Abstract
Liquid resin infusion processes are becoming attractive for aeronautic applications as an alternative to conventional autoclave-based processes. They still present several challenges, which can be faced only with an accurate simulation able to optimize the process parameters and to replace traditional time-consuming trial-and-error procedures. This paper presents an experimentally validated model to simulate the resin infusion process of an aeronautical component by accounting for the anisotropic permeability of the reinforcement and the chemophysical and rheological changes in the crosslinking resin. The input parameters of the model have been experimentally determined. The experimental work has been devoted to the study of the curing kinetics and chemorheological behavior of the thermosetting epoxy matrix and to the determination of both the in-plane and out-of-plane permeability of two carbon fiber preforms using an ultrasonic-based method, recently developed by the authors. The numerical simulation of the resin infusion process involved the modeling of the resin flow through the reinforcement, the heat exchange in the part and within the mold, and the crosslinking reaction of the resin. The time necessary to fill the component has been measured by an optical fiber-based equipment and compared with the simulation results.
Highlights
Fiber-reinforced plastics (FRPs) are experiencing widespread use in the aeronautical, automotive, marine, energy, and construction field where the need for materials that are stiff and light at the same time is constantly growing [1,2,3,4,5]
In liquid composite molding (LCM) processes, prepregs are replaced by dry fiber preforms, i.e., an assembly of dry fibers plies that have been pre-shaped to the form of the desired product [9,10], which must be impregnated with resin, either via resin transfer molding (RTM), at pressure higher than 1 bar, or liquid resin infusion (LRI), just under vacuum [11,12]
The experimental work has been devoted to the study of the curing kinetics and chemorheological behavior of the thermosetting epoxy matrix and to the determination of both in-plane and out-of-plane permeability of two carbon fiber preforms using an ultrasonic-based method recently developed by the authors
Summary
Fiber-reinforced plastics (FRPs) are experiencing widespread use in the aeronautical, automotive, marine, energy, and construction field where the need for materials that are stiff and light at the same time is constantly growing [1,2,3,4,5]. Materials 2020, 13, 4800 one-shot, the substantial reduction in tooling costs, the minimization of mold and laminate deformation during the process, and the reduced emission of volatile components into the workplace [13] Process challenges, such as consistent fiber impregnation, low porosity, and reduced filling time, can be faced only with a correct design of the process which is based on the analysis of resin flow during the infusion process [14]. Since the difference of permeability between the DM and the preform is very high, the resin flows in-plane first through the distribution medium and later within the preform following an out-of-plane direction with a resultant three-dimensional flow [26] For this reason, the through-thickness flow plays an important role in the mold filling process of large and geometrically complex composite laminates. The time necessary to fill the component has been measured by an optical fiber-based equipment and compared with the simulation results
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