Plywood-Determination of glue bond strength

Determination of bonding strength of plywood

Plywood-Determination of glue bond strength

Main contents and scope of application This standard specifies the measurement method of bonding strength of ordinary plywood defined by GB9846.2.

2. Referring to standard GB 9846.2 plywood terminology and defining GB 9846.8 plywood extraction method for measuring bond strength GB 9846.9 plywood specimen sawing GB 9846.10 plywood specimen size measurement

3 Gauges and Instruments

3.1 vernier caliper, the reading accuracy of indexing is 0.01g.

3.2 Constant temperature water bath pot, 30-100 C.

3.3 Tension tester, load reading accuracy is 5N.

3.4 Air convection drying chamber, the temperature of each point in the chamber can be maintained at 63 + 3 C.

4 Samples and specimens

4.1 Samples were taken according to GB 9846.8.

4.2 Sawing specimens according to GB 9846.9.

4.3 There should be no material defect and processing defect affecting bonding strength in the shear section of specimens.

5 Procedures

5.1 Measure the size of the specimen according to GB9846.10.

5.2 The specimens were treated under the following conditions according to the type of plywood they belong to:

A. Class I plywood: The specimen was boiled in boiling water for 4 hours, then dried for 20 hours in an air convection drying chamber at 63 +3 C, then boiled in boiling water for 4 hours, then cooled for 10 minutes at room temperature. When boiling the specimens, all the specimens should be immersed in boiling water and covered with boiling water. Note: Rapid inspection method of 3H boiling is allowed in factory production. The measured result multiplied by coefficient 0.9 is used as the bonding strength value of product inspection. However, when there is disputed demand between supply and demand sides, the method of 28h boiling-drying cycle is still used as the cutting promotion method.

B. Class II plywood: The specimens were immersed in hot water at 63, 3 C for 3 hours, and then cooled for 10 MIM at room temperature. When impregnating the specimens, all the specimens should be immersed in hot water and covered.

Note: Rapid inspection method of 63 3 C and impregnation for 1 h is allowed in factory production. The measured results multiplied by coefficient 0.82 are used as the bonding strength value of product inspection. However, when there is dispute between suppliers and demanders, the method of 3 h hot water impregnation is still used as the arbitration method.

Class C.III plywood: The specimens were immersed in water at 63 (+3 C) for 2 hours, then each specimens were separated and placed in an air convection drying box at 63 (+3 C) for 1 hour. After removal, the specimens were placed at room temperature for 10 minutes.

D.IV plywood: Dry test was carried out on specimens with water content meeting the requirements. Note: The moisture content of specimens should be controlled from 8% to 12%.

5.3 The two ends of the specimen are clamped in a pair of movable fixtures of the testing machine to form a straight line. The center of the specimen should pass through the axis of the movable fixture of the testing machine. The distance between the clamping position and the notch of the specimen should be within 5 mm.

5.4 The specimens were loaded to failure at the same speed, and the loading speed was 10 MPa/min. The maximum damage load reading should be accurate to 5N.

6. Calculation and representation of test results

6.1 According to the damage situation of the rubber layer on the shear section, the wood damage rate of the specimen is estimated by visual measurement and expressed by percentage. The estimation accuracy is 10%. Refer to Appendix B (Reference Part). If the specimen is damaged abnormally, the failure characteristics (groove breakage, surface plate splitting, core plate cutting, or surface plate peeling) are recorded. Refer to Appendix C (References). Note: When the peeling area of the surface plate exceeds half of the shear area, the damage rate of the wood can be estimated accurately to 10%.

6.2 The wood damage rate of one or more sheets is equal to the arithmetic average of the wood damage rate of all the relevant specimens, and this value should be accurate to 1%.

6.3 The bonding strength of the specimen is calculated by the following formula: XA = P/(A*B)…………………………………………………………………………………………………………………………………………………………………………………………………… (1) Type B specimen BB = P/(A*B)*0.9…………………………………………………………………………………………………………………………………………………………………………………………… (2) Formula: XA, BB – bonding strength of specimens, MPa; P – maximum damage load, N; A – width, mm; B – length, mm.

6.4 The bonding strength of thick-core plywood specimens shall be multiplied by the coefficient specified in Table 1 by the value calculated in 6.3. Table 1 Bonding Strength Ratio of Core Plate to Surface Plate with Different Thickness Ratio 1.50~2.002.00~2.502.50 or more 1.21.41.6

6.5 In the test of bonding strength of specimens, if the bonding strength of specimens is abnormal, such as groove breakage, surface splitting, mid-plate shearing, or surface peeling, the statistics of bonding strength shall be dealt with in accordance with the following provisions: a. If the bonding strength of all kinds of abnormal damaged specimens meets the minimum value of the index specified in common plywood standards, they shall be included in the statistical records. If the minimum index value does not meet the requirements, it should be excluded in advance. B. When the number of irregular damaged specimens excluded exceeds half of the total number of specimens, a separate sampling inspection shall be conducted.

6.6 The bonding strength and wood failure rate of plywood of various types and specifications are calculated at zero and recorded in statistical records when it is found that any layer of plywood has been opened in the process of specimen preparation or after wet treatment.

6.7 The calculation of bonding strength of single specimen should be accurate to 0.01 MPa.

6.8 The revision of the above calculation values is carried out according to the digital revision rule of “Rounding Six Rounding Five Single Rounding Two Rounding Method”.

7 Test Records and Report

7.1 The test records shall include the following contents: A. species and types of plywood, and all the details needed to identify the plywood; B. measured data and calculated results.

Test Records and Report

7.1 The test records shall include the following contents: A. species and types of plywood, and all the details needed to identify the plywood; B. measured data and calculated results.

7.2 The test report shall include the following contents: a. Species, categories of plywood, and all the details needed to identify the plywood; B. Measurement results and evaluation; C. Excluding any operation in this standard and possible factors affecting the determination results. 7.3 The test records and test reports are shown in Appendix A (Supplement).

Appendix A Test Record and Test Report Form (Supplement) A Physical and Mechanical Properties Test Record of A1 Plywood is shown in Table A1. 表A1 胶合板物理力学性能试验记录表见表 生产单位__________________测试单号__________________生产日期__________________ 树 种__________________类 别__________________规 格__________________ 表板厚度__________________芯板厚度__________________长中板厚度 ________ Method of specimen processing________________________\\u\\\\\\\\\\\\\\\\\\\\\\\The results of this study are as follows:1. Heavy N Bonding Strength MPa Wood Damage Rate% Test Damage Remarks Length and Width Surface Plate Split Surface Plate Peeling Medium Plate Shear Groove Breaking Bonding Strength 123.. Ratio of the number of qualified specimens to the total number of valid specimens. See Table A2, Physical and Mechanical Properties Test Report of A2 plywood, Production Unit, Test Single No.__ ________________ 树 种__________________类 别__________________规格__________________ 表板厚度__________________芯板厚度__________________长中板厚度________________ 试件处理方法______________测试张数__________________ 试验项目计量单位测试结果备注 含水率 % Assessment of the test results by the ratio of the number of qualified specimens to the total number of rubber specimens: Inspection _________________ Inspection Unit__________

Appendix B: See Figure B1 for illustrations of wood failure rate. Figure B1 for illustrations of wood failure rate: The figures in the figure are the values of wood failure rate.

Appendix C Abnormal Failure Legend (Reference) The Abnormal Failure Legend of Appendix C Specimen is shown in Fig. C1. Figure C1: Illustration Notes for Abnormal Failure Specimens: Figure 1 is surface peeling, Figure 2 is surface splitting, Figure 3 is core splitting, Figure 4 is groove breaking.

Additional Note: This standard belongs to the Institute of Wood Industry, Chinese Academy of Forestry Sciences. This standard was drafted by Institute of Wood Industry, Chinese Academy of Forestry Sciences. The main drafters of this standard are Cao Zhongrong and Huang Zhenghong.

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