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Finite element analysis is performed to virtually measure homogenized thermal conductivity of a thick 3D woven textile composite (T3DWC). Temperature-dependent thermal and mechanical properties of constituents are considered for the measurements over a wide range of temperature. A two-step homogenization approach is adopted here to simplify the analysis at the microscopic level without losing heterogeneity of the material at the macroscopic scale. First-step homogenization is carried out at a tow level using an analytical homogenization scheme. Fiber tows are homogenized and assigned with effective elastic and thermal properties. The solid tows are then implemented into a representative volume element considering the unique in-plane periodic fiber architecture of the thick composite material. Due to the unique in-plane periodicity, conventional periodic boundary conditions for thermal and mechanical loading conditions are reformulated. Anisotropic thermal conductivity of T3DWC is obtained from the second-step homogenization based on virtual thermal tests performed at ambient to elevated temperatures.

Battery-powered automobiles are emerging as a promising alternative to internal combustion engine vehicles in response to the internationally strengthening regulation on carbon dioxide emissions. Due to the heavy weight of the electric drive unit, the weight savings of the electric vehicles are often attempted on body structures by using lightweight materials such as fiber-reinforced composites with traditional metal alloys. In the present study, a new multi-material design of a battery pack structure is proposed and its performance is evaluated through random vibration fatigue tests. The fatigue tests are virtually performed on a full-scale finite element model of the battery pack. The virtual tests embody boundary and loading conditions required by a real industry specification. The vibration loading is specified in the form of a power spectral density and the fatigue analysis is conducted accordingly in frequency domain. The cumulative fatigue damage and lives of each component composing the batter pack structure are predicted. The present modeling approach could benefit the preliminary design of an automotive body structure because the performance evaluation on various prototypes can be efficiently conducted without a physical model.

Microstructural fracture behavior of a ceramic matrix composite (CMC) with nonuniformly distributed fibers is studied in the presentation. A comprehensive numerical analysis package to study the effect of nonuniform fiber dimensions and locations on the microstructural fracture behavior is developed. The package starts with an optimization algorithm for generating representative volume element (RVE) models that are statistically equivalent to experimental measurements. Experimentally measured statistical data are used as constraints while the optimization algorithm is running. Virtual springs are utilized between any adjacent fibers to nonuniformly distribute the coated fibers in the RVE model. The virtual spring with the optimization algorithm can efficiently generate multiple RVEs that are statistically identical to each other. Smeared crack approach (SCA) is implemented to consider the fracture behavior of the CMC material in a mesh-objective manner. The RVEs are subjected to tension as well as the shear loading conditions. SCA is capable of predicting different fracture patterns, uniquely defined by not only the fiber arrangement but also the specific loading type. In addition, global stress-strain curves show that the microstructural fracture behavior of the RVEs is highly dependent on the fiber distributions.

The main purpose of the present work is to demonstrate mechanical performance of a wet-compressionmolding (WCM) composite product through conventional compressive-strength-after-impact (CSAI) analysis. Biaxial non-crimp fabric (NCF) is utilized to manufacture laminated composite panels. Specimens are cut from the panels and tested to characterize fundamental mechanical properties of the NCF composite. The volume fractions of fibers and voids are also measured to evaluate the quality of the WCM product. Impact tests are carried out to examine impact resistance of the composite structure. Numerous impact characteristics at various energy levels are quantitatively measured. Internal failure patterns and damage extent are revealed via Xray CT. Compression tests on the impacted plates are followed to evaluate structural integrity and damage tolerance (SIDT). 3D DIC technique is employed and distinct buckling responses dependent on impact energy levels are successfully visualized. Experimental results are showing a promising potential of the WCM process as one of the alternatives to the conventional autoclave-based fabrication method.