Compression–compression fatigue of open cell aluminum foams: macro-/micro- mechanisms and the effects of heat treatment

This paper presents the results of an experimental study of the fatigue mechanisms of Duocel ® open cell aluminum foams and the effects of heat treatment on foam fatigue behaviour. The macro-/micro-mechanisms of fatigue were studied for the foams in the as-fabricated (F), annealed (O) and T6-strengthened (T6) conditions. The effects of annealing and T6-strengthening on the stress–strain behavior and plastic collapse strengths of foams were introduced before presenting the results of compression–compression fatigue experiments. The formation of localized deformation bands were investigated using an in-situ digital camera. Scanning electron microscopy (SEM) revealed clear evidence of the surface crack nucleation in the individual struts, prior to the abrupt strain jumps. Fractographic analysis of the failed struts also revealed fatigue striations and surface crack nucleation mechanisms in the struts. Finally, a simple compression–compression fatigue mechanism is proposed to link the observed macro- and micro-scale fatigue mechanisms in open cell aluminum foams.