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
History of Composites
Strong [10] and Johnson [11] have stated that, composite materials have been around for a long time and have been adopted in numerous forms throughout the history of humankind. One of the early instances of use of composites could be dated back to the Egyptian period, which is approximately around 1500 BC, where the Egyptians were known to mix straw and mud to make infrastructure that were sturdy and robust.
Composite restoration usage in dentistry is increasing. Because of this interest in the longevity and reliability of composite fillings also is increasing1. One problem that can occur with composite restorations is micro-leakage. This is when microgaps at the tooth-restoration interface allow fluids and bacteria into the restoration2. These gaps are formed when the material is polymerized and shrinks, which causes the material to pull away from the margins of the preporation2. Problems that can arise from micro-leakage are secondary carries, hypersensitivity, pulp stimulation, and marginal discoloration3. This is why dentists are trying to find ways to reduce micro-leakage of composite restorations.
Ceramics material falls into two major categories that reflect two distinct traditions. The earliest tradition used crushed rock as the tempering material in the manufacture of ceramics. This tradition first appears during the Early Woodland period around 500 B.C. and continues in the northern areas. The second tradition is based upon the use of the ground shell of freshwater mollusks as the tempering material and is usually associated with the prehistoric culture of the Mississippian Period. This first appears in southwestern Michigan around 1000 A.D. and continued until the Historic
Resin composite restorations are becoming have had a significant increase in popularity over the last few decades, and have become the patient’s preferred choice in filling material, due mainly due to their enhanced esthetics when compared to other restorations, as well as their ever-increasing durability. These factors have led to a large increase in demand from patients.1 As patient demand for this restorative material increases, so too do patient expectations for comfort and longevity in these restorations. An idyllic filling material would combine these effects with a perfect marginal seal, leaving no gap between the tooth structure and the restoration.2
The composite bow can either be made of wood and other materials or be made completely from different materials. In China, composite bows are comprised of newly harvested and dried bamboo. Scientists suggest that the bow originated from spear throwers and in between 18,000BC and 25,000BC fire was used to make stone arrowheads harder and feathers were added to make them more accurate. During the Mesolithic period (20,000BC-7, 500BC) and Neolithic (7,500BC-3, 500BC) period illustrations of bows from that time appear on cave walls and rock faces. Several different kinds of bows were drawn, there were many long and short simple segment bows with more of a circular shape, but there were also more complex bow shapes, which suggests that they were composite bows.
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.
(1) The development of carbon-embedded plastics, otherwise called “composits,” is an important new technology because (2) it holds the key for new aircraft and spacecraft designs. This is so because (3) these composits are not only stronger than steel but lighter than aluminum.
The ancient individuals being studied needed to have assembled reasonably significant structures utilizing wood timbers. In the vast majority of the world that did not start to happen until around 4,000 to 5,000 years before.
Concrete: The Romans invented concrete, a strong and light building material. The Colosseum was built with thousands of tons of concrete, and it is still a popular monument today, enduring milleniums. Concrete is seen as a revolution to comtempary architecture because it is used worldwide today.
Polyethylene (PE) is one of the most commonly used polymers which can be identified into two plastic identification codes: 2 for high-density polyethylene (HDPE) and 4 for low density polyethylene (LDPE). Polyethylene is sometimes called polyethene or polythene and is produced by an addition polymerisation reaction. The chemical formula for polyethylene is –(CH2-CH2)n– for both HDPE and LDPE. The formation of the polyethylene chain is created with the monomer ethylene (CH2=CH2).
Brick and stone were more commonly used in the past when materials like
Beginning with the Ancient Egyptians around 3100 B.C. furniture and buildings were very lavish and ornate with a lot of solid gold and with everyday household items having impressive designs and patterns on them.
One of their most famous inventions that is still commonly used today was the column. The Egyptians created stone columns that “served no architectural purpose” and were only used for aesthetics. Although columns were used in architecture only for aesthetics, it showed power because of the technology needed to create them and the art and designs on the side. The Egyptians also created pylons that also had very little architectural purpose. Pylons were massive walls used to “support flagpoles and to anchor the entrance doors.” Although these structures are very large and looked powerful, there were lots of easier ways to achieve their same purpose.
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
Injection moulding is the most widely used polymeric fabrication process. It evolved from metal die casting, however, unlike molten metals, polymer melts have a high viscosity and cannot simply be poured into a mould. Instead a large force must be used to inject the polymer into the hollow mould cavity. More melt must also be packed into the mould during solidification to avoid shrinkage in the mould. The injection moulding process is primarily a sequential operation that results in the transformation of plastic pellets into a moulded part. Identical parts are produced through a cyclic process involving the melting of a pellet or powder resin followed by the injection of the polymer melt into the hollow
Opus caementicium or Roman concrete is a synthetic construction substance that’s composed of an aggregate, a binding agent, and water. In Rome’s case, as discovered by UC Berkley with the extensive analysis of a sample of Roman concrete taken from a breakwater in Italy’s Pozzuoli Bay it was developed by using lime and volcanic rock which formed a mortar, the mortar and volcanic rock were then packed into wooden forms and when seawater was added a chemical reaction occurred, bonding everything together to create concrete (History, 2013). It is uncertain when Roman concrete was developed, but it was clearly in widespread and customary use from about 150 BC; some scholars believe it was developed a century before that.