Fracture strength of class II slot cavities restored with polymerizable restorative materials

This study compared the fracture strength of Class II slot cavities restored with polymerizable restorative materials. Sixty, caries-free, posterior teeth were divided into five groups of 12 teeth. The Class II slot cavities were prepared. The teeth were restored with two packable composites (Filtek P60, Surefil), a microhybrid composite (Filtek Z250)and two ormocer (Definite, Admira). The restorations were then subjected to fracture resistance tests. The marginal ridges of the restorations were loaded at an angle of 13.5° to the long axis of the tooth in an Universal Testing Machine until failure. Analysis of mean forces indicated that, Filtek P60, Surefil and Filtek Z250 exhibited better performance than Definite and Admira. The tested resin composites differed in their mechanical properties. This study suggested that fracture behavior were highly influenced by the filler system. Overall, Filtek P60, Surefil, Filtek Z250, demonstrated good fracture resistance. Copyright © 2003 John Wiley & Sons, Ltd.     

ZrB<Subscript>2</Subscript>/HfB<Subscript>2</Subscript>–SiC Ultra-High-Temperature Ceramic Materials Modified by Carbon Components: The Review

The review has been made of recent publications on modification of ZrB₂/HfB₂–SiC ultra-hightemperature ceramic composite materials (UHTC) by carbon components: amorphous carbon, graphite, graphene, fibers, and nanotubes. Available data have been presented on some aspects of oxidation of such materials at temperatures ≥1500°C and both at the atmospheric pressure and at the reduced oxygen partial pressure; structural features of the formed multilayer oxidized regions have been noted. It has been considered how the type and content of the carbon component and the conditions (first of all, temperature) of UHTC production affect the density, flexural strength, hardness, fracture toughness, and thermal and oxidation resistance of the modified ceramic composites.     

Investigation of sub‐micron size cenosphere fillers and filler loading on the mechanical and tribological peculiarity of polyester composites

This paper investigates the effect of sub‐micron size cenosphere filler and filler loading on mechanical and dry sliding wear property of polyester composites. Composites are fabricated by filling with 10 and 20 wt% of 800 and 200‐nm size of cenosphere filler particles. Neat polyester composite is also prepared for comparison analysis. Dry sliding wear test is conducted for these composites over a range of sliding distance with different sliding velocities and applied loads on a pin‐on‐disc wear test machine. Taguchi methodology and analysis of variance (ANOVA) is used to analyze the friction and wear characteristics of the composites. The artificial neural network (ANN) approach is implemented to the friction and wear data for corroboration. In this work, mechanical properties of composites such as hardness, tensile strength, tensile modulus, flexural strength, and compressive strength revealed that mechanical properties and wear resistance of the composites increase with a decrease in the particle size. The measured Young's moduli are comparable to standard theoretical prediction models. The morphology of worn composite specimens has been examined by scanning electron microscopy to understand the dominant wear mechanisms. Finally, optimal factor settings are determined using a genetic algorithm (GA). Copyright © 2017 John Wiley & Sons, Ltd.     

Waste marble dust-filled sustainable polymer composite selection using a multi-criteria decision-making technique

This research works with the optimal design of marble dust-filled polymer composites using a multi-criteria decision-making (MCDM) technique. Polylactic acid (PLA) and recycled polyethylene terephthalate (rPET)-based composites containing 0, 5, 10, and 20 wt% of marble dust were developed and evaluated for various physicomechanical and wear properties. The results showed that the incorporation of marble dust improved the modulus and hardness of both PLA and rPET. Moreover, a marginal improvement in flexural strength was noted while the tensile and impact strength of the matrices were deteriorating due to marble dust addition. The outcomes of wear analysis demonstrated an improvement in wear resistance up until 10 wt% filler reinforcement, after which the incidence of dust particles peeling off from the matrix was observed, thereby reducing its efficiency. The best tensile modulus of 3.23 GPa, flexural modulus of 4.39 GPa, and hardness of 83.95 Shore D were obtained for 20 wt% marble dust-filled PLA composites. The lowest density of 1.24 g/cc and the highest tensile strength of 57.94 MPa were recorded for neat PLA, while the highest impact strength of 30.94 kJ/m² was recorded for neat rPET. The lowest wear of 0.01 g was obtained for the rPET containing 5 wt% marble dust content. The experimental results revealed that for the examined criteria, the order of composite preference is not the same. Therefore, the optimal composite was identified by adopting a preference selection index-based MCDM technique. The findings demonstrated that the 10 wt% marble dust-filled PLA composite appears to be the best solution with favorable physical, mechanical, and wear properties.     

The addition of clay on the mechanical properties of surface‐treated CF‐filled PA66 composites

Polyamide 66 (PA66) composites filled with clay and carbon fiber (CF) were prepared by twin‐screw extruder in order to study the influence of nanoparticle reinforcing effect on the mechanical behavior of the PA66 composites (CF/PA66). The mechanical property tests of the composites with and without clay were performed, and the fracture surface morphology was analyzed. The results show that the fracture surface area of the clay‐filled CF/PA66 composite was far smoother than that of the CF/PA66 composite, and there formed a tense interface on the CF surface after the addition of clay. The tensile and flexural strength of CF/PA66 composites with clay was improved. The impact strength decreased because of the high interfacial adhesion. In conclusion, the addition of clay favored the improvement of the higher interface strength and so had good effect on improving the tensile and flexural properties of the composites. Copyright © 2017 John Wiley & Sons, Ltd.     

Effect of fiber length and loading on the properties of Schumannianthus dichotomus (murta) fiber–reinforced epoxy composites

The present work was aimed at preparing composite materials using epoxy matrix and murta fibers of varying lengths and weight percentages. The composites were analyzed on the basis of density, thermal gravimetric analysis, infrared spectroscopy, scanning electron microscopy, tensile strength, flexural strength, Izod impact strength, and Rockwell hardness studies. Twenty-five weight percent of randomly oriented fibers of 25 mm length rendered the best mechanical properties to the composite. The tensile strength of the composite was analyzed using the Hirsch model. The characterization of the composite reveals that murta fiber is a good candidate for polymer reinforcement.     

The Silk Textile Embedded in Silk Fibroin Composite: Preparation and Properties

Silk reinforced silk-fibroin-based composites were prepared by embedding of silk textile into regenerated silk fibroin(RSF)matrix. The breaking stress and breaking strain of the composites were found 37.7 MPa and 71.1% respectively at(95 ± 5)% RH.Morphological analysis was carried out to observe fracture behavior of the samples. The in vitro biodegradation test showed that the composite degraded slowly and lost 70% weight at the end of 168 h. Moreover, compared with RSF pure film, the composite kept strength and toughness much longer time. In conclusion, this composite has the potential for more accurate cytology research and biomedical tests in the future.     

Experimental and modeling analysis of mechanical-electrical behaviors of polypropylene composites filled with graphite and MWCNT fillers

The incorporation of carbon fillers can improve the thermal and electrical conductivities of polymer composites but will also have a significant effect on the flexural and tensile behavior. In this paper, two types of carbon fillers were added to polypropylene - carbon nanotubes and synthetic graphite. The influences of these filler materials on the tensile, flexural and fracture toughness characteristics were measured and the electrical conductivity of composites was also investigated. It was observed that the fillers lead to a remarkable increase in the flexural and tensile modulus of polypropylene composites. The maximum flexural and tensile strengths slightly increased with the addition of graphite, however, they were significantly increased in the case of carbon nanotubes because MWCNTs possess exceptional stiffness and strength and their length to diameter ratio is extremely high when compared with graphite. Electrical conductivity of polypropylene composites was evaluated. Noteworthy, composites based on synthetic graphite show a percolation process at one order of magnitude concentration higher than MWCNT filled polypropylene. Fracture toughness results open a wide range of applications for PP-MWCNT composites. Several prediction models were inspected in this research and it was concluded that inverse rule of mixtures model showed the most accurate predictions of the tensile modulus for composites made of polypropylene.     

A study of PP/PET composites: Factorial design,mechanical and thermal properties

Due to the economic importance of polypropylene (PP) and polyethylene terephthalate (PET), and the large amount of composites made with PP matrix and recycled PET as reinforcing material; an investigation was performed regarding the mechanical and thermal behavior of PP composites containing recycled polyethylene terephthalate fibers (rPET). Interfacial adhesion between the two materials was achieved by adding a compatibilizer, maleic anhydride grafted polypropylene, PP-g-MA. Mechanical behavior was assessed by tensile, flexural, impact and fatigue tests, and thermal behavior by HDT (Heat Deflection Temperature). Fractured surfaces and fiber were investigated by scanning electron microscopy. Multiple regression statistical analysis was performed to interpret interaction effects of the variables. Tensile strength, tensile modulus, flexural strength, flexural modulus and HDT increased after rPET fiber incorporation while strain at break, impact strength and fatigue life decreased. Addition of compatibilizer increased tensile strength, flexural strength and flexural modulus, fatigue life and HDT while tensile modulus, strain at break and impact strength decreased. However, at low fiber content, the impact strength increased, probably due to nucleation effects on PP.     

Changes in the mechanical properties of tooth-colored direct restorative materials in relation to time

The objective of this study was to determine the flexural strength, flexural modulus, Vickers hardness of a packable composite (Surefil), and an ormocer (Definite) in comparison with a microhybrid composite (Z-100), a microfil composite (Silux Plus) and a polyacid-modified composite resin (Dyract). Flexural strength and flexural modulus were determined using a three-point bending device. Microhardness was measured with a Vickers indentor. The specimens of each material were prepared according to manufacturer's instructions. The specimens were stored in artificial saliva at pH 6, all at 37°C. The groups were tested at the beginning of the test, at 3 months and at 6 months. Flexural strength values of Surefil and Definite showed a progressive increase. The highest MPa values were determined for Surefil (134.4 MPa) and the lowest MPa values were obtained for Dyract (59.6 MPa). The highest flexural modulus values were revealed for Surefil (10.000 GPa). Z-100, Silux Plus and Definite showed a tendency to decline in relation to time for their flexural modulus. GPa values of Silux Plus were stable at 3 and 6 months. Vickers hardness numbers showed that Surefil was the hardest and Dyract was the weakest material. Copyright © 2003 John Wiley & Sons, Ltd.     

Study on the preparation and mechanical properties of alumina ceramic coating reinforced by graphene and multi-walled carbon nanotube

The paper investigates preparation and mechanical performances of a composite ceramic coating reinforced by graphene and multi-walled carbon nanotube. The carbon nanotube is functionalized with the carboxyl functional group (–COOH) and un-functionalized with sodium dodecyl benzene sulfonate (SDBS). The structure of the functionalized and hybrid-functionalized carbon nanotube is identified using infrared spectroscopy (FTIR analysis). The coating is brushed on the matrix and then cures under temperature lower than 250°C. The morphological and cross section features are studied by scanning electron microscopy (SEM). The distributions of hardness and fracture toughness are determined using a microhardness tester. The adhesive strength is evaluated using a universal tensile tester. The tribological properties are detected using friction wear testing machine. The experimental results show that the structure of the composite coating is compact, and both graphene and hybridtreated carbon nanotube are well dispersed. Addition of 0.2 wt % graphene and 0.2 wt % hybrid-functionalized carbon nanotube results in a prominent increase in hardness and fracture toughness. Meanwhile, the adhesive strength between the composite coating and the metallic substrate is well improved due to the high tensile strength of both graphene and carbon nanotube. Compared with pure alumina coating, the friction coefficient as well as the wear depth and width of grinding crack of the composite coating is much lower.

     

Investigation into the Structural,Chemical and High Mechanical Reforms in B4C with Graphene Composite Material Substitution for Potential Shielding Frame Applications

In this work, boron carbide and graphene nanoparticle composite material (B₄C–G) was investigated using an experimental approach. The composite material prepared with the two-step stir casting method showed significant hardness and high melting point attributes. Scanning electron microscopy (SEM), along with energy dispersive X-ray spectroscopy (EDS) analysis, indicated 83.65%, 17.32%, and 97.00% of boron carbide + 0% graphene nanoparticles chemical compositions for the C-atom, Al-atom, and B₄C in the compound studied, respectively. The physical properties of all samples’ B₄C–G like density and melting point were 2.4 g/cm³ density and 2450 °C, respectively, while the grain size of B₄C–G was in the range of 0.8 ± 0.2 µm. XRD, FTIR, and Raman spectroscopic analysis was also performed to investigate the chemical compositions of the B₄C–G composite. The molding press composite machine was a fabrication procedure that resulted in the formation of outstanding materials by utilizing the sintering process, including heating and pressing the materials. For mechanical properties, high fracture toughness and tensile strength of B₄C–G composites were analyzed according to ASTM standard designs. The detailed analysis has shown that with 6% graphene content in B₄C, the composite material portrays a high strength of 134 MPa and outstanding hardness properties. Based on these findings, it is suggested that the composite materials studied exhibit novel features suitable for use in the application of shielding frames.     

Thermal and mechanical properties of particulate fillers filled epoxy composites for electronic packaging application

Epoxy composites containing particulate fillers‐fused silica, glass powder, and mineral silica were investigated to be used as substrate materials in electronic packaging application. The content of fillers were varied between 0 and 40 vol%. The effects of the fillers on the thermal properties—thermal stability, thermal expansion and dynamic mechanical properties of the epoxy composites were studied, and it was found that fused silica, glass powder, and mineral silica increase the thermal stability and dynamic thermal mechanical properties and reduce the coefficient of thermal expansion (CTE). The lowest CTE value was observed at a fused silica content of 40 vol% for the epoxy composites, which was traced to the effect of its nature of low intrinsic CTE value of the fillers. The mechanical properties of the epoxy composites were determined in both flexural and single‐edge notch (SEN‐T) fracture toughness properties. Highest flexural strength, stiffness, and toughness values were observed at fillers content of 40 vol% for all the filled epoxy composites. Scanning electron microscopy (SEM) micrograph showed poor filler–matrix interaction in glass powder filled epoxy composites at 40 vol%. Copyright © 2007 John Wiley & Sons, Ltd.     

Mechanical properties and fracture behaviors of C/C composites with PyC/TaC/PyC,PyC/SiC/TaC/PyC multi-interlayers

Carbon/carbon (C/C) composites with PyC/TaC/PyC or PyC/SiC/TaC/PyC multi-interlayers were prepared by isothermal chemical vapor infiltration, followed by Furan resin impregnation and carbonization. Microstructures, mechanical properties including flexural strength, ductile displacement, and fracture behaviors of composites were studied. Furthermore, composites were heat treated at 2000 °C to study the effects of heat treatment on mechanical properties and fracture behaviors. PyC/TaC/PyC and PyC/SiC/TaC/PyC multi-interlayers have been deposited uniformly in C/C composites. With the introduction of PyC/TaC/PyC multi-interlayers in C/C composites, the flexural strength decreases; however, the ductile displacement increases. The fracture behavior changes from brittleness (0% TaC) to pseudo-ductility (5% TaC) and high toughness (10% TaC). When PyC/SiC/TaC/PyC multi-interlayers are introduced in C/C composites, the flexural strength is improved remarkably from 270 MPa to 522 MPa, but the ductile displacement decreases obviously from 0.49 mm to 0.24 mm, and the fracture behavior becomes brittle again. After heat treatment at 2000 °C, the flexural strength decreases, but the ductile displacement increases and pseudo-ductility or high toughness can be obtained.     

Experimental investigation on the mechanical properties of Cyperus pangorei fibers and jute fiber-based natural fiber composites

The present era uses natural fibers as a partial replacement for synthetic fibers, thereby utilizing eco-friendly materials in a number of automotive applications (namely, bumpers, wind shields, doors, ceilings, etc.). Although there are many research findings related to natural fiber composites, in this work, a new sandwich layer of Cyperus pangorei fibers and jute fiber epoxy hybrid composites is developed using the hand lay-up technique and compared with the pure Cyperus pangorei fiber and pure jute fiber epoxy composites. The mechanical properties like tensile, flexural, compressive, impact, and hardness are performed as per ASTM standards for the developed composites. The test results show that Cyperus pangorei hybrid composite 3 had a tensile strength of 50.2 MPa, flexural strength of 301.48 N mm^?2, ultimate compression load of 15.03 KN, impact energy of 6.34 J, and Shore D hardness of 82.7, which are superior by 1.1–1.5 times to all the other developed composites. The microstructural characterizations are performed using scanning electron microscope which played a vital role in analyzing the failure morphology of the composites.     

A Novel Approach by Spark Plasma Sintering to the Improvement of Mechanical Properties of Titanium Carbonitride-Reinforced Alumina Ceramics

Ti(C,N)-reinforced alumina-zirconia composites with different ratios of C to N in titanium carbonitride solid solutions, such as Ti(C_0.3,N_0.7) (C:N = 30:70) and Ti(C_0.5,N_0.5) (C:N = 50:50), were tested to improve their mechanical properties. Spark plasma sintering (SPS) with temperatures ranging from 1600 °C to 1675 °C and pressureless sintering (PS) with a higher temperature of 1720 °C were used to compare results. The following mechanical and physical properties were determined: Vickers hardness, Young’s modulus, apparent density, wear resistance, and fracture toughness. A composite with the addition of Ti(C_0.5,N_0.5)n nanopowder exhibited the highest Vickers hardness of over 19.0 GPa, and its fracture toughness was at 5.0 Mpa·m^1/2. A composite with the Ti(C_0.3,N_0.7) phase was found to have lower values of Vickers hardness (by about 10%), friction coefficient, and specific wear rate of disc (Ws_d) compared to the composite with the addition of Ti(C_0.5,N_0.5). The Vickers hardness values slightly decreased (from 5% to 10%) with increasing sintering temperature. The mechanical properties of the samples sintered using PS were lower than those of the samples that were spark plasma sintered. This research on alumina–zirconia composites with different ratios of C to N in titanium carbonitride solid solution Ti(C,N), sintered using an unconventional SPS method, reveals the effect of C/N ratios on improving mechanical properties of tested composites. X-ray analysis of the phase composition and an observation of the microstructure was carried out.     

Kapok/cotton fabric–polypropylene composites

Kapok/cotton fabric has been used as reinforcement for conventional polypropylene and maleic anhydride grafted polypropylene resins. Treating the reinforcement with acetic anhydride and sodium hydroxide has modified the fabric (fibres). Thermal and mechanical properties of the composites were investigated. Results show that fibre modification gives a significant improvement to the thermal properties of the plant fibres, whereas tests on the mechanical properties of the composites showed poor tensile strength. Mercerisation and weathering were found to impart toughness to the materials, with acetylation showing slightly less rigidity compared to other treatments on either the fibre or composites. The modified polypropylene improved the tensile modulus and had the least toughness of the kapok/cotton reinforced composites. MAiPP reinforced with the plant fibres gave better flexural strength and the same flexural modulus at lower fibre content compared with glass fibre reinforced MAiPP.     

Characterization of the physical–mechanical properties of dental resin composites reinforced with novel micro-nano hybrid silica particles: An optimization study

Abstract

In the study, dental composites of color A2 using Bis-GMA/UDMA/TEGDMA resins (ratios 70/10/20), and silica filler (70%wt, 75%wt, and 80%wt) which is a hybrid of two silica types in nano and micro dimensions were made using two different photoinitiators namely BAPO and camphorquinone. The optimum photoinitiator was selected based on the mechanical tests results after which the composites were subjected to the following tests: FTIR to evaluate polymerization degree, microhardness test, UTM, and SEM micrographs were taken to analyze the surface fracture of samples. The results of photoinitiator selection (flexural strength test) is 36.54?MPa, 37.62?MPa, and 75.08?MPa for BAPO?+?camphorquinone, camphorquinone, and BAPO respectively. The results show that the BAPO photoinitiator exhibits better results over camphorquinone and also BAPO/camphorquinone initiator systems. Then after choosing the photoinitiator system composites with different filler contents show higher mechanical strength than existing dental composites. The results of the mechanical tests for the composites with different filler contents synthesized after initiator system selection were significantly higher than the values specified in ISO 4049:2009 (102?MPa over 80?MPa). FTIR results indicate that the degree of conversion in these composite is 25.41%, 37.68, and 40.94% for composites with different filler amounts.     

Experimental Investigation of Mechanical Properties of Golden Cane Fiber–Reinforced Polyester Composites

The main objective of this article is to introduce a new natural fiber as a reinforcement in polymers for making composites for lightweight applications. The extraction of golden cane (Chrysalidocarpus lutescens) fiber and the mechanical properties of the fiber-reinforced polyester composites are described. The composites were formulated up to a maximum volume fraction of 0.43, resulting in a mean tensile strength and modulus of 2.13 and 2.26 times and mean flexural strength and modulus of 1.94 and 2.89 times greater than those of plain polyester, respectively, at a higher volume fraction of 0.43. The work of fracture in impact is measured to be 358 J/m. The results of this study indicate that golden cane fibers have potential as reinforcing fillers in plastics in order to produce inexpensive materials with high toughness.     

Influence of accelerated ageing on the physico-mechanical properties of alkali-treated industrial hemp fibre reinforced poly(lactic acid) (PLA) composites

30 wt% aligned untreated long hemp fibre/PLA (AUL) and aligned alkali treated long hemp fibre/PLA (AAL) composites were produced by film stacking and subjected to accelerated ageing. Accelerated ageing was carried out using UV irradiation and water spray at 50 °C for four different time intervals (250, 500, 750 and 1000 h). After accelerated ageing, tensile strength (TS), flexural strength, Young's modulus (YM), flexural modulus and mode I fracture toughness (K_Ic) were found to decrease and impact strength (IS) was found to increase for both AUL and AAL composites. AUL composites had greatest overall reduction in mechanical properties than that for AAL composites upon exposure to accelerated ageing environment. FTIR analysis and crystallinity contents of the accelerated aged composites support the results of the deterioration of mechanical properties upon exposure to accelerated ageing environment.