CE 241 MATERIALS SCIENCE Introduction. What do Engineers do? Design and Build.... Design and Build.... As Civil Engineers we design and build civil structures.

CE 241CE 241 MATERIALS SCIENCE MATERIALS SCIENCE

IntroductionIntroduction

What do Engineers do?What do Engineers do? Design and Build ....Design and Build ....As As Civil EngineersCivil Engineers we design and build we design and build

civil structures (residental buildings, civil structures (residental buildings, hospitals, dams, roads, towers, ...) hospitals, dams, roads, towers, ...)

Materials Science and EngineeringMaterials Science and Engineering forms forms the bedrock for the engineering the bedrock for the engineering disciplines because the structures, disciplines because the structures, components, and devices that engineers components, and devices that engineers design and use must be made out of design and use must be made out of something, and that is a something, and that is a material.material.

The properties of the materials that The properties of the materials that are available define and limit the are available define and limit the capabilities that the device or capabilities that the device or structure can have, and the techniques structure can have, and the techniques that can be used to fabricate it. that can be used to fabricate it. Reinforced Concrete Bridges... ~5-10 Reinforced Concrete Bridges... ~5-10

m in spanm in span Prestressed Concrete Bridges... ~ 30-Prestressed Concrete Bridges... ~ 30-

40 m in span40 m in span Steel Bridges... ~ 60-70 m in spanSteel Bridges... ~ 60-70 m in span

Selecting the best material is usually a Selecting the best material is usually a difficult task, requiring tradeoffs difficult task, requiring tradeoffs between different material properties between different material properties (including cost) (including cost)

Cost of a residential building: Cost of a residential building: 65-75% materials cost65-75% materials cost 5% technical personel5% technical personel Rest is the labor costRest is the labor cost

Therefore, aTherefore, an appreciation of the n appreciation of the important materials characteristics, important materials characteristics, the connection between the behavior of the connection between the behavior of

the material in its intended design the material in its intended design setting, setting,

and the stuff the object is made from and the stuff the object is made from (and how it is made) (and how it is made)

is important to every engineer, even if is important to every engineer, even if they will never create a new material they will never create a new material but simply choose from standard and but simply choose from standard and widely available ones. widely available ones.

As civil engineers our job is to:As civil engineers our job is to: To make sure that the structure is functional To make sure that the structure is functional

during its service life (it should be strong)during its service life (it should be strong) To make sure that the structure should To make sure that the structure should

withstand the environment (it should be withstand the environment (it should be durable)durable)

To make sure that the structure is aesthetic To make sure that the structure is aesthetic and economic (it should be feasible)and economic (it should be feasible)

We need to know the properties of We need to know the properties of constructional materials. constructional materials. Physical, chemical and mechanical propertiesPhysical, chemical and mechanical properties Manufacturing processesManufacturing processes Its behavior in its final formIts behavior in its final form

The service life of a civil engineering The service life of a civil engineering structure does not ONLY depend onstructure does not ONLY depend on How good its design isHow good its design is How good its labor isHow good its labor is

You have to consider other factors such You have to consider other factors such as:as: How good the material that you pick isHow good the material that you pick is How good the quality control isHow good the quality control is How you maintain the structure!How you maintain the structure!

Think about the maintenance Think about the maintenance requirements of requirements of your car !your car ! your house !your house !

Why do we need to know Why do we need to know materials?materials?

Every engineer, whether mechanical, Every engineer, whether mechanical, civil, chemical or electrical, will at civil, chemical or electrical, will at some point deal with a design problem some point deal with a design problem involving materials. Examples might involving materials. Examples might include a transmission gear, the include a transmission gear, the superstructure of a building, an oil superstructure of a building, an oil refinery component, or an integrated refinery component, or an integrated circuit chip. circuit chip.

To conclude: To conclude:

Materials ScienceMaterials Science

Materials Science:Materials Science: The study of the The study of the nature, behavior and use of nature, behavior and use of materials. materials.

The purpose of this course is to:The purpose of this course is to: Learn the properties of materials Learn the properties of materials

(strength, ductility, impact resistance, ...)(strength, ductility, impact resistance, ...) Learn the internal structure of materials Learn the internal structure of materials

(the atomic structure, bonding, ...)(the atomic structure, bonding, ...) Learn how the internal structure of a Learn how the internal structure of a

material affects its propertiesmaterial affects its properties Metals: Metallic bonding Metals: Metallic bonding ductility ductility Ceramics: Ionic and covalent bods Ceramics: Ionic and covalent bods

brittlenessbrittleness Plastics: Covalent and Van der Waals Plastics: Covalent and Van der Waals

bondsbondsmoisture resistancemoisture resistance

Properties of MaterialsProperties of Materials

Mechanical :Mechanical : Define the behavior of the Define the behavior of the materials under loads. (Strength, elasticity, materials under loads. (Strength, elasticity, plasticity, ductility, hardness, etc.)plasticity, ductility, hardness, etc.)

Physical :Physical : Density, porosity, moisture content, Density, porosity, moisture content, shape, surface texture, etc.shape, surface texture, etc.

Chemical :Chemical : Oxide or compound composition Oxide or compound composition Physico-chemical :Physico-chemical : Shrinkage, swelling Shrinkage, swelling Thermal :Thermal : Conductivity Conductivity Acoustical :Acoustical : Sound transmission or absorption Sound transmission or absorption Optical :Optical : Color Color

Classification of Classification of Civil Engineering MaterialsCivil Engineering MaterialsThis classification can be done in so This classification can be done in so

many different ways:many different ways: According to their stateAccording to their state According to their chemical According to their chemical

composition and internal structurecomposition and internal structure According to their intended useAccording to their intended use According to their mechanical According to their mechanical

behaviorbehavior

1. According to Their 1. According to Their StateState Gases (COGases (CO22, O, O22)) Liquids (Water, Chemical Admixtures)Liquids (Water, Chemical Admixtures) Solids (Concrete, Steel)Solids (Concrete, Steel)

Semi-solids (Fresh Pastes, Mortar, Concrete)Semi-solids (Fresh Pastes, Mortar, Concrete)

2. According to Their 2. According to Their Chemical Composition and Chemical Composition and Internal StructureInternal Structure

Metals Metals → Metallic bond→ Metallic bond Ferrous (Iron, steel)Ferrous (Iron, steel) Non-ferrous (Aluminum)Non-ferrous (Aluminum)

Polymers → Long chain moleculesPolymers → Long chain molecules Natural (rubber, resin, wood) Natural (rubber, resin, wood) Artificial (plastics)Artificial (plastics)

Ceramics → Alumino silicatesCeramics → Alumino silicates Structural clay productsStructural clay products Porcelains Porcelains

Composite Materials → combination of several Composite Materials → combination of several materialsmaterials ConcreteConcrete Cement sandstoneCement sandstone

Reinforced Composite Materials Reinforced Composite Materials Reinforced concreteReinforced concrete Fiber reinforced plasticsFiber reinforced plastics

3. According to Their 3. According to Their Intended UseIntended Use

Structural Materials (concrete, steel, Structural Materials (concrete, steel, wood)wood)

Architectural Detailing Materials (glass, Architectural Detailing Materials (glass, paint, heat and sound insulators)paint, heat and sound insulators)

Preservatives (paint)Preservatives (paint)

But some materials fall into all of the But some materials fall into all of the above groups for example wood. above groups for example wood. • Load carrying memberLoad carrying member• ArchitecturalArchitectural• Coating of chipboard Coating of chipboard

4. According to Their 4. According to Their Mechanical BehaviorMechanical Behavior Elastic Materials Elastic Materials

They deform under some load and when They deform under some load and when the load is removed they return back to the load is removed they return back to their original positiontheir original position

Load

Deformation

Plastic Materials Plastic Materials They deform under some load, but They deform under some load, but when the load is removed there will when the load is removed there will be some permanent deformationbe some permanent deformation

δ

P

δperm: Permanent Deformation

Viscoelastic Materials Viscoelastic Materials

The load-deformation depends on the The load-deformation depends on the rate of loadingrate of loading

Load

Deformation