Polymer matrix composites are attractive structural materials in automotive, defense, and aerospace industries due to their high strength to low weight ratios. However, due to their low shear strength, compression dominated failure mechanisms such as plastic microbuckling lead to the development of kink bands, which are a key strength-limiting factor in modern polymer matrix composites. This phenomenon has been studied extensively, particularly for uniaxial compression; however, experimental measurements of the strain fields leading to and developing inside these bands under bending are not well explored. In this study, digital image correlation is used to measure strains inside kink bands developing during three-point bending of cross-plied [0/90] laminated composite Dyneema™ HB80. Measurements indicated large normal and shear strains developed inside the band in a way that suggested systematic increases in ply rotation angle as the band evolved with increased bending deflection. Results also suggested intermittent buckling events involving fiber bundles that correlate with oscillations observed in the load–displacement curve. Optical microscopy of failed samples showed failure resulted from a combination of plastic microbuckling and axial splitting.

中文翻译：

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弯曲下聚合物基复合材料的扭结带演化：数字图像相关性研究

聚合物基复合材料因其高强度与低重量比而成为汽车、国防和航空航天工业中极具吸引力的结构材料。然而，由于它们的低剪切强度，压缩主导的失效机制如塑料微屈曲导致扭结带的发展，这是现代聚合物基复合材料的关键强度限制因素。这种现象已被广泛研究，特别是对于单轴压缩；然而，在弯曲下导致和在这些带内发展的应变场的实验测量没有得到很好的探索。在这项研究中，数字图像相关性用于测量在交叉层合 [0/90] 层压复合材料 Dyneema™ HB80 的三点弯曲过程中产生的扭结带内的应变。测量结果表明，带内产生了大的法向应变和剪切应变，这表明随着带随着弯曲挠度的增加而演变，层板旋转角会系统地增加。结果还表明，涉及纤维束的间歇性屈曲事件与载荷-位移曲线中观察到的振荡相关。失败样品的光学显微镜显示失败是由塑料微屈曲和轴向分裂的组合引起的。