AE 684AE 684Aircraft Materials & ProcessesAircraft Materials & Processes

S.KamleS.KamleAerospace Engg. Department, IIT Aerospace Engg. Department, IIT

KanpurKanpur2015-20162015-2016

Grade Break-upGrade Break-up

Mid Sem Exam.Mid Sem Exam. 30%30% End Sem. Exam.End Sem. Exam. 40%40% Term projectTerm project 20%20% AttendanceAttendance 10%10% (Minimum Attendance requirement is (Minimum Attendance requirement is

80%. If you are absent for 8 or more 80%. If you are absent for 8 or more classes, you get automatic F grade in classes, you get automatic F grade in the course)the course)

Evolution of Engineering MaterialsEvolution of Engineering Materials

Historical PerspectiveHistorical Perspective Applications of materials in different Applications of materials in different

disciplinesdisciplines Materials to suit new product designs Materials to suit new product designs

and manufacturing processesand manufacturing processes

Material propertiesMaterial properties

General Mechanical Thermal Electrical Optical Eco-properties & Environmental

resistance Fabrication

Material properties (general)Material properties (general)

DensityDensity Cost- Material cost and processing Cost- Material cost and processing

costcost Viscosity (For gases and liquids)Viscosity (For gases and liquids) AvailabilityAvailability Magnetic propertiesMagnetic properties

Material properties (Mechanical)Material properties (Mechanical)

Elastic modulus Yield strength Ultimate strength Hardness Elongation Fatigue endurance limit Fracture toughness Creep

Material Properties (Thermal)Material Properties (Thermal)

Thermal conductivity Specific heat Thermal expansion coefficient Glass transition Temperature Melting point Maximum service temperature

Material Properties (Electrical)Material Properties (Electrical)

Electrical Resistivity Dielectric constant Breakdown potential

Material Properties (Optical)Material Properties (Optical)

Refractive index Transparent / Opaque

Mechanical Properties (EMechanical Properties (Eco- properties & Environmental Environmental

Resistance)Resistance)

Eco-properties may refer to Eco-properties may refer to properties such as properties such as Energy/kg to extract material

Environmental resistance refers to Environmental resistance refers to oxidation rate, Corrosion rate etc.oxidation rate, Corrosion rate etc.

Material PropertiesMaterial Properties(Fabrication Properties)(Fabrication Properties)

Ease of machining Ease of welding, casting, etc Hardening ability Formability Joining techniques

Periodic TablePeriodic Table

The properties of elements tend to be a The properties of elements tend to be a periodic function of their atomic numbers. periodic function of their atomic numbers. It is common practice to list the elements It is common practice to list the elements in the array shown (called the periodic in the array shown (called the periodic table). table).

The atomic number of the elements The atomic number of the elements increases horizontally in the tableincreases horizontally in the table

The vertical groupings are based on The vertical groupings are based on similarities in valence electron similarities in valence electron configurations and similarities in chemical configurations and similarities in chemical and physical properties of the elements.and physical properties of the elements.

Periodic TablePeriodic Table

The elements in group IA are called alkali The elements in group IA are called alkali metals; group IIA elements are alkaline-metals; group IIA elements are alkaline-earth metals. earth metals.

The groups listed as transition elements The groups listed as transition elements are metals with a particular electron are metals with a particular electron subshell configuration (incomplete subshell configuration (incomplete subshell). subshell).

Groups IIIA, IVA, VA, and VIIA are mostly Groups IIIA, IVA, VA, and VIIA are mostly nonmetals (as shown by the heavy line)nonmetals (as shown by the heavy line)

Periodic TablePeriodic Table

The elements in the last vertical The elements in the last vertical grouping are inert gases. grouping are inert gases.

The groups of elements in the The groups of elements in the separate horizontal blocks, separate horizontal blocks, lanthanide series and actinide serieslanthanide series and actinide series

Periodic TablePeriodic Table

The elements in each series behave the The elements in each series behave the same chemically. same chemically.

The horizontal rows are the periods. They The horizontal rows are the periods. They start from the left, and each element start from the left, and each element (going right) has one more nuclear charge (going right) has one more nuclear charge than the preceding element. than the preceding element.

These charges are neutralized by an These charges are neutralized by an additional electron. The period ends with a additional electron. The period ends with a noble gas with eight electrons in its noble gas with eight electrons in its valence (outer) shellvalence (outer) shell

Periodic TablePeriodic Table

Elements in a particular vertical Elements in a particular vertical group all have the same number of group all have the same number of electrons in their valence shellelectrons in their valence shell

Thus they have the same general Thus they have the same general chemical behavior.chemical behavior.

Periodic TablePeriodic Table

Some of the elements are used as Some of the elements are used as engineering materials in their pure engineering materials in their pure elemental state. elemental state.

Many metals fall into this category.Many metals fall into this category. Metals like beryllium, titanium, Metals like beryllium, titanium,

copper, gold, silver, platinum, lead, copper, gold, silver, platinum, lead, mercury, and many of the refractory mercury, and many of the refractory metals (w, Ta, Mo, Hf) are used to metals (w, Ta, Mo, Hf) are used to make industrial items.make industrial items.

Periodic TablePeriodic Table

In the nonmetal category, carbon is In the nonmetal category, carbon is used in industrial applications for used in industrial applications for motor brushes and wear parts and in motor brushes and wear parts and in the cubic form as diamond for tools. the cubic form as diamond for tools.

The inert gases are other nonmetals The inert gases are other nonmetals that are used in the elemental (ions that are used in the elemental (ions or molecules) form for industrial or molecules) form for industrial applications for protective applications for protective atmospheresatmospheres

Engineering MaterialsEngineering Materials A larger percentage of engineering A larger percentage of engineering

materials utilize the elements in combined materials utilize the elements in combined forms: Alloys, compounds and Mixturesforms: Alloys, compounds and Mixtures

In alloys, a metal is combined with one or In alloys, a metal is combined with one or more other elementsmore other elements

Compounds are made up of chemically Compounds are made up of chemically combined elements with definite combined elements with definite proportions of the component elements) proportions of the component elements)

Mixtures are a physical blend of two or Mixtures are a physical blend of two or more substances). These combinations of more substances). These combinations of the elements can be solids, liquids, or the elements can be solids, liquids, or gases. gases.

Engineering MaterialsEngineering Materials

Many laws of chemistry and physics Many laws of chemistry and physics control chemical bonding and the control chemical bonding and the tendencies for bonding. tendencies for bonding.

A simple rule that fits most reactions is A simple rule that fits most reactions is that atoms tend to combine in such a that atoms tend to combine in such a manner that their outer electron shell manner that their outer electron shell (containing valence electrons) will be (containing valence electrons) will be complete when it contains eight electrons.complete when it contains eight electrons.

In the water molecule hydrogen has a In the water molecule hydrogen has a valence of 1 and oxygen has a valence of valence of 1 and oxygen has a valence of 6. 6.

Water MoleculeWater Molecule

When they When they combine in a ratio combine in a ratio of two hydrogen of two hydrogen atoms to one atoms to one oxygen atom, the oxygen atom, the component atoms component atoms can share electrons can share electrons and complete their and complete their outer shells.outer shells.

Engineering MaterialsEngineering Materials

A solid can be a pure element such as A solid can be a pure element such as gold; it can be a compound such as sand, gold; it can be a compound such as sand, a compound of silicon and oxygen (SiO2); a compound of silicon and oxygen (SiO2); or it can be a combination of molecules.or it can be a combination of molecules.

Most living plants are a complex network Most living plants are a complex network of cellulose molecules. of cellulose molecules.

Some solids are mixtures of the preceding, Some solids are mixtures of the preceding, but within such solids each component but within such solids each component retains its identity.retains its identity.

Concrete is a composite of cement (a Concrete is a composite of cement (a compound) and aggregate (another compound) and aggregate (another compound).compound).

ElectronegativityElectronegativity

Electronegativity describes the tendency of an Electronegativity describes the tendency of an atom to gain an electron. atom to gain an electron.

Atoms with almost completely filled outer energy Atoms with almost completely filled outer energy levels, like chlorine, are strongly electronegative levels, like chlorine, are strongly electronegative and readily accept electrons.and readily accept electrons.

Atoms with nearly empty outer levels, such as Atoms with nearly empty outer levels, such as sodium readily give up electrons and are strongly sodium readily give up electrons and are strongly electropositive. electropositive.

High atomic number elements also have a low High atomic number elements also have a low electronegativity because the outer electrons are electronegativity because the outer electrons are at a great distance from the positive nucleus and at a great distance from the positive nucleus and are not as strongly attracted to the atom. are not as strongly attracted to the atom.

Metallic BondMetallic Bond

The metallic elements give up their The metallic elements give up their valence electrons to form a "sea" of valence electrons to form a "sea" of electrons surrounding the atomelectrons surrounding the atom

The valence electrons, which are no The valence electrons, which are no longer associated with any particular longer associated with any particular atom, move freely within the atom, move freely within the electron sea and become associated electron sea and become associated with several atom cores.with several atom cores.

Metallic BondMetallic Bond

The positively charged atom cores are The positively charged atom cores are held together by mutual attraction to the held together by mutual attraction to the electron, thus producing the strong electron, thus producing the strong metallic bond.metallic bond.

Metallic bonds are nondirectional. When a Metallic bonds are nondirectional. When a metal is bent, the direction of the bond metal is bent, the direction of the bond shifts. This permits metals to have good shifts. This permits metals to have good ductilityductility

Under the influence of an applied voltage, Under the influence of an applied voltage, the valence electrons can move easilythe valence electrons can move easily

Metallic BondMetallic Bond

Covalent BondCovalent Bond

Covalently bonded materials share Covalently bonded materials share electrons among two or more atoms.electrons among two or more atoms.

A silicon atom, which has a valence of A silicon atom, which has a valence of four, obtains eight electrons in its outer four, obtains eight electrons in its outer energy shell by sharing its electrons with energy shell by sharing its electrons with four surrounding silicon atomsfour surrounding silicon atoms

In order for the covalent bonds to be In order for the covalent bonds to be formed, the silicon atoms must be formed, the silicon atoms must be arranged so the bonds have a fixed arranged so the bonds have a fixed directional relationship with one another.directional relationship with one another.

Covalent BondCovalent Bond

Covalent BondCovalent Bond

covalent bonds are very strongcovalent bonds are very strong materials bonded by covalent bonds materials bonded by covalent bonds

have poor ductility and poor have poor ductility and poor electrical conductivity.electrical conductivity.

Ionic BondIonic Bond

When more than one type of atom is When more than one type of atom is present in a material, one atom may present in a material, one atom may donate its valence electrons to a different donate its valence electrons to a different atom, filling the outer energy shell of the atom, filling the outer energy shell of the second atom.second atom.

The atom that contributes the electrons is The atom that contributes the electrons is left with a net positive charge and is a left with a net positive charge and is a cation, while the atom that accepts the cation, while the atom that accepts the electrons acquires a net negative charge electrons acquires a net negative charge and is an anion.and is an anion.

Ionic BondIonic Bond

The oppositely charged ions are then The oppositely charged ions are then attracted to one another and produce attracted to one another and produce the ionic bond.the ionic bond.

Electrical conductivity is poor since Electrical conductivity is poor since the electrical charge is transferred by the electrical charge is transferred by the movement of entire ions which the movement of entire ions which do not move as easily as electrons.do not move as easily as electrons.

Ionic BondIonic Bond

Van der Waals BondingVan der Waals Bonding

Van der Waals bonds join molecules Van der Waals bonds join molecules or groups of atoms by weak - or groups of atoms by weak - electrostatic attractions.electrostatic attractions.

Many plastics, ceramics, water, and Many plastics, ceramics, water, and other molecules are permanently other molecules are permanently polarized; that is, some portions of polarized; that is, some portions of the molecule tend to be positively the molecule tend to be positively charged, while other portions are charged, while other portions are negatively charged.negatively charged.

Van der Waals BondingVan der Waals Bonding

Van der Waals BondingVan der Waals Bonding

Polyvinyl chloride contains many long, Polyvinyl chloride contains many long, chainlike molecules.chainlike molecules.

Within each chain, bonding is covalent, Within each chain, bonding is covalent, but individual chains are bonded to one but individual chains are bonded to one another by Van der Waals bonds. another by Van der Waals bonds.

Polyvinyl chloride can be deformed Polyvinyl chloride can be deformed significantly by breaking only the Van der significantly by breaking only the Van der Waals bonds as the chains slide past one Waals bonds as the chains slide past one another.another.

Van der Waals BondingVan der Waals Bonding