Influence of Temperature and Stress Ratio on Low-Cycle Fatigue Life Prediction of UD-CFRCs Considering Stiffness Degradation

Abstract

This study explores the feasibility of stress-based and residual-strength-based methodologies for fatigue life prediction of unidirectional carbon fiber-reinforced composites (UD-CFRCs) under low-cycle fatigue (LCF) loading. The influence of temperature and stress ratio on stiffness degradation is also investigated. Stiffness degradation increased with increasing temperature, resulting in reduced fatigue life. Similarly, higher stress ratios accelerated stiffness degradation in the UD-CFRCs. However, increasing stress ratios also prolonged Stage II, the cumulative damage progression phase, consequently increasing fatigue life. To evaluate predictive capabilities, two distinct LCF failure models were employed: one based on the Basquin equation and the other on residual strength. These models were applied across three temperatures and four stress ratios, and their results compared. The Basquin equation-based model provided better agreement with experimental observations.