Honeycomb Walls Research Articles

Quantitative reconstruction of debonding in ultra-thin honeycomb sandwich panel based on noncontact thermoelastic laser tapping

Aluminum skin honeycomb sandwich panels (HSPs) are commonly used in aerospace structures. Conventional contact-based detection methods may scratch the skin surface or result in couplant immersion, and thus a novel quantitative, baseline-free, and noncontact laser tapping (LT) algorithm is proposed to detect the debonding in the aerospace HSP with an ultra-thin 0.3 mm thick skin and a 0.04 mm thick honeycomb wall. The algorithm features an LT C-scan imaging with a baseline-free debonding index, followed by an image processing-based reference-reconstruction quantification algorithm. The numerical results validate the robustness of the proposed algorithm against strong noises with an average accuracy over 99 %. Experimentally, the proposed algorithm shows the detectability of a single debonding wall not fulfilled with the conventional contact ultrasound, and the accuracies of 90.80 % and 95.81 % experimentally in quantifying two types of debonding defects are achieved, spotlighting the application potential of the proposed technique to noncontact HSP debonding detection.

Multi-functional additively constructed honeycomb walls for housing and sheltering

Honeycomb designs have become increasingly popular in additive manufacturing due to their great mechanical properties. The honeycomb infill pattern has allowed the creation of lightweight objects without sacrificing the strength of solid objects. Honeycombs have been utilized in different applications, including architecture, aerospace, and automotive. However, there is a lack of honeycomb designs within the construction industry. With the growth of concrete additive construction, there is an opportunity to introduce honeycomb designs into construction practices. This paper proposes a methodology for manufacturing multi-functional walls through additive construction. The methodology includes several key steps, from material development and quality control testing to wall assembly and experimental investigation. Two multi-functional wall segments were additively constructed, reaching a height of 1180 mm, a width of 610 mm, and a thickness of 90 mm. These measurements led to the manufacturing of seven distinct cellular sections per wall, comprising three main, two intermediate, and two end cellular units. In addition, a columnar unit was additively constructed for corner connection, featuring two vertical octagonal cells with end brackets. A preliminary wall system made up of honeycomb wall segments was assembled using various additional materials such as sealant, clamping systems, and insulative materials. Furthermore, an additional wall segment with end connections was designed and manufactured to test its load-carrying capacity. The wall segment performed well compared to wooden stud walls and showed sufficient load-carrying capacity. Unlike traditional un-reinforced concrete structures, which are brittle and experience small plastic deformations before failing, the honeycomb wall structure experienced large plastic deformation before failure due to the use of insulation foam and silicon rubber. The preliminary testing showed that the honeycomb wall system could be an alternative to traditional housing construction, especially for shelters.

Study on the Dynamic Crushing Behaviors of Hourglass Honeycomb Sandwich Panels

In response to the problem of enclosed internal spaces in existing honeycomb sandwich panels, the concept of an hourglass honeycomb sandwich panel model is proposed for the first time, which provides a breakthrough approach for achieving the multifunctional integration of honeycomb sandwich panels. Numerical simulation methods are employed to investigate the dynamic performance of the hourglass honeycomb sandwich panels. The focus is on discussing the influences of the geometric parameters on the deformation mode, dynamic response, load uniformity, and energy absorption capacity of the hourglass honeycomb sandwich panel under different impact velocity conditions. The research results indicate that under low-velocity-impact conditions, the influence of the geometric parameters is predominant. In contrast, under high-velocity-impact conditions, the influence of the impact velocity conditions is predominant. Hourglass honeycomb sandwich panels with low density, a large inclination angle of the honeycomb wall, and small contact distances between the hourglass honeycomb cell and the panel have excellent load uniformity, and the distances between the contact points of the hourglass honeycomb cell and the panel have a great influence on the energy absorption capacity of the sandwich panels. This study provides a theoretical basis for the application of honeycombs in aerospace and other engineering areas.

Research on the equivalent stretching mechanical properties of Nomex honeycomb core considering the effect of resin coating

Abstract In this article, the equivalent elastic modulus of the resin-impregnated Nomex honeycomb core is derived by considering the bending and stretching deformation of the honeycomb wall, based on the Euler beam theory. The elastic modulus obtained by the proposed theoretical method is proved to be in good accordance with both the experimental results and numerical results. Furthermore, the effect of the geometric parameters on the equivalent mechanical properties of the honeycomb core is discussed using a dimensionless method.

Influence of feed entrance angle on transverse tearing burr formation in the milling of superalloy honeycomb with ice filling constraint

In the end milling of superalloy honeycomb cores, the contact form between the cutting tool and honeycomb wall and the force state of the honeycomb wall are variable, there will be difficulties in chip removal. The irregular extension of transverse tearing burrs can deteriorate the machining quality of honeycomb core surfaces, thereby adversely affecting the assembly and service performance of sandwich structures. Based on kinematic analysis, modeling of the removal and deflection process of honeycomb walls was conducted. The feed entrance angle in the case of machining thin walls with high feed speeds was characterized, and the force state of the honeycomb wall and the degree of shear or compression it bears were analyzed. Analytical models of damage scale and single-tooth cutting state were established under different feed entrance angles. The impact of feed entrance angle on the minimum burr length and the minimum constraint failure width was analyzed. The milling experiments of GH4099 superalloy honeycomb wall with ice filling constraint were designed and conducted to clarify the influence of different feed entrance angles on cutting force and transverse tearing burr length. The morphology of burrs and the wear form of the cutting tool were analyzed, and the formation mechanism of transverse tearing burr on the honeycomb sidewalls was revealed. The research results indicate that the feed force Fx is 2.1 to 4.7 times greater than the main force Fy or the back force Fz. When the feed entrance angle is <90°, transverse tearing burrs either do not occur, or occur crimped burrs that are gradually removed. Particularly within the range of 0° to 30°, the machining quality is better. The cutting force has a significant shearing effect on the honeycomb wall, making it susceptible to plastic deformation and reaching the fracture strain. The cutting edge can effectively remove material from the honeycomb wall, resulting in normal wear on the minor flank face and tip of the cutting tool. When the feed entrance angle is greater than 90°, it is easy to form large banded burrs, and the burr length is relatively similar to about 1500 μm. The cutting force has a significant extrusion effect on the honeycomb wall, resulting in minimal deflection deformation of the honeycomb wall, and making it difficult to fracture. The cutting tool fails to perform effective cutting, leading to increased friction between the cutting tool and honeycomb wall, which continuously induces irregular extension of the burrs. The research findings are of great significance for achieving damage control in metal honeycomb core machining and guiding process and clamping optimization.

Hybrid honeycomb structure for enhanced broadband underwater sound absorption

A hybrid honeycomb structure (HHS) with energy dissipation enhancement effect is proposed for broadband underwater sound absorption. The HHS is constructed using hexagonal honeycomb structure with embedded metal rings of different size and filled with viscoelastic rubber. A theoretical model is developed to study the sound absorption performance of the HHS by applying the transfer matrix method, and a finite element model is also developed to validate the theoretical model. The innovative introduction of metal rings concentrates rubber vibrations near the ring edges and within conical regions formed by the ring holes and the longitudinal waves in the rubber are converted into transverse waves, these vibrations increase the friction within the rubber at the rubber-metal interface, which significantly increases the friction loss at the rubber-metal interface, thus increasing the dissipation of acoustic energy. Compared to the homogeneous rubber layer and the rubber-filled honeycomb wall structure, the average increase in energy dissipation is 238 % and 181 %, respectively. The results of the energy dissipation distribution of the HHS confirm that the energy dissipation is mainly concentrated in the conical region, indicating a significant energy dissipation enhancement effect. By designing the structural parameters of the rings, the shape of the conical region can be changed, thereby achieving the regulation of energy dissipation enhancement effect. In addition, the key structural and material parameters of the hybrid honeycomb structure are optimized using the particle swarm optimization algorithm, resulting in a broadband sound absorption performance with an average sound absorption coefficient of 0.96 in the range of 1–10 kHz. This work proposes a new design concept and provides valuable guidance for the development of underwater sound absorption structures.

Aerogel honeycombs with orientation-induced microstructures for high-temperature lightweight composite sandwich structures

Lightweight honeycomb structures are widely used in applications that require high strength-to-weight ratios and low densities, including aircraft, automobiles, and various engine components. However, due to the immaturity of microstructure conditioning techniques and the fact that highly porous structures usually fracture during stretching, it is challenging to obtain both high-strength and lightweight porous structures. Herein, a newly developed multilayer interconnected polyimide aerogel-based paper honeycomb is successfully prepared based on the ice crystal reverse template method and multi-level structure regulation via chemical and physical interactions. The synergistic effect of the hot extrusion-stress strategy and the heat imidization process provides the submicron layer of the paper honeycomb wall with more orderly molecular chain stacking, excellent orientation, and an enhanced folding degree between layers. The prepared polyimide aerogel paper honeycombs have low density (approx. 8–9 kg/m3), good shear strength of 1.07 MPa (W direction) and 0.86 MPa (L direction), excellent specific compressive strength (0.38 MPa), and excellent thermal stability. These integrally molded polyimide paper honeycombs, as sandwich resin-based composite structures, provide a new versatile platform for aerospace and marine applications.

3D electronic implants in subretinal space: Long-term follow-up in rodents

Clinical results with photovoltaic subretinal prosthesis (PRIMA) demonstrated restoration of sight via electrical stimulation of the interneurons in degenerated retina, with resolution matching the 100 μm pixel size. Since scaling the pixels below 75 μm in the current bipolar planar geometry will significantly limit the penetration depth of the electric field and increase stimulation threshold, we explore the possibility of using smaller pixels based on a novel 3-dimensional honeycomb-shaped design. We assessed the long-term biocompatibility and stability of these arrays in rats by investigating the anatomical integration of the retina with flat and 3D implants and response to electrical stimulation over lifetime – up to 32–36 weeks post-implantation in aged rats. With both flat and 3D implants, signals elicited in the visual cortex decreased after the day of implantation by more than 3-fold, and gradually recovered over the next 12–16 weeks. With 25 μm high honeycomb walls, the majority of bipolar cells migrate into the wells, while amacrine and ganglion cells remain above the cavities, which is essential for selective network-mediated stimulation of the retina. Retinal thickness and full-field stimulation threshold with 40 μm-wide honeycomb pixels were comparable to those with planar devices – 0.05 mW/mm2 with 10 ms pulses. However, fewer cells from the inner nuclear layer migrated into the 20 μm-wide wells, and stimulation threshold increased over 12–16 weeks, before stabilizing at about 0.08 mW/mm2. Such threshold is still significantly lower than 1.8 mW/mm2 with a previous design of flat bipolar pixels, confirming the promise of the 3D honeycomb-based approach to high resolution subretinal prosthesis.

Enhancing impact resilience of thermal battery through honeycomb-structured aluminum buffering devices: Insights from large-scale gas-gun tests and simulations

Modern warfare relies heavily on electronic equipment, necessitating reliable energy sources like thermal batteries. Assessing their impact resilience, a study employed honeycomb-structured Al plates as buffering devices in a large-scale gas gun simulating artillery fire. Comparison between peak curves from gas-gun tests and simulations with varying honeycomb wall thicknesses revealed unique patterns, attributed to the buffering device's deformation-restoration process. Different honeycomb wall thicknesses led to varying deformation behavior and impact deceleration, complicating effective energy absorption assessment. Stepped honeycomb wall designs aimed to balance compression, extending energy absorption and reducing deceleration peaks. Prototype honeycomb buffering devices showed improved energy absorption and reduced deceleration during gas-gun tests. Gas-gun tests highlighted complexities in energy absorption assessment, with designs proposing improved energy absorption and reduced deceleration. The actual gas-gun test launched a projectile equipped with a thermal battery and buffering device, resulting in slight casing deformation, while battery cells remained intact, exceeding the standard discharge time (1 h).

Friction stir seam- and spot-welded aluminium honeycombs: Enhanced structural integrity eliminating adhesive bonding challenges

Aluminium honeycombs serve as a primary core material for energy absorption in various transportation and structural applications, with particular emphasis on their superior strength in the out-of-plane direction. However, conventional fabrication methods rely on adhesive bonding of aluminium strips, revealing poor bond strength under collapse stress. Premature structural failure arises from adhesive failure and subsequent debonding of cell walls, occurring before the aluminium strips fail. Addressing this, an innovative approach utilizing friction stir seam, and spot welding has been introduced to overcome adhesive bonding limitations. Welded joints exhibit a remarkable tenfold increase in strength compared to adhesive bonds. Notably, welded honeycombs demonstrate 32–37% higher crushing strength and an 80–84% increase in specific energy absorption capacity over adhesive-bonded variants. Collapse mechanisms involve pure buckling in seam-welded honeycombs without weld region failure, while spot-welded honeycombs display a combination of bending-shear and spot tearing, particularly evident with wider weld spacing. Obtaining longitudinal loading on seam-welded honeycomb walls is advantageous because of its 57% higher normalized maximum load capacity compared to the shear-tensile strength obtained for spot-welded walls. This study marks a significant advancement in the existing manufacturing route for honeycombs in achieving superior crushing performance.

Investigation of the influence of morphology on thermal conductivity in hexagonal honeycomb structures and computational models with varied volume fraction and conductivity ratio

The effective thermal conductivity (ETC) is a critical parameter for simulating macroscopic heat transfer processes in composite materials, which estimation is particularly critical where the thermal conductivity of the composite phases is completely different. The huge difference in thermal conductivity of the composite phases makes their volume fraction modulation a classical way to reach the desired thermal conductivity. Nevertheless, the typical manufacturing process of honeycomb cellular structures allows various degrees of stretching of the structure, leading to various honeycomb geometries. In these ‘real’ structures some of the honeycomb wall sides are twice as thick as other parts, modifying the symmetry of the system with respect to honeycomb with uniform wall side thickness. A noticeable example of these composites is that of a hexagonal metallic honeycomb structure filled with phase change material (PCM) which is a widely utilized material in the field of thermal storage and thermal management by exploiting the heat absorbed/released by the PCM phase during its melting/solidification. While the thermal response of a PCM composite during a thermal cycle is not only defined by thermal conductivity (but also by cell size), this represents the basis for the with the optimization of a system based on a composite PCM.For this reason, in this study, steady-state simulations of heat transfer in unit honeycomb cells in different directions perpendicular to the cell axis are conducted to quantify the impact of morphology on the thermal property of the different wall types within honeycomb structures. The results demonstrate that in both SHS and DHS, the porosity exhibiting maximum anisotropy of ETC decreases as the thermal conductivity ratio increases. Moreover, simple predictive models for calculating the ETC in all directions are proposed for each type of honeycomb, considering a wide range of porosity and thermal conductivity ratio, with a relative error limited to 2 %.

Static and modal analysis of sandwich panels with rib-reinforced re-entrant honeycomb

The low stiffness resulting from substantial core porosity within the re-entrant honeycomb sandwich panel can be addressed by introducing rib-reinforcements. To investigate its static and vibration characteristics, an energy-based 2D equivalent-homogenization model (2D-EHM) was derived through asymptotic analysis of the leading terms in the governing equations considering the energy-related characteristics. The accuracy of the constructed model for predicting the elastic bending performance of the sandwich panel was verified by comparing the results of a three-point bending experiment with 3D-printed specimens. Comparative analysis with a 3D FE model demonstrates that the 2D-EHM exhibits maximum errors of only 4.65% and 6.46%, respectively, in analyzing static deformation and natural frequency while improving computational efficiencies by up to 59- and 173-folds. Parameter analysis reveals that the performance of SP-RRH is minimally affected by the reinforcement-to-honeycomb wall thickness ratio. However, its performance is compromised when the honeycomb walls align in an equilateral triangle with the reinforcing walls. Comparing specific stiffness as well as static and vibration characteristics of sandwich panels with different core configurations (including traditional and diamond reinforced re-entrant honeycombs) shows that inclusion of rib reinforcements enhances deformation resistance and natural frequencies through increased specific stiffness. These findings provide valuable insights for optimizing design of re-entrant honeycomb sandwich panels.

Load-bearing capacity of composite honeycomb sandwich high-speed train floor

ABSTRACT The honeycomb sandwich structure of composite materials has broad prospects for application in the lightweight design of vehicle bodies. This study investigated the influence of relative density and height on an aluminium honeycomb’s out-of-plane quasi-static compression performance through experiments and simulations. The accuracy of the carbon fibre/aluminium honeycomb sandwich panel’s three-point bending model is verified based on the Hashin failure criterion and experimental validation. Furthermore, the load-bearing capacity of the carbon fibre/aluminium honeycomb sandwich floor is analysed, and the factors influencing the load-bearing capacity of the floor are further explored. The results show that the relative density significantly impacts the out-of-plane quasi-static compression performance of aluminium honeycomb, while the height has a minor influence. Compared with the original CRH5-type floor structure, the carbon fibre/aluminium honeycomb sandwich floor has a weight reduction of 45.23%, and it meets the strength requirements under uniformly distributed and concentrated load conditions. Changing the honeycomb wall thickness and panel thickness distribution can improve the load-bearing capacity of the floor.

Mechanical properties of an energy-efficient straw-filled honeycomb plate with cement-based skins under a hammer impact test

To promote the application of a new type of bionic energy-efficient sandwich plate with light weight and high strength in the construction field, a drop hammer impact test was adopted to determine the impact mechanical properties and influencing mechanism of fiber reinforced cement-based energy-efficient honeycomb plates with different core fillers (shredded straw and glass beads). The results show that compared with unfilled honeycomb plates (CHP), the contact force–time curves of energy-efficient plates have an obvious secondary peak, and the size of the damaged area on the back side of the upper skin is significantly reduced. Additionally, the presence of fillers in the energy-efficient plates provide a certain constraint on the deformation of honeycomb walls and skins, and slightly increase the size of the secondary peak. Furthermore, this study qualitatively reveals the influence mechanisms of the flexural stiffness of the sandwich plates, the morphology of damaged skins and fillers, the deformation pattern of the honeycomb core. The results provide a reference for subsequent research on the influence of different fillers on sandwich plates.

Effect of void defects on mechanical behavior and failure features of C/C honeycomb structure

The combination of honeycomb structure and carbon/carbon (C/C) composites offers unique high load-bearing and light-weight advantages in satellite-bearing platforms. However, the defects generated by the imperfect preparation process are inevitable. This paper employs the chemical vapor infiltration (CVI) technique to fabricate novel C/C honeycomb structures and considers the presence of internal void defects. Based on micro-computerized tomography (μ-CT) images, the void distribution and porosity as well as the micro-structure characteristics are acquired. Meso-scale representative volume element (RVE) models is established to predict the performance of honeycomb wall material. A secondary development of ABAQUS is performed to establish a model of honeycomb structure containing void defects. Multi-scale models are developed for investigating the mechanical performance of the C/C honeycomb structure. Experimental methods and finite element simulations are utilized to examine the effects of porosity and different weave structures on the compression and shear properties, as well as damage modes of C/C honeycomb structures in detail. The results demonstrate that the presence of low porosity ρ = 1 % severely diminishes the load-bearing capacity of the honeycomb and affects its damage pattern. Twill-2 weave C/C honeycomb inherits the advanced performance of the composites and exhibits superior comprehensive properties compared to plain weave and twill-1 weave honeycomb structures.

Three-dimensional electro-neural interfaces electroplated on subretinal prostheses

Objective. Retinal prosthetics offer partial restoration of sight to patients blinded by retinal degenerative diseases through electrical stimulation of the remaining neurons. Decreasing the pixel size enables increasing prosthetic visual acuity, as demonstrated in animal models of retinal degeneration. However, scaling down the size of planar pixels is limited by the reduced penetration depth of the electric field in tissue. We investigated 3-dimensional (3d) structures on top of photovoltaic arrays for enhanced penetration of the electric field, permitting higher resolution implants. Approach. 3D COMSOL models of subretinal photovoltaic arrays were developed to accurately quantify the electrodynamics during stimulation and verified through comparison to flat photovoltaic arrays. Models were applied to optimize the design of 3D electrode structures (pillars and honeycombs). Return electrodes on honeycomb walls vertically align the electric field with bipolar cells for optimal stimulation. Pillars elevate the active electrode, thus improving proximity to target neurons. The optimized 3D structures were electroplated onto existing flat subretinal prostheses. Main results. Simulations demonstrate that despite exposed conductive sidewalls, charge mostly flows via high-capacitance sputtered iridium oxide films topping the 3D structures. The 24 μm height of honeycomb structures was optimized for integration with the inner nuclear layer cells in the rat retina, whilst 35 μm tall pillars were optimized for penetrating the debris layer in human patients. Implantation of released 3D arrays demonstrates mechanical robustness, with histology demonstrating successful integration of 3D structures with the rat retina in-vivo. Significance. Electroplated 3D honeycomb structures produce vertically oriented electric fields, providing low stimulation thresholds, high spatial resolution, and high contrast for pixel sizes down to 20 μm. Pillar electrodes offer an alternative for extending past the debris layer. Electroplating of 3D structures is compatible with the fabrication process of flat photovoltaic arrays, enabling much more efficient retinal stimulation.

Damage Behavior of Multilayer Axisymmetric Shells Obtained by the FDM Method

This research rigorously explores the additive synthesis of structural components, focusing on unraveling the challenges and defect mechanisms intrinsic to the fused deposition modeling (FDM) process. Leveraging a comprehensive literature review and employing theoretical modeling and finite element analysis using ANSYS software, the study meticulously investigates the behavior of multilayer axisymmetric shells under varying internal pressure conditions. Critical parameters are identified, and the impact of design factors, including material properties, geometric parameters, and internal pressure, is quantitatively assessed using a rich digital dataset. In a series of model experiments, the study reveals specific numerical results that underscore the progressive nature of damage development in FDM-produced multilayer axisymmetric shells. Notably, under increasing internal pressure, stresses on the tank’s inner walls reach up to 27.5 MPa, emphasizing the critical importance of considering material properties in the design phase. The research also uncovers that the thickness of tank walls, while significant in resulting stresses, does not markedly impact the damage development mechanism. However, it places a premium on selecting rational parameters for the honeycomb system, including shell thickness, honeycomb height, honeycomb wall thickness, and honeycomb cell size, to minimize stress concentrations and enhance structural integrity. The inclusion of honeycomb structures in the tank design, as evidenced by specific results, provides enhanced thermal insulation properties. The research demonstrates that this design feature helps localize damage and mitigates the formation of significant trunk cracks, particularly along generative cracks.

Preparation and performance of laminated anti‐fire glass using the K2O·nSiO2‐based ultrathin and flexible membrane

AbstractWe present a new method for synthesizing cold‐resistant laminated anti‐fire glass using a K2O·nSiO2‐based ultrathin flexible membrane, which is prepared by vacuum surface treatment method with ball‐milled core–shell SiO2 emulsion (55 wt%). We systemically characterize the mechanical, optical, rheological, cold‐resistant, fire‐resistant, and weather‐resistant performances of this glass. The formation mechanism of K2O·nSiO2‐based ultrathin membrane is studied in detail using multispeckle diffusing–wave spectroscopy and scanning electron microscopy. Then, the tensile strength, plasticity, and rheological behavior of the materials with different moduli are characterized. Combined with thermal gravity analysis, we characterize the compositions of K2O·nSiO2‐based materials with different moduli. For the K2O·nSiO2‐based ultrathin flexible membrane, the appearance of air‐conducting microchannels is designed, resembling the Wu Zhu coin morphology (a square hole circular coin in ancient China) or honeycomb wall morphology. These structures endow the visible region of the anti‐fire glass with a reduced presence of microbubbles. As a type of building safety glass, the spongelike microporous insulation layer can increase the heat‐insulating time in the event of a fire. Furthermore, the weather‐resistant performance of this glass is demonstrated to be more than 3000 h through an ultraviolet test. This work also provides a new routine for synthesizing high‐quality anti‐fire glass with different shapes, including curved surfaces.

Investigation on carbon fiber fracture mechanism of honeycomb composites in longitudinal‐torsional ultrasonic‐assisted milling processes

AbstractA multi‐edge micro‐tooth longitudinal‐torsional ultrasonic‐assisted milling (LTUAM) model was established based on the hard brittle characteristics of carbon fiber honeycomb composites and the weak strength characteristics of the hole wall interface. The study analyzed the effects of ultrasonic characterization parameters on the cutting force, honeycomb wall width, and surface morphology. The results indicate that using LTUAM significantly reduced the cutting force and decreased the length and height of the burrs at an appropriate ultrasound amplitude. The spindle speed had the least impact on the width of the honeycomb wall, but increased with the longitudinal‐torsional ultrasonic amplitude and feed rate. The maximum error between the simulated and experimental cutting force values was approximately 19%. The longitudinal amplitude and torsional amplitude were 3 and 5 μm, respectively, the length of burrs decreased by 52.7%, and there was less delamination and tearing damage. LTUAM proved to be beneficial in improving cutting performance. Compared with conventional milling (CM), LTUAM resulted in regular fiber fracture morphology and smaller fragments on the honeycomb surface. In addition, the high‐frequency ultrasonic vibration promoted carbon fiber fracture and the surface roughness value under LTUAM was approximately 36.72% smaller than that of CM.Highlights Ultrasonic milling mechanism of carbon honeycomb is studied. Kinematic simulation of the tool of carbon honeycomb was studied during LTUAM. LTUAM promotes the fracture of carbon fibers. A multi‐edge micro‐tooth LTUAM model was established of carbon honeycomb. Deformation of the cell wall can be avoided by ultrasonic vibration of the cutter.

A method to in-situ synthesize surface coating of SiC nanowhiskers on cordierite honeycombs by combining aluminothermic, silicothermic and carbothermic reduction reactions

A simple in-situ method was proposed to synthesize surface coating of SiC nanowhiskers on cordierite honeycombs by aluminothermic, silicothermic, and carbothermic reduction reactions. The surface coating of SiC nanowhiskers was synthesized by controlling the partial pressure of SiO gas on the surface of honeycombs, based on the pore-forming process using aluminium(Al) agent. Increasing the porosity of the honeycombs provided aisles to volatilize SiO gas, and the growth of SiC nanowhiskers changed from inside the honeycomb wall to on the honeycomb surface. SEM and TEM observations revealed that the relatively high porosity (≥45%) and sintering temperature (1250–1300 °C) were necessary for obtaining surface coating of SiC nanowhiskers, and the nanowhisker-coating having the smooth morphology and a thickness of ∼150 µm was obtained at 1250 °C. Compared with cordierite honeycombs without SiC nanowhiskers, SiC nanowhiskers inside the honeycomb walls could improve the compressive strength and thermal conductivity with increasing rates of 121% and 123%, respectively, and the surface coating of SiC nanowhiskers increased the specific surface area of the honeycombs by 241 times.