MOLD FILLING SIMULATION IN RTM PROCESSING OF NATURAL FIBER COMPOSITE MATERIALS

FRANCUCCI GASTON MARTIN; MORAN JUAN; RODRIGUEZ EXEQUIEL SANTOS

Enschede

Congreso; FLOW PROCESSES IN COMPOSITE MATERIALS; 2014

University of Twente

In order to manufacture high quality green composite parts, advanced processing techniques should be used. Liquid composite molding (LCM) techniques like resin transfer molding (RTM) or vacuum infusion (VI) have proven to be suitable for processing natural fiber/thermoset resin composites. Numerical modeling of the mold filling stage optimizes the process and reduces the production costs, since most of the trial and error involved in mold design (inlet and vents location) can be done rapidly in a computer program. Darcy?s law is widely used to model the fluid flow through a porous medium, and it is also extensively used in modeling flow processes in composite materials manufacturing. This law allows predicting the flow front position inside the mold cavity during the filling stage. Fluid viscosity and reinforcement permeability are the main properties involved in Darcy?s law. In contrast to synthetic fibers, the permeability of natural fiber reinforcements does not necessarily remain constant along the wetted region of the fabrics throughout the infiltration process, because the porosity can change as the fibers absorb fluid and swell. In this work, two models were proposed to simulate the flow front movement during the one dimensional RTM processing of composite materials reinforced with natural fibers. These models consider the effect of fluid absorption and fiber swelling on the porosity and permeability of the preform. The homogeneously variable permeability model, that was the first approach to model the process, considers that the permeability of the preform decreases with time due to fiber swelling, but the change in permeability is uniform throughout the entire wetted perform and is only a function of the injection time. On the other hand, the permeability field model, considers the fact that different regions of the wetted perform experience higher or lower fiber swelling depending on the amount of time that they have been immersed in the fluid. This leads to a field of permeability along the wetted fiber bed. The results showed that all models that take into account the swelling of the fibers predict a much slower flow front movement that the model that assumes that permeability is constant over time. The experimental data was much better fitted by the permeability field model than by the constant permeability model when a swelling fluid was used in the permeability test.