Experimental nonlinear dynamics of a geometrically imperfect magneto-rheological elastomer sandwich beam

Experimental investigations were carried out on the nonlinear dynamic response of a clamped–clamped geometrically imperfect magneto-rheological elastomer (MRE) sandwich beam with a concentrated mass at the centre when loaded with a point excitation. Experiments have been conducted for: (i) a geometrically imperfect aluminium beam; (ii) a geometrically imperfect MRE sandwich beam in the absence of a magnetic field; (iii) a geometrically imperfect MRE sandwich beam in the presence of a magnetic field; (iv) a MRE sandwich beam with different geometric imperfection amplitudes. An electrodynamic shaker excited each system and the corresponding displacement of the concentrated mass was measured; an array of magnets has been used to investigate the effects of changing magnetic field strength on the nonlinear dynamic response of the geometrically imperfect MRE sandwich beam. It has been shown that the geometrically imperfect aluminium beam displays initial softening behaviour followed by strong hardening-type nonlinearity; with a MRE layer the motion characteristics of the geometrically imperfect sandwich beam no longer exhibits initial softening behaviour however, the MRE layer in the absence and presence of an external magnetic field all exhibit strong hardening-type nonlinearities—a significant qualitative change was observed in the nonlinear dynamical behaviour of the system.