This work investigates the dispersion characteristics and bandgap behavior of periodic carbon fiber/graphene platelet (GPL) hybrid composite curved beams. The material properties of the multi-phase hybrid composite are determined via a two-step micromechanical homogenization scheme, accounting for the GPL distribution patterns and fiber reinforcement. Based upon the Timoshenko beam theory and the Bloch theorem, an exact dynamic stiffness model along with transfer matrix formulation is developed to obtain the dispersion equation. The proposed computational model is verified by published results. The influences of curvature, carbon fiber content and orientation, GPL weight fraction and distribution type, as well as opening angle on the wave attenuation and bandgap formation are systematically investigated. Numerical results demonstrate that curvature-induced modal coupling plays a significant role in generating low-frequency bandgaps, while the tailored GPL distribution patterns and carbon fiber reinforcement enable effective bandgap tuning. Increasing the carbon fiber volume fraction from 40 to 70
The transient thermomechanical response of a hollow electrically conductive non-ferromagnetic cylinder subjected to pulsed electromagnetic excitation is investigated. The electromagnetic action is considered through two coupled physical mechanisms associated with induced currents: Joule heat generation and ponderomotive forces. Accordingly, the dynamic stress tensor is decomposed into thermal and electromagnetic contributions, allowing the individual influence of these mechanisms on the evolution of the stress state to be quantified. The temporal variation and through-thickness distribution of the stress tensor components generated by Joule heating and ponderomotive forces are analyzed. It is demonstrated that the ponderomotive contribution governs the initial stage of electromagnetic excitation, whereas the thermal contribution associated with Joule dissipation becomes dominant at later stages due to the accumulation of temperature-induced stresses. The relative contributions of both mechanisms to the total stress state are evaluated. The intensity of the combined dynamic stresses is determined, and the operational reliability of the considered hollow cylinder under pulsed electromagnetic loading is assessed using the Huber-Mises criterion. The obtained results provide insight into the transient interaction between electromagnetic forces and thermal effects in conductive cylindrical structures and establish the conditions governing their mechanical response under pulsed electromagnetic excitation.
Bio-inspired flexible wings have potential applications in high-speed aerodynamics; however, the compliance and irregular geometry of bio-inspired flexible wings pose new challenges for aeroelasticity and mechanics-based design. In this paper, a unified polygonal finite element method (PFEM) framework for the analysis and mechanics-based design of bio-inspired flexible wings in the supersonic flow regime is proposed. A shear-locking-free polygonal Reissner–Mindlin model is formulated based on Wachspress and piecewise linear shape functions to describe complicated wing geometry efficiently. The geometric nonlinearity, continuum damage, temperature-dependent material behavior, aerothermal transients, and supersonic aerodynamic loads are taken into account in the computational formulation. Second-order piston theory is used to obtain the aerodynamic pressure, and the aerodynamic influence coefficients are calculated based on velocities and displacements of the structure. In order to validate the obtained results, the proposed PFEM framework is benchmarked against available analytical solutions, existing experimental results, and also finite element (FE) simulation conducted separately for the present problem. The results show very good correspondence, thus proving the accuracy and reliability of the proposed approach. Numerical simulations of square, dragonfly-like, and trapezoidal wings prove the ability of the framework to predict geometry-specific aeroelastic properties of such structures. Critical flutter velocities span from 295.5 m/s for the stigma-less dragonfly-like wing to 496.5 m/s for the reinforced modified trapezoidal wing. The proposed framework presents an effective numerical technique for assessing aeroelastic properties of bio-inspired flexible wings under supersonic flight conditions.
A key challenge in soft robotic arm design is reconciling large deformation with sufficient load-bearing capacity. Multistable structures offer both high stiffness and substantial shape change, yet their mechanical properties are fixed after fabrication. To address this, this work proposes an origami-based pneumatic skeleton with tunability of multistability and stiffness. By integrating flexible pneumatic bellows into a multistable origami module, internal pressure can be modulated to tailor the energy landscape, thereby altering the number of stable states and continuously adjusting load-bearing capacity. A multibody dynamics model is developed, incorporating geometrically exact shell elements, revolute joint constraints, and shell-to-shell contact, complemented by an energy analysis that decomposes total potential energy into origami strain energy and airbag stored energy. Simulations show that increasing internal pressure from 1.0 to 1.6 atm eliminates the potential well of the folded configuration, enabling a controlled bistable-to-monostable transition. When integrated into a multi-module robotic arm, the pneumatic skeleton exhibits configuration-dependent stiffness: in the unfolded state, stiffness increases monotonically with pressure, yielding a 6.5-fold enhancement from 1.0 to 1.9 atm; in contrast, the folded and bent states display a counterintuitive non-monotonic trend, governed by the competition between intrinsic stability and cable-mediated stabilization. The proposed pressure-tunable multistable skeleton demonstrates feasibility for stiffness regulation in soft robotic arms, suggesting its potential for stiffness adaptation in complex and unpredictable environments.
As power grids demand higher capacity and efficiency, aluminum conductor composite core (ACCC) cables have become increasingly important. However, the reliability of these conductors depends on the structural integrity of their internal composite cores, where hidden defects are difficult to detect due to electromagnetic shielding by surrounding aluminum conductors. This paper proposes a magnetic coating interlayer integrated into the composite core to enable electromagnetic detection of internal defects. The coating enhances the magnetic permeability of the core, improving sensitivity to defect-induced field variations measured by an external sensor. The sensor configuration was optimized through electromagnetic analysis to maximize detection capability. The magnetic coating, composed of epoxy resin and magnetic particles, was further optimized by evaluating signal-to-noise ratio (SNR) and adhesion strength. Numerical simulations, cross-cut adhesion tests, and Pareto analysis were conducted to identify the optimal balance between sensitivity and durability. Experimental validation using a coated composite core embedded in an aluminum pipe confirmed the effectiveness of the proposed method. This technique provides a practical solution for both pre-installation and in-service defect monitoring of ACCC composite cores.
