Smart Composite Systems Research Articles

Artificial neural network model of the mechanical behaviour of shape memory alloy Schwartz primitive lattice architectures

This work proposes a novel artificial neural network (ANN)-based framework to explore the mechanical behaviour of shape memory alloy (SMA) Schwartz primitive triply periodic minimal surfaces (TPMSs) architectures where a loop with multiple conditions (LMCs) is introduced into the framework to improve its accuracy. Remarkably, it is found that the introduced ANN-based framework comprehends extremely well the example data and then provides a highly accurate prediction for the topology-driven mechanical behaviour of the SMA TPMS lattice architectures, which do not belong to the example. Indeed, the mechanical responses obtained from ANN-based approach excellently agree with that from numerical homogenization, with the maximum percent difference below 2.7% attained when the TPMS is subjected to tension or shear during the loading and unloading processes. More interestingly, the ANN-based approach can perform well with the increment of relative density or temperature 1000 times smaller than that in the homogenization, only requiring a little simulation time or thousands of times faster than that in the homogenization at the same computer setup. Hence, the mechanical behaviour of SMA TPMSs can be accurately characterized by the proposed framework at almost any value of the relative density or the temperature after the training. Subsequently, the ANN-based framework is used to map two-dimensionally the impact of varying relative density, temperature, and deformation on the effective hardness and superelasticity of the SMA TPMS architectures. The results show that the superelasticity of SMA TPMS scaffolds increases with decreased temperature and relative density and with increased deformation, in a nonlinear pattern. This work lays the foundation for further research on using ANN to explore the mechanical response and advanced applications of the complex SMA-based structures, such as smart composite systems, helical springs, and metamaterials at considerably reduced computational and financial costs.

Liquid Metal Smart Materials toward Soft Robotics

Unlike conventional rigid machines, soft robots generally have unique operation styles that rely heavily on soft matter engineering and smart material systems. Owing to the superior merits of both metals and fluids, liquid metal smart materials are increasingly being innovatively used as soft actuators and sensors to construct soft robots. To promote further development and prosperity in this field, this review organizes and summarizes the typical progress in liquid metal smart materials, with a special focus on their robotic response behaviors. In particular, the article emphasizes the concept of smart composite systems consisting of liquid metals and synergistic substances (e.g., solutions, particles, and polymers). The response behaviors of liquid metal smart materials under the actions of external factors (electricity, magnetism, ultrasound, light, heat, etc.) are examined and the smart properties occurring during these responses, such as motion, transformation, self‐organization, adaptive healing, and autonomous sensing, are identified. Furthermore, soft actuators, control systems, and robots based on liquid metal smart materials are summarized and elaborated upon. Finally, the potential directions worth pursuing and challenges are outlined. It is expected that this review will stimulate further investigations into liquid metal smart materials with the aim of building a new generation of soft robots.

Study of structural and optical properties of the thermochromic silver and copper tetraiodomercurates (Ag2, Cu2) HgI4 ceramics

Powders of silver (Ag2HgI4) and copper (Cu2HgI4) tetraiodomercurates were synthesized by a simple co-precipitation method. Their phase transition behavior was investigated by differential scanning calorimetry, X-ray diffraction (XRD), as well as diffuse reflectance to determine its reversibility and stability during heating–cooling cycles. Calorimetry showed a sharp transition at 51 °C when heating, and at 40 °C when cooling for Ag2HgI4 samples. For Cu2HgI4 samples in the first cycle, one peak was observed when heating at 69.6 and 49.7 °C when cooling. However, in these samples, the first peak splits into two peaks when heating during the second and third cycles (67.5 and 57.8 °C), indicating a probable loss of crystallinity. XRD and diffuse reflectance showed that the transition starts almost since the beginning of the warming-up process and is more evident around 40 °C for Ag2HgI4 and around 60 °C for Cu2HgI4. The energy bandgap indicates that Ag2HgI4 and Cu2HgI4 behave differently during the transition. Copper tetraiodomercurate follows almost the same path for heating than for cooling. Its reversible thermochromic and superionic properties are promising for several applications and open the possibility of using them as inclusions in smart composite systems.

Predicting Micro-Mechanics Damage Behaviour at a Metal-Ceramic Interface in a Reinforced Alloy

The performance of metal matrix composites (MMCs) depends critically on the quality of the matrix-reinforcement interface. The nature of the interface in turn depends on the processing of the MMCs. At the micro-level, local concentration gradients around the reinforcement are being developed during processing and due to the metal matrix attempting to deform during deformation which can be very different to the nominal conditions. This plays a crucial role in the development of micro-structural events such as segregation and precipitation at the matrix-reinforcement interface. Micro-deformation characteristics of matrix reinforcement interface are modelled using commercial FE software and compared with analytical and experimental data. A method of calculation has been applied to predict the interfacial fracture strength of aluminium silicon carbide (Al-SiC) with 20% Vol fraction. Preliminary results show that the model succeeds in predicting the trends in relation to segregation and intergranular fracture strength behaviour in these materials. The proposed hypothesis will help the design engineers to select and use the materials in structural/load bearing applications. Interfacial strengthening characteristics will in turn give more accurate life predictions of such smart composite systems.

Vibration analysis of double bonded composite pipe reinforced by BNNTs conveying oil

In the present research, nonlinear vibration in a coupled system of Boron-Nitride nano-tube reinforced composite (BNNTRC) oil pipes is studied. Single-walled Boron-Nitride nano-tubes (SWBNNTs) are arranged in a longitudinal direction inside Poly-vinylidene fluoride (PVDF) matrix. Damping and shearing effects of surrounded medium are taken into account by visco-Pasternak model. Based on piezoelectric fiber reinforced composite (PFRC) theory, properties of smart coupled BNNTRC oil pipes are obtained. The equations of motion as well as the boundary conditions are derived using Hamilton’s principle. The effects of various parameters such as volume fraction and orientation angle of fibers, viscosity and density of fluid on stability of coupled BNNTRC oil pipes are investigated. Results indicate that stability of smart composite system is strongly dependent on angle orientation and volume percent of BNNTs. Results of this investigation can be used in oil refineries.

Strain gradient shell model for nonlinear vibration analysis of visco-elastically coupled Boron Nitride nano-tube reinforced composite micro-tubes conveying viscous fluid

In the present research, nonlinear vibration in a coupled system of Boron-Nitride nano-tube reinforced composite (BNNTRC) micro-tubes conveying viscous fluid is studied. Single-walled Boron-Nitride nano-tubes (SWBNNTs) are arranged in a longitudinal direction inside Poly-vinylidene fluoride (PVDF) matrix. Damping and shearing effects of surrounded medium are taken into account by visco-Pasternak model. Based on piezoelectric fiber reinforced composite (PFRC) theory, properties of smart coupled BNNTRC micro-tubes are obtained. To enhance the accuracy of results, strain gradient theory is developed in cylindrical shell model, and the motion equations as well as the boundary conditions are derived using Hamilton’s principle. Considering slip flow regime, the effects of various parameters such as Knudsen number, volume fraction and orientation angle of fibers, temperature change, viscosity and density of fluid on stability of coupled BNNTRC micro-tubes are investigated. Results indicate that stability of smart composite system is strongly dependent on orientation angle and volume percent of BNNTs. Results of this investigation can be applied for optimum design of shell and tube heat exchangers in micro scale.

Internally Modified Halloysite Nanotubes as Inorganic Nanocontainers for a Flame Retardant

Abstract We have selectively hydrophobized halloysite nanotube lumens for efficient loading with a flame retardant for controlled releasing composite materials. The inner lumen of octadecylphosphonic-acid-modified halloysite was loaded with hydrophobic bisphenol-A bis(diphenyl phosphate). This flame retardant was released from the clay nanotubes in linear fashion over 60 h demonstrating the system potential utility as effective nanocontainers for smart composite systems.

Morphological study on twisted NiTi wires for smart composite systems

In recent years, the increasing use of shape memory alloy (SMA) actuators, in the form of wire for advanced composite structures, enhances an urgent need for the development of a reliable and secure bonding technique for ensuring a full stress transfer from actuators to composite structures. A new configuration of SMA wire, which is able to increase the bonding strength between the wire and matrix in the composite, is introduced. NiTi wires were twisted to certain numbers of turn in order to increase the wire's surface roughness before embedding into epoxy matrix cylinders. Wire pullout tests were performed to study the bonding strength of a NiTi/epoxy interface. The experimental results and SEM observations indicated that the overall bonding strength and cracks on the Ti 2NiO x film of the wires increased with increasing the numbers of turn of the embedded wires. These cracks can increase the surface roughness and, thus, increase the maximum pullout strength of smart composite systems. However, the maximum strain recovery limit of twisted wire is restricted to a total number of 15 turns, further increasing the numbers of turn results in increasing the unrecoverable strain of the wire.