ASTM D3163 Strength of Adhesively Bonded Rigid Plastic Lap-Shear Joints

Scope:

The shear strength of an adhesive bonded joint characterizes its resistance to sliding forces acting on the adhesive and adherend materials forming the joint. Test method ASTM D3163 is applicable to single-lap adhesive bonded shear joints in rigid plastic adherends. This test needs to be performed below the softening temperature of the plastic adherends and must not be used for laminates or other anisotropic plastic materials. The bond shear strength depends on the adhesive and adherend materials, surface preparation, curing achieved, and environmental conditions. This test is useful for comparative analysis of different adhesive and plastic combinations but does not provide data that can be used for the mechanical design of joints.

The ASTM D3163 single lap shear test is performed on two rectangular rigid plastic pieces bonded by an adhesive at the single-lap joint. The assembled specimen is subjected to tension forces by pulling from the opposite ends till the shear joint fails.

Procedure:

In ASTM D3163, the specimens need to be fabricated for the test, from two 7-inch × 4-inch rectangular panels of the plastic adherend. After appropriate surface preparation of the two panels, a single lap joint is formed by placing one panel over the other and applying the adhesive in the joint area as per the manufacturer’s instructions. The panel thickness and joint overlap are decided so that failure would occur preferentially at the joint and not the adherend panels. A maximum adherend thickness of 3/16 inches (4.76 mm) is recommended. Upon completion of curing at the appropriate temperature, seven identical rectangular single-lap jointed 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 apparatus. The test apparatus used for ASTM D3163 testing includes facilities to apply and measure tension forces at specified temperatures and rates of loading. The length between the jaws must be maintained constant for all samples tested. The distance from the end of the overlap to the end of the jaws should be 2-1/2 inches (63 mm). 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