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Chapter 12 404 p. 386-421

Materials and their Properties. Chapter 12 404 p. 386-421. Types of Materials. Since the time of prehistoric Man, humans have been manipulating different materials to build tools and structures to live in. The most common materials are:   Wood Ceramics Metals Alloys Plastics

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Chapter 12 404 p. 386-421

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  1. Materials and their Properties Chapter 12 404 p. 386-421

  2. Types of Materials • Since the time of prehistoric Man, humans have been manipulating different materials to build tools and structures to live in. The most common materials are:   • Wood • Ceramics • Metals • Alloys • Plastics • Modified Wood • Composites

  3. HISTORY of MATERIALS(do not copy) • Different types of rock were used to build initial tools and wood was most likely one of the first materials used to build dwellings and furniture. • Ceramic structures have been found in many historical digs. The earliest ceramics were pottery articles made from clay.

  4. HISTORY (Continued) • The arrival of plastics many centuries later were very significant in the advancement of the use of material. • With time, composites were added to the mix allowing the advancement of the manufacturing of technical objects.

  5. WOOD p. 390-391 • Primary material used by man for construction and heating. • 2 types of wood: • Hardwood • Softwood • The following properties greatly influence the choice of wood for construction: • Hardness * low thermal/electrical conductivity • Elasticity  * pliability and ability to be shaped • Colour & shades * texture and grain • Resilience and toughness   * weight

  6. Modified wood consists of wood and additional products such as glue, plastics and preservatives. Some examples: • Plywood • Particle board • Fiber board • Since wood is an organic substance it tends to degrade very rapidly. • Products such as paint, stain, hardeners and varnish, protect the wood from weathering and infestation.

  7. CERAMICS p. 392-393 • Ceramics have low electrical conductivity properties, thus making great insulators for electrical circuits. • Their durability and hardness make them very useful for construction - bricks, ceramic tiles, carbide blades, etc.

  8. Ceramics are very heat resistant and this makea them appropriate for kitchen appliances such as ovens and heating dishes. • Ceramics do not corrode and therefore are very useful for ducts and drains. • Just the same, ceramics are fragile and can be easily broken. Care must be taken in the choice of raw material and the method for baking. • Certain acids and bases (sulfuric acid and calcium hydroxide) can degrade ceramics. • Extreme changes in temperature may also crack and destroy ceramics.

  9. METALS p. 394-395 • Metals are made from extracts from mineral ore and are often shiny. • This material displays good thermal and electrical conductivity. • Many are valued for their malleability (pliability) and ductility (deform under tension - stretch). • Since metallic substances are rarely pure in nature, they are often classified as alloys. • They are produced because of their density, reactivity, electrical and thermal conductivity, and tensile strength and shear strength. • Corrosion is caused by oxidation of the substances. • Coating and surface treatments usually increase the life of the material and decrease degradation.

  10. Alloy: A mixture of a metal with one or more other substances, which can be metal or nonmetal. copper, magnesium, manganese, silicon and zinc.

  11. PLASTICS p.396-397 • Plastics are often produced from fossil fuels such as petroleum and natural gas. • Plastics can be molded because they are malleable. • Thermoplastics • Do not undergo chemical change when heated • Can be molded over and over again • Can be manipulated (molded) when heated • When cooled, the structure holds its shape • Not biodegradable but most can be recycled

  12. Thermosetting plastic • Always remains hard even when heated • Once it take shapes its form can not be altered • If overheated it will decompose • Melamine and polyesters (nylons) are examples • Harder and more resilient than thermoplastics • In Quebec cannot recycle thus have negative effects for the environment • Poor conductors • Degradation • Appears as cracks or change of color • Degradation is irreversible • Affected by certain liquids like acids, oxidation and ultraviolet rays from the sun • Addition of waterproof coatings, antioxidants and pigments can reduce degradation and protect the plastic

  13. COMPOSITES p. 399-400 • Made from two or more materials from different categories. • Two main components: • Matrix (original material) that forms structure • Reinforcement (inserted into matrix to strengthen it) • Degradation • Deformation or fracture • Avoid extremes: shocks, impact, repeated stress • Do not survive in corrosive solutions

  14. MECHANICAL PROPERTY p. 388 • The term Mechanical Property defines how a material will respond when subjected to different forces and constraints. The most common mechanical properties are: • Elasticity • Malleability • Stiffness • Hardness • Resilience • Ductility • Other properties are also very important to consider when choosing a material for construction:  Electrical Thermal Resistance to corrosion • Ex: If a car company is planning a new model of vehicle they will try to choose a material for the body structure that will be resistant to road salt and therefore rust. The use of different metalloids for hubcaps is a good example.

  15. Constraints • The study of stress factors and their effects on materials will help determine the suitability of a particular material for a specific manufacturing project. • Manufactures refer to the word constraintwhen considering stress factors.

  16. Main types of Constraints p. 387 • Tension or tensile (pulling) • Compression (pushing) • Torsion (twisting) • Shearing (cutting) • Deflection (bending) • Temperature(which can cause deformation)

  17. Types of Deformation p. 387 • FRACTURE: is when the force being applied is large enough to break the object. • ELASTIC: The constraint changes the form of the material but once the force is removed the materials returns to its original shape. • PLASTIC: the force causes a permanent deformation that remains even when the the force is removed.

  18. Mechanical Properties of Materials

  19. **Degradation of a Material: Is the decline in some of its properties due to the effects of the surrounding environment.

  20. **Protection of a Material: Is the application of procedures that prevent or delay its degradation.

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