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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.

In selective laser etching for the interfacial strengthening of Fiber Metal Laminates (FMLs), the wettability of customized structured features significantly affects their overall mechanical properties. For two-level features, their complicated geometry makes the evaluation of wettability difficult, which introduces challenges to feature design. In this study, a sandwich FMLs comprising an AA2024-O metal skin and a plain-woven carbon-fiber fabric core is investigated. Three types of two-level feature interfaces are designed and introduced into the FMLs structure. To understand the effect of two-level features on the resin flow and dynamic wetting progress in resin transfer molding, two-phase flow Computational Fluid Dynamics numerical models coupled with porous media and level-set numerical methods are built. The feasibility of the numerical simulation in the qualitative analysis was verified by comparing the results with those of the testing porosity values from X-ray scanning. In addition, the mechanisms of pore formation and transportation are revealed. These results indicate that the deeper groove structure in the etched features plays an important role in discharging residual air and determining the transformation of pores to reduce porosity. The permeability orientations of the porous media and surface structure both have significant impacts on the flow behavior and formation of pores. [ABSTRACT FROM AUTHOR]

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]

This numerical study aims to investigate the influence of I and T-shaped empty channels’ geometry on the filling time of resin in a rectangular porous enclosed mold, mimicking the main operating principle of a liquid resin infusion (LRI) process. Geometrical optimization was conducted with the constructal design (CD) and exhaustive search (ES) methods. The problem was subjected to two constraints (areas of porous mold and empty channels). In addition, the I and T-shaped channels were subjected to one and three degrees of freedom (DOF), respectively. Conservation equations of mass and momentum for modeling of resin/air mixture flow were numerically solved with the finite volume method (FVM). Interaction between the phases was considered with the volume of fluid method (VOF), and the effect of porous medium resistance in the resin flow was calculated with Darcy’s law. For the studied conditions, the best T-shaped configuration resulted in a filling time nearly three times lower than that for optimal I-shaped geometry, showing that the complexity of the channels benefited the performance. Moreover, the best T-shaped configurations were achieved for long single and bifurcated branches, except for configurations with skinny channels, which saw the generation of permanent voids.

Although various simulations have been conducted for the vacuum infusion process, most of the studies have considered only fabrics and flow medium and ignored the effect of peel ply. However, peel ply can affect resin flow because it is placed between the fabrics and flow medium. To verify this, permeability of two types of peel plies was measured, and it was found that the permeability between the peel plies differed significantly. Moreover, the permeability of the peel plies was lower than that of the carbon fabric; thus, peel ply can cause a bottleneck in the flow in the out-of-plane direction. Some 3D flow simulations were conducted in cases of no peel ply and for two types of the peel plies to confirm the effect of peel ply, and experiments were also conducted for two types of the peel plies. It was observed that filling time and flow pattern were highly dependent on the peel plies. The smaller permeability of peel ply has, the greater effect of peel ply is. These results indicate that the permeability of peel ply is one of the dominant factors and should be considered in process design in vacuum infusion. Additionally, by adding one layer of peel ply and applying permeability, the accuracy of flow simulations can be improved for filling time and pattern.

This article presents the numerical analysis and experimental investigation for the manufacturing of a foam core sandwich spoiler by vacuum-assisted resin injection (VARI) process. To find an injection scheme that guarantees both a good impregnation of the preform and a filling time compatible with the process window, the finite element model (FEM) was applied to analyze the effect of different injection schemes on the resin flow front patterns. Based on the obtained results, two optimal injection schemes are selected to form the spoiler structure. The experimental results show that the best molding quality can be achieved from the thick-end injection with a thin-end exit scheme. The comparison between simulation and experimental results shows that the overall deviation of the numerical analysis on resin flow time is 15.9%. [ABSTRACT FROM AUTHOR]

Since the existence of the complicated coupling between mould compression and resin flow, the full 3D simulation of the filling process in force-controlled compression resin transfer moulding (CRTM) has not been realized, especially when the resin flow front is irregular on the thickness direction during thick part moulding. In this paper, the coupled resin flow and mould compression behaviors are investigated firstly, a equivalent spring method is proposed to describe the preform compaction. The lubrication effect is taken into account, so the mould compression speed can be determined when the resin flow front is irregular on the thickness direction. Then the Volume of Fluid (VOF) two-phase model is established to express the resin-air flow in narrow gap and preform simultaneously, in which the narrow gap is considered as 3D area without flow resistance. Finally, the 3D numerical method for solving the above mathematical models is developed. In this method, the changing of the mould cavity is simulated by moving mesh technology, and the master-slave element method is used to simulate the resin squeezing from the infiltrated preform. Comparisons with analysis results are provided to prove the correctness of the above method, and two 3D examples are given to demonstrate the simulating capability.

In liquid composite molding (LCM) processes such as resin transfer molding (RTM), particle distribution can be problematic as the particle fillers can be filtered by the reinforcement fibers during the resin infusion process. In this paper, the filtration of alumina and silica nanoparticles in the production of aramid fiber epoxy composites is characterized. The laminates are produced by in-plane RTM and the effects of selected process variables on the laminate particle distribution are investigated. The objective is to evaluate the assumption that nanoparticles due to their small physical size inherently do not filter in resin infusion processes. The nanosilica particles are found to effectively not filter, while the nanoalumina particles are much more sensitive to filtration as they formed microscale agglomerates as small as a few microns in size prior to injection. The filtration behavior follows a simple theoretical model for micro-scale particle filtration, already existing in the literature. For the filtration sensitive particles, it was found that the filtration is influenced by the preform fiber volume content. Other common process variables such as resin viscosity, particle concentration in the injected resin, and saturated resin flow time (resin overflow volume) are found to be filtration independent and do not change the filtration behavior. POLYM. ENG. SCI., 59:22-34, 2019., INTRODUCTION In liquid composite molding (LCM) processes, a resin matrix is injected into a fibrous reinforcement. Particle fillers are often added to the matrix to enhance or provide additional properties [...]

A vacuum infusion process was implemented to produce composite specimens from a random glass filament mat and an acrylic modified polyester resin curable upon irradiation with ultraviolet (UV) light. Through localized irradiation with UV light during the reinforcement impregnation, the viscosity of the flowing resin was increased selectively. This allowed converging–diverging flow patterns with defined inclusions to be realized and racetracking along reinforcement edges to be suppressed. The approach is based on radical photopolymerisation. Here, the degree of cure and the viscosity of the resin increase under direct irradiation, such that the resin gels and the flow stalls in a matter of seconds, but remain unchanged in areas covered with an opaque mask. While this study is concerned with the feasibility of the process, potential practical applications are in flow control for Liquid Composite Moulding, that is, compensation for local variations in the fiber volume fraction and permeability of reinforcements. [ABSTRACT FROM AUTHOR]