PACCAR

New Stress & Strain Durability Fixture

To reduce the weight and improve the fuel economy of big rigs, and reduce costs, the long term durability of thermoplastics and adhesives needs to be tested under both constant and dynamic stress conditions and subject to high and low temperatures, salt fog exposure, high humidity exposure, and water submersion. A test fixture that could efficiently test a large number of samples under these wide-ranging conditions could greatly accelerate their development and adoption. A previous capstone team developed a test fixture capable of holding a chain of many test specimens in both constant and dynamic stress conditions. This student team redesigned some specific subsystems of the fixture to improve the overall performance and capability, including as using pneumatic actuators instead of electric stepper motors and load washers instead of a custom-made load cell. The team also used the fixture to test adhesive specimens bonded to a stainless steel substrate to determine if the alternatives can provide increased service life.