Fracture Analysis of Debonded Sandwich Columns Under Axial Compression

A. May, F. Avilés, Christian Berggreen

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Abstract

A sandwich structure consists of two strong and stiff face sheets bonded to a weak low density core. The large separation between the face sheets provides increased bending rigidity and strength at low weight cost. Thus, sandwich structures frequently present better mechanical properties than monolithic structures of the same weight. The vast range of applications of such materials includes wind turbines, marine, and aerospace industries. In this work, geometrically nonlinear finite element analysis is conducted to investigate the fracture parameters and debond propagation of sandwich columns containing a face-to-core debond subjected to axial compression. Bidimensional finite element models of sandwich columns containing different size debonds centered at one face/core interface were developed and used in conjunction with linear elastic fracture mechanics to predict the stress intensity factors (KI and KII) as well as the strain energy release rate (G) at the debond (crack) tip. A range of debond sizes and foam cores were investigated. The onset of debond propagation was estimated by comparing the values of G to previously measured values of the fracture toughness (GC) by the tilted sandwich debond (TSD) test. Assuming the bimaterial oscillation index () to be zero, it was found that the opening mode (mode I) dominates the fracture process, although a small mode II component exists around the crack tip, specially during the first loading stages. The amount of mode mixity decreased with increased core stiffness and was nearly independent of the debond size. The model predicts debond propagation shortly after buckling instability, consistent with experimental observations. The critical loads predicted by this analysis compare reasonably to experimental buckling loads measured by other authors for small (25 mm) debonds, and show a conservative trend for larger (50 mm) debonds.
Original languageEnglish
Publication date2007
Publication statusPublished - 2007
EventInternational Materials Research Congress - Cancun, Mexico
Duration: 1 Jan 2007 → …
Conference number: 16

Conference

ConferenceInternational Materials Research Congress
Number16
CityCancun, Mexico
Period01/01/2007 → …

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