Flexural Fatigue Behavior of Glass Fiber Reinforced Polymer-Balsa Sandwich Panels Under Hygrothermal Environment

GFRP-balsa sandwich structures with glass fiber reinforced polymer (GFRP) as face sheets and balsa wood as core are increasingly being used in the infrastructure field. But there are significant differences in the moisture absorption and thermal expansion properties of GFRP face sheets and balsa wood core, and the structures are susceptible to fatigue failure under hygrothermal environments and cyclic loading. In the paper, the fatigue behavior of GFRP-balsa sandwich panels under different temperatures with 95% relative humidity (RH) was investigated. Four-point bending fatigue tests were carried out to analyze the effects of load level, temperature, and aging time on the failure mode and fatigue life of sandwich panels. The results showed that the flexural fatigue failure modes of GFRP-balsa sandwich panels were mainly core shear damage and interface debonding, and the fatigue life decreased with the increase of load level, temperature, and aging time. Based on the test results and Weibull model, the fatigue life curves of the specimens under different survival rates were obtained (P-S-N curve). The cumulative damage model considering core shear modulus degradation was developed, which could predict fatigue damage evolution of the specimens after hygrothermal aging.