Anshul Faye

Theoretical and experimental investigations on the active structural–acoustic control of a thin plate using a vertically reinforced 1-3 piezoelectric composite

This paper deals with investigations on the active structural–acoustic control of a thin homogeneous isotropic plate using vertically reinforced 1-3 piezoelectric composite (PZC) material. A finite element model is developed for the plate which is integrated with a patch of active constrained layer damping (ACLD) treatment and coupled with an acoustic cavity to describe the coupled structural–acoustic behavior of the plate. The constraining layer of the ACLD treatment is composed of the vertically reinforced 1-3 PZC material. Both in-plane and out-of-plane actuations by the constraining layer of the ACLD treatment have been utilized for deriving the finite element model. An experiment is also carried out to investigate the performance of the patch of the ACLD treatment in which the constraining layer of the patch is made of vertically reinforced 1-3 PZC for active structural–acoustic control of the plate. Both the finite element analysis and the experimental investigation agree with each other and reveal that the vertically reinforced 1-3 PZC material performs excellently for achieving active structural–acoustic control of the isotropic plate.

A study on notch tip micromechanics in dynamic fracture of polycarbonate

The fracture behavior of notched polycarbonate (PC) is investigated as a function of loading rate ranging from quasistatic to dynamic. Complementary numerical simulations are performed using the experimentally obtained load-point displacement as the input. The results indicated that in the rage of loading rates considered, the fracture initiation toughness of PC is not sensitive to loading rate. The fracture processes near the dynamically loaded notch-tip was observed using ultra-high speed imaging. In both quasi-static and dynamic loading, defects nucleate ahead of the notch tip and coalesce before final fracture. In quasi-static tests there is considerable time lag between defect nucleation and final fracture, whereas in dynamic experiments the two are almost synchronous.

Effect of Loading Rate on Dynamic Fracture Toughness of Polycarbonate

Accurate estimation of dynamic fracture properties of materials is important for component design under impact conditions. Amorphous glassy polymers have wide engineering applications. For Polymethyl methacrylate (PMMA), which is a brittle amorphous polymer, literature indicates that the fracture toughness increases at higher loading rates compared to that under static loading conditions. Motivated by this observation, in the present work, another amorphous polymer named Polycarbonate (PC), which is ductile in nature, is considered and effect of loading rate on fracture toughness of PC is investigated. Experiments using the single edge notched (SEN) specimen subjected to 3-point bending are performed at various loading rates. A UTM is used for low loading rate experiments. High loading rate experiments are conducted using Hopkinson pressure bar. Ultra high speed imaging (100,000 fps) is used to make accurate measurement of fracture initiation time in these experiments. Attempts are being made to investigate the near notch deformation in detail. A hybrid experimental and numerical approach is pursued in which finite element simulations are performed using the boundary conditions obtained from experiments. A rate and temperature dependant constitutive model is used for PC. Stress intensity factor (SIF), evaluated from simulation is correlated with experimentally measured SIF. Results show that that dynamic fracture initiation toughness of PC does not vary significantly at higher loading rates; values remain close to that obtained under quasi-static loading conditions.