ASTM D1002 Apparent Shear Strength of Single-Lap Joint Adhesively Bonded Metal Specimens

Get Certified ASTM D1002 Testing for Reliable Adhesive Bond Data

A lap shear value means little without knowing the test conditions. A report that follows ASTM D1002, uses a calibrated testing machine, records the test rate, and documents specimen preparation and cure gives producers and buyers comparable results. The report also states how each specimen failed, which helps explain a low or scattered result. It lists the metal, its surface preparation, the adhesive, and the number of specimens tested, so buyers can judge whether two results share the same conditions.

The scope of ASTM D1002 includes

• Material type: Adhesives used to bond metals
• Property measured: Apparent shear strength of a single-lap-joint specimen
• Loading: Tension applied to the specimen until the bond fails
• Specimen: Two metal strips bonded with an overlap, 25.4 mm wide with a 12.7 mm overlap
• Metal thickness: 1.62 mm recommended, with a tolerance of 0.125 mm
• Result: Apparent shear strength in MPa, with the failure load in newtons
• Character of the method: Primarily comparative
• Limitation: Strength values are not design-allowable stresses for structural joints

What are the uses of ASTM D1002 Testing?

ASTM D1002 is mainly used to compare adhesive bonds between metals under the same conditions. The uses include

• Comparing the strength of different adhesives bonding the same metal under the same test conditions.
• Controlling surface preparation by showing how each preparation affects bond strength.
• Controlling primers and adhesive systems by comparing the strength properties of the tested systems.
• Checking that a batch of adhesive or a bonding process gives a consistent apparent shear strength.
• Showing the effect of cure and conditioning on a metal-to-metal bond.
• Identifying the weakest point in a bond, because the failure type is recorded with the strength.

What materials can be tested under ASTM D1002?

ASTM D1002 applies to adhesives that bond metals and tests them as a single-lap joint between two metal strips. The apparent shear strength from one small lap specimen may differ from that of a joint made with different adherends or by a different bonding process. For that reason, the standard says the test is not suitable for finding design-allowable stresses for joints that differ in any way from the joints tested, unless the joint and adhesive behavior are thoroughly analyzed.

Why is ASTM D1002 Important?

The standard describes the test as primarily comparative, and it has found applications in controlling surface preparations, primers, and adhesive systems. The standard warns that misuse of the strength values as design-allowable stresses could lead to product failure, property damage, and human injury. Reporting the test rate, the cure, and the failure type with every result keeps the data useful for comparison.

ASTM D1002 Testing Process and Data Collection

The adhesive joins two metal strips, which are then cured and conditioned. The specimen is gripped and pulled in tension at the specified rate until the bond fails. The laboratory records the maximum load, specimen width and overlap, test temperature, and failure type. It then calculates the apparent shear strength for each specimen. The report also lists the metal and its surface preparation, the adhesive, the cure conditions, and the number of specimens tested.

Common Challenges and Troubleshooting

Poor surface preparation is the most common cause of low or scattered results, because contamination on the metal weakens the bond. Misalignment in the grips adds bending to the joint, which lowers the measured strength, so the specimen axis must line up with the pull. Uneven overlap or width changes the bonded area and therefore the calculated strength. Inconsistent cure or conditioning changes the adhesive properties. The test rate also matters because higher rates yield higher apparent strength values for viscoelastic adhesives, so report the rate with the result.

• The laboratory reports the apparent shear strength of each specimen in MPa, the SI unit of stress, along with the average and the failure load in newtons. One MPa equals 1 N/mm².
• Technicians record the metal, the surface preparation, the adhesive, the cure, the test rate, the test temperature, and the type of failure, so others can repeat and review the test.
• Analysts divide the failure load by the bonded area to get the strength. A failure load of 6450 N over the 322.6 mm² bonded area gives an apparent shear strength of about 20 MPa, and 1 MPa is about 145 psi for older reports that use psi.
• Engineers classify each failure as cohesive failure within the adhesive or adhesive failure where the adhesive separates from a metal surface, and do not use the results as design-allowable stresses for structural joints.
• The manufacturer or purchaser compares results only when the metal, surface preparation, adhesive, cure, and test rate match, because the method is primarily comparative.

Link to ASTM D1002 Standard