Experimentally Validated Model Of The Unsaturated Resin Flow Considering Capillary Effects In The LCM Processes

Liquid Composite Molding(LCM)is a promising manufacturing technology of composite material.With advantages of low cost,high efficiency and environment friendly,it has been widely applied in numerous fields such as aviation and automobile.The numerical simulation research of LCM process will promote the optimization of the process parameters effectively,it means that industries are able to improve the process quality at less cost of time and money.However,the current numerical model of resin flow in LCM process are not able to describe the resin flow state in the dualscale fiber preform accurately,and there is also a lack of effective approaches to measure the infiltration(i.e.resin saturation)of the fiber preform.This thesis has the following work to overcome these challenges.Firstly,this work established a calculation model of the resin flow in dual-scale fiber preform.According to the structural characteristics of the dual-scale fiber preform,the governing equations were established in the inter-tow region and intra-tow region of the fabric respectively.Then a sink function was introduced to couple these two governing equations.To realize the simulation of resin flow in dual-scale fiber preform,the Finite Element/Control Volume method and an iterative algorithm were employed to solve the equations and track the flow front of the resin.Then,the numerical impregnation of unit cell of fiber tow was carried out to determine the sink term,the capillary pressure was introduced during this process.Base on the parameters such as sink term and permeability of the fabric,the one dimension constant flow rate mold-filling simulation was conducted to obtain the saturation curve in different filling time.In order to verify the reliability of this dual-scale model,the image processing method was utilized to measure the resin saturation curve during the infiltration of the fabric.The comparison between the experimental data and simulation results reveal that the model could simulate the resin flow in dual-scale fiber preform precisely.The result also indicates that capillary pressure can't be neglected in the flied of unsaturated flow of resin into a dual-scale porous fabric.Lastly,the flowing property of resin into a dual-scale porous fabric was analyzed use the example of 2-dimensional radial unsaturated flow in LCM processes.The pressure distribution and time-varying resin flow front were obtained and compared with the results of theoretical prediction of single-scale model.The simulation results show that during unsaturated flow process,pressure and pressure gradient drop significantly in the unsaturated region;the length of unsaturated region increases firstly and then keeps constant,when the saturated flow front reaches the exit the length begins to decrease;when there is a difference in permeability of two principal direction,the length of unsaturation region in direction of higher permeability is longer and the time to completely infiltrate the fabric depends on the smaller permeability.The research results have significance to reasonably predict the pressure distribution and the infiltration of the fiber preform in the resin filling process.