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COMPOSITES - Material Science For Engineering

Home > PowerPoint Slides > COMPOSITES - Material Science For Engineering
Published in: Mechanical
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COMPOSITES

Sidhant S / Bathinda

7 years of teaching experience

Qualification: mechanical engineering

Teaches: Geography, History, Mathematics, Science, Mechanical

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  1. Composites Needs of Modern Technology Unusual properties, not with conventional materials Aerospace, transportation, under water, nuclear applications Low density, strong, stiff, abrasion & impact resistant, not affected by environment Material properties extended by Composite materials Properties trade off to made for composite materials Multiphase alloys, ceramics, polymers Pearlitic steel — alternate layer of a ferrite & cementite (12%) soft& ductile hard & brittle Wood — strong & flexible cellulose surrounded by stiffer lignin Bone — coolgen & hard brittle mineral apatite Artificially made not natural — Phases Many composite materials have two phases Matrix continuous phase surrounded by Dispersed phase Properties of composites depend on constituent phases, relative amount & geometry of dispersed phase ( shape, size, distribution & orientation )
  2. Composites Classification of Composites Particle reinforced Large particle Dispersion strengthened — Fiber reinforced Continuous (aligned) Discontinuous (short) Aligned Randomly oriented — Structural Laminates Sandwich panels Longitudinal direction Transverse direction (a) Figure 15.8 Schematic representations of (a) continuous and aligned, (b) discontinuous and aligned, and (c) discontinuous and randomly oriented fiber- reinforced composites. — Large particle reinforced — not on atomic level Cermets - cemented carbide bits of WC, TiC in metal Ni, Co ' Concrete - matrix & dispersed both phases ceramics concrete/ gravel, sand, cement (asphaltic or portland) RCC - addl. Reinforcement by steel bars, rods, wires, mesh
  3. Composites Classification of Composites Dispersion —particles with 0.01 — 0.1 um (10-100nm) Uniform dispersion of very hard & inert, metallic & non metallic, oxides Thoria dispersed Nickel , Th02 3% vol, sintered Al powder (SAP) — Fiber reinforced Composites Dispersed phase is fiber with high elastic modulus Employ low density fibers & matrix Factors affecting properties of composite Fiber length — material bonds » L > 15Lc lc = of * d /20c Fiber orientation & concentration Elastic behavior for longitudinal/ traverse loading (properties anisotrpic)
  4. Composites Fiber phase — brittle material, smaller dia, stronger than bulk matrix Matrix phase — high tensile — Types of fibers Whiskers, fibers & wires Whiskers — very thin, single crystal, flaw free, high strength, extremely expensive as graphite, SiC, A1203, Silicon nitride Fibers - poly crystalline, small dia polymers, ceramics Fine wires — large dia, steel, MO, W Matrix phase Ductile; ' Functions Fiber Metals, polymers, ceramics Stage I Fiber Composite Failure Matrix Binds fibers together, transmit/ distribute stress Matrix Protect fibers from surface damage, abrasion, envi Separates fibers, barrier to crack/ flaw propagatior Strain (a) I / IStage Strain Figure 15.9 (a) Schematic stress-strain curves for brittle fiber an ductile matrix materials. Fracture stresses and strains for both materials ave note shown in part (a) are also superimposed.
  5. Composites Polymers-Matrix composite (PMCs) — Polymers resin matrix with fiber reinforcement (glass, carbon, aramid) easy to fabricate, cost effective Glass fiber reinforced polymer (GFRP) composite Glass fiber 3-20 um , easily drawn, inexpensive, readily available, inert, relatively strong, upto 200C Matrix — polyamide resins Automotive, marine bodies, plastic pipes, transport industry, containers — Carbon fiber reinforced polymer (CFRP) composite Advanced fiber, 4-10 um, continuous/ chopped fibers High performance, high strength at high temp, moisture & solvent free, diverse properties Sports good, filament wound rocket motor cases, pressure vessel, aircraft Aramid fiber reinforced polymer composite — Polymer matrix material Metal- Matrix composite (MMC) Carbon-carbon composites
  6. Hybrid Composites Hybrid Composites Relatively new fiber reinforcement composites ' Two or more different kind of fibers in a single matrix Better combination of properties Carbon and glass fibers in a polymeric resin Carbon fibers strong , relatively stiff, low density but expensive Glass fibers inexpensive but lack stiffness Carbon-glass hybrid — stronger & tougher, high impact resistance at lower cost than either all carbon or all glass Different ways to combine fibers that affect properties (mostly anisotropic) Hybrid composite in tension non catastrophic failure — Light weight land, water & air transport structural components, sporting goods, light weight orthopedic components
  7. Smart Materials Group of new and state-of-the-art materials — Influence technology Sense and respond to changes like living organisms Concept being extended to systems — consisting of both smart and traditional Sensors & actuators Actuator materials SMA, Piezoelectric ceramics, magnetostrictive and electrorheological fluids SMA - nickel-titanium and copper-zinc-aluminium alloys. Once strained, revert back to original shape above critical transformation temp — Sensor materials Optical fibers, piezoelectric material and MEMS devices MEMS — any miniature device; integrates technology, electronic & smart materials on a chip — Applications Cockpit noise/ undesirable vibrations of rotor blades of helicopter SMA - Stent for artery Micro pumps, locking system, mirror & sensors, automobile air bags

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