Creep of aluminum syntactic foams

Aluminum syntactic foams with densities of 1.2–1.5 g/cm3 were deformed at 500 ◦C under constant uniaxial compressive stresses ranging from to 14 MPa. The foam creep behavior is characterized by a short primary stage and a long secondary stage where the strain rate is constant and inimum, followed by a tertiary stage at high stresses. The minimum strain rate varies with stress according to an apparent stress exponent n with low value (n≈ 1) for stresses below 8 MPa, and a high value (n≈ 14) above 8 MPa. Finite-element modeling provides predictions for the foam train rates that are in qualitative agreement with experimental results. Modeling also shows that the matrix transfers load to the ceramic elastic pheres, explaining the exceptionally high creep resistance of these syntactic foams as compared to aluminum foams without ceramic spheres. odeling finally reveals that stresses vary with position in the matrix and time during creep, and that the onset of tertiary stage is associated with he appearance of sharp stress concentrations in the matrix. 2008 Elsevier B.V. All rights reserved.