ASTM D1002 Adhesive Lap Joint Shear Testing of Metals

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ASTM D1002 Adhesive Lap Joint Shear Testing of Metals
ASTM D1002 Adhesive Lap Joint Shear Testing of Metals

ASTM D1002 is used to determine the shear strength of metal bonding adhesives in single lap shear joint applications. These adhesives are applied to bond a variety of joints and components. Testing is important to characterize the material strength of different adhesives.

What Is ASTM D1002?

The ASTM D1002 adhesive lap joint shear test is a method of testing the shear strength of adhesive bonds of metals. The test is performed by securing a metal clip over the adhesive joint, loading the clip with a load, and then measuring the shear force needed to break the bond.

What Is Lap Shear Testing?

Shear testing forces are applied parallel to the upper and lower faces of the test specimen and can be either tension or compression based. Shear test strength and stiffness results in tension mode may vary widely from compression mode. Shear tests are commonly performed on adhesives, fasteners including bolts, machine screws and rivets. Lap shear test samples are economical, practical and easy to make. They are the most popular sample type for development, evaluation, manufacturing quality control and comparative studies used for adhesives and bonded products.

Why Perform Tests According to ASTM D1002?

ASTM D1002 is a lap shear test which is performed to determine the shear strength of an adhesive that is applied to two metal plates and pulled to failure. It can be used to compare between adhesive types or different lots within the same adhesive. ASTM D1002 is comparative in nature, and not correlated to real world performance. Different environmental conditions and joint geometries contribute to the variation of adhesive performance.

Important Considerations when Testing According to ASTM D1002

The misuse of strength values obtained from lap shear joint as design stress allowable values for structural joints could lead to product failure, property damage, and injuries.

ASTM D1002 Test Specimens

A metal substrate is used for ASTM D1002. The specific types of metals acceptable for testing include brass, copper, aluminum, titanium, steel, and corrosion resisting steel. A single lap shear geometry consists of two identical substrates with a defined overlap section where adherend is applied.

ASTM D1002 Test Report

The test report includes failure load, expressed as unit shear area, as well as the failure mode. If the failure occurs within the adhesive, then it is reported as cohesion failure of the adhesive. If the failure occurs at the bond between the adhesive and the substrate, then the adhesion to the substrate failed. If the failure occurs within both the adhesive and adhesive-substrate bond then it was a combination failure.

Test Machines for Lap Shear Tests per ASTM D1002

Our universal test machines serve multiple adhesive testing applications and are capable of performing all quasi static tension/compression tests, such as tensile, peel, adhesion, and flexural testing. The machine force capacity should be chosen by taking into account the highest force needed over the lifetime of the equipment. Machines feature a uniform constant rate of loading (CRL) and of extension (CRE), or constant velocity control mode. Force measurement complies with ASTM E4.

Given that the standard D1002 test is based on 0.5 in adherand overlap x 1 in wide specimen geometry, and assuming the maximum shear stress is 1400 psi, then the tensile load required would be 700 lbf. If purchasing a new machine, then a minimum safety factor of 3:1 would result in a need for a 2000 lb capacity load frame.

The controller needs to be set so that the specimen is controlled at a stress rate of 8.3 to 9.7 MPa (1200 to 1400 psi) of shear area per minute. The tensile force applied to the specimen translates into a shear stress applied to the area of the adhered area 12.7 mm2 (0.5 in2). Alternatively a test speed of 1.27 mm/min (0.05 in/min) which is the equivalent crosshead displacement can be used.

What Grips Are Required for ASTM D1002?

ASTM D1002 is a test performed on rigid specimens bonded via a lap joint, which causes the ends of the specimen to be offset from the load line of the test. Load string alignment is a unique gripping challenge associated with single lap shear testing. The geometry of the test specimen naturally causes the two clamped ends of the specimen to be offset. Side loading occurs if the grip selection does not account for that offset. G154 and G240G mechanical vise action grips and several models of pneumatic vise action grips have integrated offsets which allow you to manually adjust the jaw faces to the left or right. This functionality is important so that the operator can ensure that the applied force coincides with the center line of the load string.

This setup requires mechanical grips with offset jaw faces to account for this overlap to ensure a true shear force application.