Registered Electrical & Mechanical Engineer BMayer@ChabotCollege.edu Engineering 45 Composite Materials Bruce Mayer, PE Registered Electrical & Mechanical Engineer BMayer@ChabotCollege.edu

Learning Goals – Composites List The CLASSES and TYPES of Composites When to Use Composites Instead of Metals, Ceramics, or Polymers How to Estimate Composite Stiffness & Strength Examine some Typical Applications

Terms & Classifications Composite  MultiPhase Material with Significant Proportions of Each Phase Phase Components MATRIX DISPERSED Phase Matrix The CONTINUOUS Phase The Matrix Function transfer stress to other phase(s) Protect other phase(s) from the (corrosive) Environment Reprinted with permission from D. Hull and T.W. Clyne, An Introduction to Composite Materials, 2nd ed., Cambridge University Press, New York, 1996, Fig. 3.6, p. 47.

Terms & Classifications cont.1 Composite Classifications MMC  Metal Matrix Composite CMC  Ceramic Matrix Comp. PMC  Polymer Matrix Comp. Dispersed Phase (DP) Function = To Enhance the Matrix Properities MMC: increase σy, TS/σu, creep resistance CMC: increase Kc (fracture toughness) PMC: increase E, σy, TS/σu, creep resistance Classes: Particle, fiber, structural

DISPERSION Strengthened Composite Taxonomy Composites PARTICLE Reinforced FIBER Reinforced STRUCTURAL LARGE Particle DISPERSION Strengthened Continous (Aligned) DIScontinous (Short) Laminates Sandwich Panels Aligned Randomly Oriented

Composite Survey – Particle-I Particle-reinforced Fiber -reinforced Structural Examples 60 Adapted from Fig. 10.10, Callister 7e. (Fig. 10.10 is copyright United States Steel Corporation, 1971.) -Spheroidite steel matrix: ferrite ( a ) (ductile) particles: cementite ( Fe 3 C (brittle) m Adapted from Fig. 16.4, Callister 7e. (Fig. 16.4 is courtesy Carboloy Systems, Department, General Electric Company.) -WC/Co cemented carbide matrix: cobalt (ductile) particles: WC (brittle, hard) V m : 10-15vol%! 600 Adapted from Fig. 16.5, Callister 7e. (Fig. 16.5 is courtesy Goodyear Tire and Rubber Company.) -Automobile tires matrix: rubber (compliant) particles: C (stiffer) 0.75 m

ReInforced ConCrete Concrete is a PARTICLE ReInforced Composite Matrix = PortLand Cement 3CaO-SiO2 + 2CaO-SiO2 Dispersed Phases Sand+Gravel Aggregate 60%-80% by Vol Steel ReInforcing Bars (Rebar) A type of FIBER Reinforcement Improves Tensile & Shear Strength

More ReInforced Concrete Concrete ≡ gravel + SAND + cement Why sand and gravel? → Sand packs into gravel VOIDS Reinforced concrete - Reinforce with steel reBAR or reMESH Increases TENSILE strength - even if Concrete matrix is cracked PreStressed concrete - reMesh under tension during setting of concrete. Tension release puts concrete under COMPRESSIVE Stress Concrete is much stronger under compression.

Composite Survey – Particle-II Particle-reinforced Fiber -reinforced Structural Composite Material Elastic Modulus, Ec Two “Rule of Mixtures” Approximations Data: Cu matrix w/tungsten particles 20 4 6 8 10 150 250 30 350 vol% tungsten E(GPa) lower limit: 1 E c = V m + p upper limit: (Cu) ( W) “rule of mixtures” ←Springs in PARALLEL Upper Limit is like Springs in PARALLEL: if Vm ~ Vp; then larger Ei dominates Lower limit => Ec = EmEp/ (VmEp + VpEm) => Then smaller Ei dominates ←Springs in SERIES Rule-of-Mixtures Applies to Other Properties Electrical conductivity, σelect: Replace E by σelect Thermal conductivity, k: Replace E by k.

Composite Survey: Fiber-I Fibers very strong Provide significant strength improvement compared to pure matrix-material Example: fiber-glass Continuous glass filaments in a polymer matrix Strength due to fibers Polymer simply holds them in place

Fiber Materials Whiskers - Thin single crystals - large length to diameter ratio graphite, SiN, SiC high crystal perfection – extremely strong, strongest known very expensive Traditional Fibers polycrystalline or amorphous Generally polymers or ceramics Ex: Al2O3 , Aramid, E-glass, Boron, UHMWPE UltraHighMolecularWeightPolyEthylene

Composite Survey: Fiber-II Particle-reinforced Fiber-reinforced Structural Fiber Materials Whiskers - Thin single crystals with large length to diameter ratio graphite, SiN, SiC high crystal perfection – extremely strong, strongest physical form known very expensive to produce Fibers polycrystalline or amorphous generally polymers or ceramics Ex: Al2O3 , Aramid, E-glass, Boron, UHMWPE Wires Metal – steel, Mo, W

Fiber Alignment aligned continuous aligned random discontinuous Adapted from Fig. 16.8, Callister 7e. aligned continuous aligned random discontinuous

ISOstress & ISOstrain isoSTRAIN → Tensile strength and elastic modulus when fibers are parallel to the direction of stress isoSTRESS → Tensile strength and elastic modulus when fibers are perpendicular to the direction of stress

Composite Survey – Fiber-I Fiber-reinforced Particle-reinforced Structural ALIGNED, CONTINUOUS Fibers Examples Metal: g’ (Ni3Al)-a(Mo) by eutectic solidification. From W. Funk and E. Blank, “Creep deformation of Ni3Al-Mo in-situ composites", Metall. Trans. A Vol. 19(4), pp. 987-998, 1988. Used with permission. matrix: a (Mo) (ductile) fibers: g’ (Ni 3 Al) (brittle) 2 m Glass w/SiC fibers formed by glass slurry Eglass = 76GPa; ESiC = 400GPa. (a) (b) From F.L. Matthews and R.L. Rawlings, Composite Materials; Engineering and Science, Reprint ed., CRC Press, Boca Raton, FL, 2000. (a) Fig. 4.22, p. 145 (photo by J. Davies); (b) Fig. 11.20, p. 349 (micrograph by H.S. Kim, P.S. Rodgers, and R.D. Rawlings). Used with permission of CRC Press, Boca Raton, FL.

Composite Survey – Fiber-II Fiber-reinforced Particle-reinforced Structural DISCONTINUOUS, RANDOM, 2D (Planer) Fibers Example: Carbon-Carbon Process: fiber/pitch, then burn out at up to 2500C. Uses: disk brakes, gas turbine exhaust flaps, rocket nose cones. Other variations: Discontinuous, random 3D Discontinuous, 1D Fully Aligned C fibers: very stiff very strong C matrix: less stiff less strong (b) view onto plane fibers lie in plane (a) Adapted from F.L. Matthews and R.L. Rawlings, Composite Materials; Engineering and Science, Reprint ed., CRC Press, Boca Raton, FL, 2000. (a) Fig. 4.24(a), p. 151; (b) Fig. 4.24(b) p. 151. (Courtesy I.J. Davies) Reproduced with permission of CRC Press, Boca Raton, FL.

Composite Survey – Fiber-III Fiber-reinforced Particle-reinforced Structural CRITICAL fiber length for effective stiffening & strengthening: fiber diameter shear strength of fiber-matrix interface fiber strength in tension The Equation Balances (want PullOut ≥ Tear) The Fiber Load capacity → σf•[ACylXsec] = σf•[πd2/4] The Fiber Pull-Out Force→ c•[ACylSurf] = c•[πd•l] Stronger Fibers → need LONGER fiber Stronger Fiber-Matrix Shear-Bond → need SHORTER Fiber

Fiber Lengths cont. Example: FiberGlass Need Fiber Lengh > 15mm Reason for length Criteria → examine Extreme cases Very Short Fiber has very little hold-in force and would PULL-OUT (Fiber PULLS OUT before Fracture) Very Long Fiber would take almost all the axial load (Fiber FRACTURES before PullOut) Shorter, thicker fiber: Longer, thinner fiber: Poorer fiber efficiency Better fiber efficiency Adapted from Fig. 16.7, Callister 6e.

Composite Survey – Fiber-IV Fiber-reinforced Particle-reinforced Structural Typical Values for K: Aligned 1D: K = 1 (anisotropic) Random 2D: K = 3/8 2D isotropy) Random 3D: K = 1/5 (3D isotropy) TS in fiber direction (1D, Aligned) by VOLUME Weighted Average Estimate Ec and TS Valid for LONG Fiber Condition: The Elastic Modulus in Fiber Direction efficiency factor

Composite Survey – Structural Fiber -reinforced Particle-reinforced Stacked and bonded fiber-reinforced sheets Orthogonal stacking sequence: e.g., 0°/90° benefit: balanced, in-plane stiffness Sandwich panels low density, honeycomb core benefit: small weight, large bending stiffness honeycomb adhesive layer face sheet Think PLYWOOD and LAMINATED BEAM tested in the Lab Similar to Composite Beam Lab Exercise

Composite Benefits Ceramic Matrix Composites → Better FRACTURE TOUGHNESS Metal Matrix Composites → Improved CREEP RESISTANCE fiber -reinf un-reinf particle-reinf Force Bend displacement

Composite Benefits cont.1 Polymer Matrix Composites → Better E:ρ (Stiffness:Weight) ratio E(GPa) G=3E8 K=E Density, r [Mg/m 3 ] .1 .3 1 10 .01 2 metal/ metal alloys polymers PMCs ceramics Want: HI Modulus; Lo density

Specific Strength The PRIMARY Motivation for the Use of Composites → Hi-Strength, Hi-Stiffness & Lo-Weight Thus Two Important Metrics Specific STRENGTH Similarly The Specific STIFFNESS Now Specific Weight Where ρ  Density in kg/m3 g  Acceleration of Gravity (9.81 m/s2)

Specific Strength cont.1 Now Determine Units for Sσ and SE by Way of Examples For 7075 Al in the Heat treated State u = 83 ksi  = 0.101 lb/in3 For Kevlar-49 (Aramid Fiber) E = 131 GPa ρ = 1444 kg/m3 Find  Now Specific Stiffness

Sσ vs SE Comparison The High DENSITY of Metal Reduces Sσ and SE The Low STRENGTH & STIFFNESS of most Polymers Reduces Sσ and SE

Summary – Composite Matls Composites Classified by: The Matrix Material Ceramic (CMC) Metal (MMC) PolyMer (PMC) ReInforcement Geometry Particles Fibers Layers

Summary – Composites cont.1 Composites enhance matrix properties: MMC: enhance sy, TS, creep performance CMC: enhance Kc PMC: enhance E, sy, TS, creep resistance Particle ReInforced Elastic modulus can be estimated by the Rule of Mixtures Properties are isotropic

Summary – Composites cont.2 Fiber ReInforced: Elastic modulus and TS can be estimated along fiber direction By Rule of Mixtures Properties can be isotropic or anisotropic Structural: Based on build-up of sandwiches in layered form Plys HoneyCombs

WhiteBoard Work Prob 16.11 Where Given IsoStrain, Longitudinal Loading for a Continuous Fiber Composite: Where F  Force E  Elastic Modulus V  Volume fraction Sub-f → “fiber” Sub-m → “matrix” Sub-c → “composite” Then Show

Licensed Electrical & Mechanical Engineer BMayer@ChabotCollege.edu Chabot Engineering Appendix E-glass Bruce Mayer, PE Licensed Electrical & Mechanical Engineer BMayer@ChabotCollege.edu

E Glass - BackGround http://www.azom.com/details.asp?ArticleID=764 E-Glass or electrical grade glass was originally developed for stand off insulators for electrical wiring. It was later found to have excellent fibre forming capabilities and is now used almost exclusively as the reinforcing phase in the material commonly known as fibreglass. http://www.azom.com/details.asp?ArticleID=764

E Glass - Composition Composition E-Glass is a low alkali glass with a typical nominal composition of SiO2 54wt%, Al2O3 14wt%, CaO+MgO 22wt%, B2O3 10wt% and Na2O+K2O less then 2wt%. Some other materials may also be present at impurity levels. http://www.azom.com/details.asp?ArticleID=764

E Glass – Key Properties Properties that have made E-glass so popular in fibreglass and other glass fibre reinforced composite include: Low cost High production rates High strength, (see table on next slide) High stiffness Relatively low density Non-flammable Resistant to heat Good chemical resistance Relatively insensitive to moisture Able to maintain strength properties over a wide range of conditions Good electrical insulation

E Glass – Fibre Strength Table 1. Comparison of typical properties for some common fibres.

E Glass – Use in Composites The use of E-Glass as the reinforcement material in polymer matrix composites is extremely common. Optimal strength properties are gained when straight, continuous fibres are aligned parallel in a single direction. To promote strength in other directions, laminate structures can be constructed, with continuous fibres aligned in other directions. Such structures are used in storage tanks and the like. Random direction matts and woven fabrics are also commonly used for the production of composite panels, surfboards and other similar devices.