In this study, we propose a FE model for dry fabric forming simulation that can express the tension dependent shear behavior in order to predict the wrinkles, one of the major forming defects. Automakers are gradually using more carbon fiber reinforced plastic (CFRP) in mass production cars, because the development of resin transfer molding (RTM) have reduced its cycle time to less than 10 minutes. Finite element analysis (FEA) is essential to the vehicle design process, so numerical simulation of CFRP is strongly desired today. Forming simulation is especially important, because the performance of the final composite part strongly depends on changes in fiber orientation during the preforming. Moreover wrinkle is one of the major defects in preforming. RTM usually involves fabric reinforcement. During forming of fabric, large in-plane shear deformations typically occur. The reason for this is that the shear resistance is very low at the initial stage, because the deformation is governed by yarn contact friction at the cross-sections. Accurately expressing the in-plane shear behavior of fabric is very important for accurate forming simulation. In most simulation models the shear resistance of fabric is assumed to be independent from the tension along the yarn. However, meso-model predictions of the picture frame and bias-extension tests suggest this to be an invalid assumption. In this study, a micromechanical model that introduces the stress component due to the yarn rotational friction is adapted to the dry fabric forming simulation. In other words, this can express the shear behavior that depends on the tensions in the yarns. The results using this micromechanical model are in good agreement with the meso-model results in the various boundary conditions. ．その † 原稿受理 平成25年9月10日 Received

Friction spot welding (FSJ) process is very complicated in the aspects of material flow, heat generation and joining mechanism. Compared with the friction stir welding (FSW) process for a butt joint, the FSJ process is used to join two pieces of plate in the direction of thickness. Although there are several papers describing simulation models for the FSW process, we cannot find any papers relating to simulation models for the FSJ process.In order to simulate the FSJ process efficiently, an axis-symmetric two-dimensional FEM model with an adaptive re-meshing algorithm is proposed. By using the proposed model, temperature distribution, joining shape of the transverse section including toe flash on the surface and hook on the joining interface, can be simulated. The simulated results agree well with those of the experiment. Furthermore, effects of clamp position and stirring direction on material flow and joining shape are investigated.

In this paper, we propose a new FE model of a carbon fiber reinforced thermoplastic (CFRTP) in order to capture the deformation during a thermoforming process because the thermoforming process of CFRTP has increased its presence in the automotive industry for its wide applicability to the mass production car. The proposed model can describe temperature dependent non-linear bending property of CFRTP by a set of elements which consists of two shell elements with membrane elements in between them. The membrane elements represent temperature dependent anisotropic in-plane behavior by calculating stress contributions of the textile reinforcement and thermoplastic in a parallel system. By applying Reuss model to the stress calculation of thermoplastic, the in-plane shear behavior which is the key deformation mode during forming can be accurately predicted. FE model is constructed based on the results of three point bending and bias-extension experiments which are conducted in the range of the process temperature. Thermoforming simulations are presented and compared to experimental results. Simulated outline and shear angle are in good agreement with experimental results. It will be shown by sensitivity study that the effect of the temperature plays an important role in deformation during a non-isothermal forming process.

Automakers are gradually using more carbon fiber reinforced plastic (CFRP) in mass production cars because the developments of resin transfer molding (RTM) have reduced its cycle time to less than 10 minutes. Carbon fabrics are usually used as a reinforcement in RTM. First, dry carbon fabric is placed between forming dies. Then resin is injected into the preformed dry fabric and cured to create the final composite part. It is well known that the performance of the final composite part strongly depends on changes in fiber orientation during the process. Moreover wrinkles and fiber failures are major defects which occur during processes so that preforming process simulation is very important to predict fiber orientation and forming defects.Compressive and bending properties play important roles in describing wrinkles. However, many of existing researches do not consider these effects in the simulation models. In the present study, we propose a model for finite element analysis that can consider compressive and bending properties as well as tensile and shear properties of dry fabric. We conduct the hemispherical preforming simulation and verify the proposed model by comparing the results to those of meso-scale modeling model in order to showcase the capability of the method for evaluating wrinkles, fiber failures, and changes in fiber orientation.

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