Effects of Combined Delamination and Crack Damage on Natural Frequency and Strain Energy Release Rate in Adhesively Bonded Joints Under Thermal Condition: FEA and Experimental Validation

The present study investigates the combined influence of delamination and cracks within the adherend of an adhesively bonded single lap joint (SLJ) on the natural frequency response and strain energy release rate (SERR) values under a thermal environment.

The natural frequency response and SERR values of the SLJ are determined through the finite element analysis (FEA) employing Lanczos perturbation and virtual crack closer technique (VCCT), and the acquired results are verified against published data.

Furthermore, the precision of the developed FEA model is confirmed by conducting vibration tests utilizing LABVIEW software. These tests are performed under varying thermal conditions, including both ambient and elevated thermal conditions (ΔT = 5 °C, 10 °C, and 15 °C) within a controlled thermal chamber. This comprehensive methodology encompasses a variety of adhesively bonded joints with damage (delamination and crack). Multiple simulation cases are investigated while ensuring consistent environmental conditions, influencing the outcomes.

The FEA model is extended to investigate the effect of various factors, such as overlapping length (L_o), adhesive thickness ratio (a/h), delamination location, and delamination shape on natural frequency response. Similarly, the influence of fiber lay-up scheme and delamination with different orientations of the crack on SERR values is examined.