Material Science and Materials Processing (Day 1) Class

What are the Three Classifications of materials?

Material Classifications Natural materials: Occur in nature Organic: wood, cotton, hemp Inorganic: stone, clay, metals Synthetic: Human-made: rubber, plastics, nylon, Teflon Mixed materials: Combination of natural and synthetic: plywood, paper…etc.

Types of Materials (Close-up) Woods (Natural & Engineered) Metal Plastics Ceramics Composites

Types of Materials (Close-up) Woods Thickness of cell walls determines density. Color is a function of the chemicals in its cell walls. Grain is the way wood fibers grow. (Engineered): Made by combining particles and fibers of wood with adhesives: wood chips, plywood. Advantages: more strength per pound

Types of Materials (Close-up) Metal: Structure determines properties Good conductors of electricity and heat These are factors that might influence material selection. Categorized as: Ferrous: Contain iron: steel Nonferrous: Do not contain iron: aluminum

Types of Materials (Close-up) Plastics: Can be made into films, fibers, and solids; molded into a variety of products and shapes. Most plastics are made from petroleum. Plastics are polymers. Have an enormous amount of uses. Have densities less than metals, greater than most woods, and similar to crude oil. (material selection) Categorized as: Thermoplastic: can be softened by heat, then hardened again by cooling. Thermoset: cannot revert once heated and molded.

Types of Materials (Close-up) Ceramics: (material selection) Made from clay and nonmetallic inorganic materials Have an atomic structure that forms a 3-D geometric shape Compounds formed by combinations of metallic and nonmetallic elements High melting points; high strength and hardness; resistant to wear; brittle; can be transparent, translucent, or opaque; low densities Sometimes a better choice then metal because it tolerates heat well and is an electrical insulator.

Types of Materials (Close-up) Composites: Combination of two or more materials with different properties Materials retain separate identities Formed by using materials of two types: Matrix material Reinforcement material (fiber) Often lighter and provide similar or greater strength applications Cost of manufacturing is significantly higher. Often used in decks because it is resistant to rotting and insect damage. Categorized into three matrix types: Polymer, metallic, and ceramic

Types of Materials (Close-up) Why Composites?

What are some properties of materials?

Properties of Materials Key ideas: Materials are chosen based on properties that make them appropriate for particular applications. Categories: Physical, mechanical, electrical, chemical, magnetic, thermal, optical, and acoustic.

Properties of Materials Mechanical: Those that influence a material’s ability to endure and withstand applied forces Mechanical Testing: Strength Hardness Ductility Elasticity Plasticity Malleability Brittleness Toughness Yield Point

Elastic limit (yield strength) Beyond the elastic limit, permanent deformation will occur. The lowest stress at which permanent deformation can be measured. Under repetitive stresses, cracks in a metal can develop and grow and cause failure even thought the elastic limit has not been reached.

Properties of Materials Strength (forces): Flexural

Failure of Materials Buckling occurs when a given material is compressed until it gives way and collapses

Properties of Materials Physical properties: Density and freezing, melting, and boiling points Density is a measure of how tightly atoms are packed together Freezing, melting, and boiling points exist on a temperature continuum

Properties of Materials Electrical properties: Conductivity and resistivity Magnetic properties: Diamagnetic, paramagnetic, or ferromagnetic Thermal properties: Ability to conduct heat and expand when heated Optical properties: Ability to reflect, absorb, refract, or transmit light

Material Science and Materials Processing (Day 2) Class

Processing Materials Key ideas: The term “processing” means transforming basic (raw) materials into industrial materials, and then into finished products. Processing methods are categorized according to: Mass change Phase change Structure change. deformation of material Consolidation of material **Example: Processing trees into timber**

Processing Materials (cont’d.) Mass change: Cladding Electroplating Drilling Sawing Grinding Turning Phase change: Casting Pressing Injection molding Blow molding Vacuum forming Rotation molding

Processing Materials (cont’d.) Structure-change: Hardening Annealing Tempering

Processing Materials (cont’d.) Deformation: Forging Rolling Machine pressing Extrusion Drawing Consolidation: Fastening Joining Sintering Composite materials Coating

Processing Materials (cont’d.) Example Processes: Injection Molding: (Very Accurate) common industrial process used to manufacture parts. Extrusion: process whereby a continuous stream of a product is made by squeezing softened material (just below its melting point) through a small opening called a die.

Processing Materials (cont’d.) Example Processes: Sintering: is a process where powdered materials are combined with a binding material and pressed into shapes in a mold under heat and high pressure.

Factors in Selecting Materials Key ideas: Materials are chosen based on their properties, as well as other factors. Choice of material often reflects trading off competing benefits. True costs of materials extend beyond the cost of the raw material itself.

Factors in Selecting Materials (cont’d.) Properties determine suitability for applications: Cost Safety Availability Disposability Environmental impact

Factors in Selecting Materials (cont’d.) True cost of a material includes: Cost of the raw material Amount of energy and water needed Amount of pollution generated Human time and effort wasted

Factors in Selecting Materials (cont’d.) Availability of materials is a primary. Safety is also important. Disposability and environmental impact drive decisions about materials. Some materials can biodegrade. Engineers also consider the energy it takes to process materials.

Factors in Selecting Materials (cont’d.) Figure 4.70 Comparison of cost versus strength for structural materials.

Factors in Selecting Materials (cont’d.)