Three point flexural test
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The three point bending flexural test provides values for the modulus of elasticity in bending EB, flexural stress σf, flexural strain εf and the flexural stress-strain response of the material. The main advantage of a three point flexural test is the ease of the specimen preparation and testing. However, this method has also some disadvantages: the results of the testing method are sensitive to specimen and loading geometry and strain rate.
[edit] Testing Method
Calculation of the flexural stress σf
for a rectangular cross section
for a circular cross section
Calculation of the flexural strain εf
Calculation of Young's modulus EB
in these formulas the following parameters are used:
- σf = Stress in outer fibers at midpoint, (MPa)
- εf = Strain in the outer surface, (%)
- Eb = Modulus of elasticity in bending,(MPa)
- P = load at a given point on the load deflection curve, (N)
- L = Support span, (mm)
- b = Width of test beam, (mm)
- d = Depth of tested beam, (mm)
- D = maximum deflection of the center of the beam, (mm)
- m = Slope of the tangent to the initial straight-line portion of the load deflection curve, (N/mm)
[edit] See also
- Flexural strength
- ASTM materials standards organization
[edit] References
- ASTM standard test methods for flexural properties of unreinforced and reinforced plastics and electrical insulating materials
