Papers by Keyword: Flexural Modulus

Abstract: In this paper the effect of adding natural particles (pomegranate PSP and coconut shell particles CSP ) on unsaturated polyester matrix UPE reinforced with natural sisal fibers studied, some mechanical properties were performed. The natural particle percentage selected to be (5, 10, 15, 20) wt. %, while the percentage of the sisal fibers was constant (2wt. %). The main purpose was to improve UPE properties to be use in structural applications. Chemical treatment was perform on all the reinforcement materials used before the hybrid composite synthesis. Using particles size distribution (PSD) it was found that (2956.9 and 2961.6) nm were the size of PSP and CSP, respectively. Then, samples were prepared in the laboratory at room temperature using Hand-layup technique. Tests as Flexural strength, flexural modulus, impact strength, max shear strength and surface roughness were applied on the composite samples. Results were as follows: a clear improvement in the mechanical properties of the UPE reinforced with sisal fibers. As for the fiber-particle reinforced polyester (UPE) ,the results were an increase in the flexural modulus by 5wt.% when adding coconut particle, while it decreased when adding pomegranate particle at same ratio. As for the flexural strength when the adding particles ratio increases, it decreases in the case of pomegranate particles addition while increases in the coconut particles addition. Interestingly, impact strength value increased at 5wt.% for both particle addition, while for further ratio there was a value reduction. An increase in max shear strength was also found as the highest value was in the pomegranate matrix at 5wt.%, while it was in the coconut matrix at 20wt.%. Finally, that the surface roughness value gradually increases with the increase additive ratio. Also, SEM

Abstract: Cured-in-place pipe (CIPP) is one of the trenchless sewer rehabilitation methods for repairing sewer pipe using different types of resin, curing technology and reinforced polymer fiber. In the research described in this article, the chemical and temperature resistance of CIPP pipes based on vinyl ester resin, cured with hot water, were tested. The specimens of the CIPP pipes were exposed to a chemically aggressive environment and an elevated temperature, namely 20% sulfuric acid (pH = 1) and a temperature of 50°C. The samples were tested every month for short-term flexural properties as well as hardness. Changes of the flexural properties and hardness were compared with reference samples that were stored under laboratory conditions (23±0,5°C, relative humidity 50% ±10%). It was found out that the applied aggressive environment does not have a negative impact on the mechanical properties of the CIPP pipes based on vinyl ester resin even after long-term exposure. Furthermore, the influence of the aggressive environment on the microstructure of CIPP samples was monitored by digital optical microscopy.

Abstract: Polymethylmethacrylate (PMMA) resin is the main polymeric material used in removable orthodontic appliances. However, it can promote the adhesion of microbes due to its surface porosity and from long-term use. While vanillin incorporated PMMA resin has been reported to have antimicrobial effects against Candida albicans, the influence of vanillin incorporation on the physical properties of self-curing orthodontic PMMA resin has not been studied. Objective: To determine the flexural strength and flexural modulus of self-curing orthodontic PMMA resin incorporated with vanillin in different concentrations. Materials and methods: Three groups of self-curing orthodontic PMMA with incorporated vanillin concentrations of 0.1%, 0.5% as well as PMMA without vanillin as a control were prepared with ten specimens per group. Flexural strength and flexural modulus were tested by a 3-point bending machine according to ISO 20795-2:2013 specifications. One-way ANOVA and Tukey’s multiple comparison tests at a p<0.05 significance level were used to analyse the data. Results: The 0.1% vanillin incorporated group met ISO standard requirements (flexural strength = 60.48 MPa, flexural modulus = 1756.60 MPa), while the 0.5% vanillin incorporated group failed to pass this standard (flexural strength = 46.94 MPa, flexural modulus = 1423.49 MPa). The means of both flexural strength and flexural modulus showed significant differences among the three groups. Increasing the concentration of vanillin would decrease the flexural strength and flexural modulus of PMMA resin. Conclusion: The incorporation of vanillin into self-curing orthodontic PMMA resin can affect its physical properties, namely flexural strength and flexural modulus. At a concentration of 0.1% vanillin incorporation, PMMA resin displayed physical properties within the ISO standards.

Abstract: Long-term use of a denture base can be a reservoir of microbes due to porosities and mechanical wear of denture surfaces. Vanillin has an antimicrobial effect. However, its influence on physical properties after incorporated in PMMA has not yet been evaluated. The purpose of this study was to investigate physical properties of PMMA by incorporating vanillin in different concentrations. Material and method. There were three groups of PMMA with ten specimens per group. Flexural strength and flexural modulus were tested by using a 3-point bending machine, and surface hardness was determined by Vickers hardness test. One-way ANOVA and Kruskal Wallis tests were used to analyze all data at 0.05 significance level. Result. The 0.1% vanillin group yielded a significant difference in Vickers hardness number (17.15 HV) as compared to 0.5% vanillin group (16.30 HV) and without vanillin (15.30 HV). In contrast, the flexural strength and modulus showed no significant difference among test groups upon incorporation of vanillin. Conclusion. The vanillin incorporated PMMA group demonstrated higher surface hardness, compared to the group without vanillin. In addition, there were no significant differences in flexural strength and flexural modulus among the three groups. This study also found no adverse effect in physical properties of the vanillin incorporated PMMA.

Abstract: The effects of glass fiber content and the molding parameters on the mechanical properties of the material saving plastic building molding board were studied in this paper. The flexural strength and flexural modulus increase with the increment of glass fiber content; but as the molding temperature, molding pressure, molding time, or cooling pressing time increases, the flexural strength and flexural modulus initially increase and subsequently decrease or remain constant. The optimum content of glass fiber is 40%, and the production process is as follows: the hot pressing temperature is 200 ^oC, the hot pressing pressure is 4 MPa, the hot pressing time is 5 min and the cooling pressing time is 5 min.

Abstract: The flexural modulus of composite laminates subjected to cyclic loads of varying cycle periods are experimentally investigated in this work. GFRP composite laminate specimen of configuration 0/R/0/0/0, 0/R/30/60/0, 0/R/90/90/0 and 0/R/45/-45/0 are prepared by hand lay-up technique with a uniquely processed resin-rich intermediate layer for the testing. Specimens are exposed to constant amplitude cyclic loading of frequencies 4.6 Hz and 8.6 Hz. A cantilever configuration of specimen with cyclic tip loading is considered to simulate the conditions of a leaf of a laminated automobile leaf spring. The flexural response of the laminate is measured using three point bend test as per ASTM D 790 and damping by hysteresis loop. The observed reduction in flexural modulusand the increase in damping factor after loading are compared with virgin. Minimised flexural modulus deviations between the loading frequencies are favoured by the cushioning of resin rich intermediate layer in the lay-up.

Abstract: The aim of this paper was the effects of different fiber size on tensile and flexural properties. Preparation of thermoset unsaturated polyester reinforced with particle Bertam (Eugeissona tristis) was done by hand layout method. Bertam/polyester composites containing Bertam fiber of different sizes, i.e., 15, 120 and 284 μm were prepared. For each composite, eight specimens were tested to evaluate the mechanical properties. It was found that composite reinforced with Bertam having the shortest fiber length, i.e, 15 μm showed the highest tensile and flexural modulus, which were 204.14 MPa and 1826.78 MPa, respectively.

Abstract: The objective of our work is to improve the mechanical stiffness of fiber reinforced laminates. The stiffness can be characterized by flexural and tensile moduli or their derivation. We applied design of experiments (DOE) to achieve our goals, because to solve the existing analytical and numerical models is complicated.We examined the effects of the following parameters: a) composition of reinforce materials (solely carbon, or carbon and glass combination), b) modulus of resin, c) mass ratio of resin-reinforcement, d) order of layers.The samples manufactured on the basis of DOE were investigated mechanically (flexural and tensile moduli measurements) and morphologically (scanning electron microscopy). We compared the measured modulus results to calculated values.

Abstract: Objective: To evaluate the effects of interchanging the liquid components of two commercially available orthodontic auto-polymerizing acrylic resin in their flexural properties, clarity and setting time

Abstract: Polymer composites reinforced with high strength synthetic fibres have been used for many engineering applications. Environmental and economic issues, encourage the exploration on the introduction natural-synthetic fibre hybrid composites. Mechanical properties are critical to composite performance and may due to the manufacturing process conditions. This study investigates the effect of post curing temperature, natural fibre content and resin-hardener mixing ratio on mechanical properties of kenaf-Kevlar hybrid composites. A full factorial design (2³) was carried out to determine the effect these factors on the responses: flexural strength, flexural modulus and impact strength. A statistical study has been performed in order to determine the how the factors affect the responses. The study showed that post-curing temperature, kenaf content and resin-hardener mixing ratio gives significant effects on the mechanical properties of kenaf-Kevlar hybrid composites.