DEVELOPMENT OF IMAGE-BASED HIGH STRAIN RATE TESTS FOR ADHESIVELY BONDED JOINTS
Abstract
Joining of components to form operational load-bearing structures is a common, necessary feature of engineering design. Traditional joining methods include bolting and riveting, which require holes to be drilled into the components, creating weakness points where cracks can initiate. In addition, bolts and rivets add mass, which is critical for transportation applications. An alternative to these methods is adhesive bonding. Two main advantages of structural bonding is 1) very low added mass and 2) the load can be transmitted over a large area, thus avoiding stress concentrations that occur with bolts and rivets. Structural bonding is currently used in a number of engineering applications. In order to design the joint, accurate mechanical properties of the adhesives are required. For slow modes of loading ‘quasi-static’ properties are obtained with existing reliable test methods. However, when structures experience fast loading modes, like impact, blast, crash, or intense structural vibrations, specific ‘high strain rate’ properties are required to describe the behavior of the adhesive. Polymer adhesives are notorious for having vastly differences in properties between ‘quasi-static’ and ‘high strain rates’. Therefore, it is necessary to perform specific ‘high strain rate‘ tests to obtain these properties. However, testing materials at high strain rates is difficult. Current techniques using the split Hopkinson bar apparatus are notoriously inadequate for testing adhesives in situ (i.e., as a joint between two pieces of material). The present project aims at developing a new high-strain-rate test method for adhesive joints. It is based on the use of an ultra-fast camera (5 million frames per second) that can record the deformation of the joint while it is undergoing impact loading. From these images, strain and stress can be inferred to obtain material properties.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Aug 11, 2021
- Source ID
- FA86552017014
Entities
People
- Fabrice Pierron
Organizations
- Air Force Office of Scientific Research
- United States Air Force
- University of Southampton