Failure mechanisms of closed-cell aluminum foam under monotonic and cyclic loading

This paper concentrates on the differences in failure mechanisms of Alporas closed-cell aluminum foam under either monotonic or cyclic loading. The emphasis lies on aspects of crack nucleation and crack propagation in relation to the microstructure. The cell wall material consists of Al dendrites and an interdendritic network of Al4Ca and Al22CaTi2 precipitates. In situ scanning electron microscopy monotonic tensile tests were performed on small samples to study crack nucleation and propagation. Digital image correlation was employed to map the strain in the cell wall on the characteristic microstructural length scale. Monotonic tensile tests and tension–tension fatigue tests were performed on larger samples to observe the overall fracture behavior and crack path in monotonic and cyclic loading. The crack nucleation and propagation path in both loading conditions are revealed and it can be concluded that during monotonic tension cracks nucleate in and propagate partly through the Al4Ca interdendritic network, whereas under cyclic loading cracks nucleate and propagate through the Al dendrites.

[1]  Akira Kitahara,et al.  ALPORAS Aluminum Foam: Production Process, Properties, and Applications , 2000 .

[2]  Hilary Bart-Smith,et al.  On the mechanical performance of closed cell Al alloy foams , 1997 .

[3]  Lorna J. Gibson,et al.  Size effects in ductile cellular solids. Part I: modeling , 2001 .

[4]  Lorna J. Gibson,et al.  Aluminum foams produced by liquid-state processes , 1998 .

[5]  A. Mortensen,et al.  Uniaxial deformation of open-cell aluminum foam: the role of internal damage , 2004 .

[6]  R. Pippan,et al.  Fracture behaviour and fracture toughness of ductile closed-cell metallic foams , 2002 .

[7]  Fan,et al.  The influence of modified intermetallics and Si particles on fatigue crack paths in a cast A356 Al alloy , 2000 .

[8]  R. Pippan,et al.  Fatigue crack propagation in cellular metals , 2005 .

[9]  Michael F. Ashby,et al.  Fatigue crack propagation in aluminium alloy foams , 2001 .

[10]  Y. Nishi,et al.  Twisting relaxed tensile strength and its reliability of Si-Ti-C-O (tyrano) fiber , 2006 .

[11]  J. Banhart Manufacture, characterisation and application of cellular metals and metal foams , 2001 .

[12]  J. Hosson,et al.  Fracture behavior of metal foam made of recycled MMC by the melt route , 2006 .

[13]  H. Zogg,et al.  Phase transformation of the intermetallic compound Al4Ca , 1979 .

[14]  M. Hansen,et al.  Constitution of Binary Alloys , 1958 .

[15]  M. Ashby,et al.  Deformation and fracture of aluminium foams , 2000 .

[16]  P. Onck,et al.  Fracture and microstructure of open cell aluminum foam , 2005 .

[17]  M. Ashby,et al.  TOUGHNESS OF ALUMINIUM ALLOY FOAMS , 1999 .

[18]  J. Hosson,et al.  Fracture of open- and closed-cell metal foams , 2005 .

[19]  T. W. Clyne,et al.  The effect of cell wall microstructure on the deformation and fracture of aluminium-based foams , 2001 .

[20]  L. Gibson,et al.  Size effects in ductile cellular solids. Part II : experimental results , 2001 .