Adaptation of composite resin restorative materials to retentive grooves of Class I cavity preparations.
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An in vitro study was conducted to determine the adaptation of composite resin restorative material to rounded and acute-angled retention grooves of Class I cavity preparations on 24 extracted premolars. Two chemically cured (P-IO ® and Miradapt ®) and 2 lightcured (Prisma-Fil® and Ful-Fil®) composite resin materials, after being coded to create a blind study, were injected into cavity preparations containing rounded and acute-angled retention grooves. The restored premolars were cut in half and examined via SEM at 50 x magnification. A standardized method was used to determine the adaptation of each composite resin to the grooves. Interjudge evaluation showed all composite resin materials adapted well to both rounded and acute-angled retention grooves. Mean and standard deviation values revealed no significant difference in the average dentinresin gap between treatment groups and between the 2 types of retention grooves. There was only 0.6M difference between the lowest and highest mean values.Keywords:
Resin composite
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Bismaleimide composites filled with nanometer SiO 2 w ere prepared by cast molding. The mechanical and tribological properties of the composites with various content of nanometer SiO 2 were investigated. The slidi ng wear behavior of the composites against AISI-1045 steel ring was studied on an M-200 friction and wear tester. The morphologies of the worn surfaces of the composite and the steel ring were observed by scanning electron microscopy. It was found that nanometer SiO 2 filled composite exhibited considerably higher m echanical and tribological properties than the neat bismaleimide. The lowest wea r rate was obtained with the composite containing 1.0 wt.% SiO 2, while the best mechanical properties was obtained with the composite containing 0.75 wt .% SiO 2. The SEM pictures of the worn composite surface indicate that the we ar mechanism of the composite was mainly adhesion wear due to the generation of a thin,uniform and tenacious transfer film on the carbon steel ring surface, wh ile that of neat BMI-BA was mainly plastic deformation accompanied by fatigue c rackings.
Nanometre
Molding (decorative)
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Polystyrene
Shape-memory polymer
Carbon fibers
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Performance of composite materials usually suffers from process-induced defects such as dry spots or microscopic voids. While effects of void content in molded composites have been studied extensively, knowledge of void morphology and spatial distribution of voids in composites manufactured by resin transfer molding (RTM) remains limited. In this study, through-the-thickness void distribution for a disk-shaped, E-glass/epoxy composite part manufactured by resin transfer molding is investigated. Microscopic image analysis is conducted through-the-thickness of a radial sample obtained from the molded composite disk. Voids are primarily found to concentrate within or adjacent to the fiber preforms. More than 93% of the voids are observed within the preform or in a so-called transition zone, next to a fibrous region. In addition, viod content was found to fluctuate through-the-thickness of the composite. Variation up to 17% of the average viod content of 2.15% is observed through-the-thicknesses of the eight layers studied. Microscopic analysis revealed that average size of voids near the mold surfaces is slightly larger than those located at the interior of the composite. In addition, average size of voids that are located within the fiber preform is observed to be smaller than those located in other regions of the composite. Finally, proximity to the surface is found to have no apparent effect on shape of voids within the composite.
Transfer molding
Void (composites)
Molding (decorative)
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The polyurushiol (PUS)/multiwalled carbon nanotube (MWCNT) composite coatings were prepared by in situ composite method. The fracture morphology of the composite films showed that MWCNTs had been well dispersed in PUS matrix, which significantly decreased the electrical resistivity and the gloss of the composite films. The nonconducting/conducting state transition took place at approximately 3.0 wt% of MWCNTs with the volume electrical resistivity of 104 Ω cm. The results of the mechanical tests revealed that the impact of strength and the storage modulus of the coatings increased with the addition of MWCNTs. Furthermore, the PUS/MWCNTs composite films had good chemical resistance. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers
Gloss (optics)
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Fiber-reinforced composite
Woven fabric
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The effects of yarn size on the mechanical properties of silicon carbide composites reinforced with a plain woven carbon cloth with two sizes of yarns (1 and 3 k) were investigated. The experimental results show that the composite fabricated with 1 k yarns exhibits greater stiffness and strength than the composite fabricated with 3 k yarns. Microstructural observations revealed the existence of matrix microcracks in both the composites under the as‐processed condition due to the large difference of thermal expansion between the fibers and the matrix, which are more severe for the composite with 3 k yarns. The fractured surfaces of the composite with 1 k yarns showed extensive fiber pull‐out in contrast to the yarn pull‐out in the composite with 3 k yarns. The larger interyarn and intrayarn voids due to difficulties of matrix infiltration in the composite with 3 k yarns represent the primary contribution to the diminished mechanical properties. Unequal yarn sizes give rise to different yarn waviness, which may be another source of difference in the mechanical properties of composites.
Waviness
Woven fabric
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The Al foams made by space-holder method were physically inserted into carbon fiber reinforced plastic (CFRP) composite thin-wall tubes to obtain the composite structure of Al foam-filled CFRP composite thin-wall tubes. Quasi-static compression tests of CFRP composite tubes, Al foams and Al foam-filled CFRP composite thin-wall tubes were carried out to study their compression properties. Meanwhile, digital image correlation (DIC) was applied to analyze their deformation modes. Furthermore, the compressive properties, energy absorption properties and failure modes of Al foam-filled CFRP composite thin-wall tubes at different temperatures (25-150℃) were studied. The results show that Al foams as fillers change the compression deformation behavior of CFRP composite thin-walled tubes from the scattering flowering failure of a single CFRP composite tube to the fiber layer fracture failure of a foam-filled tube. Comparing to CFRP composite thin-walled tubes, the stress fluctuations of Al foam-filled CFRP composite thin-wall tubes decrease obviously. With environmental temperature increasing, both the compressive properties and energy absorption properties of CFRP composite thin-walled tubes, Al foams and Al foam-filled CFRP composite thin-wall tubes decrease. But the interaction between Al foams and CFRP composite thin-walled tubes is enhanced, the enhancement effect of Al foams on CFRP composite thin-walled tubes is more obvious at high temperature.
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