Soft Composite Materials Research Articles

Development of a Novel Wear Equation by Comparing the Wear Behaviour of Hard (AA7075) and Soft (AA6063) Hybrid Composite Materials

Development of a Novel Wear Equation by Comparing the Wear Behaviour of Hard (AA7075) and Soft (AA6063) Hybrid Composite Materials

Investigation of shaded pole stator topology for low power AC motors design

PurposeThis paper aims to investigate the features of single phase shaded pole stator with squirrel–cage rotor or permanent magnet rotor, that leads to an investigation of these topoloties as induction motor or synchronous motor. The comparative analysis is realised for the following three topologies: single phase shaded pole induction motor (SPIM) with squirrel–cage rotor, the second topology (single phase synchronous motor) has the same stator configuration but with permanent magnet rotor and the third investigated topology is similar to the second one, where the stator poles instead of iron steel are made of soft composite material.Design/methodology/approachThe investigation in this work starts with a performance analysis of single-phase SPIM. Afterwards for the same stator topology the squirrel rotor is replaced with a two-pole permanent magnet rotor and the same performance analysis is realised for this topology. Finally, the second topology is improved bay replacing the iron steel stator poles with stator poles made of soft magnetic composite material and performance analysis is realised for this third type of topology as well. The performance analysis of all topologies is realised by implementation of finite element method and finite element analysis.FindingsThe presented data and diagrams from the realized investigation show that single phase synchronous motor with shaded pole stator has an improved characteristics in comparison with the initial single-phase SPIM. Finally, the third topology realized on the bases of the single-phase synchronous motor has the best performance characteristics due to the implementation of soft magnetic material in the realization of the stator poles. The proposed methodology for structural and performance improvement of a single-phase SPIM topology opens the possibility for additive manufacturing application and significant cost reduction.Originality/valueThe focus was put on exploration the possibilities of the single-phase shaded pole stator topology for application in low-power and low-cost single phase self-starting motors. By simple replacement of the squirrel–cage rotor, in the reference AKO-16 motor, with one-piece ferrite permanent magnet rotor, the self-starting single phase synchronous motor was derived. In the next step, owing to simplify the SPPM motor production process and manufacturing, the stator poles instead of iron steel lamination were made of soft composite material Somaloy®. It opens the possibility for additive manufacturing application and significant cost reduction.

Multiscale Computational and Artificial Intelligence Models of Linear and Nonlinear Composites: A Review

Herein, state‐of‐the‐art multiscale modeling methods have been described. This research includes notable molecular, micro‐, meso‐, and macroscale models for hard (polymer, metal, yarn, fiber, fiber‐reinforced polymer, and polymer matrix composites) and soft (biological tissues such as brain white matter [BWM]) composite materials. These numerical models vary from molecular dynamics simulations to finite‐element (FE) analyses and machine learning/deep learning surrogate models. Constitutive material models are summarized, such as viscoelastic hyperelastic, and emerging models like fractional viscoelastic. Key challenges such as meshing, data variability and material nonlinearity‐driven uncertainty, limitations in terms of computational resources availability, model fidelity, and repeatability are outlined with state‐of‐the‐art models. Latest advancements in FE modeling involving meshless methods, hybrid ML and FE models, and nonlinear constitutive material (linear and nonlinear) models aim to provide readers with a clear outlook on futuristic trends in composite multiscale modeling research and development. The data‐driven models presented here are of varying length and time scales, developed using advanced mathematical, numerical, and huge volumes of experimental results as data for digital models. An in‐depth discussion on data‐driven models would provide researchers with the necessary tools to build real‐time composite structure monitoring and lifecycle prediction models.

Characterization of a 3D Printed Endovascular Magnetic Catheter

Minimally invasive endovascular procedures rely heavily on catheter devices. However, traditional catheters lack active steering requiring considerable skill on the surgeon’s part to accurately position the tip. While catheter tips could be made steerable using tendon-driven and Pneumatic Artificial Muscle (PAM) approaches, remote magnetic actuation is uniquely suited for this task due to its safety, controllability, and intrinsic miniaturization capabilities. Soft composite magnetic materials feature embedding distributed magnetic microparticles compared with attaching discrete permanent magnets proving beneficial in steerability and control. This work demonstrates the fabrication of a soft hollow magnetic tip that can be attached to a catheter to make the assembly steerable. The catheter tip is extensively characterized in terms of bending hysteresis, bending force, and dynamic response. The catheter showed average hysteresis between 5% and 10% and bending forces up to 0.8 N. It also showed a good dynamic response by changing its bending angle in <200 ms under a step response.

Piezoresistive Composites in Tension and Compression Using a Cantilevered Beam for Spot Testing and Tactile Sensing

Abstract Piezoresistive soft composite materials exhibit a change in resistance when undergoing deformation. This combined with their optical, thermal, and mechanical properties makes these composites good candidates for force sensors. Tactile force sensors have long been studied for applications in healthcare, robot–human interactions, and displacement monitoring. The main goal in this work is to characterize a soft piezoresistive layer in both tension and compression to enable a model system for a piezoresistive tactile force sensor and a characterization platform. However, the mechanisms by which these composites exhibit piezoresistivity are complex and must be characterized before use not only in bulk but at the exact locations where contact is expected. In this paper, a cantilevered beam is proposed as a base-mounted force-sensing mechanism. This mechanism allows for characterization of the composites at multiple locations across the sample using a two-probe technique. Multiwalled carbon nanotubes (MWCNTs) are mixed by weight with a soft polyurethane in 15, 16, and 17 wt. % concentrations. Because the elastic modulus of the piezoresistive layer is not known, indentation tests using Hertz theory and numerical calculations are used to simulate the effective elastic modulus and average strain. These results are then compared with the experimental stress results. In general, these tests show a greater sensitivity in tension than in compression. However, the difference lessens as the concentration increases. A linear fit is applied to the ΔR/R versus strain graphs to calculate the gauge factors. Each sensor exhibits a positive and negative gauge factor over two different ranges. ΔR/R versus strain graphs for tension and compression show gauge factors between −19 and 24 with the range decreasing with increasing MWCNT percentage.

Design and deformation analysis of an inflatable metallic cylinder based on the Kresling origami pattern

Inflatable space capsules can be compactly folded to a small volume during launch and then deployed in space to create a large enclosed place for astronauts and equipment. Current inflatable space capsules are usually made of soft composite materials and need to be rigidized after deployment, but the rigidization techniques to date cannot meet the requirements of high stiffness and low thermal expansion simultaneously. The study on cylindrical transformable volume structures based on metals is also limited due to the large in-plane deformation during manufacturing and deployment. Here, we propose a novel inflatable metallic cylinder based on the Kresling origami pattern which has a large deployment ratio and high stiffness without rigidization. The folding and deployment process of the cylinder with varying geometric parameters and inflation rates are investigated through numerical simulation that is validated by experiments, from which the deformation process, maximum plastic strain, and the deployment ratio are unveiled. The results show that the maximum plastic strain reduces with the increase in the total number of creases in the cylinder and their transition arc radius, but a large number of creases will lead to a lower deployment ratio. To achieve a deployment ratio of 3.35 which is comparable with those of the state-of-the-art inflatable space capsules, the maximum plastic strain is kept below 0.18. This proposed metallic origami cylinder thus shows great potentials in the application of space capsules.

Skin-Inspired Tough Elastomer with Moisture-Triggered Switchable Mechanical Properties.

Biological tissue usually exhibits good water adaptive mechanical properties, which can maintain high strength and toughness in both wet and dry states. However, synthetic tissue like hydrogel usually becomes hard and brittleness in its dry state. Here this challenge is met by exploring iron-catechol complex (TA-Fe3+ ) as a great platform combining extremely different polymers (elastomer and hydrogel) to construct new tissue-like soft composite materials with two different continuous phases, which have not yet been reported. In its dry state, the xerogel phase becomes a reinforced segment to increase the strength of PB without losing its toughness. In its wet state, this soft material becomes high performance hydrogel, where hydrogel phase absorbs high water and elastomer phase can sustain high loading. Such heterogeneous phase structures provide a good idea for designing the soft materials, exhibiting a trade-off between its high strength and toughness in both wet and dry states. Furthermore, its shape memory behaviors in both its wet and dry state, which shows a great potential application for complex adaptive shape transformation and engineering application like lifting of heavy objects under remote control due to high photo-thermal transition of TA-Fe3+ is explored.

Four distinct network patterns of supramolecular/polymer composite hydrogels controlled by formation kinetics and interfiber interactions

Synthetic composite hydrogels comprising supramolecular fibers and covalent polymers have attracted considerable attention because their properties are similar to biological connective tissues. However, an in-depth analysis of the network structures has not been performed. In this study, we discovered the composite network can be categorized into four distinct patterns regarding morphology and colocalization of the components using in situ, real-time confocal imaging. Time-lapse imaging of the network formation process reveals that the patterns are governed by two factors, the order of the network formation and the interactions between the two different fibers. Additionally, the imaging studies revealed a unique composite hydrogel undergoing dynamic network remodeling on the scale of a hundred micrometers to more than one millimeter. Such dynamic properties allow for fracture-induced artificial patterning of a network three dimensionally. This study introduces a valuable guideline to the design of hierarchical composite soft materials.

Numerical study on the instabilities of hard-magnetic soft materials with viscoelastic effects

As a type of soft composite material, the hard-magnetic soft materials (HMSM) can retain high residual magnetization due to the high-coercivity of hard-magnetic particles. Meanwhile, the inherent viscoelasticity of the soft polymer matrix usually causes the rate dependent behavior and affects the stability of HMSM. The effects of viscoelasticity on the finite deformation and instability of HMSM are studied in this paper. A numerical model is developed for magneto-mechanical coupled problems of the viscoelastic HMSM. With this model, the instabilities of two typical HMSM structures (i.e. beam and spherical shell) with viscoelastic effects are investigated, including the buckling and snap-through instability. The results show that the viscoelastic effects delay the onset of instability and suppress the snap-back phenomenon during the unloading process. In addition, three different buckling behaviors (i.e. fully relaxed immediate buckling, elastic immediate buckling and the delayed buckling) at different loading rate ranges are observed in both beam and spherical shell. This work provides an effective numerical model to analyze the finite deformation and instabilities of viscoelastic HMSM and may guide the design of HMSM devices.

Study on Low-Velocity Impact Behavior of Twaron® Fabric Subjected to Double-Impactor Impact from a Numerical Analysis Perspective

Abstract In the present study, a finite element impact model was developed and analyzed using commercial FEM code ANSYS® and then validated via a drop-weight impact experiment. Moreover, double-impactor impact models were designed and developed with different impact distribution and locations of two impactors to compare impact properties. A total of 18 impact scenarios comprised of asymmetric and symmetric types were performed. The effect of impact location on the impact resistance force and duration time was investigated: the closer the impact point is to the fabric center, the longer the impact duration time. In addition, the effect of impact location on impactor failure deflection was also investigated and it was concluded that regardless of the symmetric or asymmetric impact scenario, the smaller the average distance between the impact location of the two impactors from the fixed boundary, the smaller the overall average failure deflection that occurs. The relevance of impact location and fabric energy absorption capacity was also identified. Furthermore, the effect of impact location on fabric stress distribution and transverse deformation and of the variation of the impact velocity on fabric impact behaviors were investigated. These findings will provide important guidance for engineering soft body armor and composite materials.

Magnetic properties of soft magnetic composites used in electromechanical engineering

The article discusses the methods of using composite magnetic alloys for elements of electrical engineering. The main methods of obtaining soft magnetic composite materials have been studied in order to obtain high-performance MMC particles, as it should be subjected to electrically insulated powder to obtain high-density parts. High densities generally improve magnetic properties, both to keep hysteresis losses low and to obtain high flux density. These give an effect when used for the cores of electric motors based on magnetically soft composite materials.

A tissue-engineered neural interface with photothermal functionality.

Neural interfaces are well-established as a tool to understand the behaviour of the nervous system via recording and stimulation of living neurons, as well as serving as neural prostheses. Conventional neural interfaces based on metals and carbon-based materials are generally optimised for high conductivity; however, a mechanical mismatch between the interface and the neural environment can significantly reduce long-term neuromodulation efficacy by causing an inflammatory response. This paper presents a soft composite material made of gelatin methacryloyl (GelMA) containing graphene oxide (GO) conjugated with gold nanorods (AuNRs). The soft hydrogel presents stiffness within the neural environment range of modulus below 5 kPa, while the AuNRs, when exposed to light in the near infrared range, provide a photothermal response that can be used to improve the spatial and temporal precision of neuromodulation. These favourable properties can be maintained at safer optical power levels when combined with electrical stimulation. In this paper we provide mechanical and biological characterization of the optical activity of the GO-AuNR composite hydrogel. The optical functionality of the material has been evaluated via photothermal stimulation of explanted rat retinal tissue. The outcomes achieved with this study encourage further investigation into optical and electrical costimulation parameters for a range of biomedical applications.

Temperature-dependent vibration energy harvesting performance of polyimide/(Na,K)NbO3 piezoelectric composites

A composite structure of piezoelectric particles and soft polymer composite material is one of the candidates that converts environmental vibration energy into electrical energy. Presently, expanding the usage of applications is needed in terms of the working environment at harsh temperatures. Polyimide is flexible and temperature-stable polymer. In this research, we report a synthesis of polyimide/(Na,K)NbO3 (PI/NKN) flexible composites. We constructed a setup, where vibration and heat are simultaneously applied to the PI/NKN composites. The frequency and temperature dependence of the output voltage were investigated at room temperature up to 200 °C. Relative permittivity, piezoelectric constant, and output voltage of the PI/NKN showed temperature stability. Flexibility and glass transition temperature of a polymer matrix are important factors. PI/NKN composites are potential energy harvesting materials with flexibility and excellent high-temperature stability.

The Construction of Biologically Relevant Fiber-Reinforced Hydrogel Geometries Using Air-Assisted Dual-Polarity Electrospinning.

Fiber-reinforced hydrogels are a class of soft composite materials that have seen increased use across a wide variety of biomedical applications. However, existing fabrication techniques for these hydrogels are unable to realize biologically relevant macro/mesoscale geometries. To address this limitation, this paper presents a novel air-assisted, dual-polarity electrospinning printhead that converges high-strength electric fields, with low velocity air flow to remove the collector dependency seen with traditional far-field electrospinning setups. The use of this printhead in conjunction with different configurations of deformable collection templates has resulted in the production of three classes of fiber-reinforced hydrogel prototype geometries, viz., (i) tubular geometries with bifurcations and mesoscale texturing; (ii) hollow, nontubular geometries with single and dual-entrances; and (iii) three-dimensional (3D) printed flat geometries with varying fiber density. All three classes of prototype geometries were mechanically characterized to have properties that were in line with those observed in living soft tissues. With the realization of this printhead, biologically relevant macro/mesoscale geometries can be realized using fiber-reinforced hydrogels to aid a wide array of biomedical applications.

Computational Design of a Soft Robotic Myocardium for Biomimetic Motion and Function

AbstractSoft robotic devices containing multiple actuating elements have successfully recapitulated complex biological motion, leading to their utility in biomedical applications. However, there are inherent nonlinear mechanics associated with soft composite materials where soft actuators are embedded in elastomeric matrices. Predicting their overall behavior prior to fabrication and subsequent experimental characterization can therefore present a hurdle in the design process and in efficiently satisfying functional requirements and specifications. In this work, a computational design framework for optimizing the motion and function of biomimetic soft robotic composites is demonstrated by conducting a design case study of soft robotic cardiac muscle (myocardium) with a particular focus on applications including replicating and assisting cardiac motion and function. A finite element model of a soft robotic myocardium is built, in which actuators are prescribed with anisotropic strain to simulate local deformation, and various design parameters are investigated by evaluating the performance of each configuration in terms of ventricular twist, volumetric output, and pressure generation. Then, an optimized design is proposed that recapitulates the physiological motion and hemodynamics of the heart, and its thrombogenicity is further explored using a fluid‐structure interaction model. This framework has broader utility in predicting the performance of other soft robotic embedded composites.

Measuring the interfacial bonding strength between soft composite material membranes using blister test

Recently, soft materials have been utilized to build various kinds of mechanical and electronic devices, such as soft grippers, microfluidic devices, flexible electronic membranes, and flexible sensors. These soft devices are safer than rigid ones because they cause less damage to humans and other surrounding objects. This paper focused on soft composite material membranes that are composed of two well-known materials: Ecoflex and polydimethylsiloxane (PDMS). The interfacial bonding strengths between the soft composite material membranes were measured by blister test. One layer of the soft membrane was cured on top of another layer of the soft membrane. A circular unbonded region formed at the interface between both soft membranes. Subsequently, a needle was inserted into the unbonded area, and air pressure was used to inflate the unbonded area, resulting in the formation of a blister. As the applied pressure reached a critical level, the interface at the edge of the blister began to delaminate. A force model was built to compute the bonding strength at the interface with respect to the blister diameter, membrane thickness, and critical pressure. The obtained results revealed that the increased quantity of PDMS in the Ecoflex material enhances the bonding strength. The research results were useful for proper control of bonding strength between polymer composites in various engineering designs, such as microfluidic systems, lab-on-a-chip designs, etc.

Strengthen Synergistic Effect of Soft Carbon and Hard Carbon Toward High-Performance Anode for K-Ion Battery.

Synergistic effect of soft carbon and hard carbon has been proven to be useful for obtaining excellent anode materials for potassium ion battery, which is determined by the mixing degree of precursors. Inspired by the formation of proteins in biology, peptide bonds are used to connect the precursors of the two sort of carbon to prepare soft-hard hybrid carbons with stronger synergistic effects. The hard carbon domain with nanometer size is so highly distributed in the soft carbon that the synergistic effect between two sorts of carbon is significantly enhanced. After the optimization, the diffusion coefficient of as-prepared hybrid carbon (CSHC3-6-1200) is 10 times larger than that of corresponding carbon synthesized by physical method. Consequently, CSHC3-6-1200 can maintain a specific capacity of 71.6 mAh g-1 at a high current density of 1600 mA g-1. It is believed that this new preparation route may bring a new perspective to the development of soft and hard composite carbon material anodes with high power density and ultralong service life.

Structural Mechanisms in Soft Fibrous Tissues: A Review

Through years of evolution, biological soft fibrous tissues have developed remarkable functional properties, unique hierarchical architectures, and -most notably, an unparalleled and extremely efficient deformation ability. Whereas the structure-function relationship is well-studied in natural hard materials, soft materials are not getting similar attention, despite their high prevalence in nature. These soft materials are usually constructed as fiber-reinforced composites consisting of diverse structural motifs that result in an overall unique mechanical behavior with large deformations. Biomimetics of their mechanical behavior is currently a significant bioengineering challenge. The unique properties of soft fibrous tissues stem from their structural complexity, which, unfortunately, also hinders our ability to generate adequate synthetic analogs, such that autografts remain the “gold standard” materials for soft-tissue repair and replacement. This review seeks to understand the structural and deformation mechanisms of soft collagenous tissues, with a particular emphasis on tendon and ligaments, the annulus fibrosus (AF) in the intervertebral disc (IVD), skin, and blood vessels. We examined and compared different mechanical and structural motifs in these different tissue types, which are subjected to complex and varied mechanical loads, to isolate the mechanisms of their deformation behavior. Herein, we focused on their composite structure from a perspective of the different building blocks, architecture, crimping patterns, fiber orientation, organization and their structure-function relationship. In the second part of the review, we presented engineered soft composite applications that used these structural motifs to mimic the structural and mechanical behavior of soft fibrous tissues. Moreover, we demonstrated new methodologies and materials that use biomimetic principles as a guide. These novel architectural materials have tailor-designed J-shaped large deformations behavior. Structural motifs in soft composites hold valuable insights that could be exploited to generate the next generation of materials. They actually have a two-fold effect: 1) to get a better understanding of the complex structure-function relationship in a simple material system using reverse biomimetics and 2) to develop new and efficient materials. These materials could revolutionize the future tailor-designed soft composite materials together with various soft-tissue repair and replacement applications that will be mechanically biocompatible with the full range of native tissue behaviors.

A numerical study on the low-velocity impact behavior of the Twaron®fabric subjected to oblique impact

AbstractIn this study, a finite element low-velocity impact model of Twaron®plain-woven fabric was created and analyzed using the commercial code ANSYS®-AUTODYN, and then was validated by drop-weight impact experiments. As a bullet or a fragment can strike a protective system from any angle in space, it is necessary to investigate fragment impact behavior response to impact threats from all angles of space. Therefore, in-plane obliquityθ, and spatial obliquityφ, were employed in this study and 17 different simulation test impact scenarios with different impact obliquity values were carried out using a standard hemispherical-head impactor. Results showed that the energy absorption of Twaron®fabric decreases with increasingθ, whereas under the sameθ, the energy absorption increases with increasingφ. This study also evaluated and compared the low-velocity impact performance of Twaron®fabric as a function of impactor shape, such as hemispherical, flat, and ogival heads, with differentθ. The results showed that under the same density, volume, and diameter conditions and at the normal impact scenario of a flat-head impactor, the fracture mechanism of the yarn is the same with all impact scenarios for a hemispherical-head impactor; the contacted yarns of the fabric fractured almost simultaneously. For the other oblique impact scenarios of the flat-head impactor, as well as impact scenarios of the ogival-head impactor, the yarns of the fabric fractured intermittently. Additionally, for the impact scenario with the ogival-head impactor, the effect of impact obliquity on energy absorption of the fabric was completely opposite to that of the hemispherical-head impact scenario. This is because in the hemispherical-head impact scenario, the fabric yarn tends to be damaged by tension, whereas in the ogival-head impact scenario, the fabric tends to be damaged by out-of-plane shear. These findings provide important guidance for the engineering of soft body armor and composite materials.

Symbiosis between the components of a soft composite material responding to osmotic shock: The case of three-liquid systems

HypothesisFor conventional high internal phase emulsions (HIPEs) with an external osmotic pressure greater than Laplace pressure, once the osmotic balance is broken, the swelling or shrinking of the aqueous phase can easily trigger phase separation. Mixing two immiscible dispersed phases in a double HIPE can evolve differently following an osmotic shock, which is expected to create a synergistic effect that can frustrate the phase separation of the system. ExperimentsOsmotic responses of double HIPEs were studied at the surface of a NaCl solution at a range of molarities. Fluorescence confocal microscopy studies were carried out to track the responses on microscopic scales. Measurements on surface tensions revealed the interfacial behaviors of the used surfactant. FindingsA synergistic effect is achieved by a symbiotic process between the dispersed oils, where one type of droplets become more stable and pack around the other ones to halt their coalescence. The essential drive comes from the adsorption/desorption of surfactant molecules at oil–water interfaces. By directly adjusting the osmotic pressure difference, transitions between osmotic down-shock and osmotic up-shock can also be realized. This symbiosis greatly expands the potential technological applications of multiple-liquid systems, and can be used to design novel multi-functional composite materials.