Stress Relaxation of Adhesively Bonded Single Lap Shear Joints

Stress relaxation tests were performed on two configurations of single lap shear joints: Aluminum Alloy (AA) 5083 and ProSet ADV176/276; and ProSet M1002/E-Glass Composite and ProSet ADV 176/276. Preliminary studies demonstrated that the AA5083 did not exhibit any stress relaxation at room temperature. The ProSet M1002/E-Glass Composite showed linear viscoelastic behaviour while the ADV176/276 adhesive system showed a non-linear viscoelastic stress relaxation behaviour. This result led the authors to develop an experimental campaign following ASTM D1002, to determine if the non-linear viscoelastic behaviour of the adhesive would persist in a single lap shear joint configuration. The preliminary results suggest that the joint configuration may exhibit a linear viscoelastic behavior at low stress levels, while becoming non-linear at stresses that approach the failure point of the joint. Similar stress time behaviours were observed in both the aluminum and composite joints. The preliminary results suggest that a first approximation using linear viscoelastic techniques may not be a suitable simplification.