| Summary: | The fiber reinforced polymer/plastic (FRP) laminates are often subjected to random block spectrum loading in engineering. The simplified regular load in the laboratory fatigue tests is not sufficient to describe the actual fatigue damage history of FRP laminates. In order to explore the fatigue damage evolution of FRP laminates characterized by the residual stiffness degradation under complex random loads, some random block spectra are compiled based on the real engineering fatigue loads, and the fatigue tests of two FRP laminates, the E-glass/YPX-3300 glass fiber laminate and T700/YPX-3001 carbon fiber laminate, were conducted under the random block spectra. Four kinds of differently stacked laminates were prepared for each material. The residual stiffness degradation curves are obtained from the experiments. A stiffness degradation model proposed by the authors are used to correlate the residual stiffness evolution data. The results show that the residual stiffness degradation curves of different specimens can reach satisfactory consistency after correlation, though the original experiment data show a large dispersion. The residual stiffness degradation law of FRP laminates under random block spectrum is the same as that under constant amplitude spectrum. The proposed model can well characterize the residual stiffness degradation law of RRP laminates under random block spectrum.
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