The manufacturing process of Sheet Molding Compounds (SMC) induces a reorientation of fibers during the flow, which influences local properties and is of interest for structural computations. Typically, the reorientation is described with an evolution equation for the second order fiber orientation tensor, which requires a closure approximation and multiple empirical parameters to describe long fibers. However, CT scans of SMC microstructures show that fiber bundles stay mostly intact during molding. Treating hundreds of fibers in such a bundle as one instance enables direct simulation on component scale. This work proposes a direct simulation approach, in which bundle segments experience Stokes’ drag forces and opposing forces are applied to the fluid field. The method is applied to specimens with a double-curved geometry and compared to CT scans. The Direct Bundle Simulation provides increased accuracy of fiber orientations and enables prediction of fiber-matrix separation with affordable computational effort at component scale.

片状模塑料（SMC）的制造过程会在流动过程中引起纤维的重新定向，这会影响局部性能，并且对于结构计算很重要。通常，使用二阶纤维取向张量的演化方程描述重取向，这需要闭合近似和多个经验参数来描述长纤维。然而，SMC微结构的CT扫描显示，纤维束在成型过程中基本上保持完整。一次将这种束中的数百根纤维视为一个实例，就可以直接在组件规模上进行仿真。这项工作提出了一种直接的模拟方法，其中束段经历斯托克斯的拖曳力，而相反的力施加到流场。该方法适用于具有双曲线几何形状的标本，并与CT扫描进行比较。