Groups of Engineering Materials.

Based on their properties, this post has grouped engineering materials into:

(1.) Alloys (or Metals)
(2.) Plastic Materials.
(3.) Ceramics and Rubbers.
(4.) Composite Materials.

Alloys (or Metals).
An alloy can be defined as a metallic solid or liquid which is a mixture of 2 or more metals. For two metals to form a strong alloy,  they must be able to mix with each other in their molten state. Alloy may contain some non-metallic elements such as carbon. Examples of alloys are Steel,  Cast Iron.

Plastics.
These are organic materials containing molecules of high molecular weight which can be moulded to shape through the application of pressure at moderately high temperatures. Once moulded, some plastics may retain their plasticity while others may become hard and brittle. Examples of plastics are polyethene, nylon and bakelite.

(3.) Ceramics and Rubbers.
Ceramics are inorganic non-metallic materials which in most cases have been subjected to high temperature at some stages during manufacture. Examples of ceramics are natural and man-made glasses used to make bottles, windows and lenses, cements etc.
Rubbers are substances which have polymer molecules arranged in a manner that allows reversible extension to take place at normal temperatures. Well an example of rubber is the natural one derived from the sap of rubber tree.

(4.) Composite Materials.
Composite materials are groups of dissimilar materials combined together to form a new complex whose properties are different in type and magnitude from those of its seperate constituents. An example of a natural composite is wood which consists of cellulose bounded by lignin.  Other examples of composites are reinforced concrete and vulcanized rubber.