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). KeywordsComposite cables, finite element analysis, analytical model, design of experiments, uncertainty quantification.

Bending behavior of CFRP cables in the nonlinear displacement range

“…The measured friction coefficients for the GFRP/GFRP and CFRP/GFRP pairs were 0.37 ± 0.03 and 0.50 ± 0.05, respectively. And the adopted values for the CFRP/CFRP, AFRP/ CFRP and AFRP/AFRP pairs were 0.61 [15], 0.30 [23] and 0.25 [24], respectively. All these values are considerably higher than those reported for steel cables (in the 0.1-0.2 range [31]).…”

“…The free length was 305 mm, and the socketed length was 100 mm in both ends. Carbon composite rods properties and static friction coefficients were obtained from Luz et al [15]. For the latter, the rods were longitudinally cut in two halves, and the relative slippage between glass/glass, carbon/carbon and glass/ carbon was monitored through laser measurements in ramp testing of five samples for each contact pair.…”

“…It has been shown that, even for isotropic materials, analytical models for cables can significantly deviate from numerical models for large deformations [14] and for low helix angles (below 70°) [2]. On the other hand, numerical models applying FEM (finite-element method) were able to reproduce experimental tensile tests with relatively good accuracy, even for transversally isotropic materials (e.g., CFRP), for single [15] and multi-layered cables [16]. They also allow evaluation of characteristics that cannot Technical Editor: Paulo de Tarso Rocha de Mendonça, Ph.D.. be accurately measured through analytical models, such as contact pressure between wires, which is associated with wear effect and fatigue life.…”