Mechanical properties of pultruded CFRP plates at elevated temperatures

The use of fibre-reinforced polymer (FRP) composites is becoming increasingly widespread in civil infrastructure for strengthening and repair applications as well as whole FRP members and structures. A question which, however, continually arises from all stake-holders is the performance of FRP materials under elevated temperatures. An accurate understanding of the material properties and behaviour of FRP at such high temperatures is crucial, and they are necessary pieces of information that are surprisingly scarce in the literature. This paper therefore presents the mechanical properties of pultruded carbon fibre-reinforced polymer (CFRP) plates at elevated temperatures. More specifically, CFRP pultruded plate coupons were tested at steady and transient states for temperatures ranging from approximately 20 to 700 °C. The tests showed that, for the temperature ranges 20–150 °C and 450–706 °C, reductions of the tensile strength of the pultruded CFRP plate occurred. Between these temperature ranges, the tensile strength decreased by a small amount, while at 300 °C the ultimate strength was approximately 50% of the room-temperature strength. In addition, the tensile strength of the plate was as low as 7% of the room-temperature tensile strength at the approximate peak temperature of 700 °C. Finally, an equation that relates the tensile strength of the plate to the entire tested temperature range which has been calibrated with all the test data is proposed.