Lightweight and Very Strong Material

[Seraph042]

For my Mechanics of Materials class, we have a project where we are given a shaft three points, with specified lengths in between each point, a specified load at one endpoint, and an applied torque at the middle point.

We get to decide the material and its structure (constantly changing cross-section, prismatic bar, two straight bars) etc.

This project is purely theoretical and no actual manufacturing will go into it, and as such no cost is an issue

I am looking for a strong and lightweight material to use for this project, cost is no concern. Anyone have any ideas ?

Right now I'm thinking something like:
Diamond
Silicon
Carbon Fiber

 

[timmay]

From your Mechanics of Materials lectures, how have you learned to define the stress state in the bar under the application of a point load? What determines the deflection of the beam at that centre point? What will be the limiting factor in the beam's ability to carry a load? As in where will it break and what state is that region in? Thinking about these things will help you decide on material suitability as well as cross sectional area.

 

[FredGarvin]

What are you going to use as your basis for your selection? In other words, what criteria are you going to be using to select the material?

 

[Seraph042]

This is our first design project and as such is very simple. We only have to consider an axial tensile force and an applied torque. There will be no deflection considered, and it is purely design. Right now I'm looking for a lightweight strong material and have found some Spectra fibers, but am in need of its shear modulus to continue