Test method ASTM D3164 is used to determine the shear strength properties of adhesively bonded plastic lap-shear sandwich joints. It is useful for comparative shear strength assessments of adhesively bonded lap-shear sandwich joints made from various metal and plastic substrates. The ASTM D3164 test needs to be performed below the softening temperature of the plastic substrate that is sandwiched and adhesive bonded between two metal layers. It is not applicable for laminates or other anisotropic plastic materials. The shear strength of adhesive bonding depends on the adhesive and adherend materials, surface conditions, curing, and environmental conditions This test is useful for comparative analysis of different adhesive and substrate combinations but does not provide data that can be used for the mechanical design of joints.
The ASTM D3164 lap shear test is performed on a sandwich lap-joint specimen formed by two metal pieces, each 1.01 inches (25.4 mm) thick, and a plastic film of suitable thickness sandwiched and adhesively bonded between the metal plates. Thin plastic films of 0.010 inches (0.354 mm) or less are recommended, with a maximum limit of 0.064 inches (1.62 mm) thickness. The recommended overlap at the joint is about 0.5 inches (12.7 mm) The specimen is subjected to tension forces by pulling from the opposite ends till the shear joint fails.
In ASTM D3164, the specimens need to be fabricated for the test, either as single pieces or multiple pieces cut from larger fabricated sandwich panels. The panels can be made from two 7 inch × 4 inch metal pieces with a suitable plastic insert. In case aluminum is used, the recommended grade is alloy 2024-T3. After appropriate surface preparation of the surfaces, a lap-shear sandwich joint is made, applying the adhesive in the joint area as per the manufacturer’s instructions. Upon completion of curing at the appropriate temperature, seven identical rectangular test specimens of 1 inch width are cut from the bonded panels. The specimen is placed vertically in between the upper and lower jaws of a tensile testing machine with the length within the test grip at each end being 1.01 inches (25.4 mm). The test apparatus for ASTM D3164 testing includes facilities to apply and measure tension forces at specified temperatures and rates of loading. The axial tension load is increased at a rate of 8.3 to 9.7 MPa (1200 to 1400 psi) of shear area per minute (approximately 0.05 in./min crosshead speed), till joint failure. The stress value at joint failure as well as the type of failure is recorded.
Video 01: Tensile shear strength testing of adhesives
For ASTM D3164, the indicative assembled sandwich specimen dimensions are approximately 7.5 inches (190.5 mm) long and 1 inch (25.4 mm) wide with each metal layer being 0.064 inches (1.62 mm) thick.
The ASTM D3164 adhesive shear strength is reported in megapascals.
Test method ASTM D3164 is used to determine the shear strength properties of adhesively bonded plastic lap-shear sandwich joints.