Study On The Penetration Behavior Of Composite Siding During Liquid Moldin

The vacuum-assisted resin infusion process(VARI)for composite foam sandwich panels can significantly reduce the manufacturing cost of composite structures and improve weight reduction efficiency.The resin flow and infusion process in liquid composite molding(LCM)determine the mechanical performance and final thickness of the fabricated part.However,the resin infiltration behavior in the foam-core sandwich fabric preform is very complex due to the large size of the integral panel structure,the different thicknesses of the core area in the laminate zone,and the different infiltration characteristics and resin absorption in each region.In this dissertation,several scientific issues were investigated,such as the resin infiltration behavior and the mechanism of thickness variation in the aerospace foam-core sandwich structure wall panel.A method for characterizing,predicting,and regulating the infiltration behavior during the VARI liquid molding process was proposed and further verified by experiments.The main innovative work includes the following.(1)The hyperelastic fiber bundle model was applied to the numerical simulation of the unit cell at the mesoscale.A numerical algorithm for generating the microstructure of the fabric-foam interface was proposed to accurately describe the structural properties of the interface.In addition,a computational model for the permeation process considering the effect of the fabric-foam interface was established.The experimental results showed that the model could accurately capture the permeation behavior in composite foam sandwich panels.(2)The uniformity of resin permeation of composite foam core sandwich panels was characterized by the upper and lower pressure difference and the upper and lower time difference.The permeation behavior for three types of core structures,namely no treatment,perforated treatment,and slotted treatment,was analyzed by combining the resin permeation model and experiments.The combination of perforated treatment and infiltration network was selected as the structural form to regulate the infiltration process,and the parameters of perforated and infiltration network structure were further determined by experiments.(3)In order to consider the accuracy of thickness control and the unevenness of parts,a liquid molding injection method with zero resin-out effect was proposed,based on which a laminate thickness variation model was established,and its prediction value was consistent with the trend of test results.The optimal infiltration time was determined by combining with examples.In addition,a method for controlling zone thickness was developed based on the effect of excipients on resin flow rate.The tests showed that the thickness of the parts was uniform,and the deviation was within ± 5%,which was in accordance with the design tolerance.(4)Taking a high thickness foam-core sandwich panel as an example,the resin flow front and thickness were regulated by the integrated adjustment of the flow guide net,perforated isolation film and reducer belt,and the application of zero resin discharge process.The profile of the flow front of the resin was uniform,without the phenomenon of wrapping the flow front,which avoided the problem of resin accumulation on the front profile and achieved the accurate regulation of the flow front of the resin in a thick foam sandwich panel.The maximum deviation of laminate thickness was 2.49%,which met the requirement of ±5% design tolerance,and the deviation of weight was-1.39%,which met the requirement of ±10% weight tolerance.