Medium density fiberboard-Determination of static bending strength and elastic modulus

Measurement of Static Strength and Elastic Modulus of MDF

Medium density fiberboard-Determination of static bending strength and elastic modulus

1 Subject Content and Scope of Application

This standard specifies the method of measuring the static bending strength and elastic modulus of MDF.

This standard is suitable for indoor medium density fiberboard.

2 Reference Criteria

Preparation of MDF specimens in GB 11718.3

3 Equipment and measuring instruments

3.1 Wood Universal Testing Machine.

3.2 Special Fixtures.

3.3 percentile meter and fixture, measuring range about 30 mm, accuracy 0.01 mm.

3.4 vernier caliper with accuracy of 0.02mm.

3.5 micrometer, accuracy 0.01 mm.

3.6 stopwatch.

4 Sampling and specimens

Sampling and cutting of specimens are carried out according to GB 11718.3.

5 test methods

5.1 The width of the specimen is measured at the center line of the length of the specimen, which is accurate to 0.1 mm. The thickness of the specimen is measured at each end at the distance of 15 mm from the center line of the specimen length to the edge, which is accurate to 0.05 mm. The arithmetic average value of the two points is taken to 0.05 mm.

5.2 The static strength and modulus of elasticity were tested according to the figure.

5.3 The indenter must coincide with the center line of the length of the specimen. When the indenter touches the specimen and the load on the force plate is zero, the pointer of the dial indicator should be adjusted at zero.

5.4 When testing, the loading should be uniform. The loading speed is 0.125+0.063 mm/s. The loading should be stopped at least five times before loading to the failure of the specimen. The load and the corresponding deflection at five points should be recorded. The load is accurate to 10N, and the deflection value is accurate to 0.1 mm.

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6 test results

6.1 Draw the pressure-deflection curve to determine the slope of the curve; According to the measured pressure and deflection values, take the load P(N) as the ordinate and the deflection Y(mm) as the abscissa, record all the test points on the coordinate, and draw the slope line according to the points within the proportional limit (not less than three points).

6.2 Elastic modulus E (MPa) is calculated by formula (1):

E = L3/4bh3 x Pi/Yi………………………………………………………………………………………………………………………………………………………………………… (1)

Formula: L – bearing span (L – 15h, no less than 150), mm;

B – specimen width, mm;

H – specimen width, mm;

Pi – load in proportional limit, N;

Yi – Deflection value of corresponding Pi, mm.

6.3 The modulus of elasticity of each plate is the arithmetic average of the modulus of elasticity of six specimens, which is accurate to 1 MPa.

6.4 Static flexural strength_(MPa) is calculated by formula (2) and is accurate to 0.1 MPa.

_ = 3PL/2bh2…………………………………… (2)

Formula: P – failure load of specimen, N;

L – bearing span (L = 15h, not less than 150), mm;

B – specimen width, mm;

H – specimen thickness, mm.

6.5 The static strength of each plate is the arithmetic average of the static strength of six specimens, which is accurate to 0.1 MPa.

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