Cycling tests of a fibre-reinforced polymer honeycomb sandwich deck panel at very cold temperatures

The FRP deck panel with an overall geometry of 2.134×0.340×0.178 m was cyclically tested under a three-point loading setup in a cold room with the temperature as low as −55°C. The Classic Beam Theory (CBT) method and the Finite Element (FE) method were also used to predict the panel behaviour at room temperatures. Based on this research, the following conclusions were made: (1) The low-temperature stiffness was about 3.8% higher than at the high temperature as long as the low temperature was above a certain degree; (2) When the temperature was lowered from −20 to −55°C, the low-temperature stiffness decreased 11.5% comparing with the stiffness at room temperatures. This degradation in stiffness could not be recovered by raising the panel temperature; (3) During the ultimate load test at −55°C, the panel failed at 171.1 KN with a very loud noise. Visual inspections indicated the debonding of the face sheet finally led to the local buckling of the exterior plate on both sides of the panel; (4) Very cold temperature exposure resulted in matrix hardening, matrix micro-cracking and fibre-matrix debonding as demonstrated by the AE testing data at different temperatures; and (5) At the room temperatures, the FRP panel showed a little stiffer performance than both the CBT method and the FE method would predict.