Strength of carbon fiber, plastic, steel and aluminum

Rank the strength of the following materials from strongest to weakest: carbon fiber, plastic, steel, aluminum

Material science
Answer

Before start answering this question, it is important to define what "strength" means, as it has no engineering meaning and it can be misinterpreted. For instance, it can refer to: tensile strength, compressive strength, flexural strength (specifically for plastics), torsional strength, impact resistance...

Once noted this, let's assume we are using the tensile strength as a benchmark to compare the materials. Then, the strength of a given material will be linked to its yield strength \(\sigma_Y\), which is the stress limit before the material undergoes permanent deformation. In this case the material rank as shown below, from strongest to weakest:

  1. Carbon Fiber: 3200 MPa
  2. Steel: 500 MPa
  3. Aluminum: 250 MPa
  4. Plastic: 45 MPa (Nylon)

Glass-reinforced plastics can be stronger, but usually plastics are the weakest in terms of tensile yield strength.