@inproceedings{shabeer_lee_2024, title={Active Control of Dynamic Fold Propagation in Tape Springs}, url={http://dx.doi.org/10.2514/6.2024-1042}, DOI={10.2514/6.2024-1042}, abstractNote={Composite shell structures can self-deploy through the release of stored strain energy when elastically folded under stowage. Uncontrolled deployment of such structures could lead to prolonged disordered motion, self-entanglement, collision, or damage. Therefore, control mechanisms are necessary to enable coherent and reliable deployment paths. This paper demonstrates the efficacy of actively controlling the freely unfolding motion of a cantilevered composite tape spring with piezoelectric actuators called Macro Fiber Composites (MFC). The cross-sectional curvature of the tape spring near its fixed root is actively manipulated with voltage actuation from the bonded MFCs. Both unimorph and bimorph configurations are investigated. Implicit finite element analysis with experimentally tuned viscous damping simulates both the uncontrolled and piezoelectrically controlled dynamic deployment of a composite tape spring with a single localized fold. The active control scheme results in a significant attenuation of the fold propagation behavior during deployment with a reduction in the total deployment duration of up to 26.7%. The bimorph configuration is found to inhibit the fold movement more effectively than the unimorph actuator, enough to keep it nearly stationary, due to the increased actuation authority over the transverse curvature of the tape spring.}, booktitle={AIAA SCITECH 2024 Forum}, author={Shabeer, Saad and Lee, Andrew J.}, year={2024}, month={Jan} }
 @article{daye_lee_2023, title={Active Deployment of Ultra-thin Composite Booms with Piezoelectric Actuation}, volume={12483}, ISBN={["978-1-5106-6073-1"]}, ISSN={["1996-756X"]}, DOI={10.1117/12.2658004}, abstractNote={The efficacy of using piezoelectric actuators to initiate the dynamic deployment of bistable composite tape springs is evaluated in this paper. Ultra-thin composite booms such as tape springs and their cross-sectional variants have seen increased popularity in spacecraft structures due to enabling the precise deployment of flexible solar arrays, sails, reflectors, and antennas. They can elastically transition between the deployed “extended” position and the stowed “coiled” position while retaining superior stiffness, thermal properties, mass efficiency, and compactness when compared to thin-shelled metal booms and rigid articulated columns. Bistability in the coiled and extended states allows the boom to exhibit more controllable self-deployment and become reconfigurable, which could allow spacecraft to relocate, redeploy, and adapt to changing environmental conditions or mission objectives. Deployment systems commonly include motors and mechanical restraints that significantly contribute to mechanical complexity and spacecraft weight. Since bistable booms do not rely on elastic instability of packaging to initiate motion, a non-intrusive and lightweight actuation mechanism is needed to trigger deployment. This paper experimentally demonstrates how a Macro Fiber Composite (MFC) actuator can statically and dynamically excite a stowed composite tape spring to initiate unrolling into its extended state.}, journal={ACTIVE AND PASSIVE SMART STRUCTURES AND INTEGRATED SYSTEMS XVII}, author={Daye, Jacob G. and Lee, Andrew J.}, year={2023} }
 @article{lee_fernandez_daye_2023, title={Bistable Deployable Composite Booms with Parabolic Cross Sections}, volume={11}, ISSN={["1533-6794"]}, DOI={10.2514/1.A35840}, abstractNote={The stable extended and coiled states of thin-shelled composite booms with parabolic cross sections are investigated in this paper. These conic shapes potentially offer greater stiffness properties when compared to circular cross sections, which is critical for improving the load-bearing performance of deployed booms. Inducing bistability through composite layups in parabolic booms would allow for controllable self-deployment due to a less energetic coiled state when compared to monostable booms. An inextensional analytical model is used to predict the stable coiled diameters of tape spring and collapsible tubular mast (CTM) booms with parabolic cross sections. The parabolic section is discretized into circular segments using biarc spline interpolation, which allows them to be integrated into the strain energy minimization procedure used to obtain the equilibrium states. When the parabolic booms are parametrically compared against circular booms with identical layups, flattened height, and mass, the former are found to generally have better stiffness performance while being less efficient in stowed volume, as evidenced by larger coiled diameters. Analytical coiled diameters and their strain energy are verified with finite element simulations for an optimal parabolic tape spring and CTM booms. Additional validation of the parabolic tape spring’s coiled diameter is provided by experimental measurements of boom specimens.}, journal={JOURNAL OF SPACECRAFT AND ROCKETS}, author={Lee, Andrew J. and Fernandez, Juan M. and Daye, Jacob G.}, year={2023}, month={Nov} }
 @inproceedings{lee_fernandez_daye_2022, title={Bistable Deployable Composite Booms With Parabolic Cross-Sections}, url={http://dx.doi.org/10.2514/6.2022-2264}, DOI={10.2514/6.2022-2264}, abstractNote={This paper investigates how stable equilibrium states in the extended and coiled configurations can be predicted in thin-shelled composite booms with parabolic cross-sections. These conic shapes potentially offer greater stiffness properties when compared to circular cross-sections, which is critical for improving the load bearing performance of deployed booms. Inducing bistability through the choice of composite shell layups in parabolic booms would allow for controllable self-deployment due to a less energetic coiled state when compared to monostable booms. An inextensional analytical model is used to predict the stable coiled diameters of tape spring and Collapsible Tubular Mast (CTM) booms with parabolic cross-sections. The parabolic section is discretized into circular segments using biarc spline interpolation, which allows them to be integrated into the strain energy minimization procedure used to obtain the equilibrium states. When the parabolic booms are parametrically compared against circular booms with identical layups, flattened height, and mass, the former are found to generally have better stiffness performance while being less efficient in stowed volume as evidenced by larger coiled diameters. Analytical coiled diameters and their strain energy are verified with finite element simulations for optimal parabolic tape spring and CTM booms.}, booktitle={AIAA Scitech 2022 Forum}, publisher={American Institute of Aeronautics and Astronautics}, author={Lee, Andrew J. and Fernandez, Juan M. and Daye, Jacob G.}, year={2022}, month={Jan} }
 @article{lee_pellegrino_2022, title={Mass efficiency of strip-based coilable space structures}, volume={254}, ISSN={["1879-2146"]}, url={http://dx.doi.org/10.1016/j.ijsolstr.2022.111867}, DOI={10.1016/j.ijsolstr.2022.111867}, abstractNote={This paper presents a general semi-analytical study of the mass efficiency of coilable plate-like space structures. A bending architecture based on four diagonal booms that support parallel strips is compared to a cable-stayed architecture in which vertical booms and cable stays support the diagonal booms at the tip. Limiting conditions of global buckling, local buckling, material failure, and excessive deflection define the design space for each architecture. Considering pressure loads spanning several orders of magnitude, the optimal areal density of structures of size varying from a few meters to hundreds of meters is determined for both architectures. Design charts for optimal designs are provided for a range of sizes, loads, and deflection limits. It is shown that the cable-stayed architecture is always lighter than the bending architecture, from a few percent to over 30%.}, journal={INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES}, publisher={Elsevier BV}, author={Lee, Andrew J. and Pellegrino, Sergio}, year={2022}, month={Nov} }
 @book{brophy_pellegrino_lubin_alkalai_atwater_biswas_boca_carr_davoyan_frazier_et al._2022, title={Non-Nuclear Exploration of the Solar System
Study}, url={https://resolver.caltech.edu/CaltechAUTHORS:20220503-222804071}, DOI={10.7907/H62P-6328}, journal={California Institute of Technology}, institution={California Institute of Technology}, author={Brophy, John and Pellegrino, Sergio and Lubin, Philip and Alkalai, Leon and Atwater, Harry and Biswas, Abi and Boca, Andreea and Carr, Greg and Davoyan, Artur and Frazier, William and et al.}, year={2022} }
 @inproceedings{lee_pellegrino_2021, title={Cable-Stayed Architectures for Large Deployable Spacecraft}, url={http://dx.doi.org/10.2514/6.2021-1386}, DOI={10.2514/6.2021-1386}, abstractNote={Cable-stayed structural architectures, which use a combination of bending and axial loadcarrying modes, are potentially more efficient than structural architectures that rely only on bending. However, they are not widely used at present. In this paper, an analytical framework is established to compare the load carrying performance of cable-stayed vs. bending architectures by considering limiting conditions such as global buckling, local shell buckling, material failure, and excessive deflection. For structures of equal span, material properties, mass, andmaximum deflection limit, the most efficient cable-stayed geometry is determined and its performance is compared to that of the beam. It is shown that the cable-stayed architecture is more efficient at withstanding external loads and remains optimal over the bending architecture. Design charts for optimal designs of cable-stayed structures for a range of lengths and loads are provided.}, booktitle={AIAA Scitech 2021 Forum}, publisher={American Institute of Aeronautics and Astronautics}, author={Lee, Andrew and Pellegrino, Sergio}, year={2021}, month={Jan} }
 @article{lee_xie_inman_2020, title={Suppression of Cross-Well Oscillations for Bistable Composites Through Potential Well Elimination}, volume={142}, url={http://dx.doi.org/10.1115/1.4046123}, DOI={10.1115/1.4046123}, abstractNote={
 Although there have been numerous efforts into harnessing the snap through dynamics of bistable structures with piezoelectric transducers to achieve large energy conversion, these same dynamics are undesirable under morphing applications where stationary control of the structure’s configuration is paramount. To suppress cross-well vibrations that primarily result from periodic excitation at low frequencies, a novel control strategy is proposed and implemented on the piezoelectrically generated bistable laminate, which consists of only macro fiber composites (MFCs) in a [0MFC/90MFC]T layup. While under cross-well regimes such as subharmonic, chaotic, or limit cycle oscillations, a single MFC is actuated to the laminate’s limit voltage to eliminate one of its potential wells and force it into the remaining stable state. Simultaneously, a positive position feedback (PPF) controller suppresses the resulting single-well oscillations through the other MFC. This dual control strategy is numerically and experimentally demonstrated through the suppression of various cross-well regimes and results in significant reduction of amplitude. The active control capability of the laminate prevents snap through instability when under large enough external vibrations.}, number={3}, journal={Journal of Vibration and Acoustics}, publisher={ASME International}, author={Lee, Andrew J. and Xie, Antai and Inman, Daniel J.}, year={2020}, month={Jun} }
 @inproceedings{fernandez_lee_2019, title={Bistability in collapsible tubular mast booms}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85068439195&partnerID=MN8TOARS}, DOI={10.2514/6.2019-1257}, booktitle={AIAA Scitech 2019 Forum}, author={Fernandez, J.M. and Lee, A.J.}, year={2019} }
 @inproceedings{lee_inman_2019, title={Broadband energy harvesting performance of a piezoelectrically generated bistable laminate}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85048309497&partnerID=MN8TOARS}, DOI={10.1007/978-3-319-74642-5_1}, abstractNote={The vibration based energy harvesting performance of a piezoelectrically generated bistable laminate consisting of only Macro Fiber Composites (MFC) is experimentally characterized. Conventionally, piezoelectric transducers are bonded onto thermally induced bistable composite laminates and exhibit broadband cross-well dynamics that are exploited for improved power generation over linear resonant harvesters. Recently, a novel method of inducing bistability was proposed by bonding two actuated MFCs in a [0 MFC ∕90 MFC ] T layup and releasing the voltage post cure to create in-plane residual stresses and yield two cylindrically stable configurations. Forward and backward frequency sweeps at multiple acceleration levels across the first two observed modes of the laminate’s two states are performed to identify all dynamic regimes and the corresponding voltages produced by each MFC. Besides single-well oscillations, snap throughs are observed in intermittencies, subharmonic, chaotic, and limit cycle oscillations across wide frequency ranges. Resistor sweeps are conducted for each regime to determine maximum power outputs, and single and multi-frequency performance metrics accounting for laminate volume, mass, input accelerations, and frequencies are evaluated for the laminate. A performance comparison with conventional bistable composite harvesters demonstrate the laminate’s viability for energy harvesting, allowing it to be multi-functional in combination with its snap through morphing capability.}, number={213429}, booktitle={Conference Proceedings of the Society for Experimental Mechanics Series}, author={Lee, A.J. and Inman, D.J.}, year={2019}, pages={1–14} }
 @article{lee_inman_2019, title={Electromechanical modelling of a bistable plate with Macro Fiber Composites under nonlinear vibrations}, volume={446}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85060935046&partnerID=MN8TOARS}, DOI={10.1016/j.jsv.2019.01.045}, abstractNote={Vibrational broadband energy harvesting has been the most focused application of bistable composite plates paired with piezoelectric materials due to their wide array of nonlinear responses at low frequencies. Various cross-well behaviors between the two potential wells allow large amplitudes and broadband characteristics favorable for generating ample power even away from resonance. With most past works being experimental, there are limitations in the available literature for validated model predictions of the electromechanical response resulting from cross-well dynamics under harmonic excitation. This paper presents the formulation, implementation, and experimental validation of the nonlinear analytical model for the rectangular piezoelectrically generated bistable laminate with a fixed center consisting of Macro Fiber Composites (MFC) in a cross-ply layup. The full range of nonlinear responses observed in tests are predicted by the simulated electromechanical equations of motion such as intermittency, limit cycle, chaotic, and subharmonic oscillations. These responses and the corresponding voltage and power outputs are investigated for a range of excitation parameters using both time and frequency domain analysis, and they show good agreement with experimental results.}, journal={Journal of Sound and Vibration}, author={Lee, A.J. and Inman, D.J.}, year={2019}, pages={326–342} }
 @inproceedings{lee_inman_2019, title={Extension of cross-well bandwidths for a bistable oscillator}, volume={10967}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85069797360&partnerID=MN8TOARS}, DOI={10.1117/12.2514104}, abstractNote={Snap-through dynamics between the two potential wells of bistable oscillators are exhibited over a wide frequency range which narrows with decreasing harmonic excitation amplitudes until disappearing at a critical forcing level. However, for efficient conversion from vibrational to electrical energy in harvesting applications, the bistable oscillator must retain its favorable broadband cross-well response while the input excitation is minimized. To maintain effectiveness at low forcing levels, an actuation approach is proposed where external perturbations are used to extend the oscillator’s cross-well bandwidths by switching from co-existing low to high energy attractors. By utilizing Macro Fiber Composites (MFC) in a [0MFC /90MFC ]T bistable laminate, the application of rectangular voltage pulse signals are cycled through different response phases to continuously alter the basins of attraction until the desired cross-well orbit is sustained at each frequency. The pulse magnitude is where the system exhibits limit point behavior and the resulting snap through actuation mechanism brings consistency between perturbation trials. Numerical simulations show significant increase to the bandwidths inducing cross-well oscillations when the perturbation strategy is employed.}, booktitle={Proceedings of SPIE - The International Society for Optical Engineering}, author={Lee, A.J. and Inman, D.J.}, year={2019} }
 @article{lee_fernandez_2019, title={Inducing bistability in Collapsible Tubular Mast booms with thin-ply composite shells}, volume={225}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85067550899&partnerID=MN8TOARS}, DOI={10.1016/j.compstruct.2019.111166}, abstractNote={Bistable rollable booms are favorable when a low strain energy requirement for the coiled state is imposed and have more controllable deployment when compared to monostable booms. An inextensional analytical model describing the bending deformation mechanics of Collapsible Tubular Mast (CTM) booms was used to determine how design variables induce bistability, or the existence of two strain energy wells in the rolled-up and unrolled states. The effects of varying lamina material, laminate layup, and shell arc geometries between different inner and outer shell segments on the second strain energy well and stiffness properties were determined for boom cross-sections formed by circular segments. The full design space for two-walled composite CTM booms was explored to evaluate the validity of the developed analytical model. Optimized CTM boom designs were experimentally characterized for comparisons against model results. The model under-predicted the stable coiled diameter of the co-cured two-walled booms by up to 8.9% and 23.4% for the individual thin shells wrapped alone.}, journal={Composite Structures}, author={Lee, A.J. and Fernandez, J.M.}, year={2019} }
 @article{lee_inman_2018, title={A multifunctional bistable laminate: Snap-through morphing enabled by broadband energy harvesting}, volume={29}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85047413747&partnerID=MN8TOARS}, DOI={10.1177/1045389X18770895}, abstractNote={The elastic instabilities associated with buckling in bistable structures have been harnessed toward energy-based and motion-based applications, with significant research toward energy harvesting and morphing. Often combined with smart materials, structural prototypes are designed with a single application in mind. Recently, a novel method of inducing bistability was proposed by bonding two piezoelectrically actuated macro fiber composites in a [ 0 MFC / 90 MFC ] T layup and releasing the voltage post cure to yield two cylindrically stable configurations. Since the macro fiber composites are simultaneously the actuator and host structure, the resulting efficiencies enable this bistable laminate to be multifunctional, with both broadband energy harvesting and snap-through morphing capabilities. This article experimentally characterizes the vibration-based energy harvesting performance of the laminate to enable morphing. Through frequency sweeps across the first two modes of both states, the laminate exhibits broadband cross-well dynamics that are exploited for improved power generation over linear resonant harvesters. Besides single-well oscillations, snap-throughs are observed in intermittencies and subharmonic, chaotic, and limit cycle oscillations. The maximum power output of each regime and their charge durations of an energy harvesting module are assessed. The laminate’s capabilities are then bridged by utilizing harvested energy in the charged module to initiate snap-through actuation.}, number={11}, journal={Journal of Intelligent Material Systems and Structures}, author={Lee, A.J. and Inman, D.J.}, year={2018}, pages={2528–2543} }
 @inproceedings{fernandez_lee_2018, title={Bistable Collapsible Tubular Mast Booms}, booktitle={3rd International Conference on Advanced Lightweight Structures and Reector Antennas}, author={Fernandez, J.M. and Lee, A.J.}, year={2018}, month={Sep} }
 @inproceedings{lee_inman_2018, title={Broadband Energy Harvesting Performance of a Piezoelectrically Generated Bistable Laminate}, booktitle={36th International Modal Analysis Conference}, author={Lee, A.J. and Inman, D.J.}, year={2018}, month={Feb} }
 @inproceedings{lee_inman_2018, title={Electromechanical Response of a Bistable Laminate with Macro Fiber Composites from Nonlinear Vibrations}, booktitle={29th International Conference on Adaptive Structures and Technologies}, author={Lee, A.J. and Inman, D.J.}, year={2018} }
 @inproceedings{lee_fernandez_2018, title={Mechanics of bistable two-shelled composite booms}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85044437491&partnerID=MN8TOARS}, DOI={10.2514/6.2018-0938}, abstractNote={The phenomenon of bistability in single-walled composite cylindrical shells or slit tubes has been extensively studied with detailed models that represent the mechanics of these structures as they undergo large deformations from the extended to the stored state and vice versa. This study focuses on the mechanics of bistable composite booms that are formed by coupling or bonding two thin shells. A two-parameter inextensional analytical model is used to describe the behavior of the various two-shelled structures and find laminates and shell geometries of interest that induce bistability. The natural coiled diameters of all boom types are predicted analytically and compared with preliminary experimental data. Using the derived model, parametric analysis is conducted to determine optimal boom geometries that maximize stiffnesses and meet system requirements while retaining bistability.}, number={210019}, booktitle={AIAA Spacecraft Structures Conference, 2018}, author={Lee, A.J. and Fernandez, J.M.}, year={2018} }
 @inproceedings{lee_xie_inman_2018, title={Suppression of Cross-Well Oscillations With Active Control of a Bistable Laminate}, url={http://dx.doi.org/10.1115/smasis2018-7919}, DOI={10.1115/smasis2018-7919}, abstractNote={Although there have been numerous efforts into harnessing the snap through dynamics of bistable structures with piezoelectric transducers to achieve large energy conversion, these same dynamics are undesirable under morphing applications where stationary control of the structure’s configuration is paramount. To suppress cross-well vibrations that primarily result from periodic excitation at low frequencies, a novel control strategy is proposed and implemented on the piezoelectrically generated bistable laminate, which consists of only Macro Fiber Composites (MFC) in a [0MFC/90MFC]T layup. While under cross-well regimes such as chaotic or limit cycle oscillations, a single MFC is actuated past the laminate’s limit voltage to eliminate one of its potential wells and force it into the remaining stable state. Simultaneously, a Positive Position Feedback (PPF) controller suppresses the resulting single-well oscillations through the other MFC. This dual control strategy is demonstrated with an electromechanical model through the suppression of various cross-well regimes, and results in significant reduction of amplitude. The active control capability of the laminate prevents snap through instability when under large enough external vibrations and adds to its multifunctionality along with morphing and broadband energy harvesting.}, booktitle={ASME 2018 Conference on Smart Materials, Adaptive Structures and Intelligent Systems}, publisher={American Society of Mechanical Engineers}, author={Lee, Andrew J. and Xie, Antai and Inman, Daniel J.}, year={2018}, month={Sep} }
 @inproceedings{moosavian_chae_pankonien_lee_inman_2017, title={A parametric study on a bio-inspired continuously morphing trailing edge}, volume={10162}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85020192159&partnerID=MN8TOARS}, DOI={10.1117/12.2257582}, abstractNote={Inspired by the wave-like camber variation in the trailing edge feathers of large birds, the aerodynamic impact of similar variations in the geometry of morphing wings is investigated. The scope of this problem is reduced by exploring parametrically generated geometries derived from an existing morphing wing design, namely the Spanwise Morphing Trailing Edge (SMTE), which is actuated via conformally integrated Macro Fiber Composites (MFCs). Utilizing this design, the deformation of the trailing edge of the SMTE is parameterized as a function of the spanwise location using a sinusoidal relationship. The aerodynamic responses are then obtained using Computational Fluid Dynamics (CFD) simulations, while the efficacy of the proposed approach is explored using a Pareto-like frontier approach.}, booktitle={Proceedings of SPIE - The International Society for Optical Engineering}, author={Moosavian, A. and Chae, E.J. and Pankonien, A.M. and Lee, A.J. and Inman, D.J.}, year={2017} }
 @article{lee_moosavian_inman_2017, title={A piezoelectrically generated bistable laminate for morphing}, volume={190}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85008422611&partnerID=MN8TOARS}, DOI={10.1016/j.matlet.2017.01.005}, abstractNote={This letter presents the analytical and experimental results of piezoelectrically generating bistability via Macro Fiber Composite (MFC) actuators. Two stable configurations are exhibited when piezoelectric strain anisotropy is induced within a [0MFC/90MFC]T laminate. This is achieved by bonding two MFCs in their actuated states and releasing the voltage post cure to create in-plane residual stresses. The resulting shapes are cylindrical and can be snapped through and back with only piezoelectric actuation. A [0MFC/90MFC]T laminate is modeled, manufactured, and experimentally characterized. This adaptive laminate functions as both the actuator and the primary structure and its snap through capability allows full configuration control necessary in morphing, without continuous energy input or any mechanical assistance.}, journal={Materials Letters}, author={Lee, A.J. and Moosavian, A. and Inman, D.J.}, year={2017}, pages={123–126} }
 @article{lee_moosavian_inman_2017, title={Control and characterization of a bistable laminate generated with piezoelectricity}, volume={26}, url={http://dx.doi.org/10.1088/1361-665x/aa7165}, DOI={10.1088/1361-665x/aa7165}, abstractNote={Extensive research has been conducted on utilizing smart materials such as piezoelectric and shape memory alloy actuators to induce snap through of bistable structures for morphing applications. However, there has only been limited success in initiating snap through from both stable states due to the lack of actuation authority. A novel solution in the form of a piezoelectrically generated bistable laminate consisting of only macro fiber composites (MFC), allowing complete configuration control without any external assistance, is explored in detail here. Specifically, this paper presents the full analytical, computational, and experimental results of the laminate’s design, geometry, bifurcation behavior, and snap through capability. By bonding two actuated MFCs in a [0MFC/90MFC]T layup and releasing the voltage post cure, piezoelectric strain anisotropy and the resulting in-plane residual stresses yield two statically stable states that are cylindrically shaped. The analytical model uses the Rayleigh–Ritz minimization of total potential energy and finite element analysis is implemented in MSC Nastran. The [0MFC/90MFC]T laminate is then manufactured and experimentally characterized for model validation. This paper demonstrates the adaptive laminate’s unassisted forward and reverse snap through capability enabled by the efficiencies gained from simultaneously being the actuator and the primary structure.}, number={8}, journal={Smart Materials and Structures}, publisher={IOP Publishing}, author={Lee, Andrew J and Moosavian, Amin and Inman, Daniel J}, year={2017}, month={Aug}, pages={085007} }
 @inproceedings{lee_moosavian_inman_2017, title={Piezoelectrically strained bistable laminates with macro fiber composites}, volume={10164}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85024118119&partnerID=MN8TOARS}, DOI={10.1117/12.2257680}, abstractNote={The bistability and snap through capability of an unsymmetric laminate consisting of only Macro Fiber Composites (MFC) are investigated. The non-linear analysis predicts two cylindrically stable configurations when strain anisotropy is piezoelectrically induced within a [0MFC/90MFC]T laminate. This is achieved by bonding two MFCs in their actuated states and releasing the voltage post cure to create in-plane residual stresses. The minimization of total potential energy with the Rayleigh-Ritz method are used to analytically model the resulting laminate. A finite element analysis is conducted in MSC Nastran using the piezoelectric-thermal analogy approach to verify the analytical results. The effects of adhesive properties, bonding cure cycles, MFC layup, and its geometry on the curvatures, displacements, and bifurcation voltages are characterized. Finally, the snap through and reverse snap through capabilities with piezoelectric actuation are demonstrated. This adaptive laminate functions as both the actuator and the primary structure and allows large deformations under a non-continuous energy input. Its snap through capability allows full configuration control necessary in morphing applications.}, booktitle={Proceedings of SPIE - The International Society for Optical Engineering}, author={Lee, A.J. and Moosavian, A. and Inman, D.J.}, year={2017} }
 @inproceedings{lee_moosavian_inman_2016, title={An Investigation into Piezoelectrically Induced Bistability}, booktitle={27th International Conference on Adaptive Structures and Technologies}, author={Lee, A.J. and Moosavian, A. and Inman, D.J.}, year={2016}, month={Oct} }
 @article{lee_wang_inman_2014, title={Energy harvesting of piezoelectric stack actuator from a shock event}, volume={136}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84902192173&partnerID=MN8TOARS}, DOI={10.1115/1.4025878}, abstractNote={The energy harvesting performance of a piezoelectric stack actuator under a shock event is theoretically and experimentally investigated. The first method is derived from the single degree of freedom constitutive equations, and then a correction factor is applied onto the resulting electromechanically coupled equations of motion. The second approach is deriving the coupled equations of motion with Hamilton's principle and the constitutive equations, and then formulating it with the finite element method. Two experimental cases matched well with the model predictions where the percent errors were 3.90% and 3.26% for the SDOF analysis and 1.52% and 1.42% for the FEM.}, number={1}, journal={Journal of Vibration and Acoustics, Transactions of the ASME}, author={Lee, A.J. and Wang, Y. and Inman, D.J.}, year={2014} }
 @inproceedings{lee_wang_inman_2013, title={Power harvesting prediction of piezoelectric stack actuator from a shock event}, volume={8}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84896950608&partnerID=MN8TOARS}, DOI={10.1115/DETC2013-12776}, abstractNote={This paper is to study free response of a spinning, cyclic symmetric rotor assembled to a flexible housing via multiple bearings. In particular, the rotor spins at a constant speed ω3, and the housing is excited via a set of initial displacements. The focus is to study ground-based response of the rotor through theoretical and numerical analyses. The paper consists of three parts. The first part is to briefly summarize an equation of motion of the coupled rotor-bearing-housing systems for the subsequent analyses. The equation of motion, obtained from prior research [1], employs a ground-based and a rotor-based coordinate system to the housing and the rotor, respectively. As a result, the equation of motion takes the form of a set of ordinary differential equations with periodic coefficients of frequency ω3. To better understand its solutions, a numerical model is introduced as an example. In this example, the rotor is a disk with four radial slots and the housing is a square plate with a central shaft. The rotor and housing are connected via two ball bearings. The second part of the paper is to analyze the rotor’s response in the rotor-based coordinate system theoretically. When the rotor is at rest, let ωH be the natural frequency of a coupled rotor-bearing-housing mode whose response is dominated by the housing. The theoretical analysis then indicates that response of the spinning rotor will possess frequency components ωH ± ω3 demonstrating the interaction of the spinning rotor and the housing. The theoretical analysis further shows that this splitting phenomenon results from the periodic coefficients in the equation of motion. The numerical example also confirms this splitting phenomenon. The last part of the paper is to analyze the rotor’s response in the ground-based coordinate system. A coordinate transformation shows that the ground-based response of the spinning rotor consists of two major frequency branches ωH − (k + 1) ω3 and ωH − (k − 1) ω3, where k is an integer determined by the cyclic symmetry and vibration modes of interest. The numerical example also confirms this derivation.}, booktitle={Proceedings of the ASME Design Engineering Technical Conference}, author={Lee, A.J. and Wang, Y. and Inman, D.J.}, year={2013} }