerations are made in order to better perform the simulation, such as taking into account the geometric pattern of yarn's undulation in calculating the elastic constants and the influence of pure resin region within the unit cell. To validate the modeling approach, samples of 3D woven composites are fabricated with various fibrous architectures. Tensile moduli of the composite samples, both in longitudinal and transverse directions are tested. Good agreements between the theoretical predictions and experimental results demonstrate that the feasibility of the proposed model in analyzing the elastic properties of 3D woven composites.
出处
《力学学报》
EI
CSCD
北大核心
2003年第5期569-577,共9页
Chinese Journal of Theoretical and Applied Mechanics
基金
上海市重点学科建设资助项目
