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Family molds can be used to simultaneously produce a variety of parts with different shapes that are made of the same plastic material. Studies on family molds have mostly focused on the layouts of different parts in a mold or the design of runner systems. Cold runners are rarely used in the conformal cooling channel (CCC)-related studies because, under normal circumstances, the mold cavity cooling time should be shortened as much as possible. However, a runner system does the opposite by extending the cooling time to provide sufficient melt and pressure to the mold cavity and ensure high part quality; accordingly, the effect of cold runners was often overlooked in CCC-related studies to reduce variability. In this study, a cooling channel layout design (LD)-based method was developed for the design of a hive-shaped CCC. Moldflow was used to simulate and compare the performance of the channel layouts with horizontal parallel connection, horizontal series connection, vertical parallel connection, and vertical series connection. The performance of the proposed hive-shaped CCCs was also compared with an SCC and a honeycomb CCC. The results of this study verified that the proposed LD-based method can be used to establish a hive-shaped CCC automatically. Compared with other CCCs, the established hive-shaped CCC provides stronger support to the mold cavity, shortens the cooling cycle, and improves part quality. [ABSTRACT FROM AUTHOR]

This research aims at enhancing the performance of scale-model scooter decks by investigating various architected cellular metamaterial and bio-inspired core structure designs, such as honeycomb, tetrachiral, re-entrant, arrowhead, and star-shaped arrangements. An initial effort is made toward the design and rapid prototyping of small-scale deck with a uniform honeycomb core structure. More specifically, polylactic acid is utilized to fabricate complex structures via fused filament fabrication technique. Investigation is then focused on its mechanical performance, such as its bending properties obtained through a three-point bending test. Simulations are also conducted with different core configurations using a geometrically non-linear finite element method which is implemented. Experiments are carried out to verify the numerical results. After validation, various patterns are modeled, and eventually, it is observed that the functionally graded arrowhead structure has the best bending resistance, compared to other bio-inspired and mechanical metamaterial structures. At a constant force of 845 N, the functionally graded arrowhead design lowers the deflection in the middle of the scale model of scooter deck by up to 14.7%, compared to the uniform arrowhead structure. Furthermore, comparing the tetrachiral and functionally graded arrowhead configurations at a constant force, a 30% reduction in central deflection was observed. Due to the lack of similar results and designs in the specialized literature, this work could potentially advance the state-of-the-art scooter core designs and provide designers with architectures that could enhance the performance and safety of scooters. [ABSTRACT FROM AUTHOR]

The manufacture of aluminum honeycomb structures is a major concern for companies in the aerospace industry, due to its out-of-plane high strength and stiffness-to-weight ratio. However, the shaping of this type of structure represents a technical challenge for engineers and researchers in terms of premature wear of the cutting tool and the quality of the machined surface. Generally, machining studies are based on experimental tests. Nevertheless, the experimental procedure fails to follow the mechanism of chip formation due to high rotational speeds of the cutting tool. To this end, it is necessary to use robust and reliable numerical models to access instantaneous and much localized physical quantities. For this purpose, we have developed a 3D finite element model associated with real working conditions using the Abaqus/Explicit analysis software. Based on this model, an experimental validation was carried out by analyzing the appropriate behavior laws. Furthermore, the influence of the geometry of the cutting tool in terms of the number of teeth on the size of the chips, the cutting forces, and the quality of the generated surface was analyzed. The obtained results show that the integrity of the cutting tool can be optimized and the quality of the machined surface can be improved. [ABSTRACT FROM AUTHOR]

Cellular infill structures such as honeycomb have been widely used in the field of light weighting. In recent years, the emergence of additive manufacturing technologies has provided a new solution to fabricate complicated cellular infill structures. This paper presents a continuous printing path planning method for gradient honeycomb structures. Given a 2D filling region represented by a polygon, a honeycomb graph that covers the filling area is trimmed to generate an infill pattern. Then an algorithm is proposed to transform the honeycomb filling pattern into an Eulerian graph, which can be traversed by a single-stroke printing path. For each honeycomb, double-spiral paths are used to generate gradient honeycomb structures with varying wall thicknesses. Later, the 2D honeycomb infills are generalized to 3D cases that are suitable for multi-axis printing. First, three mutually orthogonal vector fields that are embedded on the tetrahedral mesh of the printed part are generated by considering the support-free condition. Then the three vector fields are used to calculate three monotonically increasing scalar distance fields, which span a non-Euclidean space. Finally, the 2D honeycomb infills are generated in the non-Euclidean space with parallel sliced layers, which are then mapped back to the Euclidean space to obtain the real self-supporting 3D honeycomb infills. The proposed 2D/3D honeycomb infill structures generation algorithms have been verified by both simulation and experimental tests. [ABSTRACT FROM AUTHOR]

Ultrathick aluminum honeycomb sandwich panels, which have high strength/stiffness-to-weight ratio, have been applied widely in satellites and other aerospace fields. However, the ultrathick aluminum honeycomb sandwich panels are difficult to be machined. In many cases, laser ablation is used for the microdrilling demand of aluminum honeycomb sandwich panels. The heat flux density is the key factor during laser machining, and the microdrilling parameters, including defocusing amount and incident angle, can lead to the change of the temperature fields of upper panel, cell walls, and lower panel. To study the microdrilling process quantitatively, the finite element model (FEM) is performed to evaluate the temperature evolution of aluminum honeycomb sandwich panels during continuous laser irradiation. Moreover, continuous laser microdrilling characteristics of upper panel, cell walls and lower panel are discussed via numerical simulation. The relative errors with respect to experimental results are in range of 8% showing that simulation results of laser microdrilling are reasonable. Thus, the mechanism of laser microdrilling revealed in this study can be significant for improving the processing quality of aluminum honeycomb sandwich panels. [ABSTRACT FROM AUTHOR]

Nomex honeycomb composite material has a wide range of applications due to its lightweight, high strength, and low-cost advantages. Using ultrasonic-assisted cutting to process it can effectively overcome the shortcomings of traditional high-speed milling. This paper takes the ultrasonic cutting acoustic system of disc cutter as the research object and studies the influence of the cutting force and temperature of the cutter on the stability of the acoustic system utilizing theoretical modeling and experiments, mainly discussing the effect of force load and temperature change on the resonant frequency and amplitude of acoustic system. According to the equation of motion of ultrasonic cutting, the cutting force model of the disc cutter is established, and the theoretical model of temperature with the resonance frequency and amplitude of the ultrasonic cutting acoustic system of the disc cutter is derived. The experiments on the influence of force load and temperature on the stability of the acoustic system are carried out, respectively. The experimental results show that with the increase of cutting force, the resonance frequency of the ultrasonic cutting acoustic system shows an upward trend, and the amplitude shows a downward trend; with the increase in temperature, both resonance frequency and amplitude decrease. In addition, the change in the inclination angle of the disc cutter during machining will also lead to the change in resonance frequency and amplitude of the acoustic system. The experimental results show the cutter's inclination angle when the machining effect is the best is 6°. This study provides a certain guiding significance for improving the stability of the disc cutter ultrasonic cutting system. [ABSTRACT FROM AUTHOR]

Aluminum honeycomb structures have been frequently used in many industrial applications, especially in aerospace and aeronautics, due to their high strength and stiffness to weight ratio. The machining quality of aluminum honeycomb structures is generally related to plastic deformation of the walls forming the honeycomb structure and burrs. Consequently, the use of this type of structure requires specific machining operations and special tools. In order to carry out in-depth studies on the milling of aluminum honeycombs, a 3D finite element model was developed with the help of Abaqus/Explicit software. The model thus developed is validated with several experimental tests and for different machining conditions. Based on the developed model, the relationship between the cutting forces and the friction coefficient between the cutting tool and the honeycomb during the cutting process is studied. The main objective of this work is to highlight the effect of physical and geometrical parameters during the milling of aluminum honeycomb structures on cutting forces, surface quality generated, chip size, and material accumulation in front of the cutting tool. The comparison between the simulated results and the experimental results indicates that the developed numerical model is in good agreement with the experimental reality. [ABSTRACT FROM AUTHOR]

Revealing the ultrasonic cutting mechanism of honeycomb composite is important for determining the acoustic parameters of the ultrasonic system and selecting the parameters of the cutting process. Understanding more details of the stress on the cell wall from ultrasonic vibrating tool and the conditions for cell wall breakage is essential to study the machining mechanism. According to the evolution of contact state between the straight edge cutter and the honeycomb cell wall in a cycle, the cutting force acting on the cell wall is divided into three stages: transverse cutting load action, longitudinal cutting load action, and no cutting load action. The cell wall deflection and stress equations under transverse cutting load were established by applying elastic thin plate small deflection theory. The deformation and fracture characteristics of the honeycomb cell wall were analyzed by combining the analytical and the finite element model. The results showed that the ultrasonic vibration of the cutter greatly improved the stiffening effect of the cell wall and its fracture was caused by the deflection under the transverse cutting load, which exceeded the maximum allowable deformation after local stiffening. In addition, with only longitudinal cutting load, it was difficult to break the critical buckling state that leads to cell wall fracture. [ABSTRACT FROM AUTHOR]

This study investigated ultraviolet-laser-induced graphene (ULIG) through the far-infrared irradiation (FIR) of polyimide films for constructing flexible electric heaters. Graphene, which has a uniform micro-scale porous structure with high electrical conductivity, was formed along the laser-induced paths through photothermal and photochemical reactions. Raman spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy were used to measure the microstructure, elemental composition, and chemical states of the ULIG films and thereby investigate their graphenization and defect level. Moreover, the surface morphology and electrical properties of the ULIG films were evaluated using a field-emission scanning electron microscope and source measurement unit, respectively. Finally, optimal processing parameters, namely a surface laser fluence of 48 J/cm2, a pulse repetition rate of 100 kHz, and a scan pitch of 0.01 mm, were used to fabricate ULIG heaters with triangular and honeycomb electrode structures. The ULIG films with FIR exhibited a high-quality and high-integrity porous structure, a low electrical resistance of 2.55 Ω, and a low sheet resistance of 14.34 ± 2.04 Ω/sq. Furthermore, the ULIG heaters exhibited ultrafast heating and cooling rates (90.93 and 89.37 ℃/s, respectively) as well as excellent heating stability and flexibility. [ABSTRACT FROM AUTHOR]

To address the problem of the poor stability of ultrasonic machining of wave-absorbing honeycomb material, this study takes ultrasonic cutting of wave-absorbing honeycomb material with a disc cutter as the research object and establishes a multi-degree-of-freedom mathematical model of the cutting system based on the relative positions of the tool, the wave-absorbing honeycomb material, and the motion characteristics of the tool. On this basis, modal analysis of the disc cutter and the honeycomb cell wall plate is carried out to draw the Lobe diagram of ultrasonic cutting stability, the process experimental parameters are determined to accord to the solved stability Lobe diagram, and machining stability verification experiments are carried out. The experimental results show that the machining parameters in the stable zone of the Lobe diagram result in a neat and clean surface, less fibre pullout, a complete outer substrate, and less tool wear than those in the critical and unstable zones, thus verifying the correctness of the theoretical model and the stability Lobe diagram. [ABSTRACT FROM AUTHOR]

The milling of aluminum honeycomb structures represents today an important scientific and technical research topic for many industrial applications: aerospace, aeronautic, automotive, and naval. The difficulties encountered when milling this type of materials are linked to the small thickness of the walls constituting the honeycomb cells and the ductility of the material structure. The milling of cellular composite structures requires specific and rigorous tools. In the present work, a 3D numerical modeling of the milling process of aluminum honeycombs has been developed using Abaqus Explicit software. The effect of milling parameters, such as the spindle speed, the tilt angle, and the depth of cut, has been particularly investigated in terms of cutting forces, surface integrity, and chip morphology. To properly analyze and optimize the cutting process, experimental validation was done through milling tests with different cutting conditions. The comparison between numerical simulations and experimental tests shows that the three-dimensional model correctly reproduces the milling of this type of structure. [ABSTRACT FROM AUTHOR]

As compared to traditional milling, ultrasonic-assisted cutting of honeycomb core materials has the advantages of small cutting force and superior surface quality. Currently, ultrasonic straight blade V-shaped machining is one of the most efficient roughing processes. The requirement of a processing path to be post-processed based on the processing characteristics of the straight blade cutter is one of the key issues faced while meeting the technological requirements of CNC machine tools for V-shaped machining. A post-processing method of NC code for V-shaped machining of straight blade cutter is proposed in this article. Initially, the V-shaped rough machining process planning is done, followed by the usage of Unigraphics (UG) to output the initial CNC code. Next, the CNC code is executed through the three key technologies of the second arrangement of cutter locations. Later, research is done on information planning of lifting and lowering cutter, along with research on planning of chip breaking toolpath. Eventually, the simulation cutting experiment is carried out through VERICUT. The results demonstrate that the post-processing method can meet the processing requirements. [ABSTRACT FROM AUTHOR]

Machining of Nomex® honeycomb materials is the biggest challenge in industry because of the complex forms and geometry of the honeycomb structure. The latter is characterized by a low density with orthotropic mechanical behavior. The thin walls of the composite structure make the shaping of this material very difficult. Studying interactions between the cutting tool and material, cutting forces, and chip formation allow to understand the machining process of Nomex® honeycomb. This paper presents 3D numerical modeling of machining Nomex® honeycomb using different orthotropic approaches and failure criteria: (i) monolayer isotropic approach, (ii) monolayer orthotropic approach with Tsai-Wu failure criteria, and (iii) monolayer orthotropic approach with Hashin failure criteria. A comparison between experiments and numerical cutting forces was performed to validate the proposed model. The interaction between the tool and the honeycomb walls, which make it possible to observe the different stages of the chip formation process, was carefully modeled. [ABSTRACT FROM AUTHOR]

The honeycomb sandwich structure has been widely used in the field of aerospace owing to extremely high specific strength and specific rigidity. However, the honeycomb core has anisotropic mechanical characteristics and in-plane weak rigidity, which brings new challenges to the cutting process. In this paper, a three-way equivalent heat conduction model including heat conduction and heat convection in the cutting process was established based on the structural characteristics of the honeycomb core. As for the milling cutter combined with the crushing blade and circular blade specified for aluminum honeycomb core, the moving surface heat source of the crushing blade and the moving line heat source of the circular blade during the milling process were proposed. A prediction model of temperature distribution in the milling of aluminum honeycomb core based on the two heat moving sources was established and verified by the milling experiments. Finally, the temperature distribution law and heat affected area of the honeycomb core during the milling process were studied. It was found that the milling temperature of the honeycomb core maintained a high temperature in the contact area, but fell sharply outside the contact area. Moreover, the heat affected area of the milling heat does not exceed three honeycomb cores. [ABSTRACT FROM AUTHOR]

Nomex honeycomb core has been widely applied in aerospace industries due to its superior strength and rigidity. However, the machining defects of honeycomb core can deteriorate the bonding strength between honeycomb core and connective face sheet. This paper investigates the tearing defects formatted in milling process of Nomex honeycomb core. Firstly, a cutting force model is proposed to predict the milling forces under various tool entrance angles. Then, finite element simulation for machining honeycomb wall is conducted to reveal the formation mechanism of tearing defects. The accuracy of the model is verified by a group of experiments under different entrance angles and the relative error is below 25% in 1-direction and 20% in 2-direction. It is found that the formation of tearing defects is closely related to the deformation of honeycomb wall and the component of cutting force in direction parallel to wall. The tool entrance angle can be thus optimized based on the reduction of tearing defects. The optimized entrance angle of double wall is among 40° and 70°. [ABSTRACT FROM AUTHOR]

Lattice structures are a class of cellular materials with greater control over the mechanical properties, relative to other common cellular materials like foams and honeycomb structures. In this paper, three lattice structures including Kelvin, Rhombic dodecahedron, and truncated cuboctahedron with identical geometric dimensions in quasi-static and dynamic loadings were investigated to identify the proper lattice structure for impact resistance applications. This study consisted of two experimental and numerical sections. In the experimental section, the lattice structures were fabricated using the selective laser melting (SLM) method from the AISI 316L material. The dynamic tests of the lattice structures were performed by the split Hopkinson pressure bar (SHPB) with a strain rate of 765 s−1. In the numerical section, the modeling was carried out by the finite element method (FEM) to predict the properties of the lattice structures. The results of the experimental tests showed that the selected lattice structures had a high strength to weight ratio and considerable impact resistance; so, they could be suitable for use in lightweight and impact-resistant structures. In addition, the modeling results revealed a good agreement with the experimental results. Finally, the specific absorbed energy of the Rhombic dodecahedron lattice structure in the quasi-static compression test and with the 50% strain was 7% and 15% higher than that of Kelvin and truncated cuboctahedron lattice structures, respectively. While, with evaluation of the dynamic results, the truncated cuboctahedron lattice structure had higher area under the specific stress-strain curve in comparison to the other two structures. [ABSTRACT FROM AUTHOR]

Due to the notable advantages of ultrasonic-assisted machining, this technology is being more and more adopted in different manufacturing processes. Aramid honeycomb structures are among materials for which ultrasonic-assisted machining has become an interesting alternative thanks to its effect in reduction of machining forces and less micro imperfections. A considerable number of research works have addressed micro machining defeats in ultrasonic application such as dust generation and fiber delamination in Aramid honeycomb workpieces. However, in this study, a great attention is dedicated to the geometrical errors observed in the workpieces in cutting process of Aramid honeycomb structures using ultrasonic technology. The effect of different elements involved in robotic-based ultrasonic-assisted cutting process of Aramid honeycomb structures on these error types has been studied. To proceed this goal, a machining force estimation model is experimentally developed using the machining forces captured during the execution of several cutting tests. An on-site measurement process for measuring the geometrical errors in resulted workpieces is presented. The compliance behavior of robot-tool system is simulated using an extended virtual joint method (VJM) approach. In this approach, the machining tool is considered an additional joint-link system attached to the 6-revolute joint industrial system. Simulation results based on this method applied on the case study showed that the portion of contribution of industrial robotic arm to the compliant errors of process is negligible compared with the one of ultrasonic cutting knife. An offline compensation algorithm is proposed based on the developed machining force and tool compliance behavior models. Experimental results supported the efficiency of the proposed compensation method in reducing the geometrical error by up to 95% based on the machining features. [ABSTRACT FROM AUTHOR]

SiC crystal has been widely used in semiconductor substrates because of its excellent physical, chemical, and photoelectric properties. As a semiconductor substrate, the SiC wafer not only needs good surface quality but also requires surface shape accuracy. In the present study, a novel lapping plate was designed for SiC wafers to improve their surface quality and shape accuracy. In the novel lapping plate, epoxy resin and a soft gel body containing diamond abrasives are combined to form a hard honeycomb structure. The cellular structure is used to support the lapping pressure to reduce the deformation of the lapping plate and improve the surface shape accuracy. The cellular structure is filled with soft gel with diamond abrasives which play the role of semifixed lapping to obtain good surface quality. Two crystalline forms of silicon carbide (4H-SiC and 6H-SiC) were selected to carry out double-sided lapping experiments with the novel lapping plate. The experimental results show that the lapped wafers have good surface quality with low surface roughness, some small scratches, and acceptable cracks. In addition, the surface shape accuracy is improved; the values of bow, warp, and total thickness variation (TTV) are all reduced after lapping. Under the same lapping conditions, the 6H-SiC has a smaller surface roughness than 4H-SiC, and for a specific crystalline form, the surface roughness of the C face is smaller than that of the Si face. The bow and warp of 4H-SiC are smaller, but the TTV is larger. The material removal rate is basically the same for 4H-SiC and 6H-SiC. [ABSTRACT FROM AUTHOR]

This work describes the compression and failure behaviour of multi-honeycomb, re-entrant honeycomb and silicomb honeycomb structures of various core height (thickness: 10, 20 and 30 mm) reinforced with different natural fibres (flax, jute and sisal). Moulds used for manufacturing the composite cores were produced using 3D printing technique with polylactic acid (PLA). Experiments based on Taguchi design (L9) were conducted to determine the effect of each factor on the ultimate compression stress, deformation and absorption energy. The magnitude of compressive stress varied into a range of 25.32 to 36.38 MPa. Also, values of absorption of energy varied from 22.34 to 33.76 Kj/m3. It was found that thickness has a significant effect on compression properties and failure behaviour. [ABSTRACT FROM AUTHOR]

In nanofluid minimum quantity lubrication (NMQL) grinding of titanium (Ti) alloy, existing nanoparticles cannot solve the technical bottleneck of high surface integrity. Therefore, graphene (GR) nanoparticles, which have excellent lubrication performance, were applied in NMQL. The tribological properties of GR nanofluid on wheel–workpiece interface were studied by friction and wear test. In the experiment, 0.5–3 nm thick GR nanoparticles were used to prepare 3% vol. palm oil-based nanofluid. Ball-disc experiment under grinding conditions was carried out on the friction and wear tester. Grinding balls with SiC abrasive grains (to simulate the grinding wheel) and Ti-6Al-4V disc (to simulate the workpiece) were used. Load force was set for simulation of pressure boundary condition of the grinding wheel–workpiece interface. Stratiform nanoparticles (MoS2, MoO3, and HBN) were used as the comparison group. Results demonstrated that GR nanofluid achieved smaller friction coefficient (0.295), error bars (0.0029), and area of scratches (182,940 μm2). GR nanoparticles with small gravity and large specific surface area improved the viscosity of nanofluid and consequently the lubrication performance. The plane hexagonal honeycomb structure determines the strong lubrication stability and abrasive resistance of the GR nanoparticles. The scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) images of the scratch surface also verified the above conclusions. [ABSTRACT FROM AUTHOR]

Traditionally processed Nomex honeycomb cores usually have apparent defects. These defects are inevitably caused by the large cutting force generated as a consequence of limit clamping mode of the honeycomb core. These defects, such as tear, burr, and other machining defects, are normally observed on the processed honeycomb cores. In this paper, a reliable predictive model for the ultrasonic assisted cutting of honeycomb cores is developed and the mechanics behind the machining process is presented. The theoretical model predicts the influence of each processing parameter on the cutting force, and the model is verified through single-factor experiment which reveals that the cutting force is influenced by four experimental factors. Comparison between the images of the workpiece surfaces obtained in the ultrasonic assisted cutting and traditional cutting experiments indicates that the ultrasonic assisted cutting is superior to the traditional cutting of Nomex honeycomb cores. The influence of the four factors on the cutting force test index in descending order as obtained from the orthogonal experiment is amplitude, oblique angle, depth of cut, and feed rate. Finally, the optimum processing parameters are determined as amplitude 25 μm and oblique angle of 30°. [ABSTRACT FROM AUTHOR]

This paper presents the first comprehensive investigation that aluminum honeycomb has inevitable machining defect in milling process, such as deformation, burr, and collapse. Ice fixation method was used to clamp workpieces, and inner-injection liquid nitrogen was employed for a series of cryogenic milling machining. In the machining process, the main machining parameters including in honeycomb orientation, milling width, cutting depth, cutting speed, and feed were executed experimental research. Meanwhile, the machining parameter optimization, range, and significant analysis were adopted to analyze the influence of machining parameters on the machining surface quality, as well as the optimal parameter combination and milling machining surface quality were predicted and verified. The results show that the ice fixation aluminum honeycomb method with cryogenic milling is much advanced than that of conventional ones, and many machining defects are effectively restrained. At the same time, the influence of machining parameters on machining qualities in descending order is cutting depth, cutting speed, honeycomb orientation, feed, and milling width. The minimum roughness value (Ra = 0.356 μm) of the predicted machining surface is similar to the actual machining result (Ra = 0.362 μm). It verifies the feasibility of the optimization method. Furthermore, it is proved that the ice fixation + liquid nitrogen cooling method has a positive effect on the high milling quality and implement efficiency for aluminum honeycomb and other difficult-to-machine materials. [ABSTRACT FROM AUTHOR]

Aerospace metal honeycomb materials with low stiffness had often the deformation, burr, collapse, and other defects in the mechanical processing. They were attributed to poor fixation method and inapposite cutting force. This paper presented the improvement of fixation way. The hexagonal aluminum honeycomb core material was treated by ice fixation, and the NC milling machine was used for a series of cryogenic machining. Considering the similar structure of fiber-reinforced composite materials, the milling force prediction model of ice fixation aluminum honeycomb was established, considering tool geometry parameters and cutting parameters. Meanwhile, the influence rule on milling force was deduced. The results show that compared with the conventional fixation milling method, the honeycomb processing effect is improved greatly. The machining parameters affect order on milling forces: the cutting depth is the most important, followed by the cutting width, then the spindle speed and the feed. Moreover, too small cutting depth (ap = 0.5 mm) will cause insufficient cutting force, while ap > 2 mm with higher force will reduce the processing quality of honeycomb. Simultaneously, the honeycomb orientation (θ) has a great influence on processing quality. Using the model, the predicted and measured error values of the feed and main cutting force are all small in θ < 90°. But, the rate is 33 and 26% for the main cutting force and feed force error in θ > 90°, respectively, while they all exhibit the smallest error in θ = 60°. This bigger error mainly is due to unstable cutting force with obtuse angle. In addition, the tool rake angle has little influence on cutting quality in θ < 90°, but bigger on that in θ > 90°. Furthermore, the calculation model successfully conforms to the main deformation mechanism and influences parameters of the cutting force in the milling process, and it can accurately predict the cutting force in θ < 90° and guide the milling process. [ABSTRACT FROM AUTHOR]

With advances in 3D printing technology, now honeycomb structures can be made with virtually unlimited unit cell geometries and cell arrangements giving a wide range of possible mechanical properties. However, studies on such structures have been mainly limited to the hexagonal honeycombs with little work done on other cell geometries. This paper investigates the effect of unit cell geometry on the in-plane compressive response and energy absorption behaviour of honeycombs using full-scale non-linear numerical simulations. Nine types of honeycombs are designed from different unit cell shapes, but having the same relative density. Finite element analysis is used to simulate the honeycombs' behaviour under uniaxial compression loading. The results showed that unit cell geometry and cell arrangement affect the honeycombs' compressive response significantly and provide different energy absorption characteristics. This comparison study shows that the honeycombs in which the deformation mode is dominated by bending of cell edges present a lower stiffness (effective modulus) and compressive strength, but a smoother plateau stress. The honeycombs having their deformation mode dominated by plastic buckling present a higher stiffness with less stable and undulated plateau stress. The results of this study provide more understanding in predicting the global behaviour of honeycomb structures and their energy absorption characteristic through their micro-topology. The effect of cell shape and its arrangement on the selection of honeycombs for energy absorption application is discussed and a methodology is proposed to balance the energy absorption with maximum transmitted stress, which is crucial for energy-absorbing design of structures. [ABSTRACT FROM AUTHOR]

Composite structures are usually subjected to a wide range of environmental conditions whereby they can absorb a substantial amount of moisture, oil, or solvent from the environment, thus reducing their mechanical, thermal, electrical, and other physical properties and service times. In this study, hydrophobic barrier films used to prevent moisture ingression into sandwich structures are investigated. Four different hydrophobic thin barrier films-polyvinyl fluoride (PVF), polyether ether ketones (12.5 and 25 μm), polyimide, and polytetrafluoroethylene-were co-bonded to the surfaces of fiber composite sandwich structures to study the changes in mechanical properties of the sandwich structures before and after immersing them into deionized (DI) water and aviation hydraulic fluid (Skydrol®). For comparison and evaluation purposes, the composite coupons underwent two different mechanical tests: sandwich flexure and compression strength compression. Test results confirmed that using barrier films as the outermost ply on composite sandwich structures significantly reduced moisture ingression, and as a result, mechanical properties were considerably increased compared to those coupons without any barrier films. [ABSTRACT FROM AUTHOR]

In the grinding of thin-walled and honeycomb-structured components made up of Hastelloy, undesired burrs are often created. The formed burrs negatively affect the quality of the products. Subsequent deburring increases overall manufacturing process time and cost. This work was focused on development of high-speed grinding process and grinding strategies to reduce burr size and improve ground surface quality. An electroplated Cubic Boron Nitride (CBN) wheel with miniature concave and convex asperities on its circumferential working surface was developed. Grinding performance with the designed CBN wheel was compared with a normal CBN wheel without surface asperities. Special fixtures with the function of adjusting honeycomb orientation (change of grinding direction) were purposely designed and fabricated. Design of experiment (DOE) was adopted for optimization of grinding parameters. It was found that less burr (even burr-free) grinding was achieved with the utilization of the specially designed CBN wheel with concave and convex asperities under optimal grinding conditions investigated, i.e., rotational speed of 5,000 RPM, depth of cut of 25 μm, and feed rate of 7,500 mm/min. [ABSTRACT FROM AUTHOR]

In this paper, a precision micromachining technique for photonic bandgap fiber (PBGF) using focused ion beam (FIB) milling was reported. Types of PBGF have the honeycomb structure with a hollow core surrounded by microstructured cladding, and the widths of the thin silica struts are only 10∼100 nm. The shape of fiber section is the most important prerequisite for maintaining good output coupling efficiency and allowing gas diffusion. Therefore, a proper machining method can avoid microstructure collapse and is crucially important for the experimental investigations. The FIB milling process was discussed and realized to improve performance of PBGF gas cell in this study. The absorption spectra of acetylene (CH) gas and methane (CH) gas have been investigated using the propose measurement system based on PBGF gas cell. The experimental results clearly indicated a high overlap between the propagating light and filled gas inside the PBGF. Therefore, these studies can contribute to highly sensitive gas sensing, higher accurate wavelength references, and other applications. [ABSTRACT FROM AUTHOR]

In the present work, an avant-garde study on Buckling of honeycomb sandwich panel of hexagonal cell has been carried out by considering simply supported boundary constraints explicitly. A novel theoretical formulation has been developed for the buckling of honeycomb panel as per Mil Standard (MIL-HDBK-23A). The laminate element type has been considered for linear static analysis using Lanczos Method (finite element method (FEM)). The buckling analysis carried out by FEM has been compared and validated with theoretical and experimental investigation for different panel aspect ratio under static load. [ABSTRACT FROM AUTHOR]

In this study, the authors applied the low-temperature ultrasonic soldering method to solder aluminum alloy honeycomb structure and investigated the effects of soldering time and soldering temperature on the properties of the solder. The following results were obtained: The wetting angle changed with applied time and applied temperature. The solder region is mainly composed of four kinds of microstructure zones: rich Sn zone, rich Pb zone, Sn–Pb eutectic phase, and rich Al zone. Microanalysis identified a continuous reaction product at the alumina–solder interface as a rich Pb zone. The wet angle data had significantly greater variability, with values ranging from 10° to 90°. The highest value was obtained for the samples soldered with Sn–Pb–Zn alloy for 30 s. Fractures occurred along the solder–alumina interface for the 6061 aluminum alloy. Fracture surface included hybrid tough fracture of dimple and tear ridge. The interface could firstly strip at the rich Bi zone with the effect of shear stress. [ABSTRACT FROM AUTHOR]