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Carbon fiber reinforced polymer composites are drawing great attention in the automotive industry due to their lightweight, high stiffness/strength properties. Fiber reinforced prepregs in various fabric architectures are preformed to a designed part shape before a final compression molding of the parts. Most of the current numerical simulation techniques are developed for woven composites, which are fabricated with bi-axial fiber orientations. There is no modeling technique for braided and NCF (Non- Crimped Fabric) prepregs with tri-axial fiber directions. In this paper, the authors’ previous work on bi-axial woven prepregs is extended to model the tri-axial braided prepregs based on a one-step analysis approach. The algorithm developed for this analysis treats the matrix and fibers as different materials. Any material model in the commercial FEA software can define the matrix, while the fiber is modeled as an elastic material. The material deformation on the final formed part is obtained by using the minimum energy method. This feature has been successfully implemented in LS-DYNA and can be activated by the modified keyword: *DEFINE_FIBERS. No tooling information is needed for the model setup. The initial prepreg shape and size can be obtained based on the final part geometry. The prediction accuracy and computational efficiency of the developed one-step analysis is demonstrated through modeling the preforming of a double dome part. Good agreement is obtained in the initial prepreg size prediction when compared to experimental data.

Automotive parts made with injection molding of carbon fiber reinforced polymers (CFRP) have shown significant advantages in lightweight vehicle development. Featured with balance between performance and cost, injection molded CFRP components are suitable for various automotive components. However, most concurrent computer aided engineering (CAE) analysis of such components still adopts homogeneous and isotropic cards for composites materials. Often is the case that high safety factor have to be used during design practice for composites parts due to incapability of accounting for anisotropic material behavior, which limits the application of the CFRP materials. While numerous studies have demonstrated the prediction of anisotropic material properties for fiber reinforced polymers through fiber orientation prediction and micromechanics calculation, validation is rarely done on an actual automobile part with complex geometry, which constrains the confidence of design engineers to perform analysis with anisotropic material properties for CFRP parts. In order to bridge such gap, in the present study, a vehicle part is manufactured using PA66/carbon fiber composites through injection molding process. Tensile tests are performed on samples cut from different locations of the part. Injection molding simulation based on actual processing parameters is performed to provide the fiber orientation predictions. The anisotropic elastic properties throughout the parts are obtained through the combined usage of micromechanics and orientation tensor averaging procedures to provide the anisotropic elastic properties in the parts, which are varying from element to element. A mapping process is also developed to transfer properties between the different meshes used in processing simulation and structural finite element analysis (FEA). To compare with the experimental results and validate the prediction of anisotropic elastic properties, the part model in FEA is virtually cut at the same locations as the real experiment samples to provide tensile bar FEA models, which enables FEA simulated tensile tests. Good match is observed between the experiments and FEA simulations at coupon level tests, indicating the accuracy of predicted anisotropic elastic properties from prediction.