BS EN 789-2004 pdf download.Timber structures — Test methods — Determination of mechanical properties of wood based panels.
6.1 Conditioning
All test pieces shall be conditioned to constant mass in an atmosphere of relative humidity (65 ± 5) % and temperature (20i2)°C.
The constant mass is considered to have been reached when the results of two successive weighing operations, carried out at an interval of 24 h do not differ by more than 0.1% of the mass of the test piece.
If the ambient conditions of testing are not the same as those In the conditioning chamber, tests shall be undertaken Immediately after the test pieces have been removed from the conditioning chamber.
NOTE The test methods specified in this document may also be used in other testing climates.
6.2 Dimensions of test pieces
6.2.1 Methods of measurement
The dimensions shall be determined in accordance with EN 325
6.2.2 Measurements to be taken
The thickness of the test pieces shall be measured at four points, two on each edge 80 mm from mid-length, but 25 mm in the case of the in-plane compression test pieces, and the average thickness t recorded. The width of the test pieces shall be measured at two points, generally 80 mm from mid-length, but 25 mm in the case of the in-plane compression test pieces, and the average width b recorded.
NOTE If the thicknesses of individual plies or layers in plywood or composite panels are required, then each should be measured to the nearest 0,1 mm at the four edges of the test piece, and averaged.
6.3 Moisture content
6.3.1 Method of measurement
The moisture content shall be determined in accordance with EN 322.
6.3.2 Measurements to be taken
The moisture content shall be determined from at least one test piece per panel and measured at the time of testing.
6.4 Density
7 Bending properties
7.1 Test piece
The test piece shall be rectangular in cross-section.
The depth of the test piece shall be equal to the thickness of the panel and the width shall be (300 i 5) mm, but see also the NOTE in 7.3.
The length of the test piece will depend on the nominal thickness of the panel, see Figure 2.
7.2 Loading equipment
The loading equipment shall be capable of measuring the load to an accuracy of 1%.
NOTE Since the test piece may twist under load, the loading equipment should be appropriately ctiosen.
7.3 Loading method
The application of the loads shall be as shown in Figure 2 with the load and reaction forces applied by rollers of (30 ± 1) mm diameter. The distance between the load points and the supports,12, shall be 16 times the nominal thickness, but not more than 400 mm and not less than 240 mm with an accuracy of ± 1 mm.
NOTE Large deflections may occur when test pieces with small bending stiffness are tested to fadure, thus alternative test arrangements may be required. In general. the test configuration described in this section is suitable for a test piece with a thickness greater than 9 mm (corresponding to a bending stiffness per unit width of about 300 kN rnm2/mm). Smaller thicknesses may be tested by using smaller diameter rollers and proportionally reducing the distances between then.
7.4.2 Measurement of length and deformation
The length I and ‘2 see Figure 2. shall be measured to the nearest 1 mm. The deflection of the test piece shall be measured on both sides midway between two points on the axis of the test piece located in the zone of uniform moment. The distance between the two points (gauge length) shall be not less than 250 mm and the points shall be spaced as far apart as possible, consistent with maintaining adequate clearance between the gauges and the loading equipment.
NOTE For thicknesses of 9 mm or less, the 250 mm gauge length may be proportionally reduced. For these cases the deflection can be taken on the outer tension side.
The deflection over the gauge length shall be measured to the nearest 0.01 mm.
7.5 Expression of results
7.5.1 Modulus of elasticity and bending stiffness
Using the data obtained and plot the load-deflection graph. Use that section of the graph between 0.1F111.Z and 0.4F for a linear regression analyses.
The bending modulus of elasticity of the test piece shall be calculated from the following formula:BS EN 789-2004 pdf download.