Search results for "composite"
showing 10 items of 4584 documents
Medium-Grade Mylonites
2009
The temperature range for the formation of this group of mylonites is approximately 500 to 650 °C. In medium-grade mylonites quartz is usually fully recrystallised, mainly by subgrain rotation, and has grown to a polygonal crystalloblastic fabric of strain free grains with an average grain size exceeding about 50 micrometers.
Micromechanisms of load transfer in a unidirectional carbon fibre-reinforced epoxy composite due to fibre failures: Part 3. Multiscale reconstruction…
2008
International audience; This third article describes a multiscale process which takes into account the most important microscopic phenomena associated with composite degradation, including fibre fractures and interfacial debonding, overloading of fibres neighbouring a fibre break as well as viscoelastic behaviour of the matrix. The results have been used to accurately predict the macroscopic failure of unidirectional carbon fibre-reinforced epoxy and quantify damage accumulation in pressure vessels made of the same material. The approach described has allowed the acoustic emission activity resulting from fibres breaks to be evaluated and shown how the residual lifetimes of such vessels, whe…
Elastic Deformation of Dispersely Failing Unidirectionally Reinforced Composites
2003
A phenomenological model is proposed for describing the elastic deformation of a unidirectionally reinforced composite capable of accumulating scattered microdamages during its loading. The composite is considered as a homogeneous transversely isotropic solid. Its damaged state at every point is characterized by a centrally symmetric scalar function on the unit sphere (the damage function), which is used to account for variations in the elastic properties of the material during its deformation. The damage itself depends on the history of some equivalent strain, for which four simplified variants are suggested. The relation between strains and stresses is defined in a differential form. Depe…
Mechanical evaluation for three-dimensional printed orthodontic springs with different heights-in vitro study
2021
Background The orthodontic spring materials in use have a significant influence on the applied forces. The prerequisite to identify the in vitro< force deflection of the CAD/CAM fabricated springs is considered mandatory to identify the material characteristics. The purpose of the present investigation was to evaluate the mechanical load on 3D printed springs using different coil heights. Material and Methods The springs were digitally designed with different coil heights using Autodesk Netfabb CAD software (San Rafael, CA, USA). Test specimens were manufactured using 3D printable experimental flexible material (Code: BM2008, GC, Tokyo, Japan). The specimens were divided according to the co…
Shear force comparative evaluation for surface treated and non- treated 3D interim printed materials with different types of glass-ionomer cements
2020
Background The purpose of this investigation was to compare shear force of different glass-ionomer cements on 3D printed interim material in combination with and without surface pretreatment. Material and Methods 120 rectangular specimens made of printable provisional material (Bego, Bremen, Germany) were used. After post-processing the specimens were blasted with aluminum oxide 110µm (Bego, Bremen, Germany). Extra 120 non-surface treated specimens were used as an experimental negative test group. All 240 specimens were divided randomly into 6 groups. All were cemented with a compressive load of 20 N using universal testing machine Z010 (Zwick/Roell, Ulm, Germany) to ensure a comparable cem…
Evaluation of bond strength of orthodontic brackets without enamel etching
2015
Background: to compare the shear bond strength of brackets with and without enamel etching. Material and Methods: In this study, 60 sound premolars were randomly divided into four different groups: 1- TXE group: Enamel etching + Transbond XT adhesive + Transbond XT composite. 2- TXS group: Transbond plus self-etch adhesive + Transbond XT composite. 3- PQ1E group: Enamel etching + PQ1 adhesive + Transbond XT composite. 4- PQ1 group: PQ1 adhesive + Transbond XT composite. The shear bond strengths of brackets were evaluated using universal testing machine at cross head speed of 0.5 mm/ min. The Adhesive Remnant Index (ARI) was also measured. One-way ANOVA, Tukey’s post hoc, Kruskal-wallis and …
Evaluation of micro shear bonding strength of two universal dentin bondings to superficial dentin by self etch and etch-and-rinse strategies
2018
Background Universal bondings can be used either with the etch-and-rinse or self-etch technique. Thus, the present study was done to evaluate the micro-shear bonding strength of two types of Universal Bondings to superficial dentin i.e self-etch and etch and rinse. Material and Methods The samples included 70 tooth blocks taken from 35 extracted sound premolar teeth. The superficial dentin was exposed to grinding by 800 grit silicon carbide Disk. The samples were randomly divided into 5 equal groups (14 samples in each group). Scotch bond universal (3M/USA) and All bond universal (BISCO/USA) were applied by self-etch and etch and rinse technique in group 1-4 and Adper Single bond 2 (3M/USA)…
Shear bond strength of metal brackets to ceramic surfaces using a universal bonding resin.
2017
BACKGROUND: Assure Plus is a recently introduced universal adhesive with the ability to bond to various restorations. This study compared the shear bond strength of brackets bonded to two types of ceramics using conventional bonding agent and Assure Plus. Surface damage caused by debonding was also evaluated. MATERIAL AND METHODS: In this in vitro study, 40 feldspathic and lithium disilicate ceramic discs were sandblasted, etched with 9.6% hydrofluoric acid and divided into two groups. In group 1, silane was applied and air-dried followed by application of Transbond XT primer, which was light-cured. In group 2, Assure Plus was applied and air-dried. In both groups, maxillary central incisor…
Effect of thermocycling and surface treatment on repair bond strength of composite.
2017
BACKGROUND Repair of composite restorations is a conservative method that can increase the longevity and durability of restorations while preserving the tooth structure. Achieving a suitable bond between the old and new composite is difficult. To overcome this problem, some methods have been recommended to increase the repair bond strength of composite.This study aimed to assess the effect of aging by thermocycling (5,000 and 10,000 cycles) and mechanical surface treatments (Er,Cr:YSGG laser and bur) on repair shear bond strength of composite resin. MATERIAL AND METHODS Totally, 120 composite blocks measuring 6x4x4 mm were fabricated of Filtek Z250 composite and were randomly divided into t…
Mechanical and dentin bond strength properties of the nanosilver enriched glass ionomer cement
2019
Background The aim of this study was to investigate the mechanical properties and dentin microshear bond strength of a conventional glass ionomer cement (GIC) compared to GIC supplemented with silver nanoparticles (SNPs) at 0.1% and 0.2% (w/w). Material and Methods SNPs were incorporated into a conventional GIC at 0.1% and 0.2% (w/w). The unmodified GIC was used as the control group. Compressive strength, flexural strength, and micro-shear bond strength (µSBS) to dentin were evaluated using a universal testing machine. Surface microhardness was determined using a Vickers microhardness tester. The data were analyzed using one-way analysis of variance (ANOVA) and Tukey’s test. Results GICs co…