Shaikh Faruque Ali

Multistable laminates have been widely analyzed in the recent past for their potential in morphing applications. However, all the analytical models developed up until now have taken into account only the free-free boundary condition. In this work two objectives are met: (a) an analytical model is developed, which extends the previously available models in literature to account for the cantilever boundary condition for a special class of hybrid bistable symmetric laminates (HBSL); (b) the previously proposed HBSL is modified by replacing the aluminum layers with bi-direction glass-epoxy prepregs in the layup. It is observed that the modified layup has a curvature similar to the previously proposed HBSL while maintaining bistability. The analytical model developed here successfully captures the equilibrium shapes and the snap-through behavior for this special class of laminates which is validated against the results obtained using ABAQUS® and experiments. The developed model is then subsequently used to study the design space and bistability characteristics of the HBSL and the proposed modified layup (m-HBSL) in the cantilever boundary condition.

Bistable laminates have posed a significant research interest in the recent past owing to their potential applications in morphing and energy harvesting. An important aspect of research has been their snapthrough analysis, wherein the use of solid state actuators like shape memory alloys (SMAs) and macro-fiber composites (MFCs) has been prevalent. These actuators however, interfere with the structural response of the laminate altering its bistability and snapthrough characteristics. Recently, reversible snapthrough was demonstrated in 3D printed thermoplastic filaments composed of PLA with finely ground iron particles embedded. Remote actuation was achieved by means of permanent magnets providing the necessary snapthrough loads. In this manuscript, a numerical model has been developed based on a Rayleigh-Ritz minimization scheme, to predict the equilibrium states and the snapthrough loads. The means of snapthrough is the interaction between the ferromagnetic layers and the nonlinear magnetic field generated by a solenoid, which has been modeled using Biot-Savart's law. The developed numerical model has been validated against finite element simulations in ABAQUS®, wherein the magnetoelastic interactions have been modeled as body forces using the DLOAD subroutine. This manuscript details one of the preliminary efforts in modeling of the remote snapthrough of switchable multistable structures and can provide valuable insights into the design of such non-contact actuation systems.

This manuscript investigates the snap-through characteristics of a special class of hybrid bistable symmetric laminate (HBSL) subjected to different loading constraints and imperfections. Understanding the behavior under various loading conditions and constraints is necessary to deploy these bistable laminates in structural applications. Towards that, detailed experimental and numerical studies are done to capture the load–displacement characteristics of: (a) an HBSL clamped at different distances at one end, (b) an HBSL clamped at one end subjected to loading at different positions, and (c) HBSL with geometric imperfection concerning the laminae thicknesses. The insights from the numerical and experimental studies are subsequently used to demonstrate the importance of the snap-through characterization in designing a smart actuation system.

In this manuscript, a concept flow control valve is designed, exploiting the bistable characteristics of a special class of hybrid laminates made of glass epoxy and carbon epoxy prepregs. The principal structural element of the device is a hybrid bistable laminate, having a multi-section layup laid in a symmetric configuration. The thermal curing process responsible for the inherent bistability is simulated in ABAQUS(Formula Presented) and the equilibrium shapes hence obtained using the FEA scheme is validated against an existing semi-analytical technique based on the Rayleigh-Ritz minimization of potential functional. These multi-stable elements are then studied for their potential in controlling a flowing stream. Toward that, the snapping response of these laminates in a flow stream is analyzed using a combination of XFOIL and ABAQUS(Formula Presented). The pressure distribution on the laminate is estimated using XFOIL, which is an interactive program for analysis of subsonic isolated airfoils in viscous/inviscid low Reynolds number flow. The pressure distribution hence obtained is used to evaluate the load-displacement characteristics of the laminate using post-buckling regime analysis capabilities of ABAQUS(Formula Presented). Using these analysis tools, the design space is explored and the possibility of using the proposed bistable design elements for flow regulation is established.