Lecture 12 - ENGR 4250 Advanced Materials Engineering...

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ENGR 4250 – Advanced Materials Engineering Lecture 12 COMPOSITES (Ch 16) Dr. A. Keshavarz - ENGR 4250U
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Classification Scheme for Composite Materials 1. Metal Matrix Composites (MMCs) - mixtures of ceramics and metals, such as cemented carbides and other cermets 2. Ceramic Matrix Composites (CMCs) - Al 2 O 3 and SiC imbedded with fibers to improve properties, especially in high temperature applications – The least common composite matrix 3. Polymer Matrix Composites (PMCs) - thermosetting resins are widely used in PMCs – Examples: epoxy and polyester with fiber reinforcement, and phenolic with powders Dr. A. Keshavarz - ENGR 4250U
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Composite Survey Large- particle Dispersion- strengthened Particle-reinforced Continuous (aligned) Aligned Randomly oriented Discontinuous (short) Fiber-reinforced Laminates Sandwich panels Structural Composites Dr. A. Keshavarz - ENGR 4250U
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Elastic modulus , E c , of composites: -- two approaches. Adapted from Fig. 16.3, Callister 7e . (Fig. 16.3 is from R.H. Krock, ASTM Proc , Vol. 63, 1963.) Composite Survey: Particle-III lower limit: 1 E c = V m E m + V p E p c m m upper limit: E = V E + V p E p “rule of mixtures” Particle-reinforced Fiber-reinforced Structural Data: Cu matrix w/tungsten particles 0 20 40 60 80 100 150 200 250 300 350 vol% tungsten E (GPa) (Cu) (W) Read section 16.2 Dr. A. Keshavarz - ENGR 4250U
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Dr. A. Keshavarz - ENGR 4250U
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Dr. A. Keshavarz - ENGR 4250U
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Fiber Alignment aligned continuous aligned random discontinuous Adapted from Fig. 16.8, Callister 7e . Dr. A. Keshavarz - ENGR 4250U
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Stress-strain relationships for the composite material (b) Dr. A. Keshavarz - ENGR 4250U (a)
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Critical Ex: For fiberglass, fiber length > 15 mm needed Composite Survey: Fiber-IV Particle-reinforced Fiber-reinforced Structural c f d τ σ > 15 length fiber fiber diameter shear strength of fiber-matrix interface fiber strength in tension Shorter, thicker fiber: c f d τ σ < 15 length fiber Longer, thinner fiber: Poorer fiber efficiency Adapted from Fig. 16.7, Callister 7e . c f d τ σ > 15 length fiber Better fiber efficiency σ (x) σ (x) Dr. A. Keshavarz - ENGR 4250U
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Composite Strength: Longitudinal Loading Continuous fibers - Estimate fiber-reinforced composite strength for long continuous fibers in a matrix Longitudinal deformation σ c = σ m V m + σ f V f but ε c = ε m = ε f volume fraction isostrain E ce = E m V m + E f V f longitudinal (extensional) modulus m m f f m f V E V E F F = f = fiber m = matrix Read section 16.5 Dr. A. Keshavarz - ENGR 4250U
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Modulus of Elasticity Cont. Fibers Dr. A. Keshavarz - ENGR 4250U
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This note was uploaded on 06/02/2011 for the course ECONMICS ECN204 taught by Professor Brenan during the Spring '08 term at Ryerson.

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Lecture 12 - ENGR 4250 Advanced Materials Engineering...

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