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A bi-stable piezoelectric energy harvester (BPEH) based on bi-stable hybrid symmetric laminate (BHSL) is proposed for energy harvesting. Due to its large deformation and low actuation, BPEH has better energy harvesting performance at low frequencies compared with traditional resonance cantilever-type energy harvester. Two types of stacking sequence and two types of piezoelectric ceramics (PZT) shapes with identical area were considered, and four types of BPEHs were designed. The stable configurations of the BPEHs and the stress states of PZT bonded on the surface of the BSHL were simulated and analyzed by finite element analysis. In addition, the four types of BPEHs were fabricated and experimentally evaluated. The BPEHs were actuated by hand shaking to transition between the two stable configurations. Using this method, the voltage outputs and power outputs were measured at two frequencies (2 Hz and 5 Hz). The results demonstrate that the BPEHs exhibited high output power because the PZTs on their surface were fully utilized due to their double curved shape and uniform deformations. The generated powers from the BPEHs were significantly higher than that observed from a similar sized cantilever-type piezoelectric harvester. Simultaneously, the influences of stacking sequence and shape of PZT on the energy harvesting performance were evaluated. The BPEHs with the second stacking sequence generated higher power than those of first stacking sequence, and the rectangular PZT performed better compared to the square. The measured maximum power output generated by the BPEH with the second stacking sequence and rectangular PZT was 37 mW at 5 Hz. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a bistable twisting CFRP-metal hybrid laminate which has an external isotropic metallic layer. Different from the pure unsymmetric CFRP laminate and the hybrid unsymmetric laminate with an inner metallic layer, the laminate presented can be transformed from one negative curvature to another negative curvature instead of from one negative curvature to another positive curvature. Their room temperature shapes can be a unique paraboloid shape, a twisted cylindrical shape, or a twisted cylindrical shape that can be snapped through to another twisted cylindrical shape. The cured shape of the hybrid laminate is studied using analytical, finite element and experimental techniques. The investigation is focused on the hybrid laminate with lay-up of [0/90/metal]T, and shows that the principal direction of cured curvature is 45°. The predicted cured shape and the snap-through loads agree well with experimental results. [Copyright &y& Elsevier]

Abstract: This paper presents a new heating actuation method to induce the snap-through phenomenon of bi-stable laminates by manipulating the residual stress in laminates. The mechanism of the heating actuation method is analyzed, and the snap-through process is simulated by the finite element method. The heating actuation experiments on two types of laminates with different stacking sequences are performed. Good agreement is obtained between the experimental data and the finite element analysis (FEA). Subsequently, the heating actuation method is applied to several different bi-stable laminates and investigated by FEA. The FEA results show that this heating actuation method is an effective way to induce the snap-through phenomenon of bi-stable laminates of different thicknesses, sizes and shapes. [Copyright &y& Elsevier]

The bistable composite is a deformable lightweight structure with two stable states, which are widely used in aerospace and space fields as deployment mechanisms and deformable structures. In this paper, a new application is proposed as an omnidirectional and directional radiation reconfigurable antenna based on a bistable composite tube. The antenna is prepared based on carbon fiber composite (CFRP) and glass fiber composite (GFRP) as the substrate and metal as the antenna layer co-cured. Mechanical behavior and material micro-interface analyses of the bistable structures are performed. Antennas of different materials and different layups are fabricated and analyzed. The results indicate that the designed antenna structure can be stabilized in the unfolded or stowed state without external support, unfolded into an omnidirectional antenna, and stowed into a directional antenna. The electromagnetic analysis is simulated and experimented to verify its performance as a multifunctional and reconfigurable antenna. Meanwhile, this bistable antenna possesses many advantages, including its lightweight, high storage ratio, and rapid reconfiguration, which make it an excellent candidate for satellite and spacecraft antennas. A bistable structure is a lightweight composite that can be deformed and has two stable forms. It is widely used in aerospace and space applications, mainly as a deployment mechanism and deformable structure. A new application direction is proposed, which is used as a multifunctional and reconfigurable antenna. The designed antenna has an ultra-high storage ratio and is ultra-lightweight because it uses carbon fiber composite materials. Due to the first design of a bistable antenna tube, the mechanical and electromagnetic properties of different fiber materials, and layups are simulated and experimentally analyzed, respectively. The results show that the designed metal hybrid antenna tube has two variable stable configurations, and the antenna energy radiation direction map and operating frequency can be switched. Meanwhile the structure can be expanded or stored within 1s. Configuration B is an ultra-wideband antenna with a bandwidth of 1 GHz. By controlling the parameter changes, the antenna frequency can be widened and used within the required range. Besides, the state B can reach a high storage ratio. The structure can be assembled on spacecraft and satellites as a versatile stowable and deployable antenna. [Display omitted] • A bistable composite antenna tube with two stable forms, which can transform into each other quickly. • The omnidirectional/directional patterns and operating frequency of the antenna can be switched. • The multi-function antenna is lightweight and can reach a high storage ratio. • Different composites and metal layups are studied to analyze their different mechanical and electromagnetic properties. [ABSTRACT FROM AUTHOR]

In this work, a bistable piezoelectric wind energy harvester (BPEH) is proposed, which is primarily made of bistable hybrid symmetric laminate (BHSL) and PZT, manufactured through a curing process. The air-solid-electric coupled finite element analysis model is established to simulate the dynamic response behavior of the BPEH and investigate the effects of varying airflow velocities on the flow field characteristics and performance output. A series of experimental studies on BPEH were conducted in the wind speed range of 8.5 m/s-16.5 m/s. The results show that at a wind speed of 14.5 m/s, the BPEH has an optimum external load of 60 k Ω , a maximum power output of 7.21 mW and a maximum amplitude of 93.065 mm. Therefore, the simple structure of the harvester proposed in this work may open a new way for bistable composite structures to acquire wind energy widely in natural environments. [Display omitted] [ABSTRACT FROM AUTHOR]

The woven composite twisted structure under cantilever load is studied using experimental and multiscale numerical methods. The uncertain geometry parameters inside the twisted specimen are identified using Micro-CT scanning technology, and quantified using multivariate Gaussian random field theory. A high-fidelity meso-Representative Volume Cell (RVC) database after data clustering is established using these uncertainties, in which the warp and weft yarns are no longer regular orthogonality, the yarn cross-sectional area and the yarns gap exhibit variability. The statistical uncertainty quantification and propagation are further integrated into the coupled Finite Element-Fast Fourier Transformation (FE-FFT) concurrent multiscale method to reveal the damage and failure mechanisms of the woven composite twisted structure. The numerical results are in good agreement with the experiment results. This study can be helpful of designing the woven composite blade structures. [Display omitted] [ABSTRACT FROM AUTHOR]