RTM Process Research Articles

Contribution to manufacturing control of particle-filled composites by RTM process

Contribution to manufacturing control of particle-filled composites by RTM process

Thermoviscoelastic modelling of highly reactive thermoset resins for liquid moulding applications

This paper presents a methodology for developing thermo-mechanical properties model for highly reactive resins and its use for Resin Transfer Moulding process (RTM) modelling and prediction of residual stresses. Cure Hardening Instantaneously Linear Elastic (CHILE), and Thermoviscoelastic (TVE) models, were implemented to analyze the mechanical behaviour of the resin. Simulation of the RTM process was developed and applied to a representative curved plate geometry. An integral approach was considered where the degree of cure gradient, generated during the filling stage due to the reactivity of the resin, was implemented as initial condition of the stress-deformation process simulation. The validation process included fabricating experimental parts with the representative geometry. The degree of cure variation of highly reactive thermosets during injection caused a significant effect on the final shape of the parts. These effects were captured by the simulations, where the TVE model showed a more accurate prediction of the part distortion.

Hybrid twin of RTM process at the scarce data limit

Hybrid twin of RTM process at the scarce data limit

Towards a numerical modeling of the coupling between RTM process and induced mechanical properties for rigid particle-filled composites

Towards a numerical modeling of the coupling between RTM process and induced mechanical properties for rigid particle-filled composites

Gel Point Determination in Resin Transfer Molding Process with Fiber Bragg Grating Inscribed in Side-Hole Elliptical Core Optical Fiber.

Material as well as process variations in the composites industry are reasons to develop methods for in-line monitoring, which would increase reproducibility of the manufacturing process and the final composite products. Fiber Bragg Gratings (FBGs) have shown to be useful for monitoring liquid-composite molding processes, e.g., in terms of online gel point detection. Existing works however, focus on in-plane strain measurements while out-of-plane residual strain prevails. In order to measure out-of-plane strain, FBG inscribed in highly birefringent fiber (HB FBG) can be used. The purpose of this research is the cure stage detection with (a) FBG inscribed in single mode and (b) FBG inscribed in highly-birefringent side-hole fiber in comparison to the reference gel point detected with an in-mold DC sensor. Results reveal that the curing process is better traceable with HB FBG than with regular FBG. Thus, the use of HB FBG can be a good method for the gel point estimation in the RTM process.

Effects of the Interlayer Toughening Agent Structure on the Flow Behavior during the z-RTM Process.

In this paper, interlayer toughening composites were prepared by the z-directional injection RTM process (z-RTM), which has the advantage of increasing the interlaminar toughness and shortening the filling time and completely impregnating the fibers. The nonwoven fabrics and dot matrix structure material were used as ex situ interlayer toughening agents. The effect of the interlayer toughening agent structure on the resin flow behavior during the z-RTM process was investigated. The macro-flowing and micro-infiltration behaviors of the resin inside the preforms were deduced. The permeability of the fabric preforms with different toughening agents was investigated. The results show that the introduction of the nonwoven structure toughening agent makes the macro flow slow, and the flow front more uniform. The toughening agent with a dot matrix structure promotes the resin macro flow in the preforms, and shortens the injection time. The z-directional permeability of the preform with a dot matrix structural toughening agent is one order of magnitude lower than that of the non-toughened preform, while being higher than the preform toughened by the nonwoven fabric preforms, which is helpful for the further applicability of the z-RTM process. Furthermore, the mode II interlaminar fracture toughness of composites was evaluated.

Promising low-viscosity phosphorus-containing epoxy compounds: Features of interaction with aromatic amines

The interaction of glycidyl esters of phosphorus acids (GEF) with aromatic amine hardeners has been studied. A comparative analysis of the reactivity of different GEF (triglycidyl phosphate (TGFT), diglycidyl methyl phosphate (DGMFT), diglycidyl methyl phosphonate (DGMFN)) has been carried out. The activity of amine hardeners in interaction with GEF has been also compared. Kinetic parameters for the curing reaction have been calculated using Thermokinetics software, and the mode of the interaction of phosphorus-containing epoxy oligomers with aromatic amines has been assessed. Complex structures have been optimized using DFT computations at the CAM-B3LYP/TZVPP level with accounting for solvent effects using the C-PCM model. Thermophysical and flame-retardant characteristics of cured phosphorus-containing epoxy polymers have been investigated. It has been shown that epoxy polymers based on GEF and amine aromatic hardeners have high values glass transition temperature. The resulting binder is self-extinguishing and displays promise for use in the RTM process.

Desarrollo de preformas para la fabricación de piezas estructurales de grandes dimensiones mediante la tecnología RTM para el sector aeronáutico

Resin Transfer Moulding Technology (RTM) is gaining attention on developing composite structural components for aeronautical industry, due to its high-cadence production, and as a consequence, a significant manufacturing cost reduction. This document describes the manufacturing of a composite fuselage frame oriented in dry reinforcement preform construction that, it’s one of the main factors that intervene in RTM process and has a direct influence on the component structural quality. It’s exposed the definition of an overlap strategy for dry Non-Crimp Fabric adaption on structural aeronautical components of large dimensions and implementation of such strategy for manufacture a real-scale demonstrator, exposing process time reduction base on a tooling design that facilitate the cycle time reduction. Simultaneously, it’s described a procedure to study the overlap influence at a dimensional and structural level and defects generation. Also, it’s exposed different overlap strategies for preform consolidation by commercial adhesives incorporation for fabrics and thermoplastic binders.

Optimization and characterization of the T_RTM process for polyamide 6

One of the advantages of the T_RTM process of polyamide 6 is that the low viscosity of the molten monomer, ɛ-caprolactam (CL), allows to infiltrate it through the fiber, in a process very similar to the RTM of the thermoset materials. In this process the APA6 polymerizes and crystallizes during the molding process, being these two factors the ones that will provide the final properties to the material. Therefore, the knowledge, modeling and simulation of the effect of the process variables on these two phenomena would allow to optimize time/properties ratio in order to develop a strong and competitive manufacturing process. In the RTM 4.0 project, the effect of the different process variables on the crystallization and polymerization of APA6 has been studied through of different characterization and monitoring techniques. This work presents the results of the study of the influence of the type of reinforcement of the polymerization of the material. The results obtained indicate that repetitive and homogeneous polymerization degrees are achieved regardless of the type of reinforcement used.

Design and manufacture of automotive components in thermoplastic composite (Part II)

The thermoplastic RTM process (T-RTM) is currently one of the most demanded process for R&D in the automotive sector. This sector tries to lighten the weight of the vehicle with highly resistant non-metallic components and with efficient manufacturing in cycle-time and cost. In the framework of the BIHARKONP project, EDERTEK-TECNALIA proposes the migration of a suspension arm, currently manufactured by means of metal stamping, to high mechanical requirements composite materials, obtaining a weight reduction of 30%. For the manufacture of this component it was proposed to redesign the component in carbon fiber (CF) and polyamide 6 matrix (APA6). The redesign (Part I) consisted in a mechanical calculation of the loads that the component had to support. The geometry has been changed with the aim of fulfilling the part specification and the peculiarities of the T-RTM process. For the manufacture of the component, a CF/APA6 composite laminate was defined and characterized and a specific CF for thermoplastics was selected. Subsequently, a T-RTM mold was designed and manufactured with inserts for fiber compaction and eight thermal control zones. The geometry of the control arm involves the manufacture of CF preforms by means of a thermal forming process with thermoplastic veils. Caprocast technology has been used to manufacture the prototype by caprolactam injection and its polymerization inside the heated mold. The prototype was subjected to bearing test, bushing insertion-extraction test and bushing strength test. The component was validated.

Study on Structural Design and Analysis of Composite Boat Hull Manufactured by Resin Infusion Simulation.

In this paper, structural design and analysis of a composite boat hull was performed. A resin transfer molding manufacturing method was adopted for manufacturing the composite boat hull. The RTM process is an advanced composite manufacturing method that allows a much higher quality product than the hand lay-up process, and less manufacturing cost compared to the autoclave method. Therefore, the RTM manufacturing method was adopted. The mechanical properties of the various aramid fibers and polyester resin were investigated. Based on this, structural design of boat hull was performed using aramid fiber or polyester. After structural design, the optimized resin infusion analysis for RTM manufacturing method was performed. Through the resin infusion analysis, it is confirmed that the designed location of resin injection and outlet is acceptable for manufacturing.

Target-detection and localization in multilayered media through mixed TR–RTM method

The problem of target detection and localization in layered media can be solved by the mixed TR–RTM. The highlight of this paper is on multilayer media, where the target is harder to detect than in double-layered media, due to the interference of multiple interface reflection signals. The core idea of the TR–RTM mixed method, namely the RTM isochronism principle, is applied for the three cases. Typically, a target under a TR–RTM process can form a mountain-like acoustic field distribution. For the interface whose reflected signal is an interference, the acoustic field distribution is disordered and inhomogeneous, with a smaller amplitude. The TR–RTM greatly improves the signal-to-interference ratio, where the position of the summit is the just position of the target, thus, detecting and localizing the target.

Macro-meso scale simulations of 3D woven composite reinforcements during the forming process

During the forming stage in the RTM process, deformations and orientations of yarns at the mesoscopic scale are essential to evaluate mechanical behaviors of final composite products and calculate the permeability of the reinforcement. However, due to the high computational cost, it is very difficult to carry out a mesoscopic draping simulation for the entire reinforcement. In this paper, a macro-meso scale simulation of composite reinforcements is presented in order to predict mesoscopic deformations of the fabric in a reasonable calculation time. The proposed multi-scale method allows linking the macroscopic simulation of the reinforcement with the mesoscopic modelling of the RVE through a macromeso embedded analysis. On the base of macroscopic simulations using a hyperelastic constitutive law of the reinforcement, an embedded mesoscopic geometry is first deduced from the macroscopic simulation of the draping. To overcome the inconvenience of the macro-meso embedded solution which leads to unreal excessive yarn extensions, local mesoscopic simulations based on the embedded analysis are carried out on a single RVE by defining specific boundary conditions. Finally, the multi-scale forming simulations are investigated in comparison with the experimental results, illustrating the efficiency of the proposed approach, in terms of accuracy and CPU time.

Moisture Adsorption and Desorption Behavior of Raw Materials for the T-RTM Process

The use of fiber reinforced plastics (FRPs) has significant potential to reduce the weight of components. As regards the sustainability of these components, thermoplastic matrices offer more potential for recycling than thermoset ones. A possible manufacturing process for the production of thermoplastic FRPs is thermoplastic resin transfer molding (T-RTM). In this very moisture-sensitive process, ε-caprolactam in addition to an activator and catalyst polymerizes anionically to polyamide 6 (aPA6). The anionic polymerization of aPA6 is slowed down or even completely blocked by the presence of water. This study analyses the sorption behavior of the matrix, fiber, binder and core materials for the production of anionic polyamide 6 composites, which are processed in the thermoplastic RTM process. Water vapor sorption measurements are used to determine the adsorption and desorption behavior of the materials. The maximum moisture loading of the materials provides information about the water adsorption capacity of the material. This knowledge is crucial for correct handling of the materials to achieve a fast process and good properties of the final product.

The method of RTM process modeling using porous medium

This paper proposes a method to simulate the Resin Transfer Molding process by using Ansys Fluent software. The offered approach permits to calculate impregnation time, to predict dry zones after impregnation and proposes a method to calculate porosity of the final product to predict the mechanical properties. The method is illustrated in the plate resin impregnation case.

Experimental and numerical investigations of pressure-controlled resin transfer molding (PC-RTM)

To increase the use of fiber reinforced lightweight structural components in the automotive industry, their manufacturing processes have to obtain demanding economic requirements. One possibility is to use Compression Resin Transfer Molding (CRTM), which is fast and can be highly automated. One disadvantage can be the very high cavity pressure during injection. To avoid this disadvantage, a pressure-controlled RTM (PC-RTM) process was developed. PC-RTM uses a variable mold gap height and an embedded pressure sensor to control the cavity pressure actively during mold filling. In this work, we investigate this process by experiments and simulations with varying initial mold gap and controlled cavity pressure. We show that PC-RTM is a viable manufacturing process with short cycle times and high robustness. Furthermore, the simulations are validated by comparison to the experiments and show the same process characteristics.

Mathematical Model of Vacuum–Resin Transfer Molding for Polymeric Composites Products

AbstractResin Transfer Molding process (RTM), is the most used technology to create large parts made by polymer matrix composites because: the production time is relative small; the consumption of materials is reduced to minimum; the obtained parts are in a constant tolerance of ±0.5 mm after de‐molding; both sides of the part are shiny and smooth; determinate resistance of the wall; it can be used with gelcoat on both sides or only on one; the reinforcement materials can be fiber glass, carbon fiber, sandwich materials, or metallic inserts; it does not need pressing during the curing of the resin; reduced cycle time, and low styrol emissions. In this paper the results of research regarding mathematical model of vacuum–RTM process for polymeric composites products are presented. It is taken into account that during mold filling and curing thin mold cavities, the thermal physical properties may vary from location to location and may change as a function of time. The studied material can be considered as homogeneous and isotropic. The results of applying some numerical schemes to solve the above model, corroborated with the results of the experimental measurements, can highlight the advantages of this method of mold filling.

RTM Process Manufacturing of Spot-weldable CFRP-metal Components

RTM Process Manufacturing of Spot-weldable CFRP-metal Components

Simulation of a resin transfer molding process using a phase field approach within the theory of porous media

In an RTM process the mold contains three constituents including fibres, a resin and a gas. Due to its similarity to a porous medium, the process can be modeled within the Theory of Porous Media (TPM), where the simulation of the moving resin front generates an inherent difficulty: In widely used approaches for mold filling simulations, that are element/control volume methods (Bruschke and Advani, 1990) and Level set methods (Soukane and Trochu, 2006), the moving resin front is either approximated roughly, such that an interface thickness of multiple finite elements arises, or respectively by a sharp interface with zero-thickness which requires a special numerical treatment. The present study intends to close this gap. To this end, we outline regularizations of the sharp interface such that the above mentioned difficulties can be overcome with a regularized sharp interface theory as a branch of phase-field models which go back to the classical Ginzburg-Landau equation. In this way, the sharp discontinuities between different phases, i.e. resin and gas, are approximated by smooth transitions of suitable order parameters, of which one is the resin fraction. Thus, the sharp interface topology as well as the surface energy of the interface are smeared out over a region proportional to a chosen regularization length scale. As an additional advantage, the phase-field method facilitates a thermodynamic treatment of phase interfaces rendering it more physically consistent in combination with the TPM, which also works within a thermodynamically sound framework. To this end, a coupled finite-element strategy is presented accounting for both, a Ginzburg-Landau- and Cahn-Hilliard-type regularization scheme for the interface. Two boundary value problems are formulated in the context of the TPM. They consider a multiphase-system, represented by deformable fibres interacting with the resin saturating the pores, that is coupled to one of both regularization schemes. Accordingly, two numerical examples demonstrate the capabilities of both regularized formulations by simulations of an RTM process.

3D simulation of transversely isotropic laminated composites in RTM using poromechanics

In the present paper we are trying to establish a 3D simulation framework for Resin Transfer Molding for a laminated preform using the already developed porous media theory for composite materials process simulation purposes. The aim here is to implement the process phenomena, such as coupling of sub-processes that are happening simultaneously, in a full 3D description of the problem. For this purpose, an 8-node solid shell element is employed to be able to handle complex 3D stress-strain states. The development is exemplified considering RTM process where the main focus of the modeling will be on the flow advancement into fiber preform and flow front capturing. To this end, the theory of two-phase porous media is used along with assuming hyper-elastic material response for the fiber bed to formulate the problem. A finite element formulation and implementation of the two-phase problem is developed, and the results are presented accordingly.