Detect the bending moment and flexural modulus ratio of artificial decorative panel panels under maximum load.
Three point bending test steps for artificial decorative panels:
- Make the test piece according to the test requirements: Size and length of the test piece: (thickness of the test piece) × 20+50）mm； Width b=(50 ± 1) mm.
For hollow structural plates with tube holes parallel to the length of the test piece, such as hole shaped or honeycomb shaped plates, the width of the test piece should be at least twice the width of the cross-sectional unit of each tube hole (i.e. twice the tube diameter plus two wall plate thicknesses). The test piece has a symmetrical cross-section as shown in Figure 9. If the tube hole of the test piece is perpendicular to the length of the test piece, the loading roller should be located directly above the wall panel. The unit is millimeters.
When measuring the static bending strength, if the deflection deformation of the specimen is large and the specimen is not damaged, the distance between the two supports should be reduced, but not less than 100mm. The testing report should specify the distance between the supports at the time of specimen failure. If such a situation occurs, the test piece should be taken again for measurement. Plywood specimens should have no significant characteristics that affect their strength.
- Sample balance treatment
If necessary, place the test piece in an environment with a temperature of (20 ± 2) ℃ and a relative humidity of (65 ± 5)% until its mass remains constant. The difference between the two weighing results after a 24-hour interval does not exceed 0.11% of the mass of the test piece, which is considered to be a constant mass.
3 Methods
3.1 Measure the width and thickness of the specimen (see 4.1). The width is measured at the center of the long side of the specimen, and the thickness is measured at the intersection of the diagonal lines of the specimen.
3.2 Adjust the span between the two supports to at least 20 times the basic thickness of the specimen. The minimum is 100mm and the maximum is 1000mm. Measure the center distance between supports to the nearest 0.5mm.
3.3 Place the test piece flat on the support, with the long axis of the test piece perpendicular to the support roller, and the center point of the test piece below the loading roller (see Figure 8).
3.4 Load at a constant speed throughout the entire experiment. Adjust the loading speed to reach the maximum load within (60 ± 30) seconds. Measure the bending deformation of the specimen at the midpoint (directly below the loading roller) to the nearest 0.1mm. Draw a load deflection curve based on the deformation and corresponding load values. The load is accurate to 1% of the measured value. If the deflection deformation measurement results in an increase in M reading, at least 6 pairs of load deflection values should be taken
3.5 Record the maximum load to the nearest 1% of the measured value.
3.6 According to the longitudinal and transverse directions of the board, take two sets of test pieces for testing. Within each group of specimens, half of the specimens face upwards and half face upwards during testing.
4、 Result representation
1 Static bending strength
1.1 Static bending strength of the specimen σ b. Calculate according to equation (6), accurate to 0.1MPa:
σ b=（3 × Fmax × l1）/（2 × b × t ²）
In the equation:
σ B – Static bending strength of the specimen, in megapascals [i (MPa):
Fmax – maximum load during specimen failure, in Newton (N):
L1- Distance between two supports, in millimeters (mm);
B – specimen width, size f>: in millimeters (mni):
T – Original degree of the specimen m millimeters (mm)
The arithmetic mean value of the static bending strength of the same part of the test piece within the group of 1.2-tensile plate specimens (see 1.7.1.6), accurate to 0.1 MPa.
2 Elastic modulus
2.1 Calculate the elastic modulus of the specimen according to equation (7), accurate to 10 MPa:
EL=l1/（l × b × t） · （F2-F1）/（a-a1）
In the equation:
EL – Elastic modulus of the specimen, in megapascals
L1- Distance between two supports, in millimeters (mm):
B – specimen width, in millimeters (mm):
T – thickness of the specimen, in milliliters (mm);
F2-F1- The increase in load in the straight section of the load deflection curve (10. F value is about 10% of the maximum load, and F value is about 10% of the maximum load), in Newton (N);
A2-a1- The increase in deformation in the middle of the specimen, that is, the deformation position of the specimen in the force F2-F1 range is in millimeters (mm):
Figure 10 Load deflection curve within the elastic deformation range
2.2 – The elastic modulus of each group of specimens (see 1.7.1.6) is the arithmetic mean value of the elastic modulus of all specimens in the same group, accurate to 10MPa
