Abstract
The variation in the viscous damping coefficient with the carbon fiber angle can be evaluated using the partial derivatives of the viscous damping coefficient with respect to the resonance frequency and modal damping ratio. However, the direct derivatives of the viscous damping coefficient were not effective solutions to the sensitivity analysis of carbon-fiber-reinforced plastic (CFRP) structures because the viscous damping from the binding matrix was not changed over the carbon fiber angle. If the identified viscous damping coefficients were assumed to be equivalent values from the parallel relationship between the binding matrix and carbon fiber, the relative error of the viscous damping coefficient of carbon fiber between the increased carbon fiber angle and reference angle could be used as the sensitivity index for the viscous damping coefficient of carbon fiber only. The modal parameters, resonance frequency, and modal damping ratio were identified from the experimental modal test of rectangular CFRP specimens for five different carbon fiber angles between 0° and 90°. The sensitivity of the viscous damping coefficient of carbon fiber was determined for two sensitivity indices: the direct derivative of the mass-normalized equivalent viscous damping coefficient and the relative error of the viscous damping coefficient of carbon fiber. The sensitivity results were discussed using the five mode shapes of the CFRP specimen, that is, three bending modes and two twisting modes.
Highlights
Variations in the dynamic characteristics of Carbon-fiber-reinforced plastic (CFRP) specimens were studied for three factors, i.e., temperature, spectral loading pattern, and carbon fiber angle, to derive the modal parameters from the representative measured frequency response function (FRF)
The experimental modal testing using an impact hammer was analyzed in the frequency domain so that the CFRP specimen suspended by the low static-stiffness rubber band did not distort the identified modal parameters (c) in a high-frequency range
The modal parameters identified from the experimental impact test were taken from a previous study [24], and sensitivity analysis was performed using the viscous damping coefficient instead of the modal damping ratio
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. The variation of system parameters, i.e., elastic modulus and modal damping coefficient, were investigated using seven CFRP specimens with different carbon fiber angles of 0◦ , 15◦ , 30◦ , 45◦ , 60◦ , 75◦ , and 90◦ [19]. The variations in both system parameters were measured using modular equipment and analyzed for two resonance frequencies. Variations in the dynamic characteristics of CFRP specimens were studied for three factors, i.e., temperature, spectral loading pattern, and carbon fiber angle, to derive the modal parameters from the representative measured frequency response function (FRF). The sensitivity results may be flawed if the effects of other damping factors are dominant compared with the viscous damping coefficient
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