ASTM D3163 Strength of Adhesively Bonded Rigid Plastic Lap-Shear Joints in Shear by Tension Loading

Get Certified ASTM Testing for Adhesively Bonded Rigid Plastics

The lap-shear test enables manufacturers to evaluate adhesive-bond quality, compare different bonding operations, and ensure the adhesive bond performs as desired. Technicians prepare rigid plastic adherends, apply the adhesive, and bond them under controlled conditions. This results in a cured joint that is then subjected to tension; the joint’s response is recorded on the testing machine, and the force level is recorded. Check for plastic type, adhesive, surface treatment, curing environment, and acceptance criteria before conducting tests.

• Specific properties: Maximum load and apparent strength of the bonded joint. 
• Each specimen was subjected to a tensile test until failure or until the test endpoint determined by the method was reached.
• Use for comparing adhesives, rigid plastic substrates and plastic surface treatments. 
• Test limitations: Method does not apply to anisotropic adherends (such as reinforced plastic laminate) and is not suitable for tests at temperatures above the softening point of the adherends. 

What Are the Uses of ASTM D3163?

Manufacturers use ASTM D3163 to test bond strength between rigid plastic parts. Engineers use the results to compare the performance of different adhesives, plastic substrates, and surface preparation techniques under identical conditions. 

Adhesive Selection: Make comparisons between the apparent shear strength of various adhesive systems. 

• Quality control: Check for uniformity in production-made bonded joints. 
• Surface treatment evaluation: To evaluate the influence of surface treatment of plastic on the adhesive joint strength. 
• Process development of the bonding process: Orientation on various bonding processes, adhesive application, and curing conditions.
• Material comparison: Tests of joints of various hard plastic adherends. 
• Research and development: Study the changes in bond performance as a result of changes in the substrate or adhesive.

Which Materials Can Be Tested?

ASTM D3163 applies to rigid plastic adherends that are joined with adhesives. The method allows comparison of joints formed from various plastic substrates and adhesive systems, if the materials and test conditions are in compliance with the method. Not for use on anisotropic adherents (such as reinforced plastic laminate). Examples of materials and joint systems that can be considered are: 

• Hard plastic to be bonded with adhesives. 
• Single lap joints of different rigid plastic substrates. 
• Bonding methods for bonding rigid plastic parts. 
• Rigid plastic joints: surface-treated for different applications. 
• Bonded plastic samples made with different applications or curing procedures of adhesives.

Why Is ASTM D3163 Testing Important?

Adhesive bonding lets manufacturers assemble plastic parts with adhesives rather than mechanical fasteners alone. But joint strength depends on the plastic substrate, bonding properties, surface treatment, and the treatment process. ASTM D3163 offers a uniform method for comparing these and exploring variation in bond performance. Interpret the results with care, as small single-lap specimens are not necessarily representative of larger structural joints or joints in different service environments. 

Testing Process and Data Collection

The testing process begins with rigid-plastic adherend preparation and bonding in a single-lap configuration. Technicians document the substrate type, adhesive, surface preparation, overlap, and curing conditions. When the joint is ready, technicians place the sample in the tensile testing machine and load it to failure or the designated endpoint. The testing system records the maximum load and bonded overlap area used to determine the apparent shear strength. Technicians also record failure appearance and deviations from the test procedure.

Common Challenges and Troubleshooting

ASTM D3163 results vary depending on the plastic/adhesive, surface preparation, and bonding conditions. Surface preparation can affect results. Use and record a consistent surface preparation procedure. Variation in adhesive coverage or bond-line thickness can affect bond strength. Be consistent in the application and assembly of the same adhesive. Misalignment leads to unwanted stresses. Fix the sample and check the machine alignment. Environmental effects (temperature and moisture)  have an effect on both the adhesive and the plastic adherend. Monitor and record the relevant conditioning/test conditions. 

• Technicians record specimen identification, rigid plastic substrate, adhesive type, surface preparation, and cure conditions. Analysts report the maximum load at failure in newtons (N).
• Technicians calculate apparent shear strength based on the maximum load and bonded overlap area and express it in megapascals (MPa). Technicians record the specimen dimensions, overlap geometry, test conditions, and any deviations from the procedure. The failure characteristics and the damage to the specimen are recorded by the analysts.
• The final report lists the materials used and the bonding process, individual results, as well as observations that may be relevant. The analyst compares the results to the product specification or project requirements. 
• Comparisons of joint design, adhesive, or bonding process are avoided since these can affect measured strength.

Link to ASTM D3163