Effect Of Composite Thickness Research Articles

Effects of composite thickness on shear bond strength to dentin

Sixty non-carious extracted human molars were used in this study. The enamelon the occlusal surface ofthe crown of the tooth was removed by a diamond bur thenthe surfaces of the teeth were ground flat. The teeth were randomly divided into sixgroups each of ten and stored in distilled water at 370 C. Two types of composite wereused in this study, Definite and Tetric. The bonding agents Etch and Prime wereprepared according to manufacturers directions and applied to the dentin surface onthe first three groups and light cured for 20 seconds. The composite Definite waspacked into either 2, 3, and 4mm thick using split metal mould in the first, secondand third groups respectively and bulk-cured from top of the composite for 40seconds, the same procedure was repeated in the remaining three groups but thecomposite used was Tetric which its corssponding bonding agent was Excite. Thebond strength was measured with universal compression machine.The results showed `that there was no significant difference between the two types of composite Tetric andDefinite used in this study. The shear bond strength was affected by the compositethickness, the 2 mm increment showed higher bond strength than the 3mm and 4mmincrement in both composites

The effect of composite thickness as thermal insulation roof coating on room temperature reduction

The increasingly widespread use of galvanized roofs certainly has an effect on the occupants in the room below. Among them is a hot room temperature. For that reason, it is necessary to make new discoveries in the field of composites of natural materials to overcome them because most natural materials, especially natural stone, have low thermal conductivity, which means they can inhibit heat propagation. This study sought to ascertain how much andesite natural stone powder, combined with epoxy, can lower the room temperature when it is layered on a galvanized roof. Different amounts of natural stone powder applied to a galvanized roof results in different thermal conductivities. The temperature readings were taken at a height of 20 cm above the roof, right at the bottom galvanic, as well as the temperature in the room below. Our results showed that adding andesite natural stone powder to the roof was able to lower the room temperature, and the thicker the composite layer in coating the galvanized roof, the lower the room temperature under the roof.

Dynamic performance of flax fiber-reinforced polymer

The study addresses the dynamic performance of flax fiber-reinforced polymer (FFRP) composites via a series of drop-weight impact tests. The experiment was performed based on ASTM standards by using an instrumented falling weight impact machine. Increasing impact energy was applied on the FFRP specimens until an occurrence of perforation. The effect of composite thickness and impact striker diameter were considered. The results showed that the striker diameter and composite thickness have a significant effect on the impact properties of the composites. It is also revealed the influence factors that control the impact behavior of FFRP composite that will be useful for developing future protective fiber-reinforced composites.

Parametric optimization of laser drilling of microwave-processed kenaf/HDPE composite

The present work focused on the investigation of hole quality characteristics in laser-drilled kenaf/high-density polyethylene (HDPE) composites. Microwave-assisted compression molding was used to fabricate kenaf/HDPE composite with 20 wt% of the kenaf fiber reinforcement. The two input parameters pertaining to the experimentation were laser power and cutting speed. Kerf taper angle, heat-affected zone (HAZ), and surface roughness were investigated to evaluate the surface quality and accuracy of the holes generated through laser drilling on composite specimens. The assessment of HAZ was performed qualitatively through image analysis on scanning electron micrographs. Additionally, the effect of composite thickness on laser drilling was also investigated for 3-, 6.7-, and 10-mm composite specimens. The central composite design was used to plan the experiments. The kenaf/HDPE composite drilled at power 120 W and speed 2 mm/s shows a minimum kerf taper angle and surface roughness of 0.056° and 3.83 ± 0.19 µm, respectively. Regression model was obtained for the establishment of relation between input variable parameters and responses. Experimental results and predicted model results exhibited good agreement with each other as they provide error less than 5.35%. The analysis of variance was carried out to obtain the significance of the model chosen for optimization of the output values, that is, surface roughness and kerf taper.

Effect of metallic fillers on the hardness of polystyrene composites: An experimental investigation

In this study, the effects of composite thickness (2.5-7.5 mm), filler content (15-45%w/w) and particle sizes (20-100 µm) on the hardness of Polystyrene metal composites were examined. The metals comparatively considered were aluminium particles and iron fillings. It was observed that smaller metal particle sizes in the composite matrix and greater filler proportions will lead to improvement in hardness. Composite thickness did not have a significant effect on the hardness of the metal composites. PS-Al composite is harder than PS-Fe composite with the optimal hardness being 43.7 and 11 respectively. The factor levels that will optimise hardness for PS-Al composite are thickness of 7.5 mm, filler of 39% and particle size of 20 µm. For PS-Fe composites they are thickness of 5.9 mm, filler of 45% and particle size of 34µm. The metallic composites (PS-Al and PS-Fe) exhibited contrasting mechanical strength when viewed under SEM with a homogenous micro-structure of high interfacial interaction between the metal particles (Aluminium) and the PS resin matrix while the PS-Fe metallic composite under micro-structural analysis displayed relatively moderate to low tensile strength and hardness with weak interfacial interaction between the Iron particles and the PS resin.

In Vitro Biocompatibility of Contemporary Bulk-fill Composites.

This study evaluated the biocompatibility of contemporary bulk-fill resin-based composites (RBCs) including PRG (pre-reacted glass ionomer) materials based on the International Organization for Standardization 10993. In addition, the effect of composite thickness on cytotoxicity was also assessed. Two standard composites, two bulk-fill PRG RBCs, and three bulk-fill non-PRG RBCs were investigated. Block-shaped specimens of 2-mm and 4-mm thickness were cured with an irradiance of 700 mW/cm(2) for 20 seconds with a light-emitting diode curing light and eluted with culture medium at 37°C for 24 hours. L929 mouse fibroblasts were exposed to extracts at varying dilutions (1:1, 1:2, and 1:10) for 24 hours. Analyses were performed to assess cytotoxicity, phase contrast microscopy, and quantitative cell viability. Among the bulk-fill RBCs, extracts of PRG materials resulted in the lowest cell viability. At 4-mm thickness, undiluted extracts of bulk-fill non-PRG RBCs had significantly higher cell viability than the standard composites. Chemical composition, specimen thickness, and testing concentrations of extracts had significant effects on cell viability and morphology. Cytotoxic effects of composites on cell viability were parallel with cell morphologic changes. Not all bulk-fill RBCs demonstrated high cell viability (>70%) at 4-mm thickness despite manufacturers' recommendations of bulk placement and curing.

Comparison of tensile and compressive characteristics of intra/interply hybrid laminates reinforced high‐density flexible foam composites

ABSTRACTThe current study focused on fabrication and mechanical evaluation of intra/interply hybrid laminates–reinforced high‐density flexible foam composites. The effects of composite thickness and expansion factor on the tensile and compressive characterization of the hybrid‐laminated composites were experimentally investigated. Double face sheets were made of high‐strength intra/interply hybrid laminates containing recycled Kevlar nonwovens and glass woven fabric. The results revealed that the hybrid laminates face sheet apparently promoted the tensile strength and tear resistance of the high‐density flexible polyurethane foam. Tearing resistance in perpendicular direction exceeded more than twice the value in parallel direction. In terms of dynamic cushioning properties, cushioning force increased with the increase in composite thickness and the decrease in expansion factor, whereas the cushioning capacity loss, however, showed a different trend with the variation of the parameters. Most samples buffered more than 95% incident force under dynamic loading. Composite thickness and expansion factor exhibited significant influence on compression and indentation properties, including hardness, initial hardness factor, and indentation modulus. Except the composites with 10 mm thickness, the intra/interply hybrid laminated composites exhibited hysteresis loss of indentation force deflection ranging from approximately 30 to 38%, which was due to the fiber and thermal bonding point failure of hybrid laminates as unrecoverable damage. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41438.

Fabrication and properties of 1-3-2 multi-element piezoelectric composite

A 2–2 type multi-element piezoelectric composite was fabricated using PZT-5 as functional part, silicon gel and polyurethane as decoupling material to ensure the independence of transmitted acoustic beam and strengthen the signal power. The effects of composite thickness and decoupling material on dielectric, piezoelectric and electromechanical coupling properties were investigated. The results show that the piezoelectric, dielectric and the electromechanical coupling properties of each piezoelectric element in the composite exhibit excellent consistency. The relative permittivity of epoxy/silica piezoelectric composites(ESP) is higher than that of epoxy resin piezoelectric composites(ERP) and epoxy/polyurethane piezoelectric composites(EPP) at the same thickness, and EPP has the lowest permittivity. Multi-element piezoelectric composites can significantly improve the thickness electromechanical coupling coefficient (Kt and reduce the mechanical quality factor(Qm), in which Kt value of EPP is up to 65.19%. With increasing the composite thickness, the Qm value of the composites slightly decreases.

Influence of Thickness Parameters on 2-2 Cement Based Piezoelectric Composite

2-2 cement based piezoelectric composite was fabricated using sulphoaluminate cement and lead magnesium niobate-lead zirconate-lead titanate ceramic (P(MN)ZT) by dice-and-fill technique. The effects of composite thickness on dielectric, piezoelectric and electromechanical properties of the composite were analyzed, respectively. The results show that the increase of composite thickness will improve the piezoelectric strain factor d33 of the composite, while decreases the piezoelectric voltage factor g33 of the composite. The relative dielectric factor εr as well as the dielectric loss tan δ of the composite also increases with increasing the thickness. The electromechanical analysis results show that the thickness electromechanical coupling coefficient Kt of the composite increases obviously with decreasing the thickness, meanwhile the mechanical quality factor Qm of the composite shows the increasing trend, thus, the receiving piezoelectric transducers can be fabricated by decreasing the thickness.

Three-dimensional size effects in composite pin joints

Mechanical fastening is commonly used in joining composite laminates. It is especially superior to adhesive bonding in joining thick composite laminates. The significant effects of composite thickness on the efficiency of pin joining have been reported in a previous study. The present study further investigated the three-dimensional (thickness as well as in-plane dimensions) size effects on pin joining. A glass-fabric/phenolic composite material was used as the studied material while double-lap-single-pin joints were used as the experimental models. Based on four different thicknesses and seven different hole diameters, in total nine composite joint configurations were prepared. The nine configurations were organized into three groups with differentH/D ratios (thickness versus hole diameter). Experimental results revealed that the load-displacement curves of the groups withH/D=0.4 and 0.75 were brittle-type while those of the group withH/D=1.5 were ductile-type. The microscopic damage modes of the joints with brittle-type curves were due to outward buckling for 8-ply cases and kink bands for 24-ply and 40-ply cases. The bearing strengths of the pin joints decreased monotonically in the group withH/D=0.4 but increased then decreased in the groups withH/D=0.75 and 1.5 as the joint size increased. It was found that both the material properties and the geometry parameters were responsible for the three-dimensional size effects.

Interlaminar Fracture of Random Short-Fiber SMC Composite

The interlaminar fracture behavior of a random short-fiber SMC composite is studied both experimentally and analytically. In the experimental phase of the study, the random short-fiber SMC-R50 composite with different thicknesses is used. The commonly used double-cantilever-beam (DCB) fracture test is employed to evaluate the mode-I interlaminar fracture toughness. In the analytical portion of the research, owing to significant deformation in the DCB test, a geometrically nonlinear analysis is introduced to account for large deflection and nonlinear load-deflection curves in the evaluation of the interlaminar fracture toughness. For the SMC-R50 material studied, the interlaminar toughness of the composite is found to be an order of magnitude higher than that of unreinforced neat resin due to unusual damage mechanisms ahead of the crack tip and significant fiber bridging across crack surfaces. The effect of com posite thickness on the interlaminar fracture is appreciable. The influence of the SMC material microstructure on interlaminar crack resistance is discussed in detail.

Recent advances in understanding of acoustic emission from fiber composites and metals

The time and frequency domains of acoustic emission signals generated during loading of Kevlar 49/epoxy composites have been studied. The effects of composite thickness, transducer type, and load level have been examined. Results indicate that relatively low frequencies predominate. A study of the frequency spectrum of acoustic emission signals generated during fatigue testing of fracture toughness specimens has been completed. In particular, the dependence of frequency on the stress intensity level was studied. Extensive tension and compression testing of unflawed 7075 and 2124 aluminum has been undertaken. Among the results are (i) a correlation between fracture toughness and the acoustic emission generated during a compression test of 2124-T851; (ii) the rate of acoustic emission energy sensed at strains greater than 1.5% is more than two orders of magnitude greater in tension than in compression; and (iii) acoustic emission can easily be used to sort out plates of 7075 aluminum which have undesired 20–60-μm inclusion particles. [This work was performed under the auspices of the U.S. Energy Research and Development Administration, under contract No. W-7405-Eng-48.]