Flexural creep test and prediction of GFRP-balsa sandwich beams

The application scope of the glass fiber reinforced plastic (GFRP)-balsa sandwich structure composed of GFRP facings and a balsa wood core is constantly expanding in the field of infrastructure. However, GFRP-balsa sandwich structures are susceptible to creep deformation due to their viscoelasticity. Under the controlled temperature of (25±1)℃ and relative humidity of 55%±5%, the three-point flexural creep performance of the GFRP-balsa sandwich beams at 20%, 25% and 30% load levels were tested for a period of 3000-8760 h using the self-designed flexural creep loading devices. Various models were used to simulate and predict the creep response of the GFRP-balsa sandwich beams. The results show that the GFRP-balsa sandwich beams exhibit linear viscoelasticity at the test load levels. Flexural creep has an important impact on the mid-span deflection of the GFRP-balsa sandwich beams, and the creep coefficients at 3000 h of all the specimens are not less than 0.35. The Findley model is applicable for fitting the time-dependent total deflection of the GFRP-balsa sandwich beams at a single load level, and the maximum relative error between the fitting value and the test value at 3000 h is only 0.7%. The Bailey-Norton model and the general power law model are applicable for predicting the creep deflection and the time-dependent total deflection of the GFRP-balsa sandwich beams when the load level does not exceed 30%, respectively. At one year, the maximum relative error between the predicted value of the Bailey-Norton model and the test value is 8.3%, and the maximum relative error between the predicted value of the general power law model and the test value is 5.9%.