Laminate Structure Research Articles

Mechanical Properties of 3D Printed Parts and Their Injection Molded Alternatives Subjected to Environmental Aging.

Additive manufacturing is the technology used in medical, industrial, or lifestyle applications. The scientific literature include works reporting various manufacturing parameters' influence on changes in additive manufacturing components' mechanical behavior, especially with fused filament fabrication (FFF). The changes in mechanical strength and toughness of FFF compared to injection molding parts were studied. In the study, the FFF and injection molded parts were aged in buffered saline solution in temperature of 37°C. The results show that by differentiating the orientation of the fibers during fabricating, it is possible to reach strength values similar to injection molded parts. Therefore, it was reported that the mechanical strength and toughness changed significantly after aging, and the FFF components lost strength more quickly than their injected alternatives. The research results can be useful during the fabrication of mechanically stable and biodegradable components, which can be more easily recycled than their injected alternatives when used with warmer temperatures and humidity. This article completes the present state of the art on the problem of environmental aging of parts produced from biodegradable materials. Especially, the research was related to the multilayer laminate structure.

The Origin of the Upper Cambrian Basin-Scale Massive Dolostones of the Xixiangchi Formation, Sichuan Basin, China

The thick Upper Cambrian Xixiangchi dolostones, developed in the Sichuan Basin, are an important deep exploration target, but their genesis is still controversial, which hinders predicting the porous dolomite distribution and related potential hydrocarbon play. Herein, based on the observation and sampling of field outcrops, combined with a microscopic thin section analysis, cathodoluminescence analysis, and geochemical study, their characteristics and genesis were investigated. The results showed that there are mainly three types of dolomite that can be distinguished: (1) fine crystalline dolomite with a low crystallinity (Type 1); (2) granular dolomite with coarse grains, maintaining the original particle structure (Type 2); and (3) grain-texture relict dolomite with a higher degree of crystal form and obvious recrystallization (Type 3). The Type 1 dolomite with a common lamina structure and the highest 87Sr/86Sr ratio implies the most continental-influenced seawater in a supratidal environment around paleouplift, where there is an evaporation pump effect in its formation. The Type 2 dolomite recorded a slightly higher diagenesis temperature and slightly lower brine salinity, which would be formed in a seepage-reflux model in the beach environment of the platform. The lowest REY content and higher dolomite temperature with structural residuals indicate that the Type 3 dolomite is the result of further burial dolomitization during the diagenetic process.

Novel zone-based hybrid laminate structures for high-velocity impact (HVI) in carbon fibre-reinforced polymer (CFRP) composites

We propose novel zone-based hybrid laminate concepts for improving the high-velocity impact (HVI) response of baseline carbon fibre-reinforced polymer (CFRP) composites while maintaining similar areal weights and retaining substantial in-plane mechanical properties by requiring that about 80% (by mass) of the baseline CFRP is kept in the hybrid concepts. We identify three zones along the thickness of the laminate according to their role during HVI and implemented tailored materials in these zones to improve the HVI response. We studied a wide range of materials, including: fibre reinforcements of carbon (thin- and thick-plies), glass, Zylon and ultra-high molecular weight polyethylene (UHMWPE); a shape memory alloy/carbon fabric; and ceramic, alumina and titanium sheets. All laminate concepts have similar areal weights for a meaningful comparison. After defining the various concepts, we manufactured and measured their specific dissipated energy under HVI, and finally carried out post-mortem analysis (including C-scan and microscopy). The results show up to 95% improvement in energy dissipation over the baseline quasi-isotropic (QI) CFRP configuration.

Topology optimization of Double-Double (DD) composite laminates considering stress control

Double–double (DD) laminates are a new type of composite layups, which can achieve different structural properties by adjusting two sets of balanced fiber orientations. The combination of topology optimization and DD laminates can further enhance the advantages of composite materials as lightweight designs. Currently, most topology optimizations use compliance as the target. Existing optimization studies implementing stress control are mostly for isotropic materials. It is a great challenge to implement stress control during topology optimization of composite laminates, because the layer-wisely distributed stress brings a lot of design constraints and leads to many local optima. In this paper, we propose a nested p-norm method that integrates the Tsai–Hill failure criterion indexes of different elements in different layers into one design response, thus realizing the effective stress control for topology optimization of laminated structures. There are two levels of p-norm nested in the process: the inner p-norm approximates the maximum failure index of all the layers for one element, and the outer p-norm approximates the maximum failure index for all elements. The nested p-norm scheme is implemented under the framework of the Solid Isotropic Material with Penalization (SIMP) model, which is extended to DD laminates by interpolating the stiffness matrix of composites. Then, the optimization model is established by minimizing the maximum Tsai–Hill failure index using the function formulated by the proposed nested p-norm method under the constraint of the structural volume fraction and compliance. Next, stress sensitivities are calculated using the adjoint method. It is noticeable that the sensitivity with respect to the filtered projection density is separately calculated to improve the computational efficiency. Finally, typical examples of topology optimization with stress singularity such as an L-shaped bracket, a crack problem, a corbel structure, and an antenna support bracket are given. It is validated that the proposed nested p-norm method can effectively and efficiently reduce the stress concentration of laminate structures compared with the methods using single p-norm and layer-wise p-norm. Additionally, the optimization results show that the DD laminate has similar optimized configurations and optimization effects as those of the conventional Quad laminate with the equivalent stiffness.

Oblique radiograph with methylene blue marking: A reliable technique for upper thoracic level localization

PurposeTraditionally, plain radiographs are used in intraoperative spinal level localization (SLL), whereas counting vertebrae is often hampered by shoulders and scapulae in lateral views, thus increasing the potential for wrong-level surgery. To improve the localization accuracy, this study evaluated the safety and feasibility of oblique radiographs with methylene blue markings for SLL and explored the optimal angle and height of oblique radiographs. MethodsThe clinical data of 33 patients with upper thoracic spine lesions who were operated on in our hospital from January 2021 to April 2022 were retrospectively analyzed. Oblique radiographs with methylene blue markings were used for intraoperative SLL. ResultsA total of 33 patients were included in this study. The average BMI was 24.3 ± 0.7 kg/m2. The ipsilateral lamina structures were clearly shown in all cases. The median radiographing times of all the patients was 3, and the median radiographing duration was 2 min and 25 s. The average angle of oblique radiographs was 55.1 ± 3.8°, and the average distance from the skin to the root of the spinous process was 4.9 ± 1.2 cm. ConclusionsUsing oblique radiographs with methylene blue markings, not only the bone structure of an upper thoracic spine can be revealed clearly, but also the positioning deviation of traditional needle localization can be avoided. The lesion segment can be precisely located by this technology during surgery. Our angle of oblique radiographs and height determination method can be used to reduce the radiation exposure and shorten the operation time.

Effect of neutron irradiation on tensile properties of advanced Cu-based alloys and composites developed for fusion applications

The effect of neutron irradiation on tensile properties and fracture mode has been investigated for several advanced CuCrZr alloys in the frame of the European fusion material development program. Five material grades utilizing different strengthening principles have been exposed to neutron irradiation up to ∼2.5 dpa (displacement per atom) in the target operational temperature range of 150–450 °C. The strengthening mechanisms are based on the application of: i) tungsten particles; ii) tungsten foils (laminate structure); iii) tungsten fibers; iv) Y2O3 particles; v) vanadium addition (0.22%). Neutron irradiation was performed in the BR2 material test reactor inside the fuel channel in order to maximize the fast neutron flux. The upper irradiation temperature of 450 °C was selected to validate the ability of the pre-selected advanced grades to sustain the high temperature irradiation, since the baseline ITER specification CuCrZr is known not to retain sufficient tensile strength above 400 °C in non-irradiated conditions and shows strong irradiation induced softening above 300 °C. Neutron irradiation at 150 °C caused severe embrittlement of tungsten-copper laminates as well as a considerable reduction of the total elongation of all other grades. The irradiation at 450 °C led to the reduction of the yield strength and ultimate tensile strength (i.e. irradiation softening) in the vanadium-doped alloy similar to CuCrZr, while all other materials preserved or increased their strength (irradiation hardening). The fracture surfaces of the tested samples were analysed to investigate the modification of the deformation mechanisms in each particular case.

Lithostratigraphy, lithofacies and deposition conditions of the late Olenekian-middle Anisian Alam Formation in the Nakhlak area, central Iran

The present study aims to investigate petrography characteristics and sedimental environments of upper Olenekian–middle Anisian deposits of Nakhlak group in the sedimentary-structural zone of central Iran. To this end, a section of these deposits with a thickness of 720 meters was first selected, and 190 samples were taken from this section for preparing thin sections. Also, quantitative and qualitative laboratory tests were performed and 25 samples of sandstone were selected for point counter analysis. The results indicated that the major deposits of this formation are related to siliciclastic, carbonate, and pyroclastic types, which are in the form of two facies associations. The facies association A at the bottom of the studied section with the thickness of 90 meters has a periodicity of clastic, carbonate, and pyroclastic facies. The clastic facies of this association consists of fine-grained sandstone. In addition, the carbonate facies in association A are characterized by two microfacies consisting of intraclast oolitic grainstone and oolitic grainstone. Further, tuffite is the only pyroclastic facies related to association A, which has a laminate structure, cross-bedding lamination, herringbone bedding, and upward-thinning and thickening cycles. The facies association, B which is deposited later, is more in the middle and top part of the section. The facies association B is 660 meters thick and has a periodicity of clastic and limestone facies. Clastic facies of this association includes four lithofacies such as conglomerate, pebble coarse-grained sandstone, medium-grained sandstone to thin layer siltstone and shale. The carbonate facies consists of four microfacies such as sandy intraclastic wackestone and mudstone. Furthermore, slumping structures, cross bedding, turbulence, boudinage structure, and convolute of sediments, along with the effects of erosional channels are observed in facies B. Field and laboratory studies conducted on this succession indicate the structure of facies association A was deposited in a mixed siliciclastic carbonate ramp. Finally, submarine canyons and submarine fan environments were left by increasing the depth of the facies association B in the deep part of sea and turbidity systems.

Construction of PES mixed matrix membranes incorporating ZnFe2O4 @MXene composites with high permeability and antifouling performance

ZnFe2O4 @MXene composites were first prepared through the coprecipitation method to enhance the permeability and antifouling properties of polyether sulfone (PES) ultrafiltration membranes. Subsequently, the ZnFe2O4 @MXene composites were blended with PES to construct mixed matrix membranes (MMMs) with good permeability and antifouling performance. Results show that the deposition of bimetallic ZnFe2O4 on the surface or in the interlayer structure of Ti3C2Tx laminates resulted in strong interactions between the materials, thus improving the dispersion of the ZnFe2O4 @MXene composites in the PES polymer. The addition of well-distributed ZnFe2O4 @MXene composites not only improved the pore structure of the MMMs but also enhanced the hydrophilicity and surface polarity of the MMMs because of the rich hydrophilic groups on the surfaces of the ZnFe2O4 @MXene composites. The permeability and antifouling performance of the resulting MMMs were thus improved. When additional ZnFe2O4 nanoparticles were uniformly deposited on the surface or in the interlayer structure of the Ti3C2Tx lamellar structures, the hydrophilic groups on the surfaces of the ZnFe2O4 @MXene composites increased. Therefore, using these composites as fillers significantly enhanced the permeability and antifouling performance of the resulting MMMs. The PES MMMs exhibited a maximum membrane flux of 492.8 L∙m−2·h−1 and a maximum bovine serum albumin (BSA) rejection rate of 92.5%. Their membrane flux could be maintained at approximately 350 L·m−2·h−1 over five cycles of BSA solution/backwashing. This result reflects the high stability of the membranes. In addition, UF-4 achieved the highest flux (324.56 L∙m−2∙h−1) and a high dye/salt separation (RCR = 97.3; RNa2SO4 = 8%), confirming that PES MMMs containing ZnFe2O4 @MXene have good application prospects for the separation of dyes from high-salinity wastewater.

Concepts for integrating electrical energy storage into CFRP laminate structures for aeronautic applications

The CleanSky2 THT project SOLIFLY is developing further structural batteries for aeronautical applications. This paper presents the concepts of structural integration and the methodology to evaluate the impact of structural battery integration on the mechanical properties of CFRP solid laminates considering the size and shape of the structural battery insert as well as its location through the laminate thickness. A fully parameterised, computationally efficient numerical strategy for finite element simulation has been implemented to evaluate the mechanical properties and, for the first time, the onset of matrix damage as the cell geometry and integration location are varied. The first mechanical characterisation data of SB cell components and cell prototypes were obtained thanks to multi-instrumented tensile tests using digital image correlation and acoustic emission. An initial assessment of the advantages and trade-offs of the SB integration concepts with respect to functionally separated components is discussed.

Mechanical Testing of Connections Blind Bolted to the Thick Glass-Fiber-Reinforced Polymer Spar Cap of a Decommissioned GE37 Wind Turbine Blade

Millions of tons of glass-fiber-reinforced polymer (GFRP) composite wind turbine blades are expected to age out of service over the next 30 years. Research is being conducted on repurposing these structures as new civil infrastructure products. The GFRP material in these decommissioned wind blades has been shown to retain significant strength and stiffness for second-life applications. However, for repurposing as new products, they will need to be connected to other structural members. The connections employed for this need to be designed, evaluated, and tested prior to their use. Here, we present the results of detailed testing of bolted connections for load-carrying appurtenances that will carry the phases and shield wires (e.g., insulators, crossarms, davits, guy wires, posts) to the spar cap of an 11-year-old 1.5 MW GE37 wind blade, intended for use as a repurposed transmission pole (i.e., a BladePole). Details of ASTM-type pull-out and bearing capacity tests using different types of blind bolts, and tests of a full-scale steel bracket connection called a “universal connector,” are reported. The effects of the different blind bolts, pin diameters, and loading directions relative to the composite laminate structure (longitudinal or transverse) for both the coupon- and full-scale connector bracket tests are described. The ability to design and construct robust connections for repurposed wind blade structures was demonstrated.

Swarm intelligence hybridized with genetic search in multi-objective design optimization under constrained-Pareto dominance

The inclusion of uncertainty in structural design optimization led to more complex design optimization formulations, where uncertainty quantification has significant influence on solution methods and computing times. Designs maintaining steady levels of performance, under uncertainty, are called robust and the combination of both robustness and performance optimality leads to a methodology called Robust Design Optimization (RDO). In this work a new approach to the RDO of angle-ply composite laminate structures is proposed. The key concept of this methodology is the hybridization between the principles of Particle Swarm Optimization and Genetic Algorithms, through the evolution of multiple populations based on local and global constrain-dominance. The RDO problem is here defined as the bi-objective minimization of the structural weight (optimality) and the determinant of the variance–covariance matrix (robustness) of the system’s response functionals, subject to stress and displacement constraints. A numerical structural design problem, representing a composite laminate engine hood shell, shows the capabilities of the proposed approach. Results display the good convergence properties of the proposed hybridizations both in the search and objective spaces.

Effect of Al Segregation on Mechanical Properties and Deformation Mechanism of Nanocrystalline NiCoAl

Solute element segregation behavior significantly changes the mechanical properties and deformation mechanism of nanocrystals. In this work, we studied the effect of segregation structure on the deformation mechanism of NiCoAl nanocrystalline by molecular dynamics. The results show that the grain boundary stability of nanocrystals is the worst when Al is completely segregated within the grain, and the metastable grain boundary cannot effectively hinder the dislocation movement, resulting in poor mechanical properties of nanocrystals. When 4% of Al transitioned to the grain boundary, the grain boundary stability was greatly improved and many lamination structures were generated. At this time, the lamination structure and stable grain boundaries were effectively nailed to dislocations, resulting in nanocrystal strengthening. With the complete segregation of Al at the grain boundary, the grain boundary shows a stable ability significantly and inhibits the nucleation of dislocation, leading to a decline in the strength of nanocrystals. In this effort, the deformation mechanism of solute element segregation is investigated from the interaction of dislocation and solid solution element, which is conducive to the design of advanced materials with excellent properties. Our work provides fascinating insights into the mechanism of plastic deformation response under solute element segregation structure.

Comprehensive study of hot deformation behavior and fracture mechanism of Al/Cu laminated composite

The hot deformation behavior of Al/Cu laminated composite was studied by isothermal tensile experiments in the temperature range of 200–500 °C and strain rate range of 0.001–1/s. The Arrhenius constitutive model was established to predict the flow stress by determining the constants of composites. In addition, based on the dynamic material model (DMM), the hot working map is established. The results show that the power dissipation efficiency is high under the conditions of high temperature, medium and low strain rate. When the strain is 0.25, there are few areas of stability due to the increasing frictional resistance at the interface. It is found that the dynamic recrystallization (DRX) is promoted by hot tensile and laminate structure. The softening mechanism of Al side is mainly dynamic recovery (DRV) and discontinuous dynamic recrystallization (DDRX), while that of Cu side is DRX. During the tensile process, the Al side grains always maintain stable Brass, Copper and S textures; the Cu side grains always maintain the Cube texture with stable-end orientation and when the deformation exceeds 60 %, the Goss unstable texture appears. It is conducive to dislocation movement and increases the recrystallization ratio. Then, the fracture mechanism of Al/Cu laminated composite is revealed. Due to the presence of the interface, the Cu side shows brittle fracture at room temperature. The snake-like sliding occurs on both sides of Al and Cu under hot deformation, showing ductile fracture, and the defects on Cu side are more serious than those on Al side. These results lay a foundation for optimizing the hot working parameters, improving the performance of the forming parts and clarifying the fracture damage mechanism of Al/Cu laminated composite.

An analytical approach of design for recycling of laminate structures by the use of magnetic pulse disassembling

Composite materials in association with metal sheets or ceramic coatings have found a variety of applications, especially as load-bearing components in composite structures. Their disassembly for recycling or maintenance has therefore become more complex. The magnetic pulse technique, usually dedicated to dynamic forming and welding processes, can be used to separate composite materials of a laminate structure of their recyclable adjacent materials. This technology profits from Lorentz forces appearing in electrically conductive materials placed in the vicinity of conductors in which high-intensity electrical discharges are performed. These body forces act locally during the fast energy discharge, from which a stress wave propagates in the structure. The propagation of this stress wave can be used to generate interfacial tensile stress in laminate structures or assemblies. Especially, this technique can be used for evaluating the dynamic bond strength of an interface. This works aims at determining the required conditions for disassembling a laminate structure using a magnetic pulse imposed on one side of the assembly, without significantly damaging the debonded layers. Ideally, the generated interfacial tensile stress should be greater than the interfacial bond strength. In this paper, a one-dimensional analytical analysis is performed in linear elastodynamics on a tri-layered laminate structure, infinite in transverse directions, based on the method of characteristics. An optimisation problem is defined, maximising the interfacial stress between the first two layers, whose solution requires to study various configurations of the assembly involving different sets of characteristics in the laminate, associated with different areas of the domain of feasibility spanned by the unknown vector. Some assumptions and introduced simplifications of the optimisation problem allows to follow a simple two-stage solution procedure, first with respect to the thickness of the first layer for a given stress pulse, then with respect to material impedances of all layers. Several configurations of the assembly are shown to create a sufficiently large interfacial tensile stress to reach the crack initiation and propagation, and a maximum tensile interface stress of twice the maximum applied pressure is obtained in the asymptotic limit.

Study on the Stability of a Repair Process for Carbon Fiber Laminates

Carbon fiber-reinforced resin matrix composites are often used in the surface structure of helicopters. In the process of flight, the structure often suffers from different degrees of damage due to the influence of the harsh environment. To explore the superiority of the repair method and obtain a good repair process, the intact and damaged carbon fiber composite laminates were prepared in this paper. The damaged specimens were repaired by single-sided double-layer patch bonding. The allowable value of tensile strength of carbon fiber laminates was tested, and the mechanical properties of carbon fiber composite laminates after repair were studied. Combined with the failure mode of the specimen after failure, the results show that the mechanical properties of the repaired specimen can be restored to about 81.9 % of the non-destructive specimen. The single-sided double-layer patch can effectively improve the mechanical properties of the middle loading area. The repair process has high reliability and good stability, which provides a new method for the repair of the composite laminate structure.

An Artificial Intelligence‐Motivated Skin‐Like Optical Fiber Tactile Sensor

Soft and stretchable tactile sensors have received extensive attention for their potential applications in wearables, human–robot interaction, and intelligent robots. Herein, inspired by the functions of skin somatosensory signal generation and processing, an artificial intelligence‐motivated skin‐like optical fiber tactile (SOFT) sensor is proposed. It features multifunctional touch interaction capabilities including tactile amplitude and position and tensile strain. Four fiber Bragg gratings (FBGs) are embedded in a skin‐like three‐layer laminate structure of the SOFT sensor, forming a flexible tactile sensing array with a stretchability larger than 20%. Fusing the two‐level cascaded neural network, the position and magnitude of the contact force can be distinguished simultaneously. The recognition accuracy for contact position is up to 92.41% and the error is less than 4.2% within the force range of 0–3.5 N. Several SOFT sensor‐based interactive applications including pressure password interface and music playback are achieved by combining the artificial intelligence spatiotemporal dynamic logic analysis. Furthermore, the sensor is also capable of complex scenes involving tension and tactile sensing, such as dexterous hand perception and human–robot interaction control. This work provides novel insights into artificial intelligence‐based integrated skin that shows broad promise in intelligent prosthetics and bionic robotic.

Dynamic response and failure behaviour of thermoplastic fibre–metal​ laminates subjected to confined blast load

Due to the confinement effect, the blast load from a confined space explosion tends to cause more severe damage to structures. When subjected to this type of confined explosion, thermoplastic fibre–metal laminate (TFML) panels would experience repeated shock waves and relatively longer durations of quasi-static pressure. A better understanding of the dynamic response and damage mechanism of TFMLs under confined blast loading can greatly benefit the design of composite structures with improved blast resistance. In the present work, TFMLs with seven different configurations were designed and fabricated. Confined-blast experiments with various masses of trinitrotoluene (TNT) were performed on these TFMLs. The experimental results, including deflection time histories and X-ray computed tomography (CT) images, have been applied to the development of a method for predicting the dynamic response of laminates under confined blast loads. The findings of this work will assist in the rapid assessment of the deformation of fibre–metal laminates and assist in the pre-design of laminate structures in confined explosions.

Prediction of lamina structure and reservoir quality in shale using well logs: The Cretaceous Qingshankou Formation, Gulong Sag, Songliao Basin, China

Lamina structure is determined by composition, thickness, continuity, and mineral assemblage. Reservoir quality in oil shale reservoirs is determined by lamina structure, which controls hydrocarbon accumulation and migration. The prediction and evaluation of multi-scale lamina structures using geophysical well logs is challenging. Recent studies demonstrate that the lamina structure classification may be based on core observation and core analysis. However, there are no corresponding high-resolution geophysical logging methods to identify and categorize lamina structure continuously in a single well. Here, an experimental approach, involving an integrated analysis of cores, thin sections, well logs such as slabs and button conductivity curves of image logs (up to 5 mm vertical resolution), is used to characterize lamina structure. T1-T2 (T1, longitudinal relaxation time, and T2, transverse relaxation time) maps of nuclear magnetic resonance (NMR) logs are applied to clarify the relationships between the lamina structure, reservoir quality, and oil-bearing properties. Results demonstrate how lamina structure in shale can be divided into three types: laminated rocks, layered rocks, and massive rocks, according to observation of core at the lamina scale. The thickness of individual lamina is less than 0.01 m in the laminated rocks, and the layered rocks have bundles of genetically related laminae thickness ranging between 0.01 m and 0.1 m. In massive rocks there is no visible layering. The well log response patterns of the three types of lamina structure are established so that the distribution of lamina structure can be predicted in a single well via well logs. Results show that the oil-bearing shale intervals are dominated by laminated rocks and layered rocks, accounting for 90% of the studied Qingshankou Formation. In addition, the layered rocks play an important role in improving reservoir quality and the laminated rocks present moderate reservoir quality. The massive rocks show poor reservoir quality. Moreover, an increased proportion of felsic mineral content favors increased oil potential in oil shale reservoirs. The method is generally applicable and is of value in developing predictive indicators of subsurface reservoir sweet spots in shale oil and gas exploration and development.

Tunable self-biased magnetoelectric effect in magnetization-graded magnetoelectric composites

Magnetoelectric (ME) composites, which are magnetostrictive-piezoelectric composites, have garnered attention for use in various application fields owing to their large ME coupling compared with single-phase multiferroic materials. The maximum ME coupling is observed when an increased DC magnetic bias field is applied, which results in large devices with degraded sensitivity due to electromagnetic noise. To address this problem, a strong self-biased ME composite that generates the maximum ME response in a zero-bias field was proposed in this study. Highly self-biased ME composites were prepared by combining soft magnetic Ni and highly permeable Metglas magnetostrictive layers with a Pb(Mg1/3Nb2/3)O3–PbZrTiO3 piezoelectric single-crystal laminate structure and inducing a magnetization gradient. The maximum ME voltage value without a DC bias field was evaluated to be 4.2 V/cm∙Oe for an MMNPNMM (M: Metglas foil, N: nickel, P: PMN-PZT) structure, which is 625 % higher than that of conventional ME composites. Therefore, the relatively bulky means of the DC-bias application on ME materials could be eliminated, resulting in a simple ME device with a small volume using the magnetization gradient concept.

A Directional Chitosan Sound Sensor Based on Piezoelectric-Triboelectric Sensing.

Herein, we have constructed a directional sound sensor based on an anisotropic chitosan aerogel. Because of the lamellar porous structure, this chitosan aerogel exhibits a distinct anisotropic behavior, featuring the compressive stress along the direction of the parallel laminate structure, being approximately 2.6 times that in the orthogonal direction. Simultaneously, the chitosan aerogel is used as a directional sound-sensing material, which exhibits excellent acoustic-electric conversion performance with a marked difference in the direction perpendicular to the laminate structure than in the parallel direction. The CSANG has an optimum electrical output of 66 V and 9.2 μA under a sound stimulation of 150 Hz and 120 dB in the orthogonal direction of the laminate structure. Therefore, this directional chitosan sound sensor with excellent biocompatibility and sound sensitivity demonstrates promising application potential in the field of intelligent sensing and artificial cochlea.