You usually want to play a 0.01 strain rate per minute or 0.10 strain rate per minute so that you can see in full detailed curve of how the material slowly reacts as stress increases over time.
- considering you have a 125 mm length, you are looking at a load rate of about 0.01 mm/min and you are aiming to allow the material to reach 0.05 strain (about 6 mm) or failure. That is a total of 600 minutes to reach 0.05 strain.
  - to be honest I don’t clearly remember how to calculate maximum depth of testing. Worth revisiting. -Tommy
  - Maximum 3 mm deflection should be enough to see the carbon fibre sample eventually reach failure. You will see in-person the stress curve and if it does not fail, then feel free to continue the experiment.
From experience, and for practical purposes, you can start at 0.5 mm/min. The testing lab technician will also like you better for this.
- If you are doing multiple tests, and you think the maximum stress will be easily captured, you can speed up to 1 mm/min.

Tensile Testing

Specimen Preparation

The minimum length of the specimen is equal to the total gripping length + 2 x width + gauge length, but greater lengths are recommended in order to minimize bending stresses.
Need to ask Mark about gripping length and tabbing options
- tabbing is required to reduce the chance of material failure at the grips
- Can ask Mark about a wedge grip that helps to reduce stress concentrations
- Can bond steel tabs at the ends of specimen

ASTM D3039 requires that the test should produce a failure within 1 to 10 minutes. The suggested test speeds are either a strain rate of 0.01 min-1 or a constant crosshead speed of 2 mm/min (0.05 in/min). The general practice is to conduct the test at a constant crosshead speed.