Experimental and numerical investigation of voltage-dependent active vibration control on a notch-cracked composite mono leaf spring

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This paper presents combined experimental and numerical research on the application of an Active Vibration Control System (AVCS) to a cracked glass-fibre-reinforced polymer (GFRP) composite mono leaf spring for automotive suspension systems, an application that, to the authors’ knowledge, has received very limited prior attention in open literature. A T-3 tapered E-glass/epoxy mono leaf spring, a typical utility vehicle suspension part, is put in a controlled transverse notch crack at mid-span position - the most harmonic displacement zone as determined by finite element harmonic analysis in HyperWorks OptiStruct. The first six natural frequencies of the undamaged and cracked spring are determined by mode analysis, both computationally (with HyperMesh/OptiStruct) and experimentally (with an OROS OR34 FFT analyzer with roving hammer excitation under free-free boundary conditions). To characterise the voltage-dependent vibration suppression response, and SP-5 H lead zirconate titanate (PZT) patch is bonded between node 3 and 4 at the anti-nodal point of maximum amplitude and energized at two different voltage levels 0.62 V and 3.56 V by custom printed circuit board. The basic natural frequency is decreased to 1.27 Hz at 3.56 V, which is a 95% suppression of the main resonance amplitude. XFEM analysis of the stress intensity factor, with AVCS activated, confirms reduction of Mode I crack-driving force by 80% when AVCS is turned on. The results of the study prove the technical feasibility of PZT-based active control, as a structural health maintenance and fatigue-life extension measure of degraded composite suspension components.