Group 2: The significance of modulus of elasticity and fracture toughness for resin composites
Kelly Griffith, Lance Gunter, Joshua Haentges, Erik Hageman, Zohra Hasham, Nellab Hashimi
Modulus of elasticity is defined as the comparative stiffness of a material. A stiffer material will have a higher elastic modulus. Fracture toughness is the amount of stress required to propagate a preexisting flaw. It describes resistance of a material with a pre-existing flaw to fail. These two properties will be evaluated for resin composites in our paper through journal articles.
Packable composites have a higher filler load and elastic modulus than flowable composites. Packing might also reduce shrinkage. Flowables have less filler and are used as liners and sealants. They cannot withstand much force, but this helps relieve stress due to shrinkage. However, this may be counteracted because they shrink upon curing. Flowable and packable composite resins were tested for shear strength 30 minutes, 1 day, and 1 week, after curing under constant pressure. The dimethacrylate resins tested were: Alert/- Flow It, Filtek P 60/Filtek Flow, Admira/Admira Flow—an ormocer resin—and a microfill composite resin. The resins increased in strength over one week. The packable composites were stronger than the flowables, but variable between manufacturers. The ormocer resin had a lower elastic modulus than other packable resins. Although the flowables have lower elastic moduli, they shrink more, so shrinkage stress might not be better than packable composites. (Helvatjoglu et al)
The article by Dr. Nuray Attar focused on the comparison of the flexural strength and elastic modulus of condensable and hybrid composite resins. The study focused on fou...
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Helvatjoglu-Antoniades M, Papadogiannis Y, Lakes RS, Dionysopoulos P, and
Papadogiannis D. Dynamic and Static Elastic Moduli of Packable and Flowable Composite
Resins and Their Development After Initial Photo Curing. Dent Mater. 2006; 22: 450-459.
Kostantinos M, Silikas N, and Watts DC. Correlation of Filler Content and Elastic Properties of
Resin Composites. Dent Mater. 2008; 24: 932-939.
Nuray, A. A Comparison of the Flexural Strength and Elastic Modulus of Condensable and
Hybrid Composite Resins. ARASTIRMA , 30, 42-50.
Roberts JC, Powers JM, and Craig RG. Fracture Toughness of Composite and Unfilled
Restorative Resins. Dent Res 1977; 56(7): 748-753.
Sabbagh J, Vreven J, and Leloup G. Dynamic and Static Moduli of Elasticity of Resin-based
Materials. Dent Mater. 2002; 18: 64-71.
Dental materials are used for a variety of reasons. The basic reason for using dental materials is to restore the tooth back to its original anatomy. Some materials are used more than others but it depends on their characteristics. Composite resin is a type of dental material. Some dental materials do not have the esthetic characteristic that composite resin has. That is why sometimes, it is more favorable than other dental materials. It is one of the most common dental materials that are used to restore a tooth back to its natural appearance.
Service life The effect of fillers on polymers is that they are very beneficial because they don’t get ruined for a long time. Glass fillers are the most commonly used fillers in polymers. This is because they last longer and their service life is longer.
Dental composites, also known as "white fillings", are a group of restorative materials composed of a mixture of powdered glass and plastic resin regularly used in modern dentistry to resemble the appearance of the natural tooth. Acrylic resin was first introduced to the dental profession in the mid 1950s. Since their introduction, acrylic based materials have continued to play a pivotal role in restorative and prosthetic dentistry. After the introduction of the bisphenol A glycidyl methacrylate, or BIS-GMA, by Bowen in the early 1960s the potential application of resins has emerged. This composition and formulation possessed a higher molecular weight and therefore better mechanical properties and reduced polymerization shrinkage, the newer polymer offered potential for much greater applications that included anterior and posterior composite resin restorations, indirect inlays/onlays, pit and fissure sealants and more wear resistant denture teeth.
As previously stated, micro-leakage is mainly caused by shrinkage of the composite during polymerization. Bulk curing of composite results in a greater leve...
Deformation of a material or strains depends on the magnitude of stress. For most metals that are stressed in tension stress and strain are proportional Deformation at which stress is proportional to stain is called elastic deformation, a plot of stress versus strain results in a linear relationship. The slope of this linear segment represents to the modulus of elasticity E. This modulus indicates the stiffness of the material or material’s resistance to el...
Up to 50% of the resin weight can be fillers but the addition of these fillers will affect the strength of the composite to varying degrees. The use of fillers can be helpful when casting thick components as pure epoxies generate substantial amounts of heat when curing and the addition of fillers can reduce this exothermic heat output.
Keywords: Bamboo strip , Bamboo composite , Young modulus , Strength ,Volume fraction , Epoxy .
Rheological behavior helps to elucidate the fundamental flow behavior of composite melts, and can directly or indirectly reflect the processing performance, internal structure, and physical and mechanical performance of WPCs. For the economical consideration, researchers are attempted to incorporate high amount of wood flour. So, a clear insight of the rheological behavior is necessary in such high wood content to facilities the processing. In addition, additives are frequently used to modify processing or end properties of WPC formulations and proper rheological tests may prove useful in characterizing the efficiency of these additives [13].
In practice, most composites consist of a bulk material (the ‘matrix’), and a reinforcement of some kind, added primarily to increase the strength and stiffness of the matrix. This reinforcement is usually in fibre form. In addition, the manufacturing process used to combinefibre with resin leads to varying amounts of imperfections and air inclusions. Typically,with a common hand lay-up process as widely used in the boat-building industry, alimit for Fibre Volume Fraction is approximately 30-40%. With the higher quality, more sophisticatedand precise processes used in the aerospace industry, Fibre Volume Fraction’s approaching 70% canbe successfully obtained.the geometry of the fibres in a composite is alsoimportant since fibres have theirhighest mechanical properties along their lengths, rather than across their widths.This leads to the highly anisotropic properties of composites, where, unlike metals,the mechanical properties of the composite are likely to be very different when testedin different directions. This means that it is very important when considering the use ofcomposites to understand at the design stage, both the magnitude and the directionof the applied
Denture teeth can be made of acrylic poly(methyl methacrylate) (PMMA) or composite resins. PMMA is a polymer - a material made the from joining of methyl methacrylate monomers. Properties of PMMA include resistance to abrasion, chemical stability and a high boiling point. (Jun Shen et al. 2011). However, weak flexure and impact strength of PMMA are of concern as they account for denture failure. (Bolayir G, Boztug A and Soygun K. 2013). Composite denture teeth are made of a three distinct phases - filler, matrix and coupling agents. Out of the types of composite teeth available, nano-filled composite teeth are preferred. Composite teeth have a PMMA coating around the tooth and a high content of filler particles. This gives them strength, higher resistance to forces than acrylic teeth and provides compete polymerization due to the PMMA coating. (Anusavice, K. J., Phillips, R. W., Shen, C., & Rawls, H. R, 2012). If the interface between the PMMA denture base and PMMA or composite teeth was weak, the denture will not be able to sustain occlusal forces, making the base-teeth interface, an entity of significance.
The flexural strength usually reported by the time the first crack appears which is corresponding to the point where the load-deformation curve moves out of linearity (Point A on Figure 4). The second value is the failure value or in other words it is called the ultimate flexural strength or the modulus of rupture (Point C on Figure 4). Johnston reported that the prismatic fibers and hooked ones have effects on the strength of the unreinforced matrices by about 100 percent. High strengths can be achieved in mortars with w/c ratio of 0.45 to 0.55. Using 1.5% of volume as fibers may increase the strength value to the range of (6.5 to 10 MPa) and Johnston experiments in 1980 showed that using 2.5% of volume as fibers may increase the strength to 13 MPa.
There are considerable differences in published property data for Metal matrix composite. This is partly due to the fact that there are no industry standards for metal matrix composites, as there are for metals. Reinforcements and composites are typically made by proprietary processes, and, as a consequence, the properties of materials having the same nominal composition can be radically different. The issue is further clouded by the fact that many reinforcements and they are still in the developmental stage, and are continually being refined. Numerous test methods are used throughout the industry, and it is widely recognized that this is a major source of differences in reported properties. Some properties cannot be measured as they would be for monolithic metals. For instance, toughness is an important but hard to define material property. Standard fracture mechanics tests and analytical methods for metals are based on the assumption of self-similar crack extension; i.e., a crack will simply lengthen without changing shape. Composites, however, are non-homogeneous materials with complex internal damage patterns. As a result, the applicability of conventional fracture mechanics to metal matrix composite is controversial, especially for fibre-reinforced ma...
The word ‘composite’ does not fully explain the wide range and varied compositions of materials that are categorized under it. This paper deals with some of the commonly used composites. Common materials such as metallic, ceramic and polymers consists of substances that can be classified as composites. The steel family, which is considered as the biggest group of material that is used in construction and complex engineering, is composed of composites that are made out of soft metallic matrix and hard ceramic components. [11] Such metallic composites could be shaped as a plate, needle, sphere or be polygonal. Polymeric composites are also found in a similar matrix model where one polymer forms the skeleton and another hard or soft polymer fills the matrix. A good example of this would be wood. Concrete is also a popular matrix composite where the Portland cement provides the matrix phase and the inner filling is made up of sands of different size. Scientists are now able to adjust the composition of these composites to suit the various needs. This adjustment is done by tweaking the microstructure of the materials by changing the state, shape, amount and distribution of the filling, which is also called as the reinforcing phase. Instead of restricting this tweaking process within a certain material class, the idea is being implementing in cross-material classes as well. Ceramics powder can be added to plastics to make hard and fireproof polymers. Ceramic powder when mixed with metals, gives cermets, which are used in tips of metal cutting tools. Another branch of the same idea is the blending of metal filaments, ceramic and polymer into one large bulk to form metal-matrix composites (MMCs), reinforced plastics (RP) and ceramic-matrix composites (CMCs). Such a radical idea of mixing all the three classes of materials has resulted in composites such as carbon fibre reinforced plastic (CFRP), glass reinforced plastic (GRP) and silicon-carbon-fibre-reinforced aluminium. Figure1 shows Comparison between conventional monolithic material and composite material. [17, 18,10and1
Charles and Keith uses synthetic materials and polyurethane to ensure affordable prices of their products (Singapore Press Holding, 2009). However, the qualities of the products are not compromised despite its inexpensive prices. The managing director Charles Wong reassured the customers that although the ...
Given such advantages as low weight compared to strength and toughness, laminated composites are now used in wide range of applications. Their increasing use has underlined the need to understand their principle mode of failure