Models for predicting elastic modulus and tensile strength of carbon, basalt and hybrid carbon-basalt FRP laminates at elevated temperatures

• Mechanical properties of basalt and carbon FRP laminates with temperature.
• Carbon, basalt and carbon-basalt sheets were used.
• The elastic modulus and tensile strength were significantly reduced.
• Analytical models were developed to predict the mechanical properties as a function of temperature.

Basalt fiber-reinforced polymers (B) composite laminates have been extensively used over the last decade in externally strengthening of reinforced concrete (RC) slabs and beams in flexure and shear. Basalt fibers have higher thermal resistance, corrosion resistance, and ductility than the commonly used carbon (C) laminates. However, there is a lack of knowledge about the mechanical properties of such laminates and their hybrid combinations when exposed to elevated temperatures. This paper presents the results of an experimental program that studies the mechanical properties of carbon (C), basalt (B), and their hybrid combinations (BC, CBC, CCB, BBC, and BCB) of multiple layers at elevated temperatures. The experimental program consists of 140 coupon specimens were prepared and tested after being exposed to different temperatures ranging from 25 to 250 °C. The results showed that both the elastic modulus and the tensile strength of the C and B laminates degraded with the increase in temperature. However, the degradation was greater in the C composite sheets. Based on the experimental results, it was also observed that the mechanical degradation was the highest in C laminates, which reached to almost 90% at 250 °C. In addition, the elastic modulus and tensile strength values had shown that the BBC and B laminates had the highest mechanical performance when exposed to elevated temperatures. In addition, analytical models are proposed from the generated test data to predict the variation in the elastic modulus and tensile strength with temperature. The obtained results and proposed models can be used as input parameters in the analysis and design of externally strengthened members with such FRP laminates. This study strongly endorses the use of B and hybrid combination of B and C laminates in strengthening RC slabs and beams.