复合材料的剪切、横向力学性能以及耐久性在很大程度上取决于纤维与基体的界面强度。复合材料界面强度通常依赖纤维和树脂基体的大小、形状、性质和空间分布。文章提出一种适用于复合材料的数值模拟计算方法，选择短切玻璃纤维复合材料为研究对象进行有限元模拟计算，对纤维的随机分布提供一种快速生成算法，分析短切玻璃纤维长度对片状模塑料力学性能的影响。结果表明，短切玻璃纤维片状模塑料弹性模量随纤维长度的增大出现先增大后变缓的趋势，通过比较随机结构和规则结构说明计算方法合理性，纤维分布的随机性对复合材料宏观弹性常数的影响较小。

The shear, transverse mechanical properties, and durability of composite materials largely depend on the interfacial strength between the fibers and the matrix. The interfacial strength of composites typically relies on the size, shape, properties, and spatial distribution of the fibers and resin matrix. The paper proposes a numerical simulation method suitable for composite materials. Short-chopped glass fiber composites were chosen as the research object for finite element simulation. A fast generation algorithm for the random distribution of fibers is provided, and the influence of short-chopped glass fiber length on the mechanical properties of sheet molding compounds is analyzed. The results show that the elastic modulus of short-chopped glass fiber sheet molding compounds increases first and then levels off with the increase in fiber length. By comparing random and regular structures, the rationality of the calculation method is demonstrated. The randomness of fiber distribution has a relatively small impact on the macroscopic elastic constants of composite materials.