How to Perform an Adhesive Lap Joint Shear Strength Test - ASTM D1002

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Shear joints impose uniform stresses across the bond area which results in the highest possible joint strength.  ASTM D1002 is commonly performed to measure the shear strength of adhesives that are used to bond metals.  This test is similar to ASTM D3163 which is for adhesives that bond rigid plastic substrates, and also ASTM D3164 which is for plastic adhesives that are used to bond both plastic and metal substrates.  All three of these specifications use a single lap joint (lap shear) specimen to determine the shear strength of adhesives.  If you are going to perform this test, you should read the entire specification from ASTM. This is a quick summary to decide if this test is right for you, and to point out what equipment you need to perform the test.  Some of the content in this blog was taken from ADMET's shear testing article in Quality Magazine.

Test Procedure:

1. Measure the amount of shear area in square inches or square centimeters.
2. Load each end of the specimen in the tensile grips.
3. Apply a force at a controlled rate to the specimen until it breaks and record the maximum force and type of joint failure. 
   1. ASTM D1002 specifies a load control rate of 1,200 to 1,400 psi/minute. A cross head control rate of 0.05 inch/minute approximates the loading rate and also is an acceptable mode of control.

Test Report:

1. Maximum force
2. Maximum shear stress
   1. Divide the maximum force by the shear area and report in units of kilogram/square centimeter or psi.
3. Type of failure (separation from adhesive to substrate, separation through the adhesive, or both)

 Equipment required:

1. Universal testing machine (tensile testing machine) with these minimum specifications:
   1. Servo-controlled to keep a constant rate of speed during the test.
   2. Breaking load should be between 15 and 85% of machine capacity.  This rule may be antiquated as there should be no trouble going to the full scale capacity of a machine.  Many strong adhesives require a 10,000 pound (50kN) capacity testing machine (ADMET eXpert 2613).  Most common is a 2,000 pound (10kN) testing machine (ADMET eXpert 2611).
2. Software or suitable electronics are required to operate the machine, report peak load, and provide a force / displacement chart.
3. Grips: Vise grips with serrated inserts are commonly used for lap shear tests. The serrated grip inserts are designed to dig into the material and prevent it from slipping. If slippage occurs with a vice grip, self-tightening grips of pneumatic or wedge design may be used. The grip inserts should be aligned so that the centerline of the grip assembly is aligned with the adhesive bond. Proper alignment is achieved with vice grips by adjusting the grip inserts from side to side so that the center line of the upper and lower grips pass through the adhesive.

Other common adhesive shear specifications:

ASTM D905 - Strength Properties of Adhesive Bonds in Shear by Compression Loading
ASTM D906 - Strength Properties of Adhesives in Plywood Type Construction in Shear
ASTM D1002 - Apparent Shear Strength of Single-Lap-Joint Adhesively Bonded Metal Specimens
ASTM D2293 - Creep Properties of Adhesives in Shear by Compression Loading
ASTM D2294 - Standard Guide for Use of Adhesive-Bonded Single Lap-Joint Specimen Test Results
ASTM D2295 - Strength Properties of Adhesives in Shear by Tension Loading at Elevated Temperatures
ASTM D2339 - Strength Properties of Adhesives in Two-Ply Wood Construction in Shear
ASTM D2557 - Tensile-Shear Strength of Adhesives in the Subzero Temperature Range from -267.8 to -55 C
ASTM D2919 - Determining Durability of Adhesive Joints Stressed in Shear by Tension Loading
ASTM D3163 - Determining Strength of Adhesively Bonded Rigid Plastic Lap-Shear Joints in Shear
ASTM D3164 - Strength Properties of Adhesively Bonded Plastic Lap-Shear Sandwich Joints in Shear
ASTM D3165 - Strength Properties of Adhesives in Shear  Single-Lap-Joint Laminated Assemblies
ASTM D3166 - Fatigue Properties of Adhesives in Shear by Tension Loading (Metal/Metal)
ASTM D3528 - Strength Properties of Double Lap Shear Adhesive Joints by Tension Loading
ASTM D3931 - Determining Strength of Gap-Filling Adhesive Bonds in Shear by Compression
ASTM D4027 - Measuring Shear Properties of Structural Adhesives by the Modified-Rail Test
ASTM D4498 - Heat-Fail Temperature in Shear of Hot Melt Adhesives
ASTM D4501 - Shear Strength of Adhesive Bonds Between Rigid Substrates by the Block-Shear Method
ASTM D4562 - Shear Strength of Adhesives Using Pin-and-Collar Specimen
ASTM D5656 - Thick-Adhered Metal Lap-Shear Joints for the Stress-Strain Behavior
ASTM D5868 - Lap Shear Adhesion for Fiber Reinforced Plastic (FRP) Bonding
ASTM D6463 - Time to Failure of Pressure Sensitive Articles under Sustained Shear Loading

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