Optimization of the infusion process with acrylic resin through physics-based simulation

In this study, a capacitive sensing based non-destructive evaluation technique is applied to a vacuum assisted resin infusion process for the fabrication of glass fibre reinforced composites, as such different steps of the fabrication process (the injection of resin, the curing and the post curing) can be better understood to increase the quality of the fabricated part and reduce the fabrication costs. An interdigital coplanar capacitive sensor was designed, fabricated, and embedded in the glass fibre reinforced composites. Experimental data clearly shows different stages of the resin infusion process: wetting of the glass fibres marked by rapid increase of capacitance; domination of ionic conduction at the early stage of the cure when the resin is still in a liquid state; the vitrification point, indicating a transition of the resin from a gelly state to a glassy state, marked by the relatively big decrease in capacitance; further polymerization during post-curing, marked by a peak in capacitance at the beginning of post-curing cycle, and finally the completion of the cure marked by the saturation of capacitance to a final value. The different phenomena observed during the experiment can be used as a tool for in situ on-line monitoring of composites cure.

This article describes a novel variant of the vacuum infusion process based on a multifunctional elastomeric reusable vacuum bag. The main innovation of this process is an elastomeric membrane having resin flow channels that can be controlled during the infusion process: they can be activated for the impregnation stage to enhance resin flow and removed during the curing stage to provide a smooth surface finish to the part. In addition, the size of the resin flow channels can be modified during the infusion providing control on the impregnation rate. This article describes the driven flow vacuum infusion (DFVI) process and presents analytical calculations regarding the effect of the geometrical design of the membrane and the processing variables on the porosity, permeability, and volume of resin transported by the flow medium. Preliminary results of unidirectional resin infusion tests comparing the DFVI process to traditional vacuum infusion and SCRIMP are also presented.

Theoretical and experimental study of foam-filled lattice composite panels under quasi-static compression loading

Flexural responses and pseudo-ductile performance of lattice-web reinforced GFRP-wood sandwich beams

This paper reports on the energy absorption characteristics of a lattice-web reinforced composite sandwich cylinder (LRCSC) which is composed of glass fiber reinforced polymer (GFRP) face sheets, GFRP lattice webs, polyurethane (PU) foam and ceramsite filler. Quasi-static compression experiments on the LRCSC manufactured by a vacuum assisted resin infusion process (VARIP) were performed to demonstrate the feasibility of the proposed cylinders. Compared with the cylinders without lattice webs, a maximum increase in the ultimate elastic load of the lattice-web reinforced cylinders of approximately 928% can be obtained. Moreover, due to the use of ceramsite filler, the energy absorption was increased by 662%. Several numerical simulations using ANSYS/LS-DYNA were conducted to parametrically investigate the effects of the number of longitudinal lattice webs, the number of transverse lattice webs, and the thickness of the transverse lattice web and GFRP face sheet. The effectiveness and feasibility of the numerical model were verified by a series of experimental results. The numerical results demonstrated that a larger number of thicker transverse lattice webs can significantly enhance the ultimate elastic load and initial stiffness. Moreover, the ultimate elastic load and initial stiffness were hardly affected by the number of longitudinal lattice webs.

Crushing behavior of multi-layer lattice-web reinforced double-braced composite cylinders under lateral compression and impact loading

Design and simulation of innovative foam-filled Lattice Composite Bumper System for bridge protection in ship collisions

Sandwich composites have gained significant attention in recent years due to their exceptional strength-to-weight ratio, bending stiffness-to-weight ratio, higher energy dissipation in impact, and versatility in applications. Due to the fatigue degradation and shear failure in conventional cores, developing novel sandwich structures made of alternative cores carries significant scientific importance in many engineering areas. This study explores the utilization of 3D Printed Acrylonitrile Butadiene Styrene (ABS) thermoplastic cores in sandwich structures to improve flexural and shear strength. The research aims to develop new sandwich composites having lightweight yet robust material properties using additive manufacturing (AM) and vacuum-assisted resin infusion process. To evaluate the flexural and shear strengths, ASTM standard sample specimens are prepared where 3-point bending tests are employed to assess the flexural strength and analyze the shear strength. The results are compared with balsa and PET foam cores having the same fiber. The findings exhibit improved flexural and shear strength in 3D Printed ABS cores compared to foam-cored composites. ABS cores also exhibit excellent load bearing while the composite skins provide the necessary stiffness in reinforcement.

This paper presents the monitoring of resin flow during resin infusion process in the fabrication of glass fiber reinforced polymer GRP wind turbine blade (WTB). Epoxy type of resin was used as the matrix and its viscosity and gel time were determined in-house. Next, resin infusions were done to obtain the permeability of the glass fiber in different directions (longitudinal and transverse), given the specific number of layers. The fabrication of composite WTB by resin infusion was conducted with the introduction of 'moldless' setup, where both upper and lower skins are covered by flexible mould/vacuum bag without any rigid female mould. However, a wooden core is used and acts as an “inner” mould to obtain the wind turbine shape. The whole infusion process was video recorded and the flow front pattern was traced at certain time intervals to investigate the infused percentage area over time. Afterward, guided by the traces of flow patterns on grid and video observation, 3D models of resin infused at interval times are generated in a CAD software. From the models, the area infused was determined. Percentage of area infused over time was compared with the analytical plot based on Darcy's law. A good agreement was found between the experimental observation and the theoretical plot.

The icing of wind blades poses a serious threat to the operation of wind turbines. The application of superhydrophobic coatings on wind blades can serve as a potential anti-icing method. This study presents the findings of simulations of the icing environment of wind blades coated with hydrophobic silicone–acrylate resin in an artificial climate chamber. Artificial icing tests were performed on NACA7715 wind blades with four different silicone–acrylate resin coatings and on uncoated wind blades, with test performed at five different wind speeds and three different angles of attack. Results show that wind blade surfaces with higher hydrophobicity yield better anti-icing performance, and that the ice mass of the wind blades decreases with increasing wind speeds and angles of attack. In addition, variations in ice mass, shape, and distribution on different wind blades indicate that increased hydrophobicity can help limit the areas that are subject to freezing. Hydrophobicity can affect the air cavities of the ice deposited on the wind blades, and surfaces with increased hydrophobicity can lead to lower ice mass and less ice adhesion. In brief, surfaces with higher hydrophobicity demonstrate better anti-icing performance and benefit from active de-icing.

The traditional processes for the manufacture of high performance composite shell structures are (i) vacuum bagging (VB)/VB with autoclave cure VB(A), (ii) resin transfer molding (RTM), and (iii) compression molding. Over recent years, there have been a number of novel “infusion” processes introduced, which span the gap between VB(A) and RTM. The new processes are known by a confusing set of names or acronyms—each company uses a distinct name, yet often the processes are near identical. The infusion processes can be mapped onto four distinct generic processes:Resin infusion in the plane of the fabric (Type I),Resin infusion with a flow medium/transport or distribution mesh (Type II),Resin film infusion (Type III), andSemipreg techniques (Type IV).This article describes the attributes of each of the four variants above and considers their relative advantages and issues.

Water-resistant hemp fiber-reinforced composites: In-situ surface protection by polyethylene film

To determine the effect of temperature variations on mixing fiberglass composite resin materials with the vacuum infusion method in the Tensile test. To determine the effect of the lowest and best temperature variations on mixing fiberglass composite resin materials with the vacuum infusion method on fotomikro. Variation fixed resin; polyester, fiber; fiberglass, vacuum; vacuum Infusion. Variable temperature of mixing resin 30˚C, 40˚C, and 50˚C. In this study, the vacuum infusion method was used, where the researcher made a specimen using the Vacuum Assisted Resin Infusion (VARI) process. In the VARI process, dry fiber is placed between the fixmold and the plastic bag, then the resin is injected after the space inside the plastic bag is under low pressure and the process continues until all parts of the fiber are wetted by the resin. After the specimen is made, then a tensile test is carried out to determine the mechanical strength of the specimen being tested. Then analyze the tensile test data using the equations used and displayed in the form of graphs and tables. This study was used to determine the effect of fiberglass composites with the vacuum infusion method on the tensile strength test. results of Tensile testing of fiberglass fiber composites and temperature variations of 30°C, 40°C, and 50°C. From the table it can be seen that the specimen with the best performance is found in the specimen with a temperature variation of 50°C, where the load that can be withheld reaches 508.56 kgf. So for maximum tensile strength it produces 11.07 MPa. Then on the specimen with a temperature variation of 40°C the best performance is 361.95 kgf. So for maximum tensile strength it produces 8.46 MPa. In specimens with a temperature variation of 30°C the best performance is 251.10 kgf. So for a maximum tensile strength of 5.67 Mpa. The average yield strength shows the results of the Tensile test of each variation, totaling 9 specimens. For the highest yield strength, a value of 9.67 MPa was obtained at a temperature variation of 50°C and for the lowest yield strength, a value of 4.13 MPa was obtained at a temperature variation of 30°C. Tensile test specimens have results where the highest yield strength or yield strength is obtained by specimens with a temperature variation of 50°C and as the stress increases, the yield strength value increases, and for the tensile strength of the material or tensile strength which has the highest value in the test, the specimens with 50°C temperature variation. Thus, the effect of temperature treatment is significant on the increase in tensile strength, but if the temperature is 30°C it will decrease the tensile strength, as at 30°C it produces an average tensile strength of 4.62 MPa. The results of the microphoto test show that at a temperature variation of 50°C there are a few voids while the 30°C variation has too many voids. Micro photo testing aims to determine the content in the composite.

Natural fiber reinforced composites serving as building block for structural parts are highly desired due to weight reduction in automotive industry. In the current study, the compressive behavior and energy absorption capacity of woven flax-epoxy composite were experimentally investigated under various strain rates. These tested cubic specimens were manufactured by the vacuum assisted resin infusion (VARI) process and tailoring operation. Quasi-static and dynamic experiments were conducted in a hydraulic servo test machine and a Split Hopkinson Pressure Bar (SHPB), respectively. Preliminary dynamic experimental results revealed significant strain rate sensitivity of woven flax-epoxy composite. The ultimate stress increased by 61.2% from 185.2 MPa to 298.6 MPa and 25.9% for specific energy absorption when the strain rate increased from 0.003/s to 2800/s. Results may serve as a guidance for the further investigation of flax fibers reinforced composites in automotive industry.

Petaloid-shaped ZnO coated carbon felt as a controllable host to construct hierarchical Li composite anode