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# Three point flexural test

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.

## Testing Method

Calculation of the flexural stress σf $\sigma_f = \frac{3 P L}{2 b d^2}$

Calculation of the flexural strain εf $\epsilon_f = \frac{6Dd}{L^2}$

Calculation of Young's modulus EB $E_B = \frac{L^3 m}{4 b d^3}$

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)

## References

• ASTM standard test methods for flexural properties of unreinforced and reinforced plastics and electrical insulating materials

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Three_point_flexural_test". A list of authors is available in Wikipedia.
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