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AbstractAfter lower limb amputation, the primary challenge is to facilitate the patient’s adoption of a prosthetic limb seamlessly, without encountering complications or discomfort. Elevated stress levels within the residual limb, experienced when wearing the socket and while standing or walking, contribute to patient discomfort. As an initial step in this study, we developed a finite element model of above-knee amputation. Additionally, we designed a prototype orthopedic implant composed of several parts, with the lower section featuring a honeycomb structure aimed at absorbing and diminishing stresses at the interface of the residual limb and prosthetic. In this study, finite element models with and without orthopedic implants were analyzed to assess the feasibility and impact of incorporating a honeycomb structure within the implants on stress distribution, particularly at the stump-prosthetic interface. Models with honeycomb-structured implants, at varying densities, showed a reduction in interface stress to approximately 2.15e-2 MPa and 2.01e-2 MPa, compared to 4.5e-2 MPa in model without honeycomb structure in the implant and 7.97e-2 MPa in models without any implants. [ABSTRACT FROM AUTHOR]

AbstractTo enhance the performance of the six-missing rib honeycomb (ASRH), two axisymmetric missing rib honeycombs, ASRH-1 and ASRH-2, are proposed in this study. First, the in-plane impact performance of ASRH, ASRH-1, and ASRH-2 is experimentally compared to verify the accuracy of the finite element model. Then, the deformation patterns, specific energy absorption (SEA), and negative Poisson’s ratio (NPR) effects of the three honeycombs under different parameters were parametrically investigated. The results indicate that ASRH-1 and ASRH-2 exhibit higher SEA than ASRH at an impact velocity of 10 m/s, but the NPR effect does not change significantly. The axisymmetric honeycomb demonstrates no advantage at 50 and 100 m/s high-speed impacts. The Poisson’s ratio effect of the three honeycombs varied greatly with the internal ligament r of the honeycomb. The axisymmetric design offers a new concept for a NPR honeycomb design. [ABSTRACT FROM AUTHOR]

The excellent shape stability of thermally expanded metamaterials and the good bandgap properties of acoustic metamaterials have a wide range of promising applications in aerospace and sensors. Here, a bi-material-directional honeycomb metamaterial (BHM) with tunable coefficient of thermal expansion (CTE) and bandgap properties is proposed. The theoretical analysis and numerical simulations are employed to reveal the thermal deformation mechanism of the BHM. In addition, the analytical expression of the effective Young's modulus is established by considering both tensile and bending deformation. Based on the Bloch theorem, the band structures of the BHM are calculated by the finite element method. Parameter analysis confirms that the CTE and bandgap of the BHM can be simultaneously regulated and drastically adjusted by changing the geometric parameters and material combinations. Meanwhile, the coupling relationship of the effective CTE, Young's modulus, and total effective bandgap width are investigated. The results show that the BHM can have tunable CTE function and large total effective bandgap width by selecting suitable parameters while satisfying stiffness requirements. This study achieves a dual objective of specific CTE properties and bandgap design through rational material selection and shape design, which makes the metamaterials have better tunability and multifunctionality. [ABSTRACT FROM AUTHOR]

Sandwich structure is one of the blasts protecting and energy absorbing materials with different types of light weight cores. This article aimed at investigating blast response of hexagonal honeycomb sandwich structure having perforations along the cell height of core over conventional honeycomb cores. The study discussed the mechanics of deformation behavior of perforated sandwich structure to improve the energy absorption characteristics of the bare honeycomb core sandwich structure. Detailed numerical analysis is conducted to accurately produce the deformation process with finite element analysis using explicit software LS-DYNA®. Blast load resulting from 1 kg TNT on the sandwich structure is applied using Conventional Weapons Effects Program (ConWep) function available in LS-DYNA. Several different parameters consisting of varying sizes of perforation by changing d/l ratio, shape, number of perforations and different facesheet and backsheet thicknesses, and different scaled distances are investigated in detail. The results indicated that both size and shape and number of perforations have significant influence on reduction of blast impulse. The variation of facesheet and backsheet thicknesses without changing the overall thickness of the structure also has evident effect in blast resistance capability of perforated honeycomb sandwich structure. The blast mitigation and energy absorption capacity of honeycomb core sandwich structure can be improved with the provision of perforations and optimizing the arrangement of holes. The perforated honeycomb core is further investigated based on analytical formulation developed using single degree of freedom (SDOF) system analysis approach. Optimization study is done further to get the best configuration based on different design variable limits. [ABSTRACT FROM AUTHOR]

In this paper, the energy absorption capacity of continuous fiber-reinforced thermoplastic auxetic structures is examined experimentally and the results compared with both numerical and analytical methods. To this extent, a 3 D printing technology of Fused Deposition Modeling (FDM) is implemented for fabricating the auxetic honeycombs and quasi-static compression test is conducted to extract the load-displacement behavior of the structure. Both hollow and foam filled lattice structures are tested, and the results revealed that the absorbed energy increased by 20% for PLA and 70% for PA specimens, when using foam. Finite element analysis is also performed using the explicit solver. The onset of failure is determined using the maximum stress criterion and VUSDFLD subroutine and the damage growth is modeled by decreasing the mechanical properties of the elements. The obtained results are in relatively good agreement with the experimental analysis. In addition, a theoretical formulation is developed and the probabilistic analysis is performed to draw the honeycomb failure design envelope, which is a practical tool for designing of various honeycomb configurations. The failure envelope shows that decreasing the strut angle increases the honeycomb failure load, however, the auxetic property of the structure decreases. [ABSTRACT FROM AUTHOR]

The special energy-absorbing structure of beak protects the head of woodpecker from being hurt when pecking tree. Inspired by the micro wavy structure of the woodpecker beak, a novel bionic sinusoidal honeycomb is proposed and its crashworthiness performance is analyzed. Results show that the bionic sinusoidal honeycomb produces more folds than the conventional honeycomb under the same mass conditions, which greatly improves the energy absorption effect. Compared with the conventional honeycomb, although the initial peak crushing force of bionic sinusoidal honeycomb is generally higher (the change ranges from −1.64% to 11.84%), the specific energy absorption of all bionic sinusoidal honeycombs is much better (the increase ranges from 30.12% to 80.99%). Moreover, the bionic sinusoidal honeycomb has a better crush force efficiency when the amplitude is small. A comprehensive comparison of the impact resistance of the bionic sinusoidal honeycomb and conventional honeycomb shows that the proposed bionic sinusoidal honeycomb has better energy absorption and application scalability than the conventional honeycomb. A novel bionic sinusoidal honeycomb (BSH) is proposed based on woodpecker beaks The impact resistance of BSH is systematically studied using finite element analysis. Its specific energy absorption (SEA) can increase by 80.99% compared to conventional honeycomb. The SEA of BSH increases as the wall thickness increases, but it is weakly related to the amplitude and the wavenumber. [ABSTRACT FROM AUTHOR]

The structure of non-pneumatic tire is complex and various, but its performance is superior to ordinary tire, so it has broad prospects. In this paper, a design method of honeycomb structure was proposed based on tangent method, and the hexagonal and circular honeycomb structure were established. The rules of displacement, radial stiffness and ground pressure of honeycomb structure with different density were studied. Meanwhile, the most basic bearing performance of non-pneumatic tire was analyzed by finite element method under static conditions. The results show that the radial stiffness of honeycomb increases with the increase of density. When the density is small, the bearing capacity of circular structure is stronger than that of hexagonal structure, the ground pressure decreases with the increase of density and the maximum stress of the two is located on the honeycomb structure. When the density is high, the maximum stress is on the contact surface between the rim and the inner circumference. This study provides a reference for other types of non-pneumatic tire structure design and builds the foundation to study contact performance analysis of non-pneumatic tire under complex working conditions. [ABSTRACT FROM AUTHOR]

It is of great essence to unveil relationship between structure, mechanical properties, and application of bionic design. Targeting at alleviating the debonding failure issue in the internal structures of the wind turbine blade, the reversed-semi-reentrant (RSRE) honeycomb and the angular gradient (AG) honeycomb with zero Poisson's ratio are considered in the design of the spar/shear web structure. Through finite element methods, the mechanical behaviors of these two types of honeycombs were compared to that of the hexagonal honeycomb. The ability of the RSRE honeycomb to reduce the shear stress on the skin–core interface is proved. The AG honeycomb also proves to have advantages in improving the shear stress distribution inside the honeycomb. Then, the RSRE honeycomb and the AG honeycomb are assembled together to build a complete model of spar/shear web structure. The results of simulations of the whole model under different loading conditions show that these two honeycombs have effectively promoted the mechanical behaviors of the whole model. [ABSTRACT FROM AUTHOR]

An analytical method is proposed to determine the displacements of a composite cylindrical shell with auxetic honeycomb core layer and variable thickness under combined axial, internal, and external pressures. The thickness and pressure profiles can be arbitrary continuous functions. The displacements are defined in the framework of the first-order shear deformation theory. The composite shell consists of three layers, in which the inner and outer layers are isotropic and the core layer is made of an auxetic honeycomb material. The constitutive equations obey the Hooke law. The equilibrium equations which are a system of coupled differential equations with variable coefficients are extracted by employing the virtual work principle, and they are solved using the matched asymptotic expansion method of the perturbation technique. The effects of different parameters such as the geometry, honeycomb structure parameters, different load profiles, and the thicknesses on the results are studied. The results are compared with the finite element method and some other references. [ABSTRACT FROM AUTHOR]

Honeycomb structure containing curved reentrant sides with negative Poisson's ratio (NPR) was designed and the impact dynamics behaviors were studied by finite element method. The Poisson's ratio and the energy absorption capacity of the honeycomb structure with different arc angle were studied under different compression velocities. The results show that the Poisson's ratio of the honeycomb structure can reach −0.373 with arc angle of 180°. The energy absorption capacity of the honeycomb structure increased with an increasing compression velocity, and the deformation mode changed from X type to V type and I type. When the compression velocity is low, the dynamic response curve of the honeycomb structure with arc angle of 180° has the characteristics of two-stage plateau region. When the compression velocity is high, the energy absorption capacity of the honeycomb structure increased with an increasing arc angle. When the arc angle is higher than 120°, the honeycomb structure has NPR effect, and the energy absorption capacity of the honeycomb structure is better than the honeycomb structure with other arc angles. [ABSTRACT FROM AUTHOR]

An appropriate finite element model is developed to simulate the high velocity impact of projectiles on polyurethane foam filled aluminum honeycomb. First, the numerical model of the high velocity impact of the projectiles on the empty aluminum honeycomb is developed using a strain rate dependent material model. A VUMAT subroutine including two different fracture criteria proposed by researchers is developed. The fracture criterion that shows similar behavior to experimental observations, is selected. The numerical model of the projectiles impact on the foam-filled honeycomb is compared with available experimental results, and the ballistic limit velocities are predicted with good accuracy. [ABSTRACT FROM AUTHOR]

Miura-ori core sandwich structures have aroused considerable research interests as a potential alternative to conventional honeycomb sandwich structures due to various superiorities, e.g., open channels and continuous manufacturing process. Although quasi-static or impact mechanical behaviors have been extensively studied, modal response of Miura-ori core sandwich structures has not been investigated yet. In this paper, carbon-fiber-reinforced Miura-ori core sandwich panels (MSPs) were fabricated with an autoclave processing method. Modal tests were carried out to investigate the structural vibration performances. A finite element analysis of MSPs was developed and validated with the tests results. Fiber orientation influences of both face sheets and core on the natural frequencies were investigated. Furthermore, a parametric study on the modal response of various MSPs models subjected to virtual free vibration was performed, through which the relationships between the fundamental frequencies and the geometric parameters were established. Compared with corrugated core sandwich panel under identical dimension and weight, MSP always possesses higher fundamental frequency, with an increase of 11.7% in the optimum case. It indicates that MSP is much stiffer and could be designed even lighter in aerospace applications. [ABSTRACT FROM AUTHOR]

Understanding the dynamic behavior of cellular foam is essential for designing anti-collision structures. In this work, the rate-sensitivity of cellular foam was analyzed on dynamic experiments of split Hopkinson pressure bar and finite element methods (FEM). A typical circular ring structure is introduced in the FEM analyses to estimate the effects of the post-buckling behavior of cell walls on the properties of stress enhancing as the strain rate increases. The quadrilateral/circular honeycomb foam structure is used to estimate the contribution of micro-structure and matrix effects. These results show that the post-buckling of a micro-structure is an important rate-sensitivity factor. [ABSTRACT FROM PUBLISHER]