抄録
Carbon fiber reinforced plastics (CFRPs) are widely used as structural materials for commercial aircrafts because of their properties, such as strength and stiffness. The elastic constants of carbon fiber significantly influence the mechanical properties of CFRPs. Therefore, correct estimation of elastic constants of carbon fibers is an important issue. However, there have been some difficulties in estimating them due to their small size and mechanical anisotropy. The method known as resonant ultrasound spectroscopy (RUS) enables the determination of elastic constants by performing iterative calculations to match the experimentally obtained resonance frequencies with the numerically calculated ones. In this work, we determined the elastic constants of carbon fiber in unidirectional CFRP specimen by a vibration-mode-pattern-matching-assisted RUS. To ensure the consistency of vibration modes, vibration patterns were matched by assessing the cosine similarity between contour plots, which depict the vibration patterns obtained from the experiment and numerical analysis. To incorporate the viscoelastic properties of the polymer matrix into the calculation of elastic constants, dynamic mechanical analysis (DMA) tests are conducted to obtain the polymer’s viscoelastic properties. To identify the composite’s transversely isotropic viscoelastic material behavior, homogenization using a representative volume element (RVE) is performed. Six load cases are considered to obtain the master curve of five independent components of homogenized complex stiffness in the frequency domain. These homogenized properties are depicted by a generalized Maxwell model (GMM) for parametrizing user-defined material models implemented in numerical analysis. Overall, the elastic constants of carbon fibers are determined by using RUS, considering viscoelastic properties of the polymer matrix of CFRPs. The proposed method can assist material designers in accuracy and efficiently determining the elastic constants of CFRPs and its carbon fibers with accurate analysis considering polymer’s viscoelastic properties.
