Presentation on theme: "Chapter 15 Composite Materials"— Presentation transcript:
1Chapter 15 Composite Materials Mechanical Behavior of Materials
2Reinforcement for Composites Different types ofreinforcement for composites:(a) particle reinforcement;(b) short fiber reinforcement;(c) continuous fiber reinforcement;(d) laminate reinforcement
3Different Composites (a) Transverse section of a boron fiber reinforcedaluminum composite. Vf = 10%.(b) Section of a short aluminafiber/aluminum matrix composite.(c) Deeply etched transversesection of a eutectic compositeshowing NbC fibers in an Ni–Crmatrix. (Courtesy of S. P. Cooperand J. P. Billingham, GEC TurbineGnerators Ltd, U.K.)
4Microstructure of a Silicon Carbide Particle silicon carbide particle (10, 20, and30%, three different volumefractions) reinforced aluminiumalloy (2080) matrix compositesmade by hot pressing of powdersfollowed by hot extrusion. Notethe preferential alignment of SiCparticles in the extrusion direction.The number and subscript pindicate the volume fraction of SiCparticles in the composites.(Courtesy of N. Chawla.)
6Interfacial Interaction TEM micrographshowing dislocations in aluminumin the region near a silicon carbideparticle (SiCp).
7Simple Composite Models models. (a) Longitudinal response(action in parallel). (b) Transverseresponse (action in series).
8Elastic Moduli An example of a linear increase in the longitudinal modulus of the composite, Ecl, as afunction of the volume fraction offiber for a glass fiber-reinforcedepoxy. (After R. D. Adams and D.G. C. Bacon, J. Comp. Mater., 7(1973) 53.)
9Particle Reinforcement Schematic of increase in modulus in a composite with reinforcement volume fraction fora different form of reinforcement – continuous fiber, whisker, or particle. Note the loss ofreinforcement efficiency as one goes from continuous fiber to particle.
10Strength of Composites Determination of Vmin and Vcrit.
11Strength in Silicon Carbide Whisker /alumina Composites Increase in strength insilicon carbide whisker/aluminacomposites as a function of thewhisker volume fraction and testtemperature. (After G. C. Wei andP. F. Becher, Am. Ceram. Soc. Bull.,64 (1985) 333.)
12Mullite Fiber Stress vs. displacement curves for mullite fiber (Nextel 550)/mullite matrixin three-point bending. Theuncoated one refers to themullite/mullite composite with nointerfacial coating, which shows acatastrophic failure. Thecomposite with a double interfacialcoating of SiC and BN shows anoncatastrophic. (Adapted from K.K. Chawla, Z. R. Xu, and J.-S. Ha, J.Eur. Ceram. Soc., 16 (1996) 293.)
13Load Transfer from Matrix to Fiber Perturbation of the matrix stress state due to the presence of fiber.
14Fiber and Matrix Elastic Load transfer to fiber. Variation in tensile stress σ in fiber and shear stress τ along the interface with the fiber length .
15Fiber Elastic and Matrix Plastic Variation in the fiber load transfer length as a functionof the aspect ratio /d
16Multiple Fracture Optical micrograph of multiple fracture of tungsten fibers in an Fe–Cu matrix.
17Fracture in Composites Scanning electron micrographs of fracture incomposites, showing the fiber pullout phenomenon. (a) Carbon fiber polyester. (b) Boron fiber aluminum 6061.
18Failure Modes in Composites Fracture of weakinterface in front of crack tip dueto transverse tensile stress; m andf indicate the matrix and fiber,respectively. (After J. Cook and J.E. Gordon, Proc. Roy. Soc. (London),A 228 (1964) 508.)Crack front andcrack wake debonding in a fiberreinforced composite.
19Interface Fracture Toughness The ratio of theinterface fracture toughness tothat of fiber, Gi/Gf, vs. the elasticmismatch α. Interfacial debondingoccurs under the curve, while forconditions above the curve, thecrack propagates through theinterface.
20Monolithic Material Schematic of variation in elastic moduli of a fibercomposite and a monolithicmaterial with the angle ofreinforcement. Ea is the axialYoung’s modulus, vat is theprincipal Poisson’s ratio, and Ga isthe axial shear modulus.
24Weibull PlotWeibull plot of tensile strength of carbon fiber/epoxy composite. (Courtesy of B. Atadero and V. Karbhari.)
25Functionally Graded Materials Schematic of afunctionally graded materialbetween a ceramic on theleft-hand side and a metal on theright-hand side. Also shown aremicropores and additives.
26ACCR Cross-section of an aluminium composite conductor reinforced (ACCR) cable. Thecentral wires consist of continuousalumina fibers in an aluminiummatrix composite while the outerwires are made of Al–Zr alloy.(Courtesy of 3M Co.)
27Flexural strength forselected monolithic and laminatedmaterials. (Adapted from M.Sarikaya, Micr. Res. Tech., 27 (1994)371.)
29PMCSchematic of a metal/polymer matrix composite (PMC) such as Arall or Glare.
30Laminate with Aluminum and Silicon Carbide Cross-section of alaminate consisting of aluminiumand silicon carbide: (a) SEM; (b)TEM. From X. Deng, K. K. Chawla,M. Koopman, and J. P. Chu, Adv.Eng. Mater., 7 (2005) 1.)