Question

Find a materials property plot of elastic modulus and density.

Identify a composite, a polymer, and a metal with densities less than 3000 kg/m³ (Mg = 10⁶ g) and the highest possible elastic modulus. Provide an example of an engineering design that might require this combination of material properties and explain why those properties would be important. What design advantages could a polymer offer over a metal even though the polymer has a lower stiffness?

Answer 1

Please find the plot below:

Material examples

1. Composite

-Carbon/epoxy

-Density-1600 kg/m³

-Young's modulus-70 GPa

2. Polymer

-Kevlar 49

-Density-1440 kg/m³

-Young's modulus-112.4 GPa

3. Metal

-Alumnium

-Density-2700 kg/m³

-Young's modulus-69 GPa

Examples in design

Low density -high Young's modulus property is important for design of bodies of moving vehicles where whe weight has to be minimum and rigidity maximum Examples are aircraft bodies, which are made of composites or alumnium alloys, car bodiies etc.

Advantage of polymer

In spite of having lower stiffness, polymers have

-lower density, hence lighter

-higher corrosion resistance, hence longer lasting in corrosive atmosphere.