Strength analysis of composite cables

Abstract Carbon Fiber Reinforced Polymer (CFRP) cables, due to their outstanding performance in terms of specific stiffness and strength, are usually found in civil construction applications and, more recently, in the Oil & Gas sector. However, experimental data and theoretical solutions for these cables are very limited. On the contrary, several theoretical and numerical approaches are available for isotropic cables (metallic wire ropes), some of them with severe simplifications, nonetheless showing good agreement with experimental data. In this study, experimental tensile results for 1×7 CRFP cables were compared to a simplified analytical model (assumed transversally isotropic) and to a 3D finite element model incorporating the experimental uncertainty in important input parameters: longitudinal elastic modulus, Poisson’s ratio, static friction coefficient and ultimate tensile strain. The average experimental breaking load of the cable was 190.25 kN (coefficient of variation of 1.74%) and the agreement with the numerical model predictions were good, with an average-value deviation of –1.15%, which is lower than the experimental variations. The simplified analytical model yielded a discrepancy above 10%, indicating that it needs further refinement although much less time consuming than the numerical model. These conclusions were corroborated by statistical analyses (i.e. Kruskal–Wallis and Mann-Whitney).摘要 碳纤维增强聚合物（Carbon Fiber Reinforced Polymer, CFRP）缆绳凭借优异的比刚度与比强度性能，已广泛应用于土木工程领域，近年来更逐步拓展至油气行业。然而，针对此类缆绳的实验数据与理论解决方案仍较为匮乏。与之相对，针对各向同性缆绳（即金属钢丝绳）的理论与数值研究方法已较为成熟，尽管其中部分方法存在严苛的简化假设，但仍与实验数据展现出良好的契合度。本研究将1×7 CRFP缆绳的拉伸实验结果与两类模型进行对比：其一为假定为横观各向同性的简化解析模型，其二为在关键输入参数（纵向弹性模量、泊松比、静摩擦系数及极限拉伸应变）中引入实验不确定性的三维有限元模型。该缆绳的平均实验断裂载荷为190.25 kN，变异系数为1.74%；其与数值模型预测结果的契合度良好，平均偏差为-1.15%，低于实验本身的变异程度。而简化解析模型的预测偏差则超过10%，表明尽管该模型的计算耗时远低于数值模型，但仍需进一步优化完善。上述结论通过克鲁斯卡尔-沃利斯（Kruskal–Wallis）检验与曼-惠特尼（Mann-Whitney）检验得到了验证。