Fiber length is an important factor affecting the mechanical properties of long fiber reinforced thermoplastic (LFRT). When LFRT is processed by injection molding, the strong shear flow usually leads to severe fiber breakage. Therefore, it is a crucial issue to reduce the loss of fiber length as much as possible during composite molding. Current work focused on constructing an effective model for predicting fiber breaking caused by shear stress during melt filling. Based on the Oseen formula, the disturbance of liquid flow caused by a single external force was studied, and the force acceptance formula of fiber immersed in flow field was derived. A mechanical model for characterizing the degree of fibers buckling and breaking and the shear stress was constructed by the Euler buckling criterion. To verify the model, glass fiber reinforced polypropylene (GF/PP) composites with initial fiber length of 3 mm and 6 mm was subjected to shear at the specific shear rate by using a rotating rheometer. The length of GF after sheared was measured by fiber length distribution analyser. The breaking ratio of fibers was predicted using the new model, and the predicted results were in good agreement with experiment, although more comparisons with experiments are necessary.

中文翻译：

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注射成型长纤维增强热塑性塑料纤维断裂预测的有效模型

纤维长度是影响长纤维增强热塑性塑料（LFRT）力学性能的重要因素。LFRT采用注塑成型加工时，强烈的剪切流通常会导致严重的纤维断裂。因此，在复合材料成型过程中尽可能减少纤维长度的损失是一个至关重要的问题。目前的工作重点是构建一个有效的模型来预测熔体填充过程中由剪切应力引起的纤维断裂。基于Oseen公式，研究单一外力对液体流动的扰动，推导出纤维浸入流场的受力公式。通过欧拉屈曲准则构建了表征纤维屈曲和断裂程度以及剪切应力的力学模型。为了验证模型，使用旋转流变仪对初始纤维长度为 3 mm 和 6 mm 的玻璃纤维增​​强聚丙烯 (GF/PP) 复合材料进行特定剪切速率的剪切。通过纤维长度分布分析仪测量剪切后的GF长度。使用新模型预测了纤维的断裂率，预测结果与实验吻合良好，但需要与实验进行更多的比较。