RE: Floor MOE(Modulus of Elasticity) / MOR(Modulus of Rupture )tests:
This topic came to the surface the other day after we had learned that there was a CCIA meeting in Shanghai was held with the container factories and 17 flooring suppliers.
It appears that there is an attempt under way to change procedures for testing flooring.
At first blush, it looks as if there is a plan to eliminate tests such as MOE (Modulus of Elasticity).
This seems that it could pose an issue especially for the hybrid bamboo floors because bamboo is dense, hard and not very flexible.
In addition, given the fact that bamboo is cheaper and more plentiful than tropical hardwood, the flooring suppliers seem to be focusing on introducing more bamboo when producing the hybrid flooring.
Besides; floor suppliers used to apply long or small grain during producing process and for the xmembers whose thickness 4.0 mm at intermediate and 4.5 mm at the widen flange where the floors are jointly mounted. Consequently, in general the current floor deflection during the ISO floor test by 7,260 kgs is about 21 mm to 24 mm max sagged down, for which a certain high elasticity of the hybrid bamboo is especially essentially required.
In the event that this should take place, floorboards will be denser, less flexible with the potential for developing cracks and failures at the bottom veneer.
Recently, to confirm these kinds of worrisome; few buyers are to pay a close attention for the following tests at independent test lab.
¢ÂFloor MOR(modulus of rupture)/ MOE(modulus of elasticity) tests pursuant to GB.T 176572013 :
t_{1} Thickness of specimen before immersion, in mm
t_{2}Thickness of the specimen after immersion, in mm
4.5.5.2 The thickness swelling rate of water absorption of a panel is the arithmetic mean of the thickness swelling rate of water absorption at all the measuring points of all the specimens in the same panel, accurate to 0.1%
4.6 Determination of 24h Water Absorption
4.6.1 Principle
Determine the ratio of the mass difference of the specimen before and after soaking for 24h to the mass before soaking
4.6.2 Apparatus
4.6.2.1 Balance, with a sensibility of 0.01g
4.6.2.2 Water tank: capable of maintaining a temperature of (20±1) ¡É
4.6.3 Specimen
4.6.3.1 Specimen dimensions
Length : l = (100±1)mm; width: b = (100±1)mm
4.6.3.2 Balancing process of specimen
If necessary, place the specimen at a temperature of (20±2)¡É and a relative humidity of (65±5)% until constant mass. Where the difference between the two weights obtained at 24h interval does not exceed 0.1% of the specimen mass, the specimen mass is regarded as constant.
4.6.4 Method
4.6.4.1 Weight the specimen to the accuracy of 0.01g
4.6.4.2 Place the specimens into the tank with water at pH7±1 and temperature of (20±1)¡É; the temperature is maintained constant during the test. Keep the specimens’ surfaces vertical to the water surface. The distances between the specimens, the specimen and the bottom/wall of water tank shall at least be 15mm. The top of the specimen is (25±5)mm below the water level.
After soaking for 24 h ± 15min, take out of the specimen, wipe off water on the surface, and complete the weighting with 10 min to the accuracy of 0.01 g. Replace the soaking water for each test.
4.6.5 Expression of results.
4.6.5.1 The 24 h water absorption, W, of specimen is calculated according to Formula (5) , to the accuracy of 0.1%
Where,
W the water absorption of the specimen (%)
m1 the mass of specimen before soaking (g)
m2 the mass of specimen after soaking (g)
4.6.5.2 The 24 h water absorption of a panel is the arithmetic mean of the water absorptions of all the specimens in the same panel, accurate to 0.1%
4.7 Determination of Static Bending Strength and Elastic Modulus (Threepoint Bending)
4.7.1 Principle
The static bending strength elastic modulus of threepoint bending are determined by applying load to the middle of twopoint supported specimen. For static bending strength, it is to determine to ratio of the bending moment to the bending modulus of section with the specimen under the maximum load; for elastic modulus, it is to determine the ratio of the loadincurred stress to the strain with the specimen within the elastic limit of material
4.7.2 Apparatus
4.7.2.1 Universal mechanical testing machine, select proper load measuring range according to the product requirements with the measuring accuracy of 1% load value. The testing machine consists of:
a) Two parallel cylindrical backup rolls (see Figure 8), the length of which should exceed the width of the test piece. The diameter of backup roll is (10 ± 0.5) mm when T ≤6 mm; When the basic plate thickness T > 6 mm, the backup roll diameter is (15 ± 0.5) mm. The distance between backup rolls shall be adjustable.
b) Cylindrical loading roller (see Figure 8), when the basic thickness of the plate T ≤ 6 mm, the diameter of the loading roller is (10 ± 0.5) mm, when the basic thickness of the plate T > 6 mm, the diameter of the loading roller is (30 ± 0.5) mm. The loading roller is placed parallel to the backup roller, and the distance between the two supports is equal.
1. Specimen
2. Loading roller
3. Backup roll
F£ºload
t : Thickness of specimen
Figure 8 schematic diagram of measuring device for static bending strength and elastic modulus (three point bending)
c) The deformation measuring instrument (such as dial indicator or similar measuring tool) is placed in the middle of the backup roll to measure the deformation of the specimen, and the graduation value is 0.01 mm.
d) The measuring system can measure the load applied to the test piece with an accuracy of 1% of the measured value.
4.7.2.2 Vernier caliper, the division value is 0.1 mm, and the ranges of 0 mm ~ 300 mm, 0 mm ~ 600 mm and 0 mm ~ 1500 mm are selected according to the length of the specimen.
4.7.2.3 micrometer, the division value is 0.01 mm, and the ranges are 0 mm ~ 25 mm, 25 mm ~ 50 mm, 50 mm ~ 75 mm according to the thickness of the specimen.
4.7.2.4 stopwatch.
4.7.3 specimen
4.7.3.1 specimen size
Length l_{2} ≥ (20 t + 50) mm, t is the basic thickness of the specimen, and 150 mm ≤ l_{2} ≤ 1050 mm; Width b = (50 ± 1) mm.
For hollow structural plates with pipe holes parallel to the length of the specimen, the width of the specimen is at least twice the width of the section unit of each pipe hole (i.e. twice the pipe diameter plus the thickness of two wall panels), and the specimen 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 shall be located directly above the panel.
Pic.9 Cross section of hollow slab
When measuring the static bending strength, if the deflection of the specimen is large and the specimen is not damaged, the distance between the two supports should be reduced, but not less than 100 mm. The test report shall indicate the bearing distance when the specimen is damaged. If this happens, the test piece shall be taken again for determination.
Plywood specimens should have no obvious characteristics that affect their strength.
4.7.3.2 specimen balance treatment
If necessary, place the specimen at temperature (20±2£©¡É. Relative humidity (65±5)% environment to constant mass. If the difference between the two weighing results after 24 hours does not exceed 0.1% of the mass of the specimen, it is considered that the mass is constant.
4.7.4 method
4.7.4.1 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; The thickness is at the diagonal intersection of the specimen. Measurement.
4.7.4.2 adjust the span of the two supports to at least 20 times of the basic thickness of the specimen, with the minimum of 100 mm and the maximum of 1000 mm. Measure the center distance between supports to the accuracy of 0.5 mm.
4.7.4.3 place the test piece on the support, the long axis of the test piece is perpendicular to the backup roll, and the center point of the test piece is below the loading roll (see Figure 8).
4.7.4.4 load at constant speed throughout the test. Adjust the loading speed so that at (60±30) s. The deflection of the specimen is measured at the midpoint of the specimen (just below the loading roller) with the accuracy of 0.1 mm. The load deflection curve is drawn according to the deformation and the corresponding load value, and the load is accurate to 1% of the measured value. If the deflection measurement is incremental, take at least 6 pairs of load deflection values.
4.7.4.5 record the maximum load to 1% of the measured value.
4.7.4.6 according to the longitudinal and transverse direction of the plate, two groups of specimens are taken for test. In each group of test pieces, half of the test pieces face up and half of the test pieces back up.
4.7.5 results
4.7.5.1 static bending strength
4.7.5.1.1 the static bending strength ¬Ò_{b} of the specimen is calculated according to formula (6), accurate to 0.1MPa;
Where:
¬Ò_{b}  static bending strength of specimen, in MPa;
F_{max}  the maximum load at failure, in Newtons (N);
l_{1}  distance between two supports, in mm;
b  the width of the specimen, in mm;
t  thickness of specimen, in mm.
4.7.5.1.2 The static bending strength of each group of specimens (see 4.7.4.6) of a plate is the arithmetic mean of the static bending strength of all specimens in the same group, accurate to 0.1 MPa.
4.7.5.2 modulus of elasticity
4.7.5.2.1 the elastic modulus E_{b} of the specimen shall be calculated according to formula (7), accurate to 10 MPa;
Where:
E_{b}  the elastic modulus of the specimen, in MPa;
l_{1}  distance between two supports, in mm;
b  the width of the specimen, in mm;
t  thickness of specimen, in mm;
F_{2}F_{1} in the load deflection curve, the increase of load in the straight line section (FIG. 10, F_{1} value is about 10% of the maximum load, F_{2} value is about 40% of the maximum load), unit: Newton (n);
a_{2}a_{1}  the increase of deformation in the middle of the specimen, that is, the deformation of the specimen in the range of force F2 ~ F1, in mm.
Fig. 10 load deflection curve in the range of elastic deformation
4.7.5.2.2 the elastic modulus of each group of specimens (see 4.7.4.6) of a plate is the arithmetic mean value of the elastic modulus of all specimens in the same group, accurate to 10 MPa.
4.8 determination of static bending strength and elastic modulus (four point bending)
4.8.1
principle
The static bending strength and elastic modulus of four point bending are the same loads applied on the specimen supported by two points and one third away from the support
¢ÃAcceptable Criteria:
•MOR>= 85 MPa
•MOE>=10,000MPa
