It is reported that the iPhone (3G and 3GS) by Apple utilizes a number of engineering materials:
(a) glass, for the front display cover,
(b) steel, for the perimeter edge trim piece, and (c) plastic, for the molded rear back. Search material property databases and select candidate materials for the (a) glass, (b) steel, and (c) plastic. List the requirements for each application and list the desired characteristics of each material.