GB/T17657-2013 Test Methods for Physical and Chemical Properties of Wood based Panels and Decorative Wood based Panels: Determination of shear strength of Adhesive Layer
18 Determination of shear strength of adhesive layer
18.1 Principle
Gradually apply compressive load to the specimen to cause shear failure of the adhesive layer, in order to determine the bonding quality.
18.2 Instruments and equipment
Artificial board universal testing machine. png
18.2.1 Universal mechanical testing machine. Select a suitable load range according to product requirements. The measurement accuracy is 1% of the load value.
- 2. 2 vernier calipers with a graduation value of 0.1 mm. Range of 0mm~150 mm
18.3 Test pieces
- 3. 1. Sample size
The shape of the test piece is as shown in Figure 23. The dimensions are specified by each product standard.
Shear surface size b × l. L1 is the length of the specimen, and t is the thickness of the specimen.
18.3.2 Specimen balance treatment
If necessary, place the test piece in an environment with a temperature of (20 ± 2) ° C and a relative humidity of (65 ± 5)% until the mass is constant. The difference between the two weighing results after 24 hours does not exceed 0.1% of the mass of the test piece, which is considered to be a constant mass.
18.4 Method
18.4.1 Measure the width and length of the shear surface of the specimen (see 4 1）。
18.4.2 Place the test piece in the fixture of the testing machine as shown in Figure 24, and do not use adjusting screws to tightly press the test piece.
Unit in millimeters
explain:
1- Test piece:
2- Adjusting screw
18.4.3 Place the fixture on the testing machine and keep the center of the specimen’s stress surface consistent with the center position of the indenter.
18.4.4 Apply uniform loading to cause the specimen to fail within (60 ± 30) seconds. Record the maximum load Fmax at the time of specimen failure, accurate to 10 N; If the load exceeds 4000 N., accurate to 100 N.
18.5 Expression of Results
18.5.1 The shear strength of the adhesive layer of the test piece shall be calculated according to Formula (15), accurate to 0 1 MPa； If the load exceeds 4000 N, accurate to 1 MPa:
In the equation:
τ—— Shear strength of adhesive layer, in MPa;
Fmax – The maximum load at the time of specimen failure, in Newton (N);
B – width of the shear surface, in millimeters (mm);
L – The length of the shear surface, in millimeters (mm).
18.5.2 The shear strength of the adhesive layer of a plate is the arithmetic mean value of the shear strength of the adhesive layer of all test pieces in the same plate, accurate to 0 1 MPa； If the load exceeds 4000 N, accurate to 1 MPa.
