Compression and in‐plane shear testing of carbon‐epoxy composites at subzero and elevated temperatures: Experiment and modeling

Mechanical properties of carbon‐epoxy composites are highly affected by the operating temperature. In this study, the effect of temperature on the compressive strength and in‐plane shear strength of composites has been analyzed. The unidirectional composites are processed by filament winding using T700 carbon fiber rovings and two different epoxy resin systems. The compressive strength measured from combined loading compression tests showed a decreasing trend with an increase in temperature. The compressive strength decreased from 700 to 400 MPa when the temperature increased from –20 to 150°C, which represents 54% reduction in strength. The in‐plane shear tests were performed using longitudinal and transverse extensometers and found that shear strength decreased by nearly 50%. Fractography of compression samples revealed that the primary compressive failure mode is micro buckling followed by kinking, at all temperatures. The existing micro mechanical model based on microbuckling and kinking for estimating the compressive strength has been modified to include temperature effects. The key model input parameters are temperature‐dependent resin tensile modulus and in‐plane shear strength. It is found that the modified model will predict the temperature‐dependent compressive strength in the temperature range of −20 to 150°C. Highlights Compressive strength decreased from 700 MPa at −20°C to 400 MPa at 150°C. Microbuckling followed by kinking failure was observed at all temperatures. In‐plane shear strength decreased from 44 MPa at −20°C to 27 MPa at 150°C. Resin tensile modulus decreased from 2.5 GPa at −20°C to 0.75 GPa at 150°C. Analytical model for compressive strength was extended for all temperatures.