Higher Flexural Strength Values Research Articles

Studies on thermal, mechanical, morphological, and viscoelastic properties of polybenzimidazole fiber reinforced high density polyethylene composites

High density polyethylene (HDPE) and polybenzimidazole fiber (PBI) composites were prepared by melt blending in a twin screw extruder. The thermomechanical properties of PBI fiber reinforced HDPE composite samples (1%, 4%, and 8%) of fiber lengths 3 mm and 6 mm were investigated using differential scanning calorimeter (DSC), universal testing machine, rheometer, and scanning electron microscopy (SEM). The effects of fiber content and fiber lengths on the thermomechanical properties of the HDPE‐PBI composites were studied. The DSC analysis showed a decrease in crystallinity of HDPE‐PBI composites with an increase of fiber loading. SEM images revealed homogeneous distribution of the fibers in the polymer matrix. The thermal behavior of the composites was evaluated from thermogravimetric analysis and the thermal stability was found to increase with the addition of fibers. The evidence of homogeneous distribution was verified by the considerably high values of tensile strength and flexural strength. In the rheology study, the complex viscosities of HDPE‐PBI composites were higher than the HDPE matrix and increased with the increasing of PBI fiber loading. POLYM. COMPOS., 5–13, 2016. © 2014 Society of Plastics Engineers

Sustainable Natural Bio Composite for FDM Feedstocks

This paper presents the development of a new Wood Plastic Composite (WPC) material for Fused Deposition Modeling (FDM) feedstocks. In this study, a biodegradable polymer matrix (POLYACTIDE, PLA) was mixed with natural wood flour (WF) by Brabender mixer, and the samples produced by injection molding machine. The effect of wood was investigated as a filler material in composite FDM feedstock and the detailed formulations of compounding ratio by weight percentage. Based on results obtained, it was found that, compounding ratio of PLA80%:WF20% has a goods result on the tensile strength and PLA60% : WF40% gave a higher value of flexural strength. An increment of 20% to 40% WF filler affected the flexural strength, and hardness results. The highly filled WF content in PLA composites increases the mechanical properties of PMC material through the injection molding process. The potential of development of a sustainable composite material will be explored as the FDM feedstocks in the rapid prototyping process.

Influence of Oxygen Plasma Modification Carbon Fiber on Flexural Strength and Hydrothermal Properties of CF/PES Composite

In this paper, low temperature oxygen plasma treatment method was adopted to process the carbon fiber surface. Flexural Strength test method was utilized to represent f composite material flexural strength. This paper observed flexural failure morphology of composite material by aid of SEM, then it compared the mechanical property, hygroscopicitiy and flexural strength retention rate of composite material before and after the plasma treatment. Results showed that the optimum treatment conditions of carbon fiber were 300W treatment power and 15-minute treatment time. Under the condition, the highest flexural strength value be increased by 19.55%.Saturated bibulous is low and bibulous rate is slow, flexural strength retention rate is 94.9%. And at the same time PES-C resin matrix can be strengthened, which will further improve the mechanical properties of composite materials.

Study on CF Reinforced Interface Properties of PES-C Resin Matrix Composite

In this paper, low temperature oxygen plasma treatment method was adopted to process the carbon fiber surface and ILSS and Flexural Strength test method were utilized to represent the interfacial shear strength and flexural strength of CF/PES-C composite material. By aid of SEM, this paper observed the interfacial shear and flexural failure morphology of CF/PES-C composite material. Then this paper compared the hygroscopicities and strength retention rates of CF/PES-C composite material before and after the plasma treatment. Results showed that the optimum treatment conditions of carbon fiber were 300W treatment power and 15-minute treatment time. Under this kind of condition, the highest ILSS value of the composite material shall be improved by 24.9% and the highest flexural strength value be increased by 19.55%. After the proper plasma treatment, the interface adhesive property of carbon fiber and PES-C resin matrix can be strengthened, which will further improve the mechanical properties of composite materials.

Determination of the Effect of the Addition of Pumice on the Technological Properties of Wall Tile Using the Factorial Design Method

In this study, the effects of the addition of pumice which has alkali and silica rich content on wall tile product properties were investigated using a factorial experimental design. A 2 2 x3 1 mixed-level factorial experimental design was used to determine the effect of three main factors and interactions between them on wall tile product characteristics. Instead of pegmatite, ground pumice was added at different amounts to the standard wall tiles recipe and five compositions were prepared. Factors affecting the properties of the product were selected as pumice grinding time (10 and 15 minutes), the amount of pumice (0%, 7% and 14%) and firing temperature (1100°C, 1150°C). Linear shrinkage, water absorption, bulk density, total porosity and flexural strength values of samples were measured and the microstructures were investigated. As the amounts of pumice were increased, the amount of the glassy phase was escalated while the total porosity and water absorption values were decreased, bulk density values was increased. Pumice addition instead of pegmatite caused the dissolution of anorthite crystals in the microstructure, facilitating a decline in the amount of anorthite crystals with its high alkaline content and flexural strength values decreased accordingly. The grinding time and the amount of pumice were found to be active on examined features such as the main factors and also the interaction factor.

Evaluation of the flexural strength of carbon, quartz, and glass fiber-based posts

Objectives: This study was done to evaluate the flexural strength of carbon, quartz, and glass fiber posts by means of three-point bending test. Materials and Methods: Thirty pre-fabricated fiber posts were used and divided into three groups. Group I carbon fiber posts (C-Post), group II quartz fiber post (Aestheti Plus), group III glass fiber post (Para Post White) Ten posts (N = 10) were used for each experimental group and were measured with digital caliper before test accomplishment. The fracture load of post specimens was measured, and flexural strength was obtained by the formula using S = 8FL/pd 3 . The values in Kgf/mm 2 were obtained and calculated to Mpa and submitted to ANOVA (a = 0.01) and to the Tukey's test. Results: The mean values of flexural strength show that group II quartz fiber posts (666 MPa) are significantly higher than group I carbon fiber (614 MPa) and group III glass fiber (575 MPa). C onclusion: Hence, this study concluded that quartz fiber post showed significantly higher flexural strength values. Further scope of this study lies in the evaluation and evolution of a restorative materials used for post and core preparation, which have modulus of elasticity in harmony with that of dentin and near-natural esthetic appearance.

Flexural strengths of conventional and nanofilled fiber‐reinforced composites: a three‐point bending test

The purpose of this study was to evaluate the effect of the introduction of nanofillers on the mechanical properties of fiber-reinforced composites (FRCs) for stabilization and conservative treatment of multiple traumatized anterior teeth. In particular, the aim of the research was to point out the force levels of two sizes (diameters 0.6 and 0.9mm) of both conventional and nanofilled FRCs. Eighty FRCs samples were divided into eight groups, each consisting of 10 specimens. Conventional (groups 1, 2, 3, and 4) and nanofilled (groups 5, 6, 7, and 8) FRC samples were evaluated. Each FRC was tested in two diameters (0.6 and 0.9mm) and under two deflections (1 and 2mm). Each sample was polymerized with the same halogen curing unit and then evaluated with a 3-point bending test on a universal testing machine after 48h of dry storage. Nanofilled FRCs showed significantly higher load values than conventional FRCs. Moreover, 0.9-mm-diameter FRCs showed significantly higher load value than 0.6-mm-diameter FRCs. Specimens tested at 2-mm deflection showed significantly higher load values than those tested at 1-mm deflection. Nanofilled FRCs showed significantly higher load values than conventional FRCs. Higher flexural strength values were recorded with 1-mm deflection for both FRC tested.

Effect of Carbamide Peroxide Bleaching Gel on Composite Resin Flexural Strength and Microhardness

This study investigated the effect of 16% carbamide peroxide (Whiteness Perfect/FGM) on the Vickers microhardness and flexural strength of the restorative composites Filtek Z100 (hybrid), Filtek Z350 (nanofill), Brilliant (micro-hybrid) and Opallis (micro-hybrid). Disc-shaped (4x2 mm; n=5) and bar-shaped (12x2x1 mm; n=10) specimens of each restorative material were randomly divided into 2 groups: (G1) 16 weeks stored in distilled water; (G2) 16 weeks stored in distilled water, with 16% carbamide peroxide application during 6 h per day for the last 4 weeks. The mechanical properties were evaluated using a Vickers microhardness tester and a mechanical testing machine. Data were analyzed by two-way ANOVA and Tukey's (HSD) post-hoc test (α=0.05). Filtek Z100 presented the highest microhardness value, followed by Filtek Z350 and finally by Brilliant and Opallis (p=0.00). Filtek Z100 and Brilliant exhibited the highest flexural strength value, followed by Filtek Z350 and Opallis (p=0.00). Bleaching treatment decreased significantly microhardness of Brilliant and Opallis (p=0.00). The flexural strength of all studied materials was not affected by the home bleaching (p=0.28).

Resistência à flexão de resinas de metacrilato de metila e bisacrilato de metila submetidas à termociclagem

OBJETIVO: Verificar a resistência à flexão de quatro resinas utilizadas para a confecção de restaurações temporárias submetidas à termociclagem. MÉTODO: Foram utilizadas as resinas da marcas Luxatemp e Structur 2, à base de bisacrilato de metila, e as resinas das marcas Duralay e Alike, à base de metacrilato de metila. Vinte espécimes de cada material foram confeccionados e divididos em dois grupos, para serem submetidos às seguintes condições: (I) - 24 horas de armazenagem em saliva artificial, e (II) - 24 horas de armazenagem em saliva artificial seguida de termociclagem (2000 ciclos, 5 °C-55°C). Cada amostra foi levada ao teste de resistência à flexão em uma Máquina de Ensaios Universal (EMIC DL 10000) e os dados obtidos foram analisados pelo teste ANOVA (dois fatores) e, em seguida, pelo teste Tukey (p < 0,05). RESULTADO: As resinas de bisacrilato apresentaram resultados superiores de resistência à flexão após ambos os tempos de armazenagem, não diferindo estatisticamente entre si após 24 horas (p = 0,3594). A resina Luxatemp apresentou os maiores valores de resistência à flexão após a termociclagem, sendo estatisticamente superior às demais. A termociclagem alterou as propriedades mecânicas de todas as resinas, diminuindo a sua resistência à flexão (p = 0,001). CONCLUSÃO: As resinas de bisacrilato apresentam maior resistência à flexão do que as resinas de metacrilato para os fatores estudados. Todos os materiais utilizados neste estudo tiveram sua resistência reduzida pela ciclagem térmica.

Comparison of the thermomechanical characteristics of porcher carbon fabric-based composites for orthopaedic applications

Prepregs of fiber-reinforced plastics based on a PORCHER-43200 carbon twill-weave fabric and two types of binders — thermoreactive and thermoplastic — were fabricated using electrostatic spraying, followed by rolling the prepregs in temperature-controlled calenders. A solid epoxy olygomer with dicyandiamine as a hardener and Fortron® polyphenylene sulfide were used as the thermoreactive and thermoplastic binders. The thermomechanical properties of carbon-fiber-reinforced plastics processed from these prepregs, as well as commercial Sigranex® PREPREGCE8201-200-45 S prepregs as model ones, and composites manufactured from them were investigated for comparison. The latter ones are being used for the design of orthopaedic products. It is shown that the composites based on polyphenylene sulfide are characterized by higher values of flexural strength, flexural and shear moduli, and interlaminar fracture toughness (G IC), the latter being the most important parameter.

An experimental and statistical study of interaction effects of matrix particle size, reinforcement particle size and volume fraction on the flexural strength of Al–SiCp composites by P/M using central composite design

Abstract In this study, the effects of reinforcement volume fraction, matrix and reinforcement particle sizes and their interactions on the flexural strength of Al–SiCp metal matrix composites manufactured by powder metallurgy method were investigated by using central composite design (CCD). An experimental plan for CCD with three factors and five levels was used to optimize the required number of experiments. The fabricated composites were reinforced with SiC particles of 2.39, 7.5, 15, 22.5 and 27.61 volume fractions. The particle sizes of 45, 62, 87, 112, and 129 μm were determined for both matrix and reinforcement particles. Experimental and numerical results show that the main effects of factors and their interactions are significant on the flexural strength. Among all factors, the main effect of volume fraction dominates the main effect of other two factors. Interaction between matrix particle size and reinforcement particle size is much more important at low volume fraction compared to that at high volume fraction. The high flexural strength values at low volume fractions are obtained when matrix particle size is equal to or smaller than reinforcement particle size while those at high volume fraction can be only reached when matrix particle size is much smaller than that of reinforcement particle.

Adhesive Strength and Toughness Improvement of Epoxy Resin Modified with Polystyrene-B-Polybutadiene-B-Poly (Methyl Methacrylate) Block Copolymer

Polystyrene-b-polybutadiene-b-poly (methyl methacrylate) block copolymer (SBM) was incorporated into epoxy resin to access the nanostructures in epoxy thermosets, knowing the different miscibility of polymeric blocks on epoxy matrix during the curing treatment. The morphology of modified SBM/epoxy resins was examined by Transmission and Field Emission Gun Scanning Electron Microscopy (TEM and FEG-SEM), reveling a nanostructured epoxy matrix with a dispersed micro-scale phase. The modified resins presented enhanced flexural properties, which were dependent on the composition of blend. The resin reinforced with low SBM contents (2.5 and 5 wt%) presented high values of flexural modulus and strength, while the blend reinforced with higher SBM load (10 wt%) showed higher elongation ability. This different behavior was explained by SEM analysis of fracture surfaces, which showed different toughening mechanisms. The adhesive strength and toughness were determined using carbon fiber/epoxy laminates with peel ply surface treatment as adherends. The results showed a dramatic enhancement of both properties for modified SBM/epoxy adhesives. The highest increases measured were 50 and 70% for lap shear strength and mode-I adhesive fracture energy, respectively.

Influence of Depth Alignment of E-Glass Fiber Reinforcements on Dental Base Polymer Flexural Strength

Abstract Fractures of denture base polymer material are one of the most frequent reasons for repair of removable dentures. The aim of this study was to determine the influence of depth alignment of glass fiber reinforcements onto denture base polymer flexural obtained with the “short beam” testing method. The study showed higher values of flexural strength when reinforcements were placed 1mm from specimen surface (130,63 to 158,55MPa) compared to 0,5mm distance from specimen surface (117,83 to 153,68MPa). Specimens tested after polymerization had higher flexural strength values than specimens tested after storage in water, while thermocycled specimens unexpectedly revealed the highest values. It could be concluded that fiber reinforcements should be positioned more than 0,5mm (up to 1mm) from the base surface of dental prostheses since lesser distance would diminish the reinforcing effect.

Effect of Water on Some Mechanical Properties for Sawdust and Chopped Reeds /UPE composites

In this study, composite materials were prepared using unsaturated polyester resin as binder with two types of fillers (sawdust and chopped reeds). The molding method is used to prepare sheets of UPE / sawdust composite and UPE / chopped reeds composite. The mechanical properties were studied including flexural strength and Young's modulus for the samples at normal conditions (N.C). The Commercial wood, UPE and its composite samples were immersed in water for about 30 days to find the weight gain (Mt%) of water for the samples, also to find the effect of water on their flexural strength and Young's modulus. The results showed that the samples of UPE / chopped reeds composite gained highest values of flexural strength (24.5 MPa) and Young's modulus (5.1 GPa) as compared with other composites at (N.C). The results showed that the wet samples of sawdust composite have lowest values of weight gain (Mt %) of water (0.043%) as compared with other composites after immersion. Also it’s showed a slight decrease in values of Young's modulus for all the samples after immersion as compared with the samples at (N.C). Finally it’s showed a slight decrease in values of flexural strength for all the samples except for the composite material formed from UPE / chopped reeds which showed an increase in the value of flexural strength after immersion, where the wet samples of UPE / chopped reeds composite gained (29 MPa) as compared with the samples at (N.C).

Effect of Water on Some Mechanical Properties for Sawdust and Chopped Reeds /UPE composites

In this study, composite materials were prepared using unsaturated polyester resin as binder with two types of fillers (sawdust and chopped reeds). The molding method is used to prepare sheets of UPE / sawdust composite and UPE / chopped reeds composite. The mechanical properties were studied including flexural strength and Young's modulus for the samples at normal conditions (N.C). The Commercial wood, UPE and its composite samples were immersed in water for about 30 days to find the weight gain (Mt%) of water for the samples, also to find the effect of water on their flexural strength and Young's modulus. The results showed that the samples of UPE / chopped reeds composite gained highest values of flexural strength (24.5 MPa) and Young's modulus (5.1 GPa) as compared with other composites at (N.C). The results showed that the wet samples of sawdust composite have lowest values of weight gain (Mt %) of water (0.043%) as compared with other composites after immersion. Also it’s showed a slight decrease in values of Young's modulus for all the samples after immersion as compared with the samples at (N.C). Finally it’s showed a slight decrease in values of flexural strength for all the samples except for the composite material formed from UPE / chopped reeds which showed an increase in the value of flexural strength after immersion, where the wet samples of UPE / chopped reeds composite gained (29 MPa) as compared with the samples at (N.C).

High-strength nanograined and translucent hydroxyapatite monoliths via continuous hydrothermal synthesis and optimized spark plasma sintering

The synthesis of high-strength, completely dense nanograined hydroxyapatite (bioceramic) monoliths is a challenge as high temperatures or long sintering times are often required. In this study, nanorods of hydroxyapatite (HA) and calcium-deficient HA (made using a novel continuous hydrothermal flow synthesis method) were consolidated using spark plasma sintering (SPS) up to full theoretical density in ∼5 min at temperatures up to 1000 °C. After significant optimization of the SPS heating and loading cycles, fully dense HA discs were obtained which were translucent, suggesting very high densities. Significantly high three-point flexural strength values for such materials (up to 158 MPa) were measured. Freeze-fracturing of disks followed by scanning electron microscopy investigation revealed selected samples possessed sub-200 nm sized grains and no visible pores, suggesting they were fully dense.

Temperature effects on mechanical behaviour of engineered stones

In this research, three types of artificial or engineered stones were compared against two types of natural stones (a limestone and a granite) in what concerns to temperature, thermal ageing and thermal shock effects on flexural strength and Young’s modulus. Temperatures of the thermal treatments, in the range from 20 to 200 °C, were intentionally chosen to simulate some practical applications of this kind of materials, for example, when they are used as kitchen tops. The results reveal the different characteristics of the materials. When tested at temperatures up to 100 °C, engineered stones show much higher values of flexural strength compared to the natural stones; and when tested at ambient temperature after being submitted to rapid cooling (thermal shock) from 200 °C down to 20 °C, engineered stones continue to show higher values of flexural strength compared to the natural stones. For the temperature range from 20 to 200 °C, thermal shock and thermal ageing effects on Young’s modulus are not very pronounced. Young’s modulus (E) of each of the materials was determined at ambient temperature, and the engineered stones keep almost the same value of E after thermal ageing or thermal shock up to 160 °C.

Properties of cellulosic fibre reinforced plaster: influence of hemp or flax fibres on the properties of set gypsum

In the last few years, eco friendly materials have become an important part of the building materials market. Natural fibres are already used in various types of materials, like plastics, concrete and lime-based products. They demonstrate different attributes like the combination of good mechanical, thermal and acoustic properties that allow these types of materials to be used for different applications. The main drawback associated with plaster is its brittleness, especially under tensile stress. Therefore, it is interesting to investigate different methods that could potentially enhance the mechanical properties of plaster. Adding fibres to gypsum to obtain a composite material is one way to improve the behaviour of the product, especially after the failure of the matrix. The aim of this work was to the study the effects of adding natural fibres, namely hemp and flax fibres, on the setting time of plaster and the mechanical properties of the composite matrix. It was shown that hemp delayed the setting of plaster, unlike flax. The initial and final setting times almost doubled when hemp was added in a plaster matrix, whereas flax fibres did not drastically change them. Different chemical treatments of hemp were tested and the impact on the setting time was measured. The setting times of both composites made with hemp and flax were reduced once the fibres were treated (25–40% reduction), compared to the setting time of the calcium sulphate hemihydrate alone. The mechanical properties of the composite materials are also discussed. The behaviour of plaster was modified from brittle to a non-linear one when fibres were added, and even at small levels of addition, flax fibres allowed slightly higher values of flexural strength to be reached.

Flexural strength and fracture toughness of dental core ceramics

Many different strengthened all-ceramic core materials are available. In vitro study of their mechanical properties, such as flexural strength and fracture toughness, is necessary before they are used clinically. The purpose of this study was to evaluate and compare the mechanical properties of 6 commonly used all-ceramic core materials using biaxial flexural strength and indentation fracture toughness tests. Specimens of 6 ceramic core materials (Finesse, Cergo, IPS Empress, In-Ceram Alumina, In-Ceram Zirconia, and Cercon Zirconia) were fabricated (n=25) with a diameter of 15 mm and width of 1.2 +/- 0.2 mm. For each group, the specimens were tested to compare their biaxial flexural strength (piston on 3 balls) (n=15), Weibull modulus, and indentation fracture toughness (n=10) (IF method). The data were analyzed with 1-way ANOVA test (a=.05). The Tamhane multiple comparison test was used for post hoc analysis. Mean (SD) of biaxial flexural strength values (MPa) and Weibull modulus (m) results were: Finesse (F): 88.04 (31.61), m=3.17; Cergo (C): 94.97 (13.62), m=7.94; IPS Empress (E): 101.18 (13.49), m=10.13; In-Ceram Alumina (ICA): 341.80 (61.13), m=6.96; In-Ceram Zirconia (ICZ): 541.80 (61.10), m=10.17; and Cercon Zirconia (CZ): 1140.89 (121.33), m=13.26. The indentation fracture toughness results showed that there were significant differences between the tested ceramics. The highest fracture toughness values (MPa x m(0.5)) were obtained with the zirconia-based ceramic core materials. Significant differences were found in strength and toughness values of the materials evaluated. Cercon Zirconia core material showed high values of biaxial flexural strength and indentation fracture toughness when compared to the other ceramics studied.

Highly conductive epoxy/graphite composites for bipolar plates in proton exchange membrane fuel cells

Carbon-filled epoxy composites are developed for potential application as bipolar plates in proton exchange membrane (PEM) fuel cells. These composites are prepared by solution intercalation mixing, followed by compression molding and curing. Electrical conductivity, thermal and mechanical properties, and hygrothermal characteristics are determined as function of carbon-filler content. Expanded graphite and carbon black are used as synergistic combination to obtain desired in-plane and through-plane conductivities. These composites show high glass transition temperatures ( T g ∼ 180 °C), high thermal degradation temperatures ( T 2 ∼ 415 °C), in-plane conductivity of 200–500 S cm −1 with 50 wt% carbon fillers, in addition to offering high values of flexural modulus, flexural strength, and impact strength, respectively 2 × 10 4 MPa, 72 MPa, and 173 J m −1. The presence of carbon fillers helps reduce water uptake from 4 to 5 wt% for unfilled epoxy resins to 1–2 wt%. In addition, morphology, electrical, mechanical, and thermal properties remain unchanged on exposure to boiling water and acid reflux. This data indicate that the composites developed in this work meet many attributes of bipolar plates for use in PEM fuel cells.