Ma Yifan, Li Yazhi, Liu Lu
Department of Aeronautical Structural Engineering, School of Aeronautics, Northwestern Polytechnical University, Xi'an 710072, China.
Department of Aircraft Design, School of Aircraft, Xi'an Aeronautical Institute, Xi'an 710077, China.
Materials (Basel). 2022 Aug 12;15(16):5547. doi: 10.3390/ma15165547.
This paper presents an experimental investigation on the mechanisms of damage onset and evolution in unidirectional PEEK/AS4 carbon fibre reinforced thermoplastic (CFRTP) composites subjected to off-axis compressive loadings. A test fixture was designed to prevent buckling, splitting, and end collapsing of the specimens during the test. A series of compression tests were conducted with specimens of various off-axis angles. The displacement and strain fields of all specimens during the tests were evaluated by the digital image correlation (DIC) method. In combination with the DIC results, the influence of the off-axis angles on the failure mechanisms and nonlinear stress-strain responses were analysed. The corresponding failure mechanisms were examined by scanning electron microscopy (SEM). The fracture angles of the tested specimens were evaluated and analysed according to Puck's theory. The off-axis compression failure envelope based on LaRC05 and Hashin criteria was presented and compared to the experimental results. It was shown that the LaRC05 criterion can provide accurate predictions when the off-axis angle is larger than 15°. The complex failure mechanisms were analysed to better understand the effect of ductility of the thermoplastic matrix to the composites. The series of tests provide an experimental failure envelope in combined stress states and can be used for the evaluation of failure theories and the criteria of thermoplastic composites.
本文对单向聚醚醚酮（PEEK）/AS4碳纤维增强热塑性复合材料（CFRTP）在偏轴压缩载荷作用下的损伤起始和演化机制进行了实验研究。设计了一种试验夹具，以防止试样在试验过程中发生屈曲、劈裂和端部破坏。对不同偏轴角度的试样进行了一系列压缩试验。通过数字图像相关（DIC）方法评估了所有试样在试验过程中的位移和应变场。结合DIC结果，分析了偏轴角度对破坏机制和非线性应力-应变响应的影响。通过扫描电子显微镜（SEM）检查了相应的破坏机制。根据普克理论对测试试样的断裂角度进行了评估和分析。给出了基于LaRC05和哈希因准则的偏轴压缩破坏包络线，并与实验结果进行了比较。结果表明，当偏轴角度大于15°时，LaRC05准则能够提供准确的预测。分析了复杂的破坏机制，以更好地理解热塑性基体的延性对复合材料的影响。该系列试验提供了组合应力状态下的实验破坏包络线，可用于评估热塑性复合材料的破坏理论和准则。
