Numerical Simulation Of Resin Flowing In Shell-shaped Fiber Preform

In early studies of Liquid Composite Molding(LCM)process,the resin filling process is assumed to be the problem of the Newtonian fluid flowing in single-scale porous media fiber preform,and the area where the resin arrives is completely saturated.But the dual-scale porous media characteristic of the fiber preform is presented in the LCM process,where there is a semi-saturation region near the flow front in the filling process.It is a challenge to the previous hypothesis for the semi-saturation phenomenon.Based on the semi-saturation phenomenon,the mathematic model with sink term is adopted to study the resin flowing in the dual-scale LCM process.Due to the disadvantages of time-consuming and high cost of experimental study,then the experimental studies are seldom conducted.The numerical simulation method is adopted to study the resin filling process.In this paper,the process of the resin flowing in the shell-shaped fiber preform is investigated.Based on the theoretical analysis,the MATLAB program is compiled and executed to simulate the process of resin filling in the shell-shaped fiber preform.The pressure distribution and the saturation distribution are obtained.The main research contents are as follows:1.The finite element method is introduced.The interpolation function of quadrilateral isoparametric element,tetrahedral element,curved shell element are introduced,and the finite element integral equation on the shell element is described in detail.2.The mathematical model is built.The mathematical model of the resin flowing in dual-scale LCM process is built by using the method of volume homogenization.And the expression of sink term is obtained by analyzing the resin flow in single cell.The control volume method is used to describe the resin flowing,and the finite element method is used to set up the finite element equation of the pressure field.3.The algorithm flow is designed.Based on the mathematical model of resin flowing,the algorithm flow in the process of resin filling is designed.The preform isseparated into the fixed finite element,the method of filling the node and the method of updating the next filling node are designed.When all the nodes are completely filled,the filling process ends.4.The process of numerical simulation is executed.The MATLAB program is compiled to simulate the process of the resin filling in the parabolic shell and hemispherical shell fiber preform.It is obtained that the pressure distribution,the change of the pressure value and the saturation distribution in the preform when the resin flow front reaches the different position.In the resin flowing process,the resin flow front appears semi-saturated area,this phenomenon reflects the dual-scale porous media characteristic of the fiber preform,and verifies the reliability of the program.Under the condition of constant pressure,when the resin flow front is close to the injection port at the initial injection,the pressure decreases rapidly and the curve gradient is very large of the pressure and flow front.With the filling process proceeding,the volume fraction of the resin in the preform is increased,the pressure decreases slowly and the gradient decreases.