Multi-Criteria Decision Approach to Design a Vacuum Infusion Process Layout Providing the Polymeric Composite Part Quality

The increasingly widespread use of vacuum assisted technologies in the manufacture of polymer-composite structures does not always provide the required product quality and repeatability. Deterioration of quality most often appears itself in the form of incomplete filling of the preform with resin as a result of the inner and outer dry spot formation, as well as due to premature gelation of the resin and blockage of the vacuum port. As experience shows, these undesirable phenomena are significantly dependent on the location of the resin and vacuum ports. This article presents a method for making a decision on the rational design of a process layout. It is based on early forecasting of its objectives in terms of quality and reliability when simulating its finite element model, on the correlation analysis of the preliminary and final quality assessments, as well as on the study of the cross-correlation of a group of early calculated sub-criteria. The effectiveness of the proposed method is demonstrated by the example of vacuum infusion of a 3D thin-walled structure of complex geometry.

Mechanical properties of polyester/corn husk fibre composite produced using vacuum infusion technique

Issues pertaining to deforestation, environmental pollution and natural wastes are increasing day by day. These issues can be resolved by introducing a new composite material, in which natural waste is used as fibre and as a replacement of wood plastic composite. The different lengths (3, 6 and 9 cm) of corn husk fibre filled polyester composites were produced using the vacuum infusion method. Several mechanical properties of these polyester composites, such as tensile and flexural properties, were evaluated. The results revealed that both the tensile and flexural properties of polyester composites increased with increment of corn husk fibre length from 3 to 6 cm. However, the results decreased for 9 cm of fibre length filled composites. Similar trends were recorded after alkali treatment of the corn husk fibre filled polyester composites. The alkali treatment with sodium hydroxide had improved the tensile strength (33%), Young’s modulus (23%), elongation (14%), flexural strength (42%) and flexural modulus (8.5%) of the polyester/corn husk fibre composites with 6 cm of fibre length by enhancing the mechanical interlocking bonding between treated corn husk fibres and polyester.

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.

PME and CaCl2 vacuum infusion maintains the firmness and physicochemical characteristics of tomato fruits

Tomato is a fruit of great commercial importance and highly cultivated. However, postharvest losses represent one of the main problems of this crop and can be minimized as alternative techniques. Therefore, the objective of the present work was to maintain tomato firmness by applying calcium chloride-associated pectin-methylesterase (PME) by the vacuum infusion method. Tomatoes of cultivar IAP-6 were submitted to vacuum infusion with water, vacuum infusion with 5% calcium chloride and vacuum infusion with PME associated with 5% calcium chloride, fruits without infusion were used as control. Fresh mass loss, fruit firmness, peel color, soluble solids content, pH, total acidity, PME activity and calcium activity were evaluated. The experiment was carried out in a completely randomized design in a 4x5 factorial scheme with three replications for 12 days, evaluated every 3 days. The means were compared using the Tukey test (p <0.05). Data were analyzed graphically with confidence interval (CI p <0.05). Regarding the loss of fresh mass there was an increase over time in all treatments. The PME + CaCl2 5% treatment was the most suitable for reducing firmness loss, as well as presenting the smallest variation of PME activity, as well as low levels of organic acids. Therefore, vacuum infusion with PME + CaCl2 in tomatoes maintains acceptable firmness and physicochemical characteristics as well as CaCl2 infusion.

Void Content Minimization in Vacuum Infusion (VI) via Effective Degassing

This paper addresses the major concern which component porosity represents in Vacuum Infusion (VI) manufacturing due to resin gelation at pressures close to absolute vacuum. Degassing is a fundamental step to minimize or even avoid resin outgassing and enhance dissolution of voids created during preform impregnation. The efficacy of different degassing procedures based on vacuum degassing, and assisted by adding a nucleation medium, High Speed (HS) resin stirring and/or later pressurization during different time intervals have been analyzed in terms of final void content is studied. Through a rigorous and careful design of the manufacturing process, outgassing effects on final void content were isolated from the rest of porosity causes and specimens with two clearly identifiable regions in terms of porosity were manufactured to facilitate its analysis. Maximum void content was kept under 4% and porous area size was reduced by 72% with respect to conventional vacuum degassing when resin was stirred at HS; therefore, highlighting the importance of enhancing bubble formation during degassing.

PENGARUH DEBIT ALIRAN RESIN BISPHENOL A LP-1Q-EX PADA METODE VACUUM INFUSION RESIN TERHADAP KEKUATAN TARIK KOMPOSIT SERAT KULIT POHON WARU (HIBISCUS TILIACEUS)

Research on natural fiber composites is being carried out in various parts of the world to produce solutions to environmental problems by utilizing natural fiber materials prepared for environmentally friendly and renewable materials. The natural fiber currently being developed for composite reinforcement is hibiscus bark fiber. This study aims to determine the effect of the flow rate of bisphenol A resin LP-1Q-EX on the vacuum infusion resin method on the tensile strength of hibiscus bark fiber composites. The method used in this study is the fiber structure model in the direction of tensile load, composite using hibiscus bark fiber (Hibiscus tiliaceus), composite using bisphenol A resin LP-1Q-EX, composite using mass fraction with a ratio of 60 fibers: 40 resin, Waru tree bark was treated with 6% NaOH alkaline soaking (aquades 938.8 grams, and NaOH 61.2 grams) for 120 minutes, the number of hibiscus tiliaceus bark fibers in one composite material was 22 fibers with a material thickness of 3.2 mm (according to ASTM D638-03 Type 1 standard), the composite was produced using the vacuum infusion resin method with variations in resin flow rate of 1.19 ml/s, 3.66 ml/s, 4.67 ml/s. The testing process in this study is a composite tensile test using the ASTM D638-03 Type I standard. The analysis of the fractures that occur in each specimen uses macro photos, namely the process of taking several photos of the fracture after the specimen is subjected to a tensile test using a digital camera placed on the ground. topped a tripod. The results of the composite tensile test showed that the variation of resin flow rate of 1.19 ml/s had the lowest tensile strength of 282.94 MPa, while the variation of flow discharge of 3.66 ml/s had the highest tensile strength of 301.75 MPa. and the flow variation of 4.67 ml/s has a tensile strength of 284.54 MPa. Based on the results of the tensile test of the hibiscus tiliaceus bark fiber composite using the vacuum infusion resin method, the highest strength was obtained at a variation of the resin flow rate of 3.66 ml/s.

The driven flow vacuum infusion process: An overview and analytical design

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.