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Compression resin transfer moulding (CRTM) has been widely used to manufacture automotive parts with reduced production cycle times. With the development of fast curing thermosetting resins, the CRTM process is a viable option for the high production rates in the transportation industry. However, the dynamic resin curing behaviour poses a potential risk of manufacturing defects in the part. In order to reduce the risk during the development of the tool and the process parameters, this paper proposes a modelling framework for the CRTM process when using fast curing resin systems. The work specifically focused on the coupling between heat transfer, resin cure, resin flow and preform compaction using a commercial code, PAM-RTM. The tool captures accurately the preform filling, temperature and resin pressure evolution during the injection and compression phase. The application of the framework was demonstrated for a complex 3D demonstrator. The predicted preform filling had an accuracy of 73% for the flow front evolution compared to the experimental results. This work demonstrates the validity of the framework proposed when dealing with resin systems that are challenging to process. [ABSTRACT FROM AUTHOR]

Impregnation and in-plane resin flow of film-stacking material under compression process were investigated. The understanding of this phenomenon is the key to optimize the impregnation process under pressure rollers in a double-belt press for organo-sheet production. The stack of carbon fiber woven fabrics and viscous fluid were compressed in a flat open-edge mold under various controlled conditions using a testing machine. The impregnation, in-plane flow, and pressure profile were characterized from the experimental observations. Furthermore, a theoretical model was developed to describe the impregnation and in-plane flow behavior. The model prediction showed decent agreement with the experimental data. The developed model will be useful to optimize the process parameters of double belt press process. [ABSTRACT FROM AUTHOR]

The present study investigated a numerical simulation of molding-defect formation during resin transfer molding using boundary element method and line dynamics. The proposed method enables to simulate small molding defects by increasing the node for required position during time evolution; thereby, the method computes high-resolution flow front without being affected by the initial mesh geometry. The method was applied to the radial injection RTM with single inlet, and it was confirmed by comparison with theoretical value based on Darcy’s law that the flow advancement was computed with high accuracy. In addition, the method was also applied to the flow advancement for inclusion problem with cylinder, and four-point injection problem. The simulated flow behavior, void formation, and shrinkage agreed with the results in references. Finally, the method was compared with experiments using two-point injection problem. The computed configuration of the flow front and weld line agreed well with the experimental results. [ABSTRACT FROM AUTHOR]

The depletion of fossil fuels is forcing the automotive, aerospace and transport industries to focus on increasing both energy efficiency and mileage per unit of fuel consumed. To this end, many fibre reinforced composite materials have been adopted. Among these, carbon fibre reinforced plastic (CFRP) is one of the most attractive materials given its high strength and rigidity. The mechanical properties of CFRP are influenced greatly by the fractions of reinforcements and matrix. In this study, a CFRP U channel was produced by hot compression moulding. The epoxy fraction was measured at different pressures and clearances. It was found that clearance is important for determining the mechanical properties and epoxy flow. When the clearance is ≧1, the mechanical properties at the side positions decrease to 250-400 MPa. For the clearance of 0·7, the thickness at the side positions decreases, thus allowing the bending stress to increase to 790-800 MPa. Macroscopic observation of the epoxy flow shows that clearance plays a dominant role in epoxy flow behaviour within the mould cavity and excessive pressure causes large quantities of epoxy to flow out of the mould. [ABSTRACT FROM AUTHOR]

In liquid composite molding (LCM) processes, the resin is injected into the mold cavity, which contains preplaced reinforcement fabrics, through openings known as gates, while the displaced air leaves the mold through openings called vents. Under nominal conditions, the last points to fill are chosen as vent locations. However, due to imperfect preform cutting and placement, gaps and channels may form along the edges and curvatures in a mold, offering a path with less resistance for resin flow. The faster advance of resin through these gaps and channels, a common disturbance known as racetracking, will cause the last filled regions to vary, which complicates the vent selection process. In this study, probabilistic racetracking modeling is used to capture last-filled region distribution over the mold geometry. Success criteria for mold filling are defined in terms of dry spot tolerances, and vent fitness maps, which display potential vent locations, are created. Next, exhaustive search algorithm is coupled with vent fitness maps to determine optimal vent configurations. The map-based exhaustive search is demonstrated on three geometries and results are compared with existing combinatorial search results. The performance of the optimal vent configurations is evaluated in a virtual manufacturing environment. Sensitivity analyses are conducted to determine the influence of optimization parameters on the results. [ABSTRACT FROM AUTHOR]

In liquid composite molding processes, the resin is injected into a mold cavity containing preplaced reinforcement fabrics through openings known as gates, and the air leaves the mold through openings called as vents. Under nominal conditions, the last points to fill are chosen as vent locations. However, due to imperfect preform placement, gaps and channels may form along the edges and at curvatures in a mold, offering a path with less resistance for resin flow. The faster advance of resin through these gaps and channels, a common disturbance known as racetracking, will cause the last filled regions to vary, which complicates the vent selection process. We introduce a methodology that uses set and probability theories to forecast racetracking conditions in a mold and have developed a combinatorial search algorithm to locate corresponding optimal vent locations. The accuracy, efficiency and usefulness of the approach is illustrated with three case studies. [ABSTRACT FROM AUTHOR]