Filling Time Reduction in Liquid Composite Molding Processes

Abstract

The quality of Liquid Composite Molding (LCM) manufactured components is strictly related to the fibrous preform impregnation. As Darcy’s law suggests, the resin flow is influenced by the pressure gradient, geometrical features of the reinforcement, and resin viscosity. The former two parameters are dictated by the requirements of the component and other constraints; therefore, they are hardly modifiable during the process. Resin preheating increases its fluency, thus enhancing the impregnation and saturation flow, and reducing the mold filling time. In the present work, a microwave heating system has been integrated within a vacuum bag resin infusion process, to analyze the effect of the online preheating on the fiber impregnation. To monitor the resin flow a dielectric sensors-based system is used. Results from resin infusion tests conducted with and without the resin pre-heating were compared: the outcomes indicated an advance of approximately 190 s of the flow front when microwave heating is applied with respect to the unheated tests.

An Overview of the Measurement of Permeability of Composite Reinforcements

“…In many cases, visual monitoring is used to validate other measurement techniques [ 64 , 65 , 66 , 67 , 68 , 69 , 70 ]. Its main limitation is the impossibility of observing flow inside the composite structure, especially when a large sample is considered; however, it remains the simplest and most cost-effective method for permeability measurement.…”

“…Rubino et al [ 65 ] employed three dielectric sensors to monitor resin flow and to compare resin infusion with and without resin preheating by a microwave heating system. The analyzed sample consisted of twelve layers of glass twill 2/2 fabric infused with epoxy resin, while the dielectric sensors were formed by two square copper plates (25 × 25 mm 2 ).…”

Crush core forming: An innovative technology to manufacture structural sandwich parts with variable thickness

“…Sandwich panels usually are produced by means of autoclave processes bonding the composite skins with the core under the action of pressure and heat, however in the last years new pre-pregs, which can be processed by out-of-autoclave (OoA) techniques and can be cured under vacuum condition and with conventional ovens, have been commercialized [2,3]. Moving from the autoclave manufacturing toward OoA processes allows to significant cost saving and faster production routes without sacrificing the performances of the components [4][5][6][7]. Despite these progresses, composite sandwiches are commonly produced only in simple shape and have constant thickness.…”