Influences of long-term immersion of water and alkaline solution on the fatigue performances of unidirectional pultruded CFRP plate.

Graphical abstract Highlights • We studied static tensile, fatigue property and moisture absorption of CFRP plates with DW, AS, NI invasion for 2 years. • We got 3 prediction formula by S - N curve, Whitney's, and Sendeckyj's method. • We studied fatigue failure mechanism of CFRP with DW, AS invasion by microstructure and thermal behavior. Abstract Moisture absorption rate (M t), static tensile strength (f u), fatigue life (N), stiffness degradation curves of unidirectional pultruded CFRP plates during two years distilled water (DW), alkaline solution (AS), and non-immersion (NI) were comprehensively studied along with their thermal behavior, microstructure and fatigue failure mechanism; Their stress level (S)- N curves were further fitted and predicted by three methods. Results reveal, the N of the pultruded CFRP plate with AS is much lower than those with DW and NI. The corresponding microstructure deteriorations with AS are more serious, and the resin ripples under higher S and AS are much more and bigger than with DW and NI. When the N reaches 2 million, the allowable S in S - N prediction curves is 69.28% f u , 68.72% f u and 60.75% f u with NI, DW and AS for 2 years, respectively. The corresponding allowable S in Whitney's method and Sendeckyj's method with a reliability of 95% is 73.39% f u , 72.72% f u , 68.55% f u and 65.00% f u , 65.93% f u , 54.41% f u , respectively. [ABSTRACT FROM AUTHOR]