Abstract
In the present article, the low-cycle fatigue lifetime of carbon/epoxy laminated composites has been investigated. The sensitivity analysis has been also performed to study effects of the displacement amplitude and the loading frequency on the low-cycle fatigue lifetimes in composites. For such objective, displacement-control low-cycle fatigue testing has been done on the open-hole standard specimen. Fatigue tests included 4 different displacement amplitudes at 200 mm/min of the loading frequency and 4 different loading frequencies under 7 mm of the displacement amplitude. The sensitivity analysis was carried out by the MINITAB software, considering a linear function for fitting experimental data by the predicting model. Experimental results showed that by increasing the displacement amplitude, the low-cycle fatigue lifetime decreased, as expected. In addition, when the loading frequency enhanced, the low-cycle fatigue lifetime of composites decreased. Besides, the maximum stress had a reverse behavior, compared to the fatigue lifetime. The sensitivity analysis depicted that the displacement amplitude was sensitive on both the fatigue lifetime and the maximum stress. The loading frequency was sensitive on the maximum stress and was not sensitive on the fatigue lifetime.
Highlights
Nowadays, composite structures have been widely in the aerospace industry
In this field of study, including the fatigue behavior of laminated polymer matrix composites (PMC), different researches have been presented until now, which details can be found in the literature
Constant amplitude tests were conducted at two different R-ratios and the block amplitude tests involved two or more stress levels
Summary
Composite structures have been widely in the aerospace industry. Such components are exposed to cyclic loadings, which lead to the fatigue fracture. De Baere et al [4] have a research on the interlaminar behavior of a carbon fabric reinforced thermoplastic lap shear specimen under quasistatic and tension-tension fatigue loading They showed that no crack growth was visible during quasi-static experiments, except near the lifetime end, whereas significant crack growth was present during fatigue experiments. Ma et al [7] presented the off-axis tensile fatigue assessment based on residual strength for the carbon fiberreinforced composite, at room temperature They conducted tension-tension cyclic fatigue tests under load controlling at a sinusoidal frequency of 10 Hz to obtain the stress-fracture cycles (S-N) relationship. For such objective, the sensitivity analysis on experimental data was carried out by the MINITAB software. Obtained results have been reported in figures and tables
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