A Closed Form Solution for Flow During the Vacuum Assisted Resin Transfer Molding Process

Abstract

A closed form solution to the flow of resin in vacuum assisted resin transfer molding process (VARTM) has been derived. VARTM is used extensively for affordable manufacturing of large composite structures. During the VARTM process, a highly permeable distribution medium is incorporated into the preform as a surface layer. During infusion, the resin flows preferentially across the surface and simultaneously through the preform giving rise to a complex flow front. The analytical solution presented here provides insight into the scaling laws governing fill times and resin inlet placement as a function of the properties of the preform, distribution media and resin. The formulation assumes that the flow is fully developed and is divided into two regimes: a saturated region with no crossflow and a flow front region where the resin is infiltrating into the preform from the distribution medium. The flow front region moves with a uniform velocity. The law of conservation of mass and Darcy’s Law for flow through porous media are applied in each region. The resulting equations are nondimensionalized and are solved to yield the flow front shape and the development of the saturated region. It is found that the flow front is parabolic in shape and the length of the saturated region is proportional to the square root of the time elapsed. The results thus obtained are compared to data from full scale simulations and an error analysis of the solution was carried out. It was found that the time to fill is determined with a high degree of accuracy while the error in estimating the flow front length, d, increases with a dimensionless parameter ε=K2xxh22/K2yyd2. The solution allows greater insight into the process physics, enables parametric and optimization studies and can reduce the computational cost of full-scale 3-dimensional simulations. A parametric study is conducted to establish the sensitivity of flow front velocity to the distribution media/preform thickness ratio and permeabilities and preform porosity. The results provide insight into the scaling laws for manufacturing of large scale structures by VARTM. [S1087-1357(00)02002-5]

Mechanical and thermal properties of MWCNT-reinforced epoxy nanocomposites by vacuum assisted resin transfer molding

“…Composite forming methods include press molding, hand lay-up, extruding, and resin transfer molding. Vacuum assisted resin transfer molding (VARTM) provides advantages of low cost, easy forming, continuous production, the possibility of manufacture of various forms, and mass production of composites such as flat shapes is possible [18][19][20][21][22]. For example, thin film composites made via the VARTM method have various application fields ranging from potable supplies to electrode industries.…”

Experimental Validation of a Closed-Form Fluid Flow Model for Vacuum-Assisted Resin-Transfer Molding

“…(2) n The flow simulations can be either two-dimensional (2-D) or 3-D. In 2-D flow modeling [5][6][7], the flow of resin through the thickness is considered uniform, and the finite element discretization is applied along the other two directions.…”

“…In earlier work, a closed-form solution for the flow of resin in VARTM process was derived [2]. The analytical solution for 2-D porous media focuses on a representative cross section (x-y plane shown in Figure 2) consisting of the distribution layer (the high permeability material) and the structural layer (the preform material).…”

“…In addition, modeling and simulation of the flow can enable optimization of the process design variables, such as the cycle time and the distance between resin inlets as functions of the permeabilities of the distribution medium and the fiber preform, resin viscosity, and preform thickness. An analytical model [2] been developed previously that captures the important process physics.…”

Permeability characterization of stitched carbon fiber preforms by fiber optic sensors

“…This procedure requires a series of experiments in order to determine the optimal positioning of the resin injection gates and vacuum vents. To overcome critical manufacturing issues (dry zones) and optimize the process, some authors have developed numerical simulations able to model the resin infusion [1][2][3][4][5][6][7][8][9] during a VARTM process and active flow control methodologies to guarantee a filling uniformity [10,11]. To predict the resin flow and model accurately the process, key input parameter is the permeability behaviour of the dry reinforcement preforms.…”