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.

Data Processing

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Results

Table #1: List of variables recorded for experiment

Variable	Quantity	Note
L = Support Span (mm)	31.6	Approximate measurement
b = Width of test beam (mm)	Varied by Specimen	Averaged measurement
d = depth of beam (mm)	Varied by Specimen	Averaged measurement
Load rate (mm/min)	1 mm/min	Greater than standard, but was used for sake of time and practicality
Maximum deflection (mm)	3 mm	Greater than standard, but allowed to show the material’s properties consistently up to failure

Table #2: Dimensions of test specimens

Specimen	L = Support Span (mm)	b = Width of test beam (mm)	d = depth of beam (mm)	m (N/mm)
1	31.6	16.51, 15.92, 15.53 avg = 15.987	1.15, 1.33, 1.09 avg = 1.19	120
2	31.6	14.63, 15.61, 14.39 avg = 14.877	1.38, 1.59, 1.42 avg = 1.463	94
3	31.6	15.24, 15.35, 15.10 avg = 15.23	0.98, 0.96, 0.93 avg = 0.957	35.7
4	31.6	13.70, 14.42, 14.62 avg = 14.247	0.98, 0.92, 0.92 avg = 0.94	10.4

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.