Resin transfer molding is a popular manufacturing process for composite materials because of its ability to manufacture complex-shaped parts with high efficiency and low pollution. Despite the intense interest in the modeling and simulation of this process, minimization of mold filling time without losing the part quality remains an important issue in the resin transfer molding process. Various methods in the literature are suggested to achieve this. However, inappropriate injection methods lead to numerous air entrapments, and fiber mat deformation. In this study, we are interested in developing and improving new methods to optimize the cycle time. The effects of several parameters on the filling process are deeply investigated. A computer code based on the control volume finite element method is developed to study the mold filling process in all cases. The validity of the computer code used is checked by analytical results and close agreement is found.
: Liquid composites moulding processes are now widely used in the aeronautical and the aerospace fields. For the automobile sector, this type of processes is more and more used and still has very high potential. Optimizing moulding parameters, particularly the time cycle and improving the quality of the obtained parts, are key to increasing use of this type of process. When closing the mould in the LCM processes, the compression phase followed by the reinforcements' relaxation are important stages that influence all process parameters. This work presents a theoretical modelling based on two approaches. The results are compared to the experimental ones obtained within our laboratory. In the experimental results, the compressibility behaviour of the reinforcements according to their type; number of ply, lubrication and compression speed were studied. The test results highlight the influence of these parameters on the compressibility and the relaxation of the reinforcements and identify the nesting and the anisotropy as being two important factors. For the theoretical modelling, two approaches are proposed. In the first one, based on the equation of continuity, Darcy's law and the Terzhagui model; the total stress in the mould is equal to a viscous stress due to the fluid flow and an elastic stress due to the fibers response. The equation of Chen and Al, used to model elastic stress allows us to predict the compressibility of the impregnated reinforcements. The second approach is a rheological one where the models of Zener, Burger and Maxwell are used. The results analysis highlights the influence of some moulding parameters and fibrous reinforcement's compression rules. A good agreement is noted between the experimental and the theoretical compression curves of the fibrous reinforcements. The rheological model of Maxwell gives the best prediction of reinforcements behaviour in both compression and relaxation phase.
The use of composite materials with continuous fibers in the aeronautic and aerospace industries requires reliable and precise methods for the prediction of failure. Predicting failure stresses and failure modes in composite laminates is very difficult. The choice between failure criteria is complex, and there is a lack of experimental study to validate the result obtained partly because the biaxial tests are still difficult to perform. This work employs a mixed methodology based on a theoretical and an experimental approach to develop a procedure for the choice and the validation of the failure criterion. The comparison is concerned not only with the macroscopic failure but also with the succession of the failure, the failure mode, and the effect of the geometrical parameters of the test specimen. The most general failure criteria are tested by using two approaches of the stiffness reduction. A finite element code has been elaborated within our laboratory for postfailure treatment. The numerical simulation results are compared with the experimental ones and permit us to make a conclusion on the validity of the failure criteria used.
International audienceThe numerical simulation of mass and heat transfer model for the curing stage of the resin transfer molding (RTM) process is known as a useful method to analyze the process before the mold is actually built. Despite the intense interest in the modeling and simulation of this process, the relevant work is currently limited to development of flow models during filling stage. Optimization of non-isothermal mold filling simulation time without losing the efficiency remains an important challenge in RTM process. These were some reasons that motivate our work; namely the interested on the amelioration of the performance of RTM simulation code in term of execution time and memory space occupation. Our approach is accomplished in two steps; first by the modification of the control volume/ finite element method (CV/FEM) and second by the implementation in the modified code of an adapted conjugate gradient algorithm to the compressed sparse row storage scheme. The validity of our approach is evaluated with analytical results and excellent agreement was found. The results show that our optimization strategy leads to maximum reduction in time and space memory. This allows one to deal with problems with great and complex dimensions mostly encountered in RTM application field, without interesting in the constraint of space or time
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