Resin Injection Research Articles

An improved semi-discrete approach for simulation of 2.5D woven fabric preforming

The geometry of the textile composite reinforcements plays an important role in the mechanical properties of the final composite part and resin injection of the RTM forming process. An improved semi-discrete approach is proposed for simulation of 2.5D woven fabric forming. Transverse compaction, in-plane shear and bending are further considered in this paper, the corresponding internal nodal loads of the user-defined element are derived based on the principle of virtual work and implemented in finite element (FE) software ABAQUS/Explicit with user element subroutine (VUEL). Three experiments are conducted to determine the mechanical behaviors of the fabric. A combined deformation of cylindrical bending and torsion of the fabric is experimentally and numerically studied. A satisfactory agreement is achieved between the simulated and the experimental results. Both indicate that this combined deformation can be equivalent to the sequential superposition of in-plane and bending. The mechanism of the combined deformation is also discussed.

Impact and CAI behavior of SGF mat filled sandwich panels made from foam core and FRP facesheet

The interlaminar bonding property between the facesheet and foam core plays an important role in enhancing the impact damage resistance ability of sandwich panels. In this paper, we filled short glass fiber (SGF) mat between the facesheet and foam core to enhance their bonding strength. The newly designed sandwich panels were manufactured by vacuum-assisted resin injection processing. A series of SGF mat filled sandwich panels with glass and/or carbon fiber facesheets were manufactured. The low-velocity impact as well as the compression-after-impact (CAI) performence were investigated. Failure modes of the sandwich panels were analyzed. Low-velocity impact results show that SGF mat filled sandwich panels with pure glass fiber facesheet displayed the maximum contact force. In the CAI test, wrinkling of the facesheet, buckling of the foam, and debonding between them are the major failure modes. Compared with contrast samples, SGF toughened sandwich panels show the highest strength increase rate.

Monitoring the Effects of Slope Hazard Mitigation and Weather on Rockfall along a Colorado Highway Using Terrestrial Laser Scanning

Rockfall is a frequent hazard in mountainous areas, but risks can be mitigated by the construction of protection structures and slope modification. In this study, two rock slopes along a highway in western Colorado were monitored monthly using Terrestrial Laser Scanning (TLS) before, during, and after mitigation activities were performed to observe the influence of construction and weather variables on rockfall activity. Between September 2020 and February 2021, the slopes were mechanically scaled and reinforced using rock bolts, wire mesh, and polyurethane resin injection. We used a state-of-the-art TLS monitoring workflow to process the acquired point clouds, including semi-automated algorithms for alignment, change detection, clustering, and rockfall-volume calculation. Our initial hypotheses were that the slope-construction activities would have an immediate effect on the rockfall rate post-construction and would exhibit a decreased correlation with weather-related triggering factors, such as precipitation and freeze-thaw cycles. However, our observations did not confirm this, and instead an increase in post-construction rockfall was recorded, with strong correlation to weather-related triggering factors. While this does not suggest that the overall mitigation efforts were ineffective in reducing rockfall hazard and risk of large blocks, we did not find evidence that mitigation efforts influenced the rockfall hazard associated with the release of small- to medium-sized blocks (<1 m3). These results can be used to develop improved and tailored mitigation methods for rock slopes in the future.

Evaluation of the vacuum infusion process objectives at the early stages of computer simulation

Increasing the quality and reliable reproducibility of large-size composite structures molding using the vacuum infusion method, which is gaining popularity in various industries, is achieved in practice through numerous tests by try and errors that require significant costs and time. The purpose of these tests is to determine the layout of the ports for the resin injection and vacuum supply, as well as the temperature regime that ensures the absence of isolated non-impregnated zones, the minimum porosity and the required reinforcement volume fraction in the composite. The proposed approach removes the simplifying assumptions used in commercial software for modeling the process, which reduce the accuracy of reconstruction of its dynamics and the sensitivity to the formation of unrepairable defects such as dry spots. It involves multiphysics modeling of resin filling in a porous preform by describing the resin front dynamics by the phase field equation, pressure distribution in an unsaturated porous medium by the Richards equation, the evolution of the degree of cure by the convection / diffusion / thermokinetics equation, and thermal processes by the heat transfer equation using modified models of viscosity, the diffusion coefficient of the degree of cure, the boundary condition for the vacuum port. To reduce the finite element computation time of the investigated variants of the process, which is necessary for its computer optimization, the predictive partial sub-criteria were used, which give a reliable prediction before the beginning of the resin gel and solidification. Due to this, a gain in computation time is 30-50% with a significant prediction accuracy of quality objectives and the presence of possible defects.

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.

Laboratory study of properties of sand grouted by dual-component resins

Nowadays, technologies of chemical action on a rock mass, including the injection of polymer resins, the filling of voids by plugging with foaming compounds etc., are widely used to stabilize, to strength fractured rocks and to waterproof underground mines during development of solid minerals. In the paper we consider the issues of enhancing of the physical and mechanical properties of loose sedimentary rocks by chemical grouting with dual-component polymer resins. We perform laboratory experiments to strength fine-grained siliceous sand by the dual-component silicate-isocyanate and the foamed polyurethane resins. The grouting is performed through 10 cm diameter columns, which are filled with fine-grained siliceous sand. The main particle size fraction of the used sand is 0,150 – 0,210mm. The resin pumping into the test samples is carried out by two methods. The first method consists in sequential pumping of separate components of the polymer compounds. In this case, the solidification of the polymer compositions begins inside the rock sample. The second method consists in pumping of the fully prepared polymer compounds (two components are mixed immediately before injection in the rock sample). In this case, the solidification of the polymer compositions begins before the pumping in the rock, which leads to a rapid increase of the viscosity of the injected compositions. For both methods, the pumping is performed both with a pulse pressure increase and with a gradual (stepwise) pressure increase in the range from 0 to 15 bar. Based on the experimental results, the volume of the strengthened sand is determined. It was obtained that the volume of the strengthened (consolidated) sand is on average 2-3.5 times greater with separate-component injection, than with the injection of fully prepared compositions. For both pumping methods, a larger volume of consolidated rock is provided with a gradual (stepwise) pressure increase. Cylindrical specimens are cut out of the consolidated sand, and deformation-strength and filtration tests of the obtained material are carried out. The results show that the sequential pumping of separate components of the dual-component polymer compounds provides the greatest rock strengthening. It is obtained that the hardened sand uniaxial compressive strength is on average 1,5 times more for the sequential pumping of separate components compared to the injection of the fully prepared compositions. Similarly, the deformation modulus of hardened sand is 2,5 - 6 times more for the sequential pumping of separate components compared to the injection of the fully prepared compositions. The use of the dual-component silicate-isocyanate compositions provides more effective strengthening of loose sedimentary rocks compared to the foaming polyurethane compositions. The uniaxial compressive strength and the deformation modulus of the consolidated fine-grained sand are on average 10 - 12 times more for the dual-component silicate-isocyanate compositions compared to the foaming polyurethane compositions. The obtained data can be used to select and optimize the method of pumping of dual-component polymer compositions to stabilize disturbed mines.

Compression Resin Transfer Molding Using Inflatable Seals

Compression resin transfer molding using inflatable seals is a new variant of LCM (“Liquid composite molding”) processes, which uses the inflatable seals to compress the fiber reinforcements and drive the resin to impregnate the fabric preform, resulting to fill the entire mold cavity. During resin injection, the preform is relaxed. Consequently, the resin enters easily and quickly into the mold cavity. After, the necessary resin is injected into the mold cavity, the compression stage takes place, in a stepwise manner, by swelling the inflatable seals. The objective of this paper is to present this new process and study the effect of the number of inflatable seals on the filling time.

Thermal Characterization of Resin Concrete Elaborate By Infusion

This paper presents the results of numerical simulation to investigate the effect of temperature on the performance of resin concrete. Resin concrete is a composite material in which polymeric materials are used to bond the aggregates in a fashion similar to that used in the preparation of cement concrete. In this paper, at first the temperature distribution in gravel preform heated with epoxy resin injection was investigated. Furthermore, a thermo-mechanical study is presented. For this purpose, prismatic and cylindrical specimens were prepared for flexural and compressive tests, respectively, at different temperatures. The effect of heating on the thermal conductivity and elastic modulus were evaluated.
 Finally, the thermal behavior of resin concrete has been compared to that of cement concrete. When exposed to high temperatures the epoxy polymer concrete shows a significant loss of strengths mainly due to the thermo-oxidative degradation of the epoxy polymer and to the debonding between aggregates and the binder. Results show that when exposed to temperatures less than 250°C the epoxy polymer concrete is still more efficient than cement based concrete.

High degree of non-genetic phenotypic variation in the vascular system of crayfish: a discussion of possible causes and implications

In this study, the hemolymph vascular system (HVS) in two cambarid crayfishes, i.e. the Marbled Crayfish, Procambarus virginalis Lyko, 2017 and the Spiny Cheek Crayfish, Faxonius limosus (Rafinesque, 1817), is investigated in regard of areas of non-genetic phenotypic variation. Despite their genetic identity, specimens of P. virginalis show variability in certain features of the HVS. Thus, we describe varying branching patterns, sporadic anastomoses, and different symmetry states in the vascular system of the marbled crayfish. We visualize our findings by application of classical and modern morphological methods, e.g. injection of casting resin, micro-computed tomography and scanning electron microscopy. By comparing our findings for P. virginalis to the vasculature in sexually reproducing crayfishes, i.e. F. limosus and Astacus astacus, we discuss phenotypic variation of the HVS in arthropods in general. We conclude that constant features of the HVS are hereditary, whereas varying states identified by study of the clonal P. virginalis must be caused by non-genetic factors and, that congruent variations in sexually reproducing F. limosus and A. astacus are likely also non-genetic phenotypic variations. Both common causal factors for non-genetic phenotypic variation, i.e., phenotypic plasticity and stochastic developmental variation are discussed along our findings regarding the vascular systems. Further aspects, such as the significance of non-genetic phenotypic variation for phylogenetic interpretations are discussed.

МОДЕЛИРОВАНИЕ ПРОЦЕССОВ ВАКУУМНОЙ ИНФУЗИИ В ПРОИЗВОДСТВЕ КРУПНОГАБАРИТНЫХ КОМПОЗИТНЫХ КОНСТРУКЦИЙ

The article presents the technology of computer simulation of the vacuum infusion processin the production of large-sized polymeric composite structures, which is attracting more andmore attention in the aircraft industry, due to the ease of implementation and the relatively lowcost of production preparation. The difficulty of industrial implementation of the process and ensuringthe required quality is due to its high sensitivity to modes - temperature, vacuum pressureand the layout of the vacuum ports and resin injection. The purpose of the developed methodologyfor computer modeling of the process with the possibility of its subsequent optimization is to excludethe currently used lengthy and very expensive trial and error method when working out thetechnology. The proposed mathematical model of the process linking the equation of the phasefield, which reconstructs the interface between the resin and the void region of the preform, theRichards equation for the propagating viscous fluid in an unsaturated porous medium, the thermalkinetics of the resin and thermal conductivity, is implemented in the environment of a finite elementpackage. Computer implementation of the model provides an accurate reconstruction of thedynamics of the front of the propagating resin in a porous preform, the possibility of the emergenceand localization of non-impregnated zones of the molded structure, thereby eliminating theformation of irreparable defects. The results obtained demonstrate the ability of the developedtechnique to ensure the stability of the quality of the produced composite structures with increasedrequirements for the continuity of its microstructure and its structural strength.

Closed Repair Technique: Innovative Surface Design for Polymethylmethacrylate Denture Base Repair.

This study aimed to evaluate the repair strength of a newly introduced repair technique involving zero-gap repair width. A total of 36 rectangular prism specimens with dimensions of 64 × 10 × 3.3 mm were prepared from heat-polymerized acrylic resin. Nine specimens were kept intact. The other specimens were sectioned into halves and modified to create repair gaps of 2.5-mm beveled (2.5B) as control, 0-mm beveled (ZB), and 0-mm inverse bi-beveled (ZIBB). The ZIBB group was prepared with a V-shaped internal groove on both halves (repair tunnel), while the intaglio and cameo surfaces were kept intact except for two small holes at the cameo surface for repair resin injection. The 2.5B and ZB groups were repaired conventionally while the ZIBB group was repaired by injecting repair resin into the tunnel through one of the holes until excess material oozed from the other hole. Repaired specimens were thermally cycled at 5 and 55°C for 10,000 cycles with 1 min dwell time. A 3-point bending test was conducted using a universal testing machine for flexural strength and elastic modulus measurement. Kruskal-Wallis/Mann-Whitney tests and ANOVA/post hoc Tukey tests were applied for data analysis (α = 0.05). The flexural strength of repaired specimens was substantially lower than that of intact specimens, and significant differences were present between repaired groups (p ˂ 0.05). ZB and ZIBB had higher flexural strength (p ˂ 0.001) and elastic modulus (p ˂ 0.05) than 2.5B. Among the ZB and ZIBB groups, ZB showed the highest flexural strength, and ZIBB had the highest elastic modulus. The closed repair technique improved the flexural strength and elastic modulus of repaired acrylic denture base.

Micro-mesoscopic prediction of void defect in 3D braided composites

Void defects will inevitably occur in 3D braided composites during Resin Transfer Molding (RTM) process, which may reduce mechanical properties of 3D braided composites. Therefore, this paper focuses on void generation in 3D braided composites and optimizes its manufacturing technology. First, the basic governing equations considering flow, temperature changing and resin curing process are derived to describe the conservation of momentum, energy and mass of resin during RTM process. Second, the whole RTM process for 3D braided preform cell is simulated by means of finite element method (FEM), which indicates the distribution of resin flow speed, pressure and void content. Third, influences of resin injection flow volume, outlet pressure, volatile content in resin and curing temperature on void distributions and contents in 3D braided composite cell are investigated. The results will provide theoretical basis for analyzing void generation and evaluating the quality of 3D braided composites made by RTM technology.

Resin Transfer molding of High-Fluidity Polyamide-6 with modified Glass-Fabric preforms

In Resin Transfer Molding (RTM), resin precursors of thermoset or, more recently, thermoplastic polymers are generally employed, raising issues related to the chemical reaction taking place during and after part processing. In this study, already polymerized polyamide-6 with low melt-viscosity (~30 Pa·s at 280 °C), is injected at low pressure (<30 bar) in a custom-made mold, so as to impregnate glass fabric preforms via in-plane impregnation. Composite plates were produced using interply spacers acting as flow-enhancers. A three-step impregnation strategy, involving fast in-plane resin injection, a successive saturation step through transverse flow, followed by further micro-saturation caused by the collapse of the spacers, ensured industrially relevant impregnation kinetics. The influence of the spacer, the saturation time, pressure and temperature on the process kinetics and part quality were evaluated with three-point bending tests as well as microstructural analyses. Optimum processing parameters were identified and scaled up for a given part geometry.

Improvement of impregnation quality on out-of-autoclave processed CFRP aircraft wing spar through resin flow simulation

Vacuum-assisted resin transfer molding (VaRTM) is becoming one of the most robust alternatives for autoclave processes. VaRTM, which applies the resin injection method in a vacuum environment, generally uses fiber reinforcement and a polymer matrix separately in the process. The VaRTM is mainly dominated by the characteristics of constituent materials, such as preform permeability and resin viscosity. Among them, process design with the arrangement of resin inlet/outlet locations is closely related to process defects, and inappropriate inlet/outlet layouts cause voids, etc, which has a decisive effect on quality degradation. Therefore, in this study, a highly curved and twisted spar structure was fabricated by the VaRTM, and both flow simulations using Programs for Applied Mechanics–Resin Transfer Molding software and experimental test parts built with three different inlet/outlet line conditions were performed and compared to predict and improve impregnation quality. There was good agreement between the simulation and built test specimen for the three cases that the shorter inlet and outlet length resulted in improved impregnation quality. It was verified that impregnation and inner quality could be improved through flow simulation analysis during the VaRTM process.

Sand production control mechanisms during oil well production and construction

Sand production is considered as one of the significant production issues that significantly reduce wellbore productivity. The process of sand or solids production in production operations is one of the crucial operational inefficiencies that can lead to wells collapsing. Besides, the drilling mud might erupt through the formation. Therefore, it is essential to properly determine what types of solids or sand are produced to correctly predict efficient sand control mechanisms. This paper aimed to compare different sand production control mechanisms and how to control or minimize sand production. Moreover, we consider injection pressure and sand moisture on the sand production rate. According to this study’s findings, pressure injection and moisture increase had caused sand production increase, which should be considered in operational performances. Furthermore, chemical injection such as resin and hydrogel injection usually has efficient sand production control methods. An expandable sand screen is an expandable three-layer component that is driven into the well and expanded.

Bayesian inversion algorithm for estimating local variations in permeability and porosity of reinforcements using experimental data

A novel Regularising Ensemble Kalman filter Algorithm based on the Bayesian paradigm was applied to RTM processes to estimate local porosity and permeability of fibrous reinforcements using measured values of local resin pressure and flow front positions during resin injection. The algorithm allows to detect locations of defects in the preform. It was tested in virtual experiments with two geometries, a two-dimensional rectangular preform and a more complex 3D shape, as well as in laboratory experiments. In both the virtual and laboratory experiments, it was demonstrated that the proposed methodology is able to successfully discover defects and estimate local porosity and permeability with good accuracy. The algorithm also provides confidence intervals for the predictions and estimations of defect probabilities, which are valuable for analysis of the process.

Evaluation of Flow-Mesh Influence in Resin Injection Processes

Liquid molding is a versatile composite family of processes largely used in naval and automotive industries. In these processes, a polymeric resin is forced through a mold cavity previously filled with a reinforcement medium. In several cases, the impregnation stage may be too long and, to avoid that a flow-mesh (FM) may be placed over the reinforcement. This FM has very high permeability and high porosity, thus the resin first advances inside it and then impregnates the reinforcement medium. The FM commonly covers the entire reinforcement medium, however this may not the best solution for all situations, since it may produce an irregular resin flow front inside the mold cavity, resulting in void formation or waste of resin. This work performs a study on the most suitable FM length, in relation to the mold length, for rectilinear injections. Main goal is to produce a data set to determine FM length based on mold thickness and in-plane to transverse permeability ratio ( $$\uppsi ={K}_{xx}/{K}_{zz}$$ ). Results have shown that for common industrial application, where $$\uppsi \sim 10$$ , mold length must be 2.5 times as long as the FM for thick reinforcements. Moreover, for more extreme cases, with $$\uppsi \sim 1000$$ , this value may reach 25.

A review of liquid silicone rubber injection molding: Process variables and process modeling

AbstractLiquid silicone rubber (LSR) is an elastomer molded into critical performance components for applications in medical, power, consumer, automotive, and aerospace applications. This article reviews process behavior, material modeling, and simulation of the (LSR) injection molding process. Each phase of the LSR injection molding process is discussed, including resin handling, plastication, injection, pack and hold, and curing; and factors affecting the molding process are reviewed. Processing behavior of LSR is marked by transient interactions between curing, shear rate, temperature, pressure, and tooling. Therefore, current LSR models for curing, viscosity, pressure, and temperature are discussed. Process dynamics and material modeling are combined in LSR injection molding simulations with applications in mold design, troubleshooting process‐induced defects, and management of shear stress and non‐uniform temperatures between LSR and substrates during overmolding. Finally, case studies using commercial simulation software are presented, which have shown cavity pressure and flow front advancement within 3% of experimental values. Optimization of LSR materials, data collection, model fitting, venting, and bonding remain areas of continued interest.

Research of Kinetic Impregnation Process Based on the Structure of Reinforcing Filler

The present work studies the impregnation process through a carbon-fiber-reinforced plastic (CFRP) during the resin injection filling stage of a vacuum infusion process by using simulation software PAM-RTM. Our work aims to study the resin injection time of carbon fabric composite laminate based on the type of weaving fabrics, permeability and porosity of reinforced fabric and to define the optimal structure of reinforced fabric based on simulation and experimental results. The resin infusion method procured from simulation and experimental results can effectively avoid the high cost caused by the trial-and-error method.

Development of Gap-filling Impregnation Method of ITER TF Coils

The ITER Toroidal Field (TF) coil is composed of a Winding Pack (WP) and a TF coil case (TFCC). In the manufacturing of a TF coil, the gap between the WP and the TFCC is filled with radiation resistant Triglycidyl-p-aminophenol (TGPAP) resin. Vacuum Pressure Impregnation (VPI) is adopted. The selected resin system displayed two potential problems: high viscosity and cracking after cure. A series of production optimizations have been performed to develop techniques to apply the selected resin for the TF coil production: crack countermeasure, narrow gap injection, and pressure control. For crack countermeasure, the addition of fiberglass tape or sheet layer was found to be effective in preventing fragmentation of cracked resin. Since the cracked resin would not harm the TF coil quality as long as it stays in the original position, addition of confining fiberglass layers solves the problem. In narrow gap qualification tests, resin injection into a 2 mm wide space was observed with proper selection of fiberglass layer addition conditions. The pressure qualification test showed that resin cured without additional pressurization can satisfy the compression strength requirements. From those results, techniques for the TF coil production have been developed, and with the implementation of those techniques the gap-filling of the first TF coil in Japan was successfully completed in 2019. Since then, two more TF coils have completed the gap-filling process with some improvements.