Research On Thickness Variation Of Fiber Preform In Vacuum Infusion Molding Process

Vacuum infusion molding process(VIMP)is one of overall processfor large-scale compositespreparation.In this paper,the controlof thickness,one of the two major technical problems of the VIMP is studied.The influences of flow behavior,the number of layers,the post-injection process control,and the cure shrinkage of the resin on the thickness of the composites were investigated.The effect of single factor on the thickness of fiber preform was investigated by using seepage test of oil and epoxy resin.The one-dimensional flow is the basis of coupled flow,and the flow in the actual process is coupled flow.This paper investigates the variation of the thickness of preforms in two one-dimensional flow models(one-dimensional in-plane seepage and one-dimensional Z-direction seepage)and two coupled flow models(model A and model B).The results showed that the springback of the No.1 dial gauge was 0.062 mm,0.337 mm and 1.087 mm respectively when the injection was over in the 10,20 and 30 layers of fabric in one-dimensional in-plane seepage;the springback of the No.3 dial gauge was 3.500 mm,3.651 mm and 3.758 mm when the injection was over in the 10,20 and 30 layers of fabric in Z-direction one-dimensional seepage,respectively;the springback of the No.1 dial gauge was 0.533 mm,0.975 mm,1.354 mm,1.919 mm and 2.355 mm respectivelywhen the injection was over in the10,20,30,40 and 50 layersof fabric in the model A;the springback of the No.1 dial gauge was 0.544 mm,2.695 mm,4.915 mm and 6.590 mm respectivelywhen the injection was over in the10,50,100 and 150 layersof fabric in the model B.The variation rule of the fiber preform thickness in the post-injection stage was investigated when in the coupled flow models.The results showed that there are obvious differences between the two process control modes(continuous vacuum packing control and resin collector holding pressure control)in the post injection stage,the traction effect ofthe continuous vacuum packing control is stronger.The apparent shrinkage rate of the resin was defined as the free shrinkage rate of the resinin the preforms whenthe viscosity was low.The apparent shrinkage rate of the resin in the fiber preform was 3.15% by pipette simulation.The apparent shrinkage rate of the resin in the fiber preform was3.10% by seepage test of oil and epoxy resin.The thickness reduction caused by cure shrinkageof the fiber preform at the position of the No.1 dial gauge in the model A-10,model B-10,model A-50,model A-50 layers was 0.121 mm,0.127 mm,0.519 mm and 0.592 mm,respectively,by pipette simulation.The thickness reduction caused by cure shrinkageof the fiber preform at the position of the No.1 dial gauge in the model A-10,model B-10,model A-50,model A-50 layers was0.119 mm,0.125 mm,0.511 mm and 0.583 mm,respectively,by seepage test of oil and epoxy resin.The results show that the variation of fiber thickness will decrease the fiber volume fraction by about 2% in all simulation experiments and epoxy resin preparation experiments.