Materials, Properties and Design 
Table of Contents
The Effect of Shape
· Once a careful selection has been made of the materials from which the structure may be fabricated, the shape of the part becomes important. The same material with a different shape will have a different mechanical response.
· The material (green free-form) is converted into a structural component (in this case a girder) by selecting an I-shape that distributes the material mainly at the top and bottom of the structural component. Experiment shows that this shape is good in sustaining vertical bending loads, and I-beams of this type are employed in building construction. Selection of different shapes, or the same shape but with different height-to-width ratios will change the material performance as a structural element. 
Material + Shape = Component 
From: Ashby, 
"Materials Selection in Mechanical Design," Pergamon (1993)