Metallic, Polymeric, Ceramic, and Composite Materials

Metallic Materials

Metallic materials are inorganic substances containing one or more elements. They may contain metals and also some non-metallic elements. The metallic elements include iron, copper, aluminum, nickel, magnesium, and titanium. Non-metallic elements include carbon, nitrogen, and oxygen.

Characteristics of Metal Components

• Have a crystalline structure
• Are good thermal and electrical conductors
• Many have mechanical resistance and are ductile at room temperature
• Can also exhibit high strength at elevated temperatures

A metal alloy is a combination of two or more metals. They are normally divided into two classes:

• Ferrous metals and alloys that contain a high percentage of iron
• Nonferrous metals and alloys containing no iron or relatively small amounts of iron

Polymeric Materials

Polymeric materials are formed by very large molecules with molecular weights ranging from a few thousand to millions of grams per mol. Most are organic polymers, i.e., containing carbon and hydrogen and often other non-metal atoms, especially oxygen and nitrogen.

Polymer Classification

Polymers can be classified into two groups:

• Thermoplastic polymers: Long chains that are not covalently connected to each other
• Thermoset polymers: Molecular chains strongly linked, making them rigid, strong, and more fragile than thermoplastics

Polymerization

Polymerization occurs when small molecules combine to produce larger molecules. The structure can be of long-chain (thermoplastic) or networks (thermosets). Thermoplastic materials are used to produce polyethylene plastic bags. Thermoset materials include resins and vulcanized rubber.

Ceramic Materials

Ceramic materials are inorganic, non-metallic materials consisting of metal and non-metal elements. They can be chemically bonded crystalline, amorphous, or mixtures thereof.

Features of Ceramic Materials

• High hardness and temperature resistance
• Low weight and good insulating properties
• Low toughness and ductility, mechanical fragility
• High melting temperature and high chemical stability

Composite Materials

Composite materials in engineering are generally defined as a material system comprising a mixture or combination of two or more micro or macro constituents that differ in shape and chemical composition and are essentially insoluble in each other.

Most Important Composites

• Fiber-reinforced plastic
• Concrete
• Asphalt
• Wood