Table of Contents

Materials and Structure





The low power that humans can provide in steady-state imposes a strong requirement on the mechanical design of the vehicle. Aircraft, bicycles, and to some extent boats need to be both light and strong. To achieve this goal requires a careful selection of the materials from which the structure is to be made as well as the shape in which the material is fabricated. The same material with a different shape will have a different mechanical response.

The diagram below illustrates this concept. 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.

From: Ashby,
"Materials Selection in Mechanical Design," Pergamon (1993)