Master of Science in Mechanical Engineering (MSME)
Composite adhesively bonded joint structures have seen increased use over conventional riveted due to their ease of manufacturing and quality strength-to-weight ratios. However, adhesively bonded joints lack the rigidity and failure strength of riveted assemblies, due to high stress concentrations which develop in the adhesive layer, which makes them prone to undesirable deformation and failure. Piezoelectric materials feature the ability to produce mechanical strain when subjected to an applied voltage and vice-versa. Therefore, it is proposed to use piezoelectric actuators to transmit counterbalancing forces to increase the rigidity and strength of composite joints. Existing studies have been limited in that they have focused on the effect of piezoelectric actuators bonded to or embedded in a single beam. This work studies the use of surface bonded piezoelectric linear strain actuators, and their effect on induced static deflection of composite joint structures. Euler-Bernoulli beam theory is utilized to derive the elastic curves of the proposed structures due to actuation forces and external loading, while accounting for physical parameters of the structures. By decreasing the deflection within the adhesively bonded region, especially at the critical joint locations where high stress concentrations are developed in the adhesive layer, the overall strength of the joint can be improved. The effects of straight beam actuation and small beam curvature actuation are discussed. A numerical study is performed at evaluating the effectiveness of piezoelectric actuation based on straight beam and small curvature beam actuation, as well as bond location. It is shown that small beam curvature actuation increases the amount of deflection which can be produced by the piezoelectric actuator. The effects of four possible piezoelectric bond regions are analyzed. It is shown that bonding the piezoelectric actuator in Region II most effectively reduces detrimental deflections caused by tensile loading at the critical joint locations.
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Meyer, Ryan Michael, "Enhancement of single-lap joint strength under tension using piezoelectric actuation" (2010). LSU Master's Theses. 2730.