A methodology to reduce variability during vacuum infusion with optimized design of distribution media

Abstract

a b s t r a c t Seemann Composites Resin Infusion Molding Process (SCRIMP) is a widely used version of VacuumAssisted Resin Transfer Molding (VARTM) in which a highly permeable layer (distribution media) is placed on top of the dry preform to distribute the resin with very low flow resistance to reduce the filling and hence the manufacturing time. The flow patterns during filling may vary from part to part due to the variability associated with the material, part geometry, and layup of the assembly, which may result in race-tracking channels. The process is considered as reliable and robust only if the resin completely saturates the preform despite changing filling patterns caused by flow disturbances.The resin flow pattern can be manipulated with a tailored distribution media layout as it does impact the flow patterns significantly. The continuous distribution media layout over the entire part surface works well for very simple geometries with no to little potential for race-tracking along the edges. In this study we address complex cases, which require placement of an insert within the assembly, which will introduce race-tracking along its edges, and hence uniform placement of distribution media over the entire top surface will fail to yield a void free part. We introduce a methodology using a predictive tool to design an optimal shape of distribution media, which accounts for the flow variability introduced due to race-tracking along the edges of the inserts. This iterative approach quickly converges to provide the placement of distribution media on selective areas of the preform surface that ensures complete filling of the preform despite the variability. This approach has been validated with an experimental example and will help mitigate risk involved in manufacturing complex composites components with Liquid Molding.

In situ resin age assessment using dielectric analysis and resin cure map for efficient vacuum infusion

“…VI can be a cost-effective alternative to the conventional autoclave prepreg process, especially for the manufacture of large and complex unitized composite structures [1][2][3][4][5][6][7][8]. In VI, a dry fiber preform is placed on a one-sided rigid mold and sealed with a flexible vacuum bag, and resin is infused into the preform under vacuum pressure, then heated and cured [6][7][8][9][10][11][12]. Interest in VI has grown rapidly in recent years, particularly in the aerospace industry, which seeks to reduce the manufacturing costs associated with prepreg processing.…”

“…Interest in VI has grown rapidly in recent years, particularly in the aerospace industry, which seeks to reduce the manufacturing costs associated with prepreg processing. However, because vacuum pressure alone is applied during infusion, VI involves much slower infusion rates and thus longer fill times relative to resin transfer molding (RTM), in which resin is injected under positive pressure [1,6]. Inserting a high-permeability flow distribution medium on top of the preform (e.g.…”

“…Inserting a high-permeability flow distribution medium on top of the preform (e.g. SCRIMP, Seemann Composites Resin Infusion Molding Process) can enhance resin flow and reduce fill times, but also can induce unacceptable void contents, particularly for large parts with complex geometries [1,6]. To mitigate this issue, resin is often heated during filling, although doing so increases resin degree of cure and viscosity with flow time and distance [1,13].…”

Experimental investigation of a method to avoid channel marks during vacuum infusion

“…An advantage of this flow media is that the partly very large fibre composite components are additionally impregnated in the laminate thickness direction. 1 However, additional resin is also needed, which must be removed from the component after the infusion with the flow media. Thus, the additional resin is necessary only for the infusion process, but does not contribute to the finished component from a mechanical viewpoint.…”

Process Induced Defects in Liquid Molding Processes of Composites

“…The tailored solution for the part geometry ensures successful filling despite the presence of race tracking. Recently, Sas et al (2015) introduced an optimum distribution media layout design method for successful filling for all possible disturbances caused by different race tracking scenarios around inserts. A tree search algorithm was adopted via discretization of the domain into finite regions to define the distribution media design.…”