In this work, the ductile to brittle transition behavior of short carbon fiber (SCF)-reinforced polypropylene (PP) composite is studied. Initially, the SCF-reinforced PP composites with a varying composition of SCF in the range of 0–40 wt% loading were first melt-mixed in a twin-screw extruder and later injection-molded to produce the testing samples. The experimental results indicate that with an increase in SCF loading, an increase in the tensile modulus and strength was observed along with a rapid decrease in the values of strain at break. A sudden decrease in strain at break was observed in composites in the range of 10–15 wt% SCF. To further study the sudden decrease in strain at break, an investigation was performed on composites that contained 10–15 wt% of SCF loading, starting from 10 wt% with a 1% increment to 15 wt% of SCF. The results of this study show that a decrease in strain at break was not linear; on the contrary, it was accompanied by a ductile to brittle transition, which specifically occurred in the range of 12–13 wt% of SCF loading and then continued to decrease with an increase in SCF loading.

中文翻译：

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短碳纤维增强聚丙烯复合材料的韧脆转变

在这项工作中，研究了短碳纤维（SCF）-增强聚丙烯（PP）复合材料的韧脆转变行为。最初，SCF 增强 PP 复合材料的 SCF 成分在 0-40 wt% 的范围内变化，首先在双螺杆挤出机中熔融混合，然后注塑以生产测试样品。实验结果表明，随着 SCF 载荷的增加，观察到拉伸模量和强度增加，同时断裂应变值迅速降低。在 10-15 wt% SCF 范围内的复合材料中观察到断裂应变突然降低。为了进一步研究断裂应变的突然减少，对含有 10-15 wt% SCF 负载的复合材料进行了研究，从 10 wt% 开始，增加 1% 到 15 wt% SCF。这项研究的结果表明，断裂应变的减少不是线性的；相反，它伴随着韧性到脆性的转变，特别是在 SCF 负载的 12-13 wt% 范围内发生，然后随着 SCF 负载的增加而继续下降。