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Excessive vibration has always been a serious problem for conical shell structures, while the application of the graphene-based free-constrained layer (GFCL) based on carbon fiber-reinforced composite (CFRC) structure is a novel way to improve structural performance. An analytical model for vibration and dynamic characteristics of the GFCL-CFRC conical shell resting on the Winkler–Pasternak elastic foundation with arbitrary boundary conditions is constructed, and four types of GFCL porosity distribution and GFCL dispersion pattern are considered in this model. The multi-segment technique and virtual spring technique are utilized to simulate arbitrary boundary conditions. Then, the first-order shear deformation theory (FSDT) and Hamilton's principle are employed to obtain the motion equation of the GFCL-CFRC conical shell, and the motion equation of the GFCL-CFRC conical shell is solved by the Ritz method. In conclusion, the dispersion mode of GFCL, thickness ratio of GFCL, and fiber angle have influence on the dynamic performance. With a reasonable design, the dynamic performance of the GFCL-CFRC conical shell can be further improved. [ABSTRACT FROM AUTHOR]

A lumped parameter model is constructed to accurately predict the dynamic degradation characteristics of the fiber-reinforced composite sheet based on the thermal vibration measurement data. In the modeling process, a multiple-lumped-mass division technique is adopted along the longitudinal and width directions with consideration of thermal degradation on the connective stiffness and damping matrix. By solving the natural frequencies and vibration responses of the structure, a determination method for the key parameters of the model, such as the additional thermal stiffness matrix, the connective stiffness, and the damping coefficients, is proposed. In addition, the constructed model is verified by comparing the theoretical natural frequencies and vibration responses with the experimental results at different degradation time points and temperatures, and the calculation errors are within an acceptable range. Both the theoretical and experimental results reveal a gradual weakened downtrend of natural frequencies and a firstly increasing and then decreasing resonant response phenomenon. Also, some possible reasons for the above complex dynamic degradation phenomenon are provided. [ABSTRACT FROM AUTHOR]

• The equivalent model of the MRE-filled corrugated structure is obtained by employing the representative volume element (RVE). • The governing motion equations of the sandwich plate are derived via the first-order shear deformation theory (FSDT). • Based on the modified Fourier series and the Rayleigh-Ritz method, the energy functions of the sandwich plate are solved. The main barrier to the application of corrugated structures in vibration suppression is their low loss factor. The use of magnetorheological elastomer (MRE) as a novel type of smart material has the potential to improve the energy dissipation capacity of the corrugated structure. In this study, the dynamic behavior of the corrugated composite sandwich plate filled with MRE resting on elastic foundations is investigated. The equivalent model of the MRE-filled corrugated structure is obtained by employing the representative volume element (RVE). Then, the governing motion equations of the sandwich plate are derived via the first-order shear deformation theory (FSDT). Based on the modified Fourier series and the Rayleigh-Ritz method, the energy functions of the sandwich plate are solved. In this work, the analysis of geometric parameters, loading type, and magnetic field on the dynamic behavior of the corrugated sandwich is conducted. Numerical results show that increasing the magnetic field intensity, stiffness of boundary, and elastic foundation improves the dynamic performance of the structure. This reveals that the response behavior of the structure is significantly affected by the magnetic field intensity, as well as the stiffnesses of the boundary and elastic foundation. [ABSTRACT FROM AUTHOR]

• A novel class of sandwich shallow shell reinforced by the GPLs-FGP is proposed. • The structural thermal stability is improved by embedding the SMA wires. • The dynamic behaviors of the sandwich shallow shell are analyzed by using the Jacobi-Ritz method. • The hygrothermal loading model is constructed by using the energy method. In this research, the dynamic analysis of graphene platelets (GPLs) reinforced functionally graded porous (FGP) sandwich shallow shell embedded shape memory alloy (SMA) wires with general boundary conditions under hygrothermal loading is conducted. Four different porosity distributions of FGP reinforced with four various GPLs dispersion patterns are considered. Based on the Brinson formulation, the constitutive equation of the SMA is established. The energy functional of the sandwich shallow shell is constructed by employing the Hooke's law and the first-order shear deformation theory (FSDT). Ultimately, the dynamic characteristics of the sandwich shallow shell are obtained by solving the energy functional with the Rayleigh-Ritz method. After the verification of accuracy and reliability, parametric studies on the effects of material properties, geometrical parameters, and boundary conditions are investigated. [ABSTRACT FROM AUTHOR]

• The FGP design shows good regulation on the structural resonance frequencies. • The FGP-VSC sandwich plate shows high stiffness and high damping capacity. • A stable performance increasing interval can be determined by the core size. • The FGP-VSC sandwich plate shows better robustness to the boundary variations. The dynamic characteristics of functionally graded porous (FGP) sandwich plates with viscoelastic material-filled square‐celled core (VSC) are investigated based on the constructed sandwich plate model. The dynamic model is built by combining the first-order shear deformation theory, the equivalent theory of material mechanics, the virtual spring technology, the modified Fourier-Ritz method, and the Newmark-Beta approach. Furthermore, the model validation is conducted, including the convergence study and the numerical validation under different geometrical parameters, material parameters, and boundary conditions. With the validated model, the parameter analysis is conducted to investigate the influence of the porous types, geometrical parameters, structure types, boundary conditions, and load types on the dynamic performance of the FGP-VSC sandwich plate. [ABSTRACT FROM AUTHOR]

Based on the interesting Janus-type all- cis 1,2,3,4,5,6-hexafluorocyclohexane (1) molecule, a novel type of excess electron compounds MF- 1 -MH (MF = Li, Na and K, MH = Zn, Cd and Hg) were designed theoretically. The geometric structures, electronic structures and nonlinear optical properties of MF- 1 -MH compounds were studied by density functional theory. Our results show that in Li- 1 -MH, the obvious charge transfer between Li and MH can be observed while in Na/K- 1 -MH, the charge transfer between Na/K and MH is negligible. Particularly, the MF- 1 -MH exhibit remarkable nonlinear optical (NLO) response and the first hyperpolarizability of the K- 1 -Zn almost achieve 1.0 × 106 au. We hope this work will further enrich the family of excess electron compounds, so that more experimental interests and efforts can be attracted to propose and synthesize new excellent NLO materials. Table of contents synopsis: A novel type of NLO compounds which were designed by using transition metal atoms (Zn, Cd and Hg) and alkali metal atoms (Li, Na and K). [Display omitted] • A novel type of excess electron compounds using Group 12 elements (Zn, Cd and Hg) with large nonlinear optical responses is proposed. • Using the electron localization function (ELF), localized orbital locator (LOL) and Independent gradient model (IGM) methods to study the electronic structures of proposed compounds. • The low transition energies can lead to high nonlinear optical responses. [ABSTRACT FROM AUTHOR]

A unified modeling method is proposed in this work to obtain the exact solution for dynamic analysis of carbon fiber reinforced composite (CFRC) circular arche with porous graphene platelet coating (PGPC) and general boundary conditions in hygrothermal environment. The modeling method adopts first-order shear beam theory to express the displacement field of the in-plane vibration first, and then the stress is given by using Hooke's Law. According to the definition of classical mechanics, the energy of dynamic model is expressed in terms of stress and strain. Also, the stored energy of general boundary is introduced by the virtual boundary springs technology. Furthermore, the hygrothermal environment is also considered in this work, and the effects of the hygrothermal environment are given in details. Finally, the stability and effectiveness of proposed method are validated, and the dynamic response of the CFRC-PGPC circular arche with different parameters, such as geometry, material and environment variables are calculated. [ABSTRACT FROM AUTHOR]