Effect of temperature on the dynamic young's and shear moduli of unidirectional carbon fiber-epoxy composite beams

The resonance frequencies of unidirectional carbon fiber reinforced/epoxy composite beams were studied over the temperature range 24–225°C. Longitudinal Young's moduli E₁₁ and longitudinal-transverse shear moduli G₁₂ were computed from the experimental data by the use of Timoshenko beam theory. The effects of transverse shear deformation (a function of E₁₁/G₁₂) were found to increase in importance with increasing temperature. Values of G₁₂ were found to be approximately proportional to the shear modulus G_m of matrix material but were about 30% lower than predicted by the theory of Hashin and Rosen. The anisotropy of the carbon filaments and voids in the composite samples were proposed to account for the discrepancy between theory and experiment.