Scope:

ASTM D2734 (Test method A) test is used for the determination of the void content of reinforced plastics or

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 fiber-reinforced plastic (FRP) adherends.

Test Procedure:

The lap shear test is done by measuring the square inch or square centimeters of the shear area. 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 fiber 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)