Determination of bonding strength of plywood

A main content and scope of application of the provisions of this standard as defined by the GB9846.2 ordinary plywood bonding strength measurement method.

2 Reference Standard GB 9846.2 plywood terms and definitions GB 9846.8 plywood bonding strength of the extraction methods of measurement of GB 9846.9 plywood specimens sawn GB 9846.10 plywood specimen size measurement

3 Measuring and equipment

3.1 vernier caliper, sub-degree reading accuracy of 0.01g.

3.2 The water bath pan, 30 ~ 100 ℃.

3.3 Tensile testing machine, load reading accuracy of 5N.

3.4 air convection oven, the temperature inside the points to maintain 63 ± 3 ℃.

4 samples and test pieces

4.1 according to the provisions of GB 9846.8 extraction model.

4.2 according to the provisions of GB 9846.9 sawn specimens.

4.3 Specimen cut-plane should not affect the bonding strength of materials containing defects and processing defects.

5 Procedure

5.1 according to the provisions of GB9846.10 measured specimen size.

5.2 Test piece of plywood in accordance with their respective categories were handled by the following conditions:

a. Ⅰ type of plywood: The specimens placed in boiling water for 4h, then 63 ± 3 ℃ air convection oven drying 20h, and then cooked in boiling water for 4h, cooled at room temperature after taking out 10min. The specimen should be cooked all the specimens immersed in boiling water and boil stamped. Note: The factory production 3h boiled in allowing the use of rapid testing methods, the measured results of 0.9 multiplied by the coefficient of bonding strength test as a product value, but in case of supply and demand sides of the dispute needs to re-inspection class Ⅰ plywood when the cook is still 28h bake cycle of law as a means to promote the CD.

b. Ⅱ type of plywood: the sample on the 63 ± 3 ℃ for hot water in the dipping 3h, cooled at room temperature after taking out 10mim. Dipping the specimen should be immersed in hot water in the entire specimen, and stamped.

Note: The factory production allows the use of 63 ± 3 ℃, impregnated 1h rapid testing methods, the measured coefficient of 0.82 multiplied by the result of the bonding strength test as a product value, but in case of dispute the need for both supply and demand of Class Ⅱ, re-inspection when the plywood , still 3h hot dipping method of arbitration as a method of

c. Ⅲ type of plywood: The test piece impregnated in the 63 ± 3 ℃ water 2h, and then separated from each sample flat on the 63 ± 3 ℃ in the air convection oven drying 1h, after taking out at room temperature 10min.

d. Ⅳ type of plywood: The moisture content to meet the requirements for dry-shaped test specimen. Note: the sample moisture content should be controlled at 8% ~ 12%

5.3 clamped at both ends of the specimen in the testing machine a fixture of activities, so that a straight line, the specimen center activities through testing machine fixture axis. Gripping the specimen notch position and the distance should be within 5mm.

5.4 with constant velocity of the sample loading to destruction, loading speed 10MPa/min. The greatest damage to the load readings should be precise, 5N.

6 The calculation and test results indicated that

6.1 According to shear surface layer damage, with the visual damage is estimated that the rate of the sample timber, with the percentage of that estimate accurate to 10%, refer to Appendix B (refer to items). Such as the destruction of the specimen as non-normal, then jotting down the destruction of characteristics (notch broken, the table panels divided, Core cut, or the table board stripping), refer to Appendix C (reference items). Note: All table plates cut the area of spin-off, covering more than half, according to estimates of rates of timber damage, accurate to 10%.

6.2 one or more of the Zhang board is equal to the rate of wood destruction of all the relevant rate of the sample timber damage arithmetic mean, this value should be accurate to 1%.

6.3 The bonding strength test piece determined by the formula: A-type specimen XA = P / (A × B)
(1 ) B-type specimen BB = P / (A × B) × 0.9
 (2) formula: XA, BB - Test parts of the bonding strength, MPa; P - the greatest damage load, N; A - cut the surface of the specimen width, mm; B - cut the surface of the length of the specimen; mm.

6.4 pairs of thick plywood core structure of the bonding strength test piece should be calculated according to the value of 6.3 multiplied by the coefficient provided in Table 1 of the bonding strength as the value of the specimen. Table 1 of different thickness of the bonding strength values than the Core and table plate thickness less than the coefficient of 1.50 ~ 2.00 2.00 ~ 2.50 2.50 less than 1.2 1.4 1.6

6.5 In the specimen bonding strength test, the right-notch broken, the table panels divided, the board cut, or form sheet stripping and other non-normal damage, its bonding strength, when the value of statistical treatment according to the following provisions: a. such as various non-normal undermine the value of bonding strength test pieces of plywood meet the general indicators of the minimum standard requirements to include statistical records; do not meet the specified minimum target value, the pre-to remove do not count. b. a result of excluding the non-normal damage, excluding the number of specimens of more than half the total number of specimen shall be a separate sample.

6.6 a variety of categories, all kinds of plywood in the manufacturing process or through the test piece wet processing, such as found in any specimen has opened a plastic adhesive layer, then the bonding strength values of the specimen and timber damage rates calculated according to the zero side by side into the statistical records.

6.7 a single specimen to be accurate calculation of the value of bonding strength to 0.01MPa.