![Assignment
A continuous and aligned glass fiber-reinforced composite consists of 40 vol%
of glass fibers having a modulus of elasticity of 69 GPa and 60 vol% of a polyester
resin that, when hardened, displays a modulus of 3.4 GPa.
(i) Compute the modulus of elasticity of this composite in the longitudinal
direction. [30 GPa]
(ii) If the cross-sectional area is 250 mm2 (0.4 in.2) and a stress of 50 MPa is applied
in this longitudinal direction; compute the magnitude of the load carried by
each of the fiber and matrix phases. [11,640 N]
(iii) Determine the strain that is sustained by each phase when the stress in part (ii)
is applied.[m =f = 1.69 x 10-3]](https://image.slidesharecdn.com/seng213-230215145021-0ea2fcbc/85/SENG-213-Composites-ppt-notes-pptx-20-320.jpg)
SENG 213 ..Composites ppt notes.pptx
- 1. Composites Materials By Dr. S. Kimutai
- 2. Course content Classification, general properties and applications of: iron and carbon steels, copper, aluminum, zinc, magnesium, nickel and titanium alloys and new metals. Cast iron: powder metallurgy. Corrosion- types and prevention. Plastics processing, classification, general properties, application of polymer materials; polymerization mechanism. Copolymers. Elastomers, ceramics and composites and their applications in manufacturing
- 3. Introduction Metal, glass, plastics, ceramics require materials with unusual combinations of properties that cannot be met by the conventional metal alloys, ceramics, and polymeric materials. This is especially true for materials that are needed for aerospace, underwater, and transportation applications. For example, aircraft engineers are increasingly searching for structural materials that have low densities, are strong, stiff, and abrasion and impact resistant, and are not easily corroded. This is a rather formidable combination of characteristics. strong materials are relatively dense; also, increasing the strength or stiffness generally results in a decrease in impact strength. classification distinguishes between (i) traditional and (ii) synthetic composites.
- 4. Classification of composites Metal Matrix Composites (MMCs) include mixtures of ceramics and metals, such as cemented carbides and other cermets, as well as aluminum or magnesium reinforced by strong, high stiffness fibers. Ceramic Matrix Composites (CMCs) are the least common category. Aluminum oxide and silicon carbide are materials that can be imbedded with fibers for improved properties, especially in high temperature applications. Polymer Matrix Composites (PMCs). Thermosetting resins are the most widely used polymers in PMCs. Epoxy and polyester are commonly mixed with fiber reinforcement, and phenolic is mixed with powders. Thermoplastic molding compounds are often reinforced, usually with powders. classification of composite materials is shown in Figure below, which consists of three main divisions: particle- reinforced, fiber-reinforced, and structural composites; Composite = matrix (glue) + reinforcements (strength) Fibers • Various materials are used as fibers in fiber-reinforced composites: metals, ceramics, polymers, carbon, and boron. • The most important commercial use of fibers is in polymer composites. However, use of fiber- reinforced metals and ceramics is growing.
- 5. Concrete, Reinforced Concrete and Laminar composite Concrete Concrete implies a composite material consisting of an aggregate of particles that are bound together in a solid body by some type of binding medium, that is, cement. Reinforced Concrete The strength of Portland cement concrete may be increased by additional reinforcement. This is usually accomplished by means of steel rods, wires, bars (rebar), or mesh, which are embedded into the fresh and uncured concrete. Thus, the reinforcement renders the hardened structure capable of supporting greater tensile, compressive, and shear stresses. Even if cracks develop in the concrete, considerable reinforcement is maintained. Steel serves as a suitable reinforcement material because its coefficient of thermal expansion is nearly the same as that of concrete. In addition, steel is not rapidly corroded in the cement environment, and a relatively strong adhesive bond is formed between it and the cured concrete. Laminar composite A laminar composite structure consists of two or more layers bonded together to form an integral piece. The layers are usually thick enough that this composite can be readily identified—not always the case with other composites. The layers are often of different materials, but not necessarily. Plywood is such an example; the layers are of the same wood Examples of laminar composite structures: Automotive tires (rubber reinforced with carbon black), Windshield glass
- 6. Reinforced Concrete/Fiber reinforced plastics
- 8. As a comparison between composites and metals, the composites materials are some advantages as: Lightweight, High specific stiffness and strength, Easy moldable to complex forms, Easy bondable, Good dumping, Low electrical conductivity and thermal expansion, Good fatigue resistance, Part consolidation due to lower overall system costs, Low radar visibility, Internal energy storage and release.
- 10. Roles of matrix In a composite material, the matrix material serves the following functions: to give shape to the composite part, protect the reinforcements to the environment, transfer loads to reinforcements and toughness of material, together with reinforcements. Holds the fibres together Protects the fibres from environment Distributes the loads evenly between fibres so that all fibres are subjected to the same amount of strain Enhances transverse properties of a laminate Improves impact and fracture resistance of a component Helps to avoid propagation of crack growth through the fibres by providing alternate failure path along the interface between the fibres and the matrix Carry interlaminar shear
- 11. Aims of reinforcements to get strength, stiffness and other mechanical properties, dominate other properties as coefficient of thermal extension, conductivity and thermal transport.
- 13. COMPOSITES COMMERCIAL APPLICATIONS Applications include aerospace, transportation, construction, marine goods, sporting goods, and more recently infrastructure, with construction and transportation being the largest. In general, high-performance but more costly Continuous-carbon-fiber composites are used where high strength and stiffness along with light weight are required, and much lower-cost fiberglass composites are used in less demanding applications where weight is not as critical.
- 14. Important Properties of composites Very strong and stiff, yet very light in weight, giving them strength to weight and stiffness-to-weight ratios several times greater than steel or aluminum. Improved torsional stiffness is also enhanced. These properties are highly desirable in applications ranging from commercial aircraft to sports equipment. Fatigue properties are generally better than for the common engineering metals. Toughness is often greater, too. Do not corrode like steel; this is important in automotive and other applications. This include improved weatherability of composites in a marine environment possible to achieve combinations of properties not attainable with metals, ceramics, or polymers alone. Better appearance and control of surface smoothness are possible with certain composite materials. It is easier to achieve smooth aerodynamic profiles for drag reduction also
- 15. RULE OF MIXTURE For particulate composites, the rule of mixtures predicts the density of the composite as well as other properties (although other properties may vary depending on how the dispersed phase is arranged) Density, ρc, is given as a fraction, f, as: Fm + Ff = 1 f f m m c f f f m f f 1 that Note f f m m c K f K f K f f m m c f f The rule of mixtures can also be used to predict the modulus of elasticity when the fibers are continuous and unidirecti f f m m c E f E f E f f c E f E Since the matrix now contributes little to the stiffness, the modulus is approximated by: Thermal and electrical energy can be transferred through the composite at a rate that is proportional to the volume fraction, f of the conductive material
- 16. Longitudinal Loading, Am + Af = Ac
- 18. Exercise A uniaxial composite material is made into a circular rod with a 1.27-cm diameter from 70 volume percent continuous carbon fibers and 30 volume percent epoxy. The rod is subject to an axial force of 100,000 N. The composite material in Example Problem 12.1 is to be replaced with a less expensive composite made of 70 volume percent continuous E-glass fibers and 30 volume percent epoxy. The elastic moduli are 5 GPa for the epoxy resin and 72.4 GPa for the E-glass. (a) Compare the elastic modulus, composite strain, fiber and matrix stresses, and density of this composite with the carbon epoxy composite. Use the density of UHM carbon, and assume the density of the epoxy is 1.2 g/cm3. (b) Can both the E-glass fiber and matrix withstand the applied force?
- 19. Solution
- 20. Assignment A continuous and aligned glass fiber-reinforced composite consists of 40 vol% of glass fibers having a modulus of elasticity of 69 GPa and 60 vol% of a polyester resin that, when hardened, displays a modulus of 3.4 GPa. (i) Compute the modulus of elasticity of this composite in the longitudinal direction. [30 GPa] (ii) If the cross-sectional area is 250 mm2 (0.4 in.2) and a stress of 50 MPa is applied in this longitudinal direction; compute the magnitude of the load carried by each of the fiber and matrix phases. [11,640 N] (iii) Determine the strain that is sustained by each phase when the stress in part (ii) is applied.[m =f = 1.69 x 10-3]