Geometric model of multi-axial warp knitted composite preform

With a view of better understanding the microstructure of complex multi-axial warp knitted composite preform,a modular construction geometric model of multi-axial warp knitted composite preform with chopped strand mat was developed based on the further research on the structure of multi-axial warp knitted composite preform and the analysis of its microstructure by reasonable hypothesis.According to the model,the relation between geometric parameters and process variables was derived,and the theoretical fiber volume fraction formula of the preform was worked out.Furthermore,using multi-axial warp knitted composite preforms of different specifications as samples,the theoretical value of fiber volume fraction was calculated rapidly by using CAD software.Comparing the theoretical value with the experimental value,it indicated that they were in good agreement,which means that the model was practical.Finally,the factors leading to deviations between theoretical value and experimental value were analyzed,they were mainly attributed to the ideal assumption of the preform,the resin-rich zones in the composites after molding and so on.