In this work, cotton fabric-reinforced polypropylene laminates (CFRLs) were prepared as an example to analyze the effect of viscoplastic deformation on the mechanical properties of natural fiber-reinforced composites. Compared with neat polypropylene (PP), the tensile strength and modulus of CFRLs are significantly enhanced in all directions. However, CFRLs are more prone to plastic deformation than PP during static tensile tests. The tensile strength of CFRLs could be affected by the processing factors. As the drawing speed was reduced from 20 to 0.1 mm/min, the tensile strength of CFRLs decreased by 27%. Cyclic tensile tests were used to analyze the effect of viscoplastic deformation on the tensile strength of CFRLs, and the results showed that when the viscous deformation increased, the strain increased, leading to rapid fracture of CFRLs under cyclic tensile stress much lower than the tensile strength. By simulating the stress conditions of pressure vessels and pipes with different curved surfaces, CFRLs are shown to be more suitable for cylindrical curved structures, which has developable surface; While, they are not suitable for complex curved structures, such as spherical surfaces, that are undevelopable surface.

中文翻译：

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棉织物增强聚丙烯复合材料的粘塑性变形

在这项工作中，以棉织物增强聚丙烯层压板（CFRLs）为例，分析粘塑性变形对天然纤维增强复合材料力学性能的影响。与纯聚丙烯（PP）相比，CFRLs的拉伸强度和模量在各个方向都有显着提高。然而，在静态拉伸试验中，CFRL 比 PP 更容易发生塑性变形。CFRL 的拉伸强度可能受加工因素的影响。随着拉伸速度从 20 降低到 0.1 mm/min，CFRL 的拉伸强度降低了 27%。采用循环拉伸试验分析粘塑性变形对CFRLs抗拉强度的影响，结果表明，当粘塑性增大时，应变增大，导致CFRL在远低于抗拉强度的循环拉应力下快速断裂。通过模拟不同曲面压力容器和管道的受力情况，CFRLs更适用于具有可展曲面的圆柱曲面结构；但是，它们不适用于复杂的曲面结构，例如不可展曲面的球面。