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The Role of Instabilities on the Mechanical Response of Cellular Solids and Structures.

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Final rept. Feb 95-Jan 97,

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The project delt with the in-plane crushing of aluminum honeycombs with hexagonal cells and polymeric honeycombs with circular cells. The relatively regular and periodic microstructure of these two-dimensional materials makes them excellent models for studying the mechanisms that govern the compressive response of cellular materials. Under displacement- controlled loading, the load-displacement response of such materials consists of a relatively sharp initial rise to a load maximum followed by an extended load plateau which is terminated by a sharp rise in load. It has been shown that these characteristics are associated with inelastic buckling and a localization process in which only a narrow zone of cells experiences collapse at any given time. The collapse spreads in a steady-state fashion until all the material is affected. The crushing processes have been simulated numerically by modeling appropriately the underlying nonlinearities of geometry, material and contact. Aluminum was modeled as an elastic-plastic solid and the polycarbonate as an elastic-powerlaw viscoplastic solid. Results from analyses involving characteristic cells and from large scale simulations of cushing have been produced. Both are in very good agreement with the experimental results. The numerical models were also used to conduct parametric studies of the mechanical properties of these two types of honeycombs. The methods developed are currently being extended to the three-dimensional setting to enable similar parametric studies of foams.

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  • Structural Engineering and Building Technology
  • Mechanics

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