Metal Matrix Composites The demand for materials having high strength and high toughness and capable of operating effectively under adverse conditions has led to the development of a new generation of materials known as Metal matrix composites. Attractive physical and mechanical properties that can be obtained with metal matrix composites (MMCs), such as high specific modulus, strength and thermal stability have made them the materials of the future and this fact has been documented extensively. MMCs combine metallic properties (high strength and high modulus), leading to greatest strength in shear and compression and higher service temperature capabilities. Interest in MMCs for aerospace, automotive and other structural applications has
Corrosion resistance: Fiberglass has superior weather resistance and is resistant to wide range of chemicals (mild acid and alkali). Aluminum undergo galvanic corrosion. Wood can rot, wrap exposed to water or chemicals. Hence require protective coatings. 8.
Polymer matrix composites Composites Composite material is a multiphase combination material of two or more components with different properties and different class , it will not appear with the characteristics of main components rather than they show new characteristics that are not possessed by any of component. Composites must have following characteristics: • Non –homogeneous material • Great improvement in performance • Volume fraction of component material are larger than 10% Composites are multiphase system consist of matrix and reinforcing material. Matrix is a continuous phase , it may consist of metal , non-metallic or polymer material. Reinforcing material include glass fiber
POLYMER MATRICES Composite materials, as we know, are composed of a matrix and a reinforcement. Very commonly polymer matrix are used. PMC’S or polymer matrix composites are made up of a variety of short or continuous fibers bound together by an organic polymer matrix. These are designed so that the mechanical loads to which the structure is subjected in service are supported by the reinforcement. The function of the matrix is to bond the fibers together and to transfer loads between them.
These types of composites contain particulate materials as the dispersed phase. The particles can be either metallic or non-metallic. Particulate composites have advantages such as improved strength, increased operating temperature, oxidation resistance, etc. Examples: Mica flakes in polymers to improve electrical and heat insulating applications,
An increase in amount of needling decreases the fabric weight produced from a particular web weight per square unit. The decrease in fabric weight/square unit is due to the drafting and spreading of fibers during punching, which increases as needling is increased. As the number of needle penetrations are increased, increased fiber locking causes a decrease in thickness. So when the needle is withdrawn, it resists the fibres to bounce back to their original
Advantages of Compsites Light weight. Composites are light in weight, compared to most woods and metals. Their lightness is important in automobiles and aircraft, for example, where less weight means better fuel efficiency (more miles to the gallon). People who design airplanes are greatly concerned with weight, since reducing a craft’s weight reduces the amount of fuel it needs and increases the speeds it can reach. Some modern airplanes are built with more composites than metal including the new Boeing 787, Dreamliner.
The used filler materials are graphite, carbon, wax, polyteraflouroehtylene (PTFE), polyethylene terephthalate (PET), silica , carbon nanotube , carbon fibre and high density polyethylene (HDPE). Some researchers (Sung et al 1979 , Li et al 2002 , Chen et al 2008 and Kowandya et al 2008) reported that the mechanical and wear resistance improved when the polymers are reinforced with fillers. It has been well documented that the general
The factors which affect the final properties of composites are: • Material selection for the matrix and reinforcement (fiber) • Specific strength of the material used (rigidity/stiffness) • Orientation of the fibers • Processing cost • Material availability • Application The selection of the fiber properties plays a dominating role for the properties of the composite materials. Reinforcement forms of fibers affects the final properties of composite materials. Some of the factors which are taken into account while selecting fiber includes: • Thermal, physical and mechanical properties relevant to application • Size, thickness, diameter of the fiber • Surface treatments for bonding with the matrix • Cost, manufacturing time (lead time) and availability And the considerations for selecting resin include: • Fiber size compatibility • Curing time and temperatures • Flow characteristics • Thermal and mechanical properties • Toxicity and health concerns • Cost and
Concrete has many advantages, such as high compressive strength, ability to cast in almost any desired shape, economical and fire resistance. Yet, there are some disadvantages, like low tensile strength, low ductility and cracking. Regardless those disadvantages, concrete is still one of the chosen materials in construction. Reinforced concrete (RC) is a very complex composite material resulting from a combination of two materials, concrete and steel, both of which have entirely different mechanical properties. Steel can be considered a homogeneous material and its tensile strength and ductility are very high.