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In this paper, an equivalent model on coefficient of hygrothermal expansion for composite layer and a multi-scale model for calculating the strain and stress of composite plates are proposed. These two models also can be applied to thermal expansion problems and guide the structure design of the composite materials. A model descripting the coupling behavior of moisture diffusion and stress in composite laminates is proposed based on the second Fick’s law. Compared to other models, this model can accurately predict the anomalous behavior in the process of moisture absorption. A number of experiments and finite-element simulations are conducted to validate this model. A comparison of the model’s predictions with experimental data shows a good agreement. [ABSTRACT FROM AUTHOR]

Abstract: This paper develops a multi-stable lattice structure consisting of tri-stable lattice cell which is made by bistable laminates. The multi-stable lattice structure with N tri-stable lattice cells, which can exhibit 2 N stable states, is successfully designed and fabricated. The critical loads snapping lattice structure are investigated by the experimental and finite element techniques. The method to simulate the behaviors of contact and constraint between the neighboring bistable laminates are presented. The snap through process of multi-stable lattice structures among multiple states are numerically simulated and experimentally validated. The multiple stabilities highlight the potential to achieve a smooth shape variation in the large area multi-stable structures. [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]

Bi-stable composite laminates with piezoelectric transducers have been shown to capture energy over a wide frequency range and deliver significantly greater energy than resonant devices. In this work, the influence of lay-up design on the performance of bi-stable piezoelectric energy harvester (BPEH) based on bi-stable hybrid symmetric laminate (BHSL) is analyzed and verified. The initial voltage induced by stable configuration and longitudinal curvature of BPEH with different lay-up and hybrid width were calculated and analyzed by a static finite element analysis. The lay-up can vary initial voltage and longitudinal in opposite directions, and hybrid width can adjust these two variables in the same direction. The strain variations of piezoelectric transducer between two stable configurations were also analyzed. The initial voltage of BPEH depends on strain variations in the two directions. And then the finite element results are verified by experiment. Three types of BPEH were manufactured and actuated by two methods to measure their output powers. These BPEHs presented different dynamic responses, and the output powers under different vibration modes were measured. The highest output power of BPEH in this work is 42.2 mW and the highest power density is 78.1 mW/cm 3 . [ABSTRACT FROM AUTHOR]

Bistable composite laminates have the potential advantage in the fields of wind energy harvesting and deformable wings, which involve many fluid–structure interaction issues. This paper presents the fluid–structure interaction analysis of a cantilevered bistable hybrid symmetrical laminate (BHSL) in the uniform wind. In this work, a finite element model based on the Lattice Boltzmann Method (LBM) is used to analyze the wind-induced response of the BHSL and its variations with respect to wind speed and laminate length. Then, the wind-induced vibration behavior of BHSL is verified by wind tunnel tests. The finite element analysis (FEA) results are in good agreement with the experimental results. The results show that as the wind speed increases, the BHSL transitions from a single-well vibration response to a cross-well vibration response. The wind-induced vibration analysis of BHSL will provide analytical methods for its application in deformable wings and energy harvesting for wind-induced vibration. [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 mechanical behaviors of the twisted profiled textile composite structures with different twist angles were studied by using a novel cantilever beam experiment. The strain distributions on the upper surface of the specimen were monitored by using DIC. Several strain gauges were located at different positions on the lower surface of the specimen. With the increase of cantilever load, the deformation of twisted specimen experienced from the initial torsion to the bending-torsion coupling deformation. The effects of twist angles on stiffness and strength of the twisted composite structures were analyzed. The stiffness distributions of the twisted composite structures are determined by using the finite element analysis (FEA) combining with the experimental results. There is a cubic polynomial function relationship between the macroscopic local twisted angle and the local material stiffness. The stiffness and strength of 135° twisted specimen are higher than that of 45°twisted specimen. The dominant failure mode was the compression fracture at the edge of the lower right corner of the twisted specimen. This study can be helpful of guiding the design of the twisted profiled textile composites structures. [ABSTRACT FROM AUTHOR]

The quasi-zero-stiffness (QZS) vibration isolator is usually composed of positive and negative stiffness elements in parallel. The negative stiffness element usually requires specific constraint boundaries to form negative stiffness characteristics, which cannot meet the lightweight design of spacecraft structures. So the bi-stable hybrid symmetric laminate (BHSL) is presented as a negative stiffness element. A finite element model (FEM) is developed to carry out static and dynamic analyses of this vibration isolator. An equivalent theoretical model is developed based on the restoring force–displacement curve of BHSL. The approximate analytical solutions and direct numerical solutions are obtained by employing the averaging method and the Runge-Kutta method, respectively. Different types of the steady-state response are obtained, namely the symmetrical multi-harmonic response, the asymmetric multi-harmonic response and the single-harmonic response. There exists a small gap between the analytical solutions and the Runge-Kutta solutions or the FEM results only at the low frequency excitation due to the super-harmonics. The displacement transmissibility is used to quantify the vibration isolation performance of this vibration isolator. The experiment is designed to verify the theoretical and FEM models from static and dynamic analysis perspectives. The results show adjusting geometric parameters and lay-up designs can improve the vibration isolation performance. [ABSTRACT FROM AUTHOR]

Tool-part interaction during the manufacture of the bistable composite shells with initial curvature is inevitable, which has a noticeable influence on stable configurations. The effect of tool-part interaction is considered by introducing a shear layer whose parameters are determined by a series of experiments. This paper develops an analytical model with shear layer effect based on the Rayleigh-Ritz model to capture the configuration variation with bistable composite shell with initial curvature. The model reveals the rule of curvature change in different radii and plies, which provides a criterion for the existence of bistability. The results show tool-part interaction has a significant influence on thin bistable composite shells with initial curvature whose prediction accuracy is improved. The analytical predictions are verified by results based on the experiments and finite element models. Moreover, the influences of initial radius, cross-section angle, stacking sequence, and twisting response are analyzed. The twist behavior of two stable configurations is investigated, which can provide a guide for designing the bistable composite structures. [ABSTRACT FROM AUTHOR]