Olurin, Fleck, Ashby/Joining of Metal Foams with Fasteners
[4] B. Viala, J. Degauque, M. Baricco, E. Ferrara, M. Pasquale,
F. Fiorillo, J. Magn. Magn. Mater. 1996, 160, 315.
[5] J. C. Bavay, J. Verdun, J. Mater. Eng. Perform. 1993, 2, 169.
[6] K. I. Arai, K. Ohmori, Metall. Trans. 1986, 17A, 1295.
[7] I. Ibarrondo, J. San Juan, J. Gonzalez, J. Magn. Magn.
Mater. 1991, 101, 83.
screws and the like; however, as they indent easily, compres-
sive attachments like rivets and through-thickness clamps
(nut and bolt assemblies, for example) can work loose.
The load-carrying capability of a joint depends upon: joint
design, the manner in which the joint is loaded, and the envi-
ronment the joint experiences in service.
[8] M. Baricco, E. Mastandrea, C. Antonione, B. Viala, J.
Degauque, E. Ferrara, F. Fiorillo, Mater. Sci. Eng. A 1997,
226±228, 1025.
[9] I. Ibarrondo, J. Degauque, Proc. 40th Mechanical Working
and Steel Processing Conference, October 25±28, 1998,
Pittsburgh PA, USA, 499.
[10] I. Ibarrondo, J. Degauque, Vacuum 1999, 53, 75.
[11] I. Ibarrondo, S. Surinach, J. Gonzalez, J. Magn. Magn.
Mater. 1992, 112, 232.
[12] K. Okada, T. Yamaji, K. Kasai, ISIJ Int. 1996, 36, 706.
[13] J. C. Russ, Practical Stereologie, Plenum Press, New York
1986, p. 46.
With proper precautions, metal foams can be joined using
welding, mechanical fasteners and/or adhesives. This com-
munication explores the static and cyclic load a joint can
withstand prior to failure. Models to explain the failure mech-
anisms are presented.
The aluminum foam investigated (Alporas[1]) is an alloy
containing 0.2±8 % weight of calcium to enhance viscosity
and 1±3 % weight of titanium hydride as a foaming agent.
The relative density r (the ratio of the density of metallic
foam rf to that of the solid cell-wall material rs) is in the range
0.08±0.15.
The density of the cell walls is very close to that of pure
aluminum (rs = 2.7 Mg m±3). The yield strength ry of the solid
cell walls was measured by infiltrating the surface of the
foam sample cut by spark machining with epoxy and then by
micro-indenting the cell edges. An approximate value for the
cell-wall yield strength is found by dividing the hardness H
by 3, giving a value of ry = 160 MPa. Samples of the foams
were cut by electrodischarge machining. Details of the micro-
structure characterization (cell shape, cell size, and cell-wall
thickness) and relative density, r, have been reported else-
where.[2] The specimens were of rectangular section 150 ´
50 mm; the height was 50 mm for monotonic pull-out tests,
and 25 mm for fatigue pull-out tests. Specimens of dimension
100 ´ 40 ´ 15 mm and 100 ´ 70 ´ 15 mm were used for mono-
tonic and fatigue bearing-load tests, respectively. All tests
were performed at room temperature on a servohydraulic
test machine, and the load and load-line displacement re-
corded on computer.
Four types of mechanical fasteners were studied: wood
screws, nails, threaded inserts, and studs. Figure 1 shows a
sketch of a wood screw and a stud. Two sets of investigation
were carried out. In the first, dry fasteners were driven di-
rectly into the foam; in the second, fasteners were embedded
in epoxy adhesive (¹Araldite Rapidª cured 24 h at room tem-
perature) in pre-drilled pilot holes in the foam giving a com-
bination of mechanical and adhesive attachment.
[14] R. S. M. B. Horta, W. T. Roberts, D. V. Wilson, Trans.
AIME 1969, 245, 2525.
[15] B. Viala, J. Degauque, Thesis, INSA-CNRS, Toulouse,
1994, p. 196.
Joining of Metal Foams with
Fasteners**
By Olujide B. Olurin,* Norman A. Fleck, and
Michael F. Ashby
Recent developments in manufacturing methods have
given rise to a wide range of recyclable foams made from alu-
minum alloys. Aluminum foams have low density and are at-
tractive as cores of sandwich panels, shells, and tubes. They
have high energy absorption, high acoustic damping, rela-
tively low thermal conductivity, and good electric conductiv-
ity. Commercially available foams include the open cell
Duocel and the closed cell Alporas, Alulight, and Cymat. For
the successful application of metallic foams, effective and effi-
cient ways must be found for joining them. Since they are
plastically compressible, they can been joined by wood
Tensile pull-out tests were performed in displacement con-
trol at a rate of 0.08 mm s±1, and the load and load-line dis-
placement were recorded. The parameters of interest, see Fig-
[*] Dr. O. B. Olurin, Prof. N. A. Fleck, Prof. M. F. Ashby
Cambridge University Engineering Department
Cambridge, CB2 1PZ (UK)
Email: obo21@eng.cam.ac.uk
[**] The authors are grateful to DARPA/ONR for their financial
support through MURI grant number N00014-1-96-1028 on
the Ultralight Metal Structures project at Harvard University.
OBO is grateful for financial assistance of Cambridge Com-
monwealth Trust, Cambridge University Engineering Depart-
ment, and Churchill College (Cambridge).
Fig. 1. Typical fastener joints: a) wood screw, b) stud.
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