Seminar Report on ceramic composites


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Seminar Report on ceramic composites

  1. 1. PVG’s COLLEGE OF ENGINEERING & TECHNOLOGY PUNE – 411 009 CERTIFICATE This is to certify that the SEMINAR titled “Ceramic Composites: Case Study of Ballistic Impact” has been completed in the academic year 2012-13 by Deshpande Jaydeep Sanjeev Roll No. 22 (T.E. Mechanical) In partial fulfillment of the Bachelor Degree in MECHANICAL ENGINEERING As prescribed by the University Of Pune.Prof. P.G. Kulkarni Dr. Mrs. S. S. Sane (Guide) Head of the Dept. 1
  2. 2. Contents1. Introduction……………………………………………… 3 1.1 Constituents2. History……………………………………………………. 53. Ceramic Processing……………………………………… 74. Applications……………………………………………… 10 4.1 Aerospace 4.2 Space Shuttle Tiles 4.3 Military5. Case Study……………………………………………….. 15 5.1 Steel Plate 5.2 Monolithic Ceramic Tile 5.3 Composite Tile6. Conclusion……………………………………………….. 20 2
  3. 3. 1. Introduction Composite materials, often shortened to composites or called compositionmaterials, are engineered or naturally occurring materials made from two or moreconstituent materials with significantly different physical or chemical propertieswhich remain separate and distinct within the finished structure. A common example of a composite would be disc brake pads, which consistof hard ceramic particles embedded in soft metal matrix. Another example is found inshower stalls and bathtubs which are made of 3iberglass. Imitation granite andcultured marble sinks and countertops are also widely used. The most advancedexamples perform routinely on spacecraft in demanding environments.1.1 Constituents1.1.1 MatricesCommon matrices include mud (wattle and daub), cement (concrete), polymers (fiberreinforced plastics), metals and ceramics. Road surfaces are often made from asphaltconcrete which uses bitumen as a matrix. Unusual matrices such as ice are sometimeproposed as in pykecrete. 1.0.1 ResinsTypically, most common polymer-based composite materials, including fiberglass,carbon fiber, and Kevlar, include at least two parts, the substrate and the resin. 1.0.2 Reinforcements: FibresFiber-reinforced composite materials can be divided into two main categoriesnormally referred to as short fiber-reinforced materials and continuous fiber-reinforced materials. Continuous reinforced materials will often constitute a layeredor laminated structure. The woven and continuous fibre styles are typically availablein a variety of forms, being pre-impregnated with the given matrix (resin), dry, uni-directional tapes of various widths, plain weave, harness satins, braided, and stitched. 3
  4. 4. The short and long fibers are typically employed in compression moulding and sheetmoulding operations. These come in the form of flakes, chips, and random mate(which can also be made from a continuous fibre laid in random fashion until thedesired thickness of the ply / laminate is achieved). Fig1: Examples of reinforcements (a) Continuous fibre (b) Discontinues fibre (c) Whisker 4
  5. 5. 2. History Fig2: Old Egyptian Buildings Showing Reinforcement The word “ceramic” is derived from the Greek word κεραμικός (keramikos)meaning pottery. It is related to the older Indo-European language root “to burn”,“Ceramic” may be used as a noun in the singular to refer to a ceramic material or theproduct of ceramic manufacture, or as an adjective. The plural “ceramics” may beused to refer the making of things out of ceramic materials. Ceramic engineering, likemany sciences, evolved from a different discipline by today’s standards. Materialsscience engineering is grouped with ceramics engineering to this day. 5
  6. 6. Yield Strength of Various Materials 600 500 Superalloy C/C Composite 400Yield Strength (MPa) 300 Carbon Ste e l Zircaloy 200 Stainle ss Ste e l 100 Graphite 0 0.0 400.0 800.0 1200.0 1600.0 Temperature (°C) Fig3: Variation in Yield Strength w.r.t. Temperature 6
  7. 7. 3. Ceramic Processing Substantial interest has arisen in recent years in fabricating ceramic composites.While there is considerable interest in composites with one or more non-ceramicconstituents, the greatest attention is on composites in which all constituents areceramic. These typically comprise two ceramic constituents: a continuous matrix, anda dispersed phase of ceramic particles, whiskers, or short (chopped) or continuousceramic fibers. The challenge, as in wet chemical processing, is to obtain a uniform orhomogeneous distribution of the dispersed particle or fiber phase. Consider first the processing of particulate composites. The particulate phase ofgreatest interest is tetragonal zirconia because of the toughening that can be achievedfrom the phase transformation from the metastable tetragonal to the monocliniccrystalline phase, aka transformation toughening. There is also substantial interest indispersion of hard, non-oxide phases such as SiC, TiB, TiC, boron, carbon andespecially oxide matrices like alumina and mullite. There is also interest tooincorporating other ceramic particulates, especially those of highly anisotropicthermal expansion. Examples include Al2O3, TiO2, graphite, and boron nitride. In processing particulate composites, the issue is not only homogeneity of the sizeand spatial distribution of the dispersed and matrix phases, but also control of thematrix grain size. However, there is some built-in self-control due to inhibition ofmatrix grain growth by the dispersed phase. Particulate composites, though generallyoffer increased resistance to damage, failure, or both, are still quite sensitive toinhomogeneities of composition as well as other processing defects such as pores.Thus they need good processing to be effective. Particulate composites have been made on a commercial basis by simply mixingpowders of the two constituents. Although this approach is inherently limited in the 7
  8. 8. homogeneity that can be achieved, it is the most readily adaptable for existing ceramicproduction technology. However, other approaches are of interest. From the technological standpoint, a particularly desirable approach to fabricatingparticulate composites is to coat the matrix or its precursor onto fine particles of thedispersed phase with good control of the starting dispersed particle size and theresultant matrix coating thickness. One should in principle be able to achieve theultimate in homogeneity of distribution and thereby optimize composite performance.This can also have other ramifications, such as allowing more useful compositeperformance to be achieved in a body having porosity, which might be desired forother factors, such as limiting thermal conductivity. There are also some opportunities to utilize melt processing for fabrication ofceramic, particulate, whisker and short-fiber, and continuous-fiber composites.Clearly, both particulate and whisker composites are conceivable by solid-stateprecipitation after solidification of the melt. This can also be obtained in some casesby sintering, as for precipitation-toughened, partially stabilized zirconia. Similarly, itis known that one can directionally solidify ceramic eutectic mixtures and henceobtain uniaxially aligned fiber composites. Such composite processing has typicallybeen limited to very simple shapes and thus suffers from serious economic problemsdue to high machining costs. Clearly, there are possibilities of using melt casting for many of these approaches.Potentially even more desirable is using melt-derived particles. In this method,quenching is done in a solid solution or in a fine eutectic structure, in which theparticles are then processed by more typical ceramic powder processing methods intoa useful body. There have also been preliminary attempts to use melt spraying as ameans of forming composites by introducing the dispersed particulate, whisker, orfiber phase in conjunction with the melt spraying process. 8
  9. 9. Other methods besides melt infiltration to manufacture ceramic composites withlong fiber reinforcement are chemical vapor infiltration and the infiltration of fiberpreforms with organic precursor, which after pyrolysis yield an amorphous ceramicmatrix, initially with a low density. With repeated cycles of infiltration and pyrolysisone of those types of ceramic matrix composites is produced. Chemical vaporinfiltration is used to manufacture carbon/carbon and silicon carbide reinforced withcarbon or silicon carbide fibers. Besides many process improvements, the first of two major needs for fibercomposites is lower fiber costs. The second major need is fiber compositions orcoatings, or composite processing, to reduce degradation that results from high-temperature composite exposure under oxidizing conditions. 9
  10. 10. 4. Applications The products of technical ceramics include tiles used in the Space Shuttleprogram, gas burner nozzles, ballistic protection, nuclear fuel uranium oxide pellets,bio-medical implants, jet engine turbine blades, and missile nose cones. Its products are often made from materials other than clay, chosen for theirparticular physical properties. These may be classified as follows:Oxides: silica, alumina, zirconiaNon-oxides: carbides, borides, nitrides, silicidesComposites: particulate or whisker reinforced matrices, combinations of oxides andnon-oxides (e.g. polymers). Ceramics can be used in many technological industries. One application is theceramic tiles on NASA’s Space Shuttle, used to protect it and the future supersonicspace planes from the searing heat of reentry into the Earth’s atmosphere. They arealso used widely in electronics and optics. In addition to the applications listed here,ceramics are also used as a coating in various engineering cases. An example wouldbe a ceramic bearing coating over a titanium frame used for an airplane. Recently thefield has come to include the studies of single crystals or glass fibers, in addition totraditional polycrystalline materials, and the applications of these have beenoverlapping and changing rapidly. 4.0 AerospaceEngines:shielding a hot running airplane engine from damaging other components.Airframes: Used as a high-stress, high-temp and lightweight bearing and structuralcomponent.Missile nose-cones:shielding the missile internals from heat. 10
  11. 11. Fig4: High Temperature Exhaust Nozzle – 3D braided ceramic composite Fig5: High Temperature Exhaust Nozzle 11
  12. 12. 4.1 Space Shuttle tiles Space-debris ballistic shields – ceramic fiber woven shields offer betterprotection to hypervelocity (~7 km/s) particles than aluminum shields of equalweight.Rocket nozzles, withstands and focuses the exhaust of the rocket booster. Unmanned Air Vehicles- Implications of ceramic engine utilization inaeronautical applications (such as Unmanned Air Vehicles) may result in enhancedperformance characteristics and less operational costs. Fig 6: Space Shuttle Booster Exhaust Nozzles 12
  13. 13. 4.2 Military There is an increasing need in the military sector for high-strength, robustmaterials which have the capability to transmit light around the visible (0.4–0.7micrometers) and mid-infrared (1–5 micrometers) regions of the spectrum. Thesematerials are needed for applications requiring transparent armor. Transparent armoris a material or system of materials designed to be optically transparent, yet protectfrom fragmentation or ballistic impacts. The primary requirement for a transparentarmor system is to not only defeat the designated threat but also provide a multi-hitcapability with minimized distortion of surrounding areas. Transparent armorwindows must also be compatible with night vision equipment. New materials that arethinner, lightweight, and offer better ballistic performance are being sought. Suchsolid-state components have found widespread use for various applications in theelectro-optical field including: optical fibers for guided lightwave transmission,optical switches, laser amplifiers and lenses, hosts for solid-state lasers and opticalwindow materials for gas lasers, and infrared (IR) heat seeking devices for missileguidance systems and IR night vision. In most of the cases quarter to half inch thick steel plates are used asreinforcing members. Armored steel is good to defend against projectiles, but it isheavy. Increase in weight demands for higher power of the armored vehicles, alsoservicing becomes difficult. Armored tiles cannot be easily replaced as steel needs tobe cut out of the hull by gas cutter and the new tile needs to be welded again. Solutionto this problem is Ceramic Reinforced Tiles. Weight Strength 13
  14. 14. Ceramic reduced weight and yet maintains or improves the strength of the tiles. Tiles are easily replaceable Better multishot capability Light in weight Withstand higher temperatures 14
  15. 15. 5. Case Study: Ballistic Impact on Steel, Monolithic, Composite Ceramic Tiles5.1 Steel:- Steel Shows good multihit capability. But the stresses developed are localizedand thus the projectile can pierce through the plate without damaging the rest of thetile. But it creates a hole where projectile strikes. Whenever projectile comes in contact with the armor plate, extreme heat isgenerated at the contact point. As a result during further course of the projectile, bulletmaterial as well as the armor plate material plastically flows. If bullet is softer, itsmaterial completely flows out till all of its energy is vanished. But, if the bulletmaterial is harder, then it manages to pierce through steel. Fig7 shows the localized Plastic Strain developed in a 12mm thick armoredSteel plate when a 9 mm Steel projectile at 500 m/s hits Fig7: Plastic Strain in Impact Zone 15
  16. 16. Weight is an important factor which limits the use of steel. If one were to usesteel for personal body armor, then it will not be any lighter than 8kg. Thus itbecomes necessary to search a material of similar or better properties.5.2Monolithic Ceramic:- Monolithic ceramics provide good impact resistance by its failure mechanism.Ceramics are brittle in nature. Thus on impact ceramic fails at the point of impact.The stress wave thus generated travels through the material as a compressive wave.Ceramics typically are extra-ordinary in compressive strength. Thus all of the materialholds up the stress wave. But, when the stress wave reflects back from the boundaries,it reflects back as a tensile wave. As the ceramic is very poor in tensile strength,material fails. Fig8 shows the propagation of the stress wave, and also the deformation of theplate. Plate is an Al2O3 ceramic plate, struck with 9mm Steel projectile. Fig8: Propagation of Stress Wave But, as the projectile is still penetrating, it provides no escape path for thefailed ceramic material. This escaping material provides extremely high resistance to 16
  17. 17. the incoming projectile. Thus in the course, the projectile plastically flows and breaksdown into small fragments before all of its energy is exhausted. Fig9: Monolithic Ceramic Armor Tiles (ArmorTech™)5.2.1 Limitations: As the monolithic ceramic is uniform, it allows crack propagation easily. Alsowhen the material fails, there is nothing to hold the failing material. Thus the tilewhich is brittle, crumble downs. This limits its multi-hit capability. 17
  18. 18. Fig10: Deformation of Monolithic Ceramic Plate After ImpactFig11: Deformation of Monolithic Ceramic Plate After Impact 18
  19. 19. 5.3Ceramic Composites:- As previously mentioned, monolithic ceramic is good, but not good enough tobe used directly. Thus adding reinforcement greatly improves overall characteristics. Reinforcements such as glass wool, carbon fibre are added in the ceramicmatrix. These fibres take up the tensile loading in the reflected shockwave. Thus itminimizes the damage dealt to the original matrix. Thus ceramic is protected fromcrumbling. The reinforcement also helps in holding up the matrix in case of severeimpacts. Multihit capability is vastly improved.Fig12: SiC Whiskers Reinforced Ceramic Composite 19
  20. 20. 6 Conclusion: Thus wherever weight constraints hinder the use of thick steel plates, Ceramic composites provide the best solution. In defense applications ceramic composite tiles are popularly used in ballistic impact protection tiles and vests.Ceramic composites are also popularly used in high temperature applicationssuch as rocket nozzles and reactors 20
  21. 21. of Wisconsin, Open CoursewareUniversity of Michigan at Ann Arbor, Open Courseware“Introduction to Advanced 3D Reinforced Composites”: FredrikStig, KTH, Stockholm“Properties of 3D-woven Composites”: Fredrik Stig, KTH,StockholmAdvanced Ceramic Composites: US Department of Defense 21