Effect of Injection Rate and Post-Fill Cure Pressure on Properties of Resin Transfer Molded Disks

Abstract

The effects of flow rate andpost-fill cure pressure, i.e., packing pressure, on the mechanical properties of resin transfer molded disks are experimentally investigated. An experimental molding setup is constructed to fabricate fiber-reinforced, center-gated, disk-shaped composite parts. Disks are molded at different flow rates and packing pressures in order to observe the effects of these parameters on the mechanical properties andvoidcontent of the final parts. Specimens are cut from three different locations in the molded disks for testing. Specimens from the first two locations are tensile testedto obtain strength and stiffness properties, and the third location is usedfor microscopic analysis to determine void content and void properties. Increased injection rate is found to reduce both the strength and stiffness of the molded parts due to more voids induced by the faster moving fluidfront. Packing pressure is also foundto have a significant effect on specimen properties. At higher packing pressures fewer voids and improved strength andstiffness are observed. Mechanical properties are correlatedwith total void fraction for disks molded at different packing pressures. Exponential decrease in both tensile strength andelastic modulus is observedwith increasing voidfraction. Doubling the voidvolume fraction from 0.35 to 0.72% results in a 15% decrease in strength and a 14% decrease in stiffness. The results demonstrate that selection of suitable injection rate and addition of packing pressure to resin transfer molding (RTM) process can improve mechanical properties of molded parts considerably.

Keywords

resin transfer molding packing pressure voids injection rate

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