ASTM D3167

ASTM D3167 is a standardized peel test method used to measure the bond strength of adhesive joints, specifically using a floating roller fixture to apply a 90-degree peel. It is commonly applied to bonded metal-to-metal or metal-to-composite assemblies in industries such as:

• Aerospace

• Automotive

• Defense

• Industrial adhesives and composites manufacturing

This method is especially useful for high-strength adhesives, where traditional peel tests (like ASTM D903) may not apply due to substrate deformation or excessive peeling force.

What ASTM D3167 Measures

• Average peel resistance over a specified length of bonded material

• Expressed in terms of force per unit width, typically N/mm or lbf/in

• Provides a controlled and reproducible way to measure peel strength of rigid materials

Key Advantages

• Designed for rigid or semi-rigid adherends where flexible peel testing is not suitable

• Floating roller fixture reduces bending stresses and ensures a constant 90° peel angle

• Often more representative of real-world bonded assemblies

Equipment Required

1. Universal Testing Machine (UTM)

• Equipped with a load cell appropriate for the expected peel force (commonly 500 N to 5 kN)

• Capable of maintaining a constant crosshead speed, typically 254 mm/min (10 in/min)

2. Floating Roller Peel Fixture (90-Degree Roller Assembly)

• The roller is unloaded and free-floating, minimizing applied pressure

• Guides the flexible adherend to peel at a constant 90° angle

• Mounted to the UTM base or traveling crosshead

• Constructed to allow low-friction movement and consistent roller alignment

3. Grips

• A mechanical vise grip or pneumatic grip is used to hold the flexible adherend (typically an aluminum or composite foil)

• The rigid adherend is supported on the fixture’s baseplate or clamped horizontally

Specimen Preparation

Sample Construction:

• A flexible adherend (e.g., thin aluminum or composite foil) is bonded to a rigid or semi-rigid panel

• The adhesive layer should be applied as per manufacturer recommendations or internal specifications

• The unbonded tab section of the flexible adherend is left free for gripping

Dimensions:

• Width: Typically 1 inch (25.4 mm), but other widths are acceptable as long as results are normalized

• Length: Sufficient to produce a peel length of at least 127 mm (5 inches)

• Bondline thickness: Should be controlled and recorded (shims can be used if necessary)

Conditioning:

• Standard lab conditions: 23 ± 2°C and 50 ± 5% relative humidity

• Condition specimens for at least 24 hours prior to testing

Test Procedure (Step-by-Step)

1. Condition the test samples in the standard lab environment

2. Mount the rigid adherend on the base of the peel fixture or secure it horizontally

3. Loop the free end of the flexible adherend under the floating roller and clamp it into the upper grip of the UTM

4. Set the crosshead speed to 254 mm/min (10 in/min), unless otherwise specified

5. Begin the test: the flexible adherend peels away at a constant 90-degree angle as the crosshead pulls upward

6. Continue the peel for a minimum of 127 mm (5 inches) to obtain a stable average force

7. Record the force vs. extension data throughout the test

Calculated Results

Peel Strength = Average Force ÷ Specimen Width

Where:

• Average Force is measured over a 5-inch (127 mm) segment of peeling

• Specimen Width is the width of the bonded section, in inches or millimeters

Example:

If the average peel force is 20 N and the sample is 25 mm wide:

Peel Strength = 20 N ÷ 25 mm = 0.8 N/mm

Test Report Requirements

Your test report should include:

• Specimen width and bondline thickness

• Average peel strength (N/mm or lbf/in)

• Type and dimensions of adherends

• Adhesive type and application method

• Conditioning time and environment

• Crosshead speed

• Description of failure (adhesive, cohesive, or substrate failure)

• Graph of force vs. displacement (optional but recommended)

Typical Applications

• Structural adhesives used in aerospace and automotive

• Metal foil bonding to composites or rigid plastics

• Testing durability after environmental exposure (heat, humidity, salt spray)

• Adhesive QC testing in production environments

Failure Mode Classification

After testing, examine the peeled surface for failure types:

• Adhesive failure (separation at the adhesive/substrate interface)

• Cohesive failure (failure within the adhesive itself)

• Substrate failure (tearing or fracture of the adherend material)

• Mixed failure (combination of the above)

This can provide insight into whether the adhesive is performing as intended.

Related Standards

• ASTM D903 – Standard peel test for flexible adherends at 180°

• ASTM D3330 – Peel adhesion of pressure-sensitive tapes

• ASTM D1876 – T-peel test for flexible bonded materials

• ASTM D6862 – 90-degree peel for rigid substrates using a test fixture (alternative to D3167 when no roller is available)

• ISO 11339 – Peel test for flexible-to-rigid bonded assemblies

Summary

ASTM D3167 is a specialized peel test method that allows accurate and repeatable evaluation of adhesive bond strength between a flexible and a rigid adherend using a floating roller fixture. It is ideal for applications requiring high-strength adhesive bonding and is widely used in aerospace, automotive, and structural bonding research and production.

By controlling variables like speed, adhesive thickness, and peel angle, ASTM D3167 provides a reliable measurement of peel resistance, helping engineers select the right adhesive for high-performance bonding applications.