Presentation on theme: "Ahmed W. Moustafa Lecture (1)"— Presentation transcript:
1 Ahmed W. Moustafa Lecture (1) Composite MaterialsAhmed W. MoustafaLecture (1)
2 Composite MaterialTwo inherently different materials that when combined together produce a material with properties that exceed the constituent materials.
3 Composite Material Defined A materials system composed of two or more physically distinct phases whose combination produces aggregate properties that are different from those of its constituents
4 Composite Material Defined Examples:Cemented carbides (WC with Co binder)Plastic molding compounds containing fillersRubber mixed with carbon blackWood (a natural composite as distinguished from a synthesized composite)
5 Why Composites are Important Composites can be very strong and stiff, yet very light in weight, so ratios of strength‑to‑weight and stiffness‑to‑weight are several times greater than steel or aluminumFatigue properties are generally better than for common engineering metalsToughness is often greater tooComposites can be designed that do not corrode like steelPossible to achieve combinations of properties not attainable with metals, ceramics, or polymers alone
6 Disadvantages and Limitations Properties of many important composites are anisotropic ‑ the properties differ depending on the direction in which they are measured – this may be an advantage or a disadvantageMany of the polymer‑based composites are subject to attack by chemicals or solvents, just as the polymers themselves are susceptible to attackComposite materials are generally expensiveManufacturing methods for shaping composite materials are often slow and costly
7 Classification of Composite Materials Traditional composites – composite materials that occur in nature or have been produced by civilizations for many yearsExamples: wood, concrete, asphaltSynthetic composites - modern material systems normally associated with the manufacturing industries, in which the components are first produced separately and then combined in a controlled way to achieve the desired structure, properties, and part geometry
8 Components in a Composite Material Nearly all composite materials consist of two phases:Primary phase - forms the matrix within which the secondary phase is imbeddedSecondary phase - imbedded phase sometimes referred to as a reinforcing agent, because it usually serves to strengthen the compositeThe reinforcing phase may be in the form of fibers, particles, or various other geometries
9 Functions of the Matrix Material (Primary Phase) Provides the bulk form of the part or product made of the composite materialHolds the imbedded phase in place, usually enclosing and often concealing itWhen a load is applied, the matrix shares the load with the secondary phase, in some cases deforming so that the stress is essentially born by the reinforcing agent
10 Composites Offer High Strength Light Weight Design Flexibility Consolidation of PartsNet Shape Manufacturing
11 Fiber Reinforced Polymer Matrix Transfer Load to ReinforcementTemperature ResistanceChemical ResistanceReinforcementTensile PropertiesStiffnessImpact Resistance
13 Matrix Considerations End Use TemperatureToughnessCosmetic IssuesFlame RetardantProcessing MethodAdhesion Requirements
14 Matrix Types Polyester Polyesters have good mechanical properties, electrical properties and chemical resistance. Polyesters are amenable to multiple fabrication techniques and are low cost.Vinyl EstersVinyl Esters are similar to polyester in performance. Vinyl esters have increased resistance to corrosive environments as well as a high degree of moisture resistance.
15 Matrix TypesEpoxyEpoxies have improved strength and stiffness properties over polyesters. Epoxies offer excellent corrosion resistance and resistance to solvents and alkalis. Cure cycles are usually longer than polyesters, however no by-products are produced.Flexibility and improved performance is also achieved by the utilization of additives and fillers.
18 Aramid Kevlar™ & Twaron™ Para aramid fiber characterized by high tensile strength and modulusExcellent Impact ResistanceGood Temperature ResistanceDensity g/ccTensile Strength 400 ksiTensile Modulus 18 MsiElongation 2.5%
19 Carbon Fiber PAN: Fiber made from Polyacrylonitrile precursor fiber High strength and stiffnessLarge variety of fiber types availableStandard Modulus Intermediate ModulusDensity g/cc g/ccTensile Strength 600 ksi ksiTensile Modulus 33 Msi 42 MsiElongation 1.8 % %
20 Weight Considerations Aramid fibers are the lightestg/ccCarbon1.79 g/cFiberglass is the heaviest2.4 g/cc
21 Strength Considerations Carbon is the strongestksiFiberglassksiAramids400 ksi
22 Kevlar is the toughest Fiberglass Carbon Impact ResistanceKevlar is the toughestFiberglassCarbon
23 Stiffness Considerations Carbon is the stiffest30-40 msiAramids14 msiFiberglass10-13 msi
24 Cost Considerations Fiberglass is cost effective $5.00-8.00/lb. Aramids$20.00/lbCarbon$30.00-$50.00/lb
25 Fabric StructuresWoven: Series of Interlaced yarns at 90° to each otherKnit: Series of Interlooped YarnsBraided: Series of Intertwined, Spiral YarnsNonwoven: Oriented fibers either mechanically, chemically, or thermally bonded
26 Woven FabricsBasic woven fabrics consists of two systems of yarns interlaced at right angles to create a single layer with isotropic or biaxial properties.
27 Construction (ends & picks) Weight Thickness Weave Type Physical PropertiesConstruction (ends & picks)WeightThicknessWeave Type
33 BraidingA braid consists of two sets of yarns, which are helically intertwined.The resulting structure is oriented to the longitudinal axis of the braid.This structure is imparted with a high level of conformability, relative low cost and ease of manufacture.
36 Triaxial YarnsA system of longitudinal yarns can be introduced which are held in place by the braiding yarnsThese yarns will add dimensional stability, improve tensile properties, stiffness and compressive strength.Yarns can also be added to the core of the braid to form a solid braid.
37 Conclusions Composite materials offer endless design options. Matrix, Fiber and Preform selections are critical in the design process.Structures can be produced with specific properties to meet end use requirements.