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Non-isothermal infusion processes can suffer from inhomogeneous cure, causing undesirable residual stresses or deformations. Heat transfer phenomena have been thoroughly described for double sided, rigid mold infusion but are still less explored for single sided, rigid mold infusion such as vacuum bagging techniques. In this study, an analytical through-the-thickness temperature gradient model derived for resin transfer molding is proposed and implemented numerically. An experimental validation study has been performed using representative set-ups of typical vacuum bagging processes. The results demonstrate that the analytical model can reproduce the through-the-thickness temperature gradient of the tests with good accuracy despite its simplified thermal problem description and numerical implementation.

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The concept stage in the design for a new composite part is a time when several fundamental decisions must be taken and a considerable amount of the budget is spent. Specialized commercial software packages can be used to support the decision making process in particular aspects of the project (e.g. material selection, numerical analysis, cost prediction,...). However, a complete and integrated virtual environment that covers all the steps in the process is not yet available for the composite design and manufacturing industry. This paper does not target the creation of such an overarching virtual tool, but instead presents a strategy that handles the information generated in each step of the design process, independently of the commercial packages used. Having identified a suitable design parameter shared in common with all design steps, the proposed strategy is able to evaluate the effects of design variations throughout all the design steps in parallel. A case study illustrating the strategy on an industrial part is presented.

In the past, simulation of liquid composite moulding processes was often based on the assumption that resin viscosity could be implemented as a constant value. However, viscosity can be subject to changes during the infusion process and now, non-constant and process parameter dependent expressions have become more common in simulation practice. Nevertheless, even with the inclusion of more advanced resin viscosity models, the prediction of flow front propagation in large, thick composite parts or in slow infusion processes is often still inaccurate when compared to the real application. Discrepancies are found to be most pronounced in the final stages of the infusion process, exactly where high accuracy predictions are 670 Appl Compos Mater (2012) 19:669-688 most valued. A new simulation method based on an infusion time-dependent resin viscosity expression is proposed in this work. The method not only incorporates nonlinear viscosity behaviour, but also takes into account the impact of reinforcement fibre sizing and fibre bed architecture on resin viscosity characteristics. Such fibre bed effects are not identifiable in neat resin viscosity characterization tests but are thought to have substantial impact on in-situ viscosity values during infusion, especially for large, thick composite part applications and slow infusion processes. An application case study has been included to demonstrate the prediction capability of the proposed simulation method. The design of an infusion process for a composite pressure vessel was selected for this purpose. Results show high predictive power throughout the infusion process, with most pronounced benefit in the final infusion stages.