Scope:

Lap Shear value determined by ASTM D1002, ASTM D3163, ASTM D5868 is useful in ascertaining the shear strength of adhesives for bonding materials such as metals, plastics when tested on a standard single-lap-joint specimen. A sliding failure that happens along a flat surface is termed as shear.

This test is used to determine adhesive strengths, surface preparation criteria, comparative shear strength data, and adhesive environment durability. ASTM single-lap-joint shear testing covers ASTM D1002 that specifies the apparent shear strength for bonding metals, ASTM D3163 for rigid plastic adherends, and ASTM D5868 for fibre-reinforced plastic (FRP) adherends.

Test Procedure:

For ASTM D1002, ASTM D3163, ASTM D5868 tests, each end of the sample is loaded in the tensile grips. A force is adjusted at a fixed rate to the sample until it fractures and the maximum force and the kind of joint failure are recorded. The test procedures for three different ASTM are: (a) ASTM D1002 specifies a load control rate of 1,200 to 1,400 psi/minute. A crosshead control rate of 0.05 inch/minute approximates the loading rate and also is an acceptable mode of control; (b) Two samples are bonded along with an adhesive and cured as needed for ASTM D3163 for rigid, adhesively bonded plastic. The test samples are put in a universal test machine and pulled up to failure at a speed of 1.3 mm/min; and (c) ASTM D5868 recommends a loading rate of 13 mm/min (0.5 in/min) for fibre reinforced plastic.

Sample Size:

Two samples are bonded along with the adhesive, each with 25.4 x 101.6 mm (1 inch4 inches) such that the overlap is enough to cause the adhesive to malfunction and not the substrate. The common overlaps are 12.7 mm and 25.4 mm (0.5 inch and 1 inch). Adhesives are applied following the adhesive manufacturer’s suggestions. 

Data:

Maximum, minimum, and average failure load values

Failing Stress in megapascals (pounds-force per square inch)

Different type of failure (cohesive, adhesive, or substrate)

Conclusion:

ASTM D1002 is a standard test method determining adhesive lap joint shear testing of metals and ASTM D3163 is a lap shear strength test of adhesively bonded plastics while  ASTM D5868 is lap shear adhesion test for fibre reinforced plastics (FRP).