Experimental and Analytical Study on Residual Stiffness/Strength of CFRP Tendons under Cyclic Loading

Based on tension–tension fatigue tests, this paper investigated the mechanical property degradation of carbon fiber reinforced polymer (CFRP) tendons from a macroscopic perspective. According to the degradation regularity, this paper proposed a normalized phenomenological fatigue model based on the residual stiffness/strength of CFRP tendons during the fatigue loading process. In this paper, the residual stiffness of CFRP tendons were tested at five stress ranges, while the residual strength was tested at four stress ranges. In order to validate the reliability and applicability of proposed fatigue damage model, the predictions of proposed model and cited models from the literature are discussed and compared. Furthermore, experimental results from literatures were adopted to verify the accuracy of the proposed model. The results showed that the proposed model is applicable to predict both residual stiffness and residual strength throughout fatigue life cycle and has a better accuracy than models from the literature. Moreover, the three-stage degradation can be observed from the degradation processes of stiffness and strength at each stress level.

Initiation and Tolerance of Macro-Damage of First Ply (FBF) in a Process of Damaging of Hybrid Multi-Ply Structures Due to Reinforcement Archtecture

The objective of this paper was study and analysis of damaging process of multi-ply structure applied in dentistry. The aim was to analyze and experimentally evaluate tolerance of macro-damage of first ply (FPF - first ply failure) of multi-ply composite. A studied structure of composite makes a carrying structure for dental applications e.g. adhesive bridges. Influence of reinforcement structure on the residual carrying capacity of the studied multi-ply materials has been demonstrated. It has been shown that the type of fiber and fiber ribbon architecture play a major role in strength of studied reinforcements. Structures included in the study differ by the moment of macro-damage occurrence, carrying capacity and residual stiffness.