What are common materials? • Wood & Modified Wood • Hardness, elasticity, resilience, and toughness. • Low electrical and thermal conductivity. • Ceramics • Low electrical and thermal conductivity. • High degree of hardness, low corrosion. • Downside – Often very fragile.
What are common materials? • Metals and Alloys • Alloys are mixtures of a metal with other elements. • High thermal and electrical conductivity. • Malleable and ductile. • Plastics • Very high variety of properties and characteristics. • Developed from fossil fuels – oil and natural gas. • Composites • Combine the properties of the different component materials.
Materials may degrade over time. • Wood & Modified Wood • Varnish • Paint • Treatment with copper (Greenish blue color) • High temperature • Ceramics • Heating • Coating with enamel • Avoiding exposure to acids, bases, and thermal shock • Generally very durable – found in archeological digs.
Materials may degrade over time. • Metals & Alloys • Coatings: Paint, enamel, grease, resin. • Metallic coatings: zinc, copper, gold, silver, nickel, aluminum, & lead. • High heat can make the material harder (steel). • Plastics • Waterproof coatings • Adding antioxidants like carbon to prevent oxidation • Adding pigments that absorb UV rays.
Materials may degrade over time. • Composites • Two main problems that lead to degradation are deformation and loss of adherence between the materials. • Preventive measures depend on the materials used and by applying protective coatings.
Materials: Constraints • Constraints are external forces applied to a material and has the tendency to deform the material.
Materials: Mechanical Properties • Mechanical properties describe how a material reacts when subjected to a constraint. • Hardness – Ability to resist indentation (nicks) or abrasion (scratches). • Elasticity – Ability to return to their original shapes after undergoing a constraint. • Resilience – Ability to resist shocks without breaking.
Materials: Mechanical Properties • Ductility – Ability to be stretched without breaking. • Malleability – Ability to be flattened or bent without breaking. • Stiffness – Ability to retain their shapes when subjected to various constraints
Materials: Other Properties • Resistance to corrosion – Ability to resist effects of corrosive substances (Ex. rust). • Electrical conductivity – Ability to carry an electric current. • Thermal conductivity – Ability to transmit heat.