LOW-VELOCITY IMPACT AND CONTACT ANALYSES OF ADHESIVELY BONDED ALUMINUM HONEYCOMB SANDWICH PANELS

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Authors
Sun, Mengqian
Keyword
honeycomb sandwich panel , low-velocity impact , plasticity , impact damage , adhesive fillet , contact algorithm , Hamilton’s principle
Abstract
Adhesively bonded aluminum honeycomb sandwich panels are widely used in the aerospace industry. They are used to form lightweight structures with high strength and stiffness. The main drawback of this composite structure is that it is susceptible to impact damage in service. Numerous studies using analytical methods, finite element methods, and physical experiments, were conducted to study the impact response of the sandwich structures under low-velocity impact. Accurate modelling of the adhesively bonded aluminum honeycomb sandwich under low-velocity impact can provide the impact response of the sandwich panel and knowledge about the design of sandwich structures. Besides, the contact between two bodies of the contact process introduces complicated nonlinearities in the low-velocity impact and significantly affects the computational time in FE studies. This project aims to advance the current understanding of the impact response through a comprehensive experimental study of impact damage as well as computational and analytical modelling of adhesively bonded aluminum sandwich panels under low-velocity impact. A series of studies has been conducted to investigate the parameters that affect the impact damage and the damage mechanism of each component of the sandwich structure. The main conclusions are summarized below: (1) An improved prediction of surface dent profile can be obtained when the analytical equation used considers the radius of the contact area. The depth of the core damage was observed to be within 2mm for different dents with a range of impact energies. (2) The assumption of full plasticity in the face-sheet can give a sufficient prediction of the impact response for deeper dents, but for low impact energies, that lead to shallow dents, both elasticity and plasticity should be considered. (3) The dent depth can be linearly correlated with the core damage depth. The intercept depends on both the honeycomb configuration and adhesive fillet height, while the slope of the linear relationship is only dependent on the core configuration. The variation of the adhesive fillet height for different cell walls significantly influences the core damage depth. (4) The efficiency of a contact algorithm (contact between the impactor and the face-sheet) in predicting low-velocity impact damage depends on both the contact search process and the contact constraint enforcement methods. The constrained Hamilton’s principle was shown to have the ability to update an active contact area and solve the nonlinear contact constraint equation simultaneously, potentially improving the computational efficiency.
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