Development of Liquid Diene Rubber Based Highly Deformable Interactive Fiber-Elastomer Composites

The preparation of intelligent structures for multiple smart applications such as soft-robotics, artificial limbs, etc., is a rapidly evolving research topic. In the present work, the preparation of a functional fabric, and its integration into a soft elastomeric matrix to develop an adaptive fiber-elastomer composite structure, is presented. Functional fabric, with the implementation of the shape memory effect, was combined with liquid polybutadiene rubber by means of a low-temperature vulcanization process. A detailed investigation on the crosslinking behavior of liquid polybutadiene rubber was performed to develop a rubber formulation that is capable of crosslinking liquid rubber at 75 °C, a temperature that is much lower than the phase transformation temperature of SMA wires (90–110 °C). By utilizing the unique low-temperature crosslinking protocol for liquid polybutadiene rubber, soft intelligent structures containing functional fabric were developed. The adaptive structures were successfully activated by Joule heating. The deformation behavior of the smart structures was experimentally demonstrated by reaching a 120 mm bending distance at an activation voltage of 8 V without an additional load, whereas 90 mm, 70 mm, 65 mm, 57 mm bending distances were achieved with attached weights of 5 g, 10 g, 20 g, 30 g, respectively.     

Integrated Temperature and Position Sensors in a Shape-Memory Driven Soft Actuator for Closed-Loop Control

Soft actuators are a promising option for the advancing fields of human-machine interaction and dexterous robots in complex environments. Shape memory alloy wire actuators can be integrated into fiber rubber composites for highly deformable structures. For autonomous, closed-loop control of such systems, additional integrated sensors are necessary. In this work, a soft actuator is presented that incorporates fiber-based actuators and sensors to monitor both deformation and temperature. The soft actuator showed considerable deformation around two solid body joints, which was then compared to the sensor signals, and their correlation was analyzed. Both, the actuator as well as the sensor materials were processed by braiding and tailored fiber placement before molding with silicone rubber. Finally, the novel fiber-rubber composite material was used to implement closed-loop control of the actuator with a maximum error of 0.5°.     

Present State of the Art of Composite Fabric Forming: Geometrical and Mechanical Approaches

Continuous fibre reinforced composites are now firmly established engineering materials for the manufacture of components in the automotive and aerospace industries. In this respect, composite fabrics provide flexibility in the design manufacture. The ability to define the ply shapes and material orientation has allowed engineers to optimize the composite properties of the parts. The formulation of new numerical models for the simulation of the composite forming processes must allow for reduction in the delay in manufacturing and an optimization of costs in an integrated design approach. We propose two approaches to simulate the deformation of woven fabrics: geometrical and mechanical approaches.     

Analysis of Polygonal Computer Model Parameters and Influence on Fabric Drape Simulation

Contemporary CAD systems enable 3D clothing simulation for the purpose of predicting the appearance and behavior of conventional and intelligent clothing in real conditions. The physical and mechanical properties of the fabric and the simulation parameters play an important role in this issue. The paper presents an analysis of the parameters of the polygonal computer model that affect fabric drape simulation. Experimental research on physical and mechanical properties were performed for nine fabrics. For this purpose, the values of the parameters for the tensile, bending, shear, and compression properties were determined at low loads, while the complex deformations were analyzed using Cusick drape meter devices. The fabric drape simulations were performed using the 2D/3D CAD system for a computer clothing design on a disk model, corresponding to real testing on the drape tester in order to allow a correlation analysis between the values of drape parameters of the simulated fabrics and the realistically measured values for each fabric. Each fabric was simulated as a polygonal model with a variable related to the side length of the polygon to analyze the influence of the polygon size, i.e., mesh density, on the model behavior in the simulation. Based on the simulated fabric drape shape, the values of the areas within the curves necessary to calculate the drape coefficients of the simulated fabrics were determined in the program for 3D modelling. The results were statistically processed and correlations between the values of the drape coefficients and the optimal parameters for simulating certain physical and mechanical properties of the fabric were determined. The results showed that the mesh density of the polygonal model is an important parameter for the simulation results.     

Haptic manipulation of deformable CAD parts with a two-stage method

Real-time interaction between a designer and a deformable mock-up in Virtual Reality environments is a promising paradigm to evaluate design feasibilities. In this paper we focus on the haptic-aided deformation verification process of industrial deformable parts by combining small deformations and relatively large rigid-body motions. First, concerning the modelling process of small deformations, we propose a two-stage method extended from the linear modal analysis. In this two-stage method, modal deformation sub-spaces are pre-computed in an off-line phase, and real-time deformations are quickly reproduced by superimposing the responses of certain modes which are selected depending on interaction requirements. Based on this two-stage method, we propose a mesh analysis method to enrich the off-line pre-computations corresponding to different anticipated interaction scenarios. Furthermore, we apply a real-time division scheme which divides the deformation response process into two separate modules, so that stable haptic interactions are guaranteed. Second, concerning the purpose of global deformation verifications, we combine relatively large rigid-body motions resulting from the integration of classical motion equations and small deformations resulting from the aforementioned two-stage method. We have implemented the two-stage method to model small deformations and rigid-body motions. Real-time experiments are carried out by coupling a single haptic device with a simulation framework and experimental results validate the deformation accuracy on one hand, and demonstrate a good and stable haptic interaction experience on the other.     

Machine Learning Enhanced Dynamic Response Modelling of Superelastic Shape Memory Alloy Wires

Superelastic shape memory alloy (SMA) wires exhibit superb hysteretic energy dissipation and deformation capabilities. Therefore, they are increasingly used for the vibration control of civil engineering structures. The efficient design of SMA-based control devices requires accurate material models. However, the thermodynamically coupled SMA behavior is highly sensitive to strain rate. For an accurate modelling of the material behavior, a wide range of parameters needs to be determined by experiments, where the identification of thermodynamic parameters is particularly challenging due to required technical instruments and expert knowledge. For an efficient identification of thermodynamic parameters, this study proposes a machine-learning-based approach, which was specifically designed considering the dynamic SMA behavior. For this purpose, a feedforward artificial neural network (ANN) architecture was developed. For the generation of training data, a macroscopic constitutive SMA model was adapted considering strain rate effects. After training, the ANN can identify the searched model parameters from cyclic tensile stress–strain tests. The proposed approach is applied on superelastic SMA wires and validated by experiments.     

Effect of Loading Rate and Initial Strain on Seismic Performance of an Innovative Self-Centering SMA Brace

In order to improve the energy dissipation capacity and to reduce the residual deformation of civil structures simultaneously, this paper puts forwards an innovative self-centering shape memory alloy (SMA) brace that is based on the design concepts of SMA’s superelasticity and low friction slip. Seven self-centering SMA brace specimens were tested under cyclic loading, and the hysteresis curves, bond curves, secant stiffness, energy dissipation coefficient, equivalent damping coefficient, and the self-centering capacity ratio of these specimens were investigated, allowing us to provide an evaluation of the effects of the loading rate and initial strain on the seismic performance. The test results show that the self-centering SMA braces have an excellent energy dissipation capacity, bearing capacity, and self-centering capacity, while the steel plates remain elastic, and the SMA in the specimens that are always under tension are able to return to the initial state. The hysteresis curves of all of the specimens are idealized as a flag shape with low residual deformation, and the self-centering capacity ratio reached 89.38%. In addition, both the loading rate and the initial strain were shown to have a great influence on the seismic performance of the self-centering SMA brace. The improved numerical models combined with the Graesser model and Bouc–Wen model in MATLAB were used to simulate the seismic performance of the proposed braces with different loading rates and initial strains, and the numerical results are consistent with the test results under the same conditions, meaning that they can accurately predict the seismic performance of the self-centering SMA brace proposed here.     

Adjusting the Residual Stress State in Wire Drawing Products via In-Process Modification of Tool Geometries

After conventional forming processes, the residual stress distribution in wires is frequently unfavorable for subsequent processes, such as bending operations. High tensile residual stresses typically occur near the wire surface and normally limit further processability of the material. Additional heat treatment operations or shot peening are often used to influence the residual stress distribution in the material after conventional manufacturing, which is time- and energy-consuming. This paper presents an approach for influencing the residual stress distribution by modifying the forming process, especially regarding die geometry. The aim is to reduce the resulting tensile stress levels near the surface. Specific forming elements are integrated into the dies to achieve this residual stress reduction. These modifications in the forming zone have a significant influence on process properties, such as plastic strain and deformation direction, but typically do not influence product geometry. This paper describes the theoretical approach and model setup, the FE simulation, and the results of the experimental tests. The characterization of the residual stress states in the specimen was carried out through X-ray diffraction using the sin²Ψ method.     

Research on the Manufacturing Quality of Co-Cured Hat-Stiffened Composite Structure

The stringer-stiffened structure is widely used due to its excellent mechanical properties. Improving the manufacturing quality of stringer-stiffened structure which have complex geometry is important to ensure the bearing capacity of aviation components. Herein, composite hat-stiffened composite structures were manufactured by different filling forms and bladders with various properties, the deformation of silicone rubber bladder in co-curing process was studied by using the finite element method. The thickness measurement at different positions of the hat-stiffened structure was performed to determine the best filling form and bladder property. Moreover, in view of the detection difficulties in R-zone of stringer, numerical simulation was performed to get the sound pressure and impulse response of at the R-zone of stringer by Rayleigh integration method, and an effective equipment which could stably detect the manufacturing quality of R-zone was designed to verify the correctness of sound field simulation and realize the detection of stringer. With the optimum filling form and bladder properties, hat-stiffened composites can be manufactured integrally with improved surface quality and geometric accuracy, based on co-curing process.     

Study of the Mechanical,Sound Absorption and Thermal Properties of Cellular Rubber Composites Filled with a Silica Nanofiller

This paper deals with the study of cellular rubbers, which were filled with silica nanofiller in order to optimize the rubber properties for given purposes. The rubber composites were produced with different concentrations of silica nanofiller at the same blowing agent concentration. The mechanical, sound absorption and thermal properties of the investigated rubber composites were evaluated. It was found that the concentration of silica filler had a significant effect on the above-mentioned properties. It was detected that a higher concentration of silica nanofiller generally led to an increase in mechanical stiffness and thermal conductivity. Conversely, sound absorption and thermal degradation of the investigated rubber composites decreased with an increase in the filler concentration. It can be also concluded that the rubber composites containing higher concentrations of silica filler showed a higher stiffness to weight ratio, which is one of the great advantages of these materials. Based on the experimental data, it was possible to find a correlation between mechanical stiffness of the tested rubber specimens evaluated using conventional and vibroacoustic measurement techniques. In addition, this paper presents a new methodology to optimize the blowing and vulcanization processes of rubber samples during their production.     

Compressive and Tensile Elastic Properties of Concrete: Empirical Factors in Span Reinforced Structures Design

Concretes with the same strength can have various deformability that influences span structures deflection. In addition, a significant factor is the non-linear deformation of concrete dependence on the load. The main deformability parameter of concrete is the instantaneous modulus of elasticity. This research aims to evaluate the relation of concrete compressive and tensile elastic properties testing. The beam samples at 80 × 140 × 1400 cm with one rod Ø8 composite or Ø10 steel reinforcement were experimentally tested. It was shown that instantaneous elastic deformations under compression are much lower than tensile. Prolonged elastic deformations under compression are close to tensile. It results in compressive elasticity modulus exceeding the tensile. The relation between these moduli is proposed. The relation provides operative elasticity modulus testing by the bending tensile method. The elasticity modulus’s evaluation for the reinforced span structures could be based only on the bending testing results. A 10% elasticity modulus increase, which seems not significant, increases at 30–40% the stress of the reinforced span structures under load and 30% increases the cracking point stress.     

Influence of Type of Modified Binder on Stiffness and Rutting Resistance of Low-Noise Asphalt Mixtures

Low-noise asphalt mixtures are characterized by increased air void content. Their more open structure contributes to faster degradation within the operating temperature range. For this reason, binder modification is used in their production. The correct selection of modifiers allows one to significantly improve the technical properties of the mixtures. The article presents the results of tests of six types of mixtures: stone mastic asphalt (SMA8), porous asphalt (PA8), stone mastic asphalt reducing tire/road noise (SMA8 LA) and stone mastic asphalt reducing tire/road noise, with 10%, 20% and 30% content of rubber granulate (RG). Bitumen 50/70 modified with copolymer styrene butadiene styrene (SBS) and crumb rubber (CR) was used for the production of the mixtures. In order to determine the differences in the technical properties of the mixtures, the following parameters were tested: stiffness modules by indirect tensile testing of cylindrical specimens (IT-CY) in a wide range of positive temperatures, and resistance to permanent deformation using the British and Belgian methods with the use of double wheel tracker (DWT). The test results and their analysis confirmed that there was a significant improvement in the IT-CY stiffness modules of SBS and CR modified mixtures. Replacing more than 20% of coarse aggregate with RG causes a significant decrease in the stiffness of the mixture (by 90% in relation to the reference mixture SMA8 LA). The SMA mixtures obtained lower values of rutting resistance parameters (WTS and PRD) in water (Belgian method) compared to the results obtained in the air tests (British method). On the other hand, mixtures of PA, thanks to the compression of stresses in pores filled with water, obtained better results when the rutting resistance test was performed in the water (Belgian method).     

Investigation of Phase Transitions in Ferromagnetic Nanofilms on a Non-Magnetic Substrate by Computer Simulation

Magnetic properties of ferromagnetic nanofilms on non-magnetic substrate are examined by computer simulation. The substrate influence is modeled using the two-dimensional Frenkel-Kontorova potential. The film has a cubic crystal lattice. Cases of different ratio for substrate period and ferromagnetic film period are considered. The difference in film and substrate periods results in film deformations. These deformations result in a change in the magnetic properties of the film. The Ising model and the Metropolis algorithm are used for the study of magnetic properties. The dependence of Curie temperature on film thickness and substrate potential parameters is calculated. Cases of different values for the coverage factor are considered. The deformation of the film layers is reduced away from the substrate when it is compressed or stretched. The Curie temperature increases when the substrate is compressed and decreases when the substrate is stretched. This pattern is performed for films with different thicknesses. If the coating coefficient for the film is different from one, periodic structures with an increased or reduced concentration of atoms are formed in the film first layer. These structures are absent in higher layers.     

Two-Way Bending Properties of Shape Memory Composite with SMA and SMP

A shape memory composite (SMC) was fabricated with a shape memory alloy (SMA) and a shape memory polymer (SMP), and its two-way bending deformation and recovery force were investigated. The results obtained can be summarized as follows: (1) two kinds of SMA tapes which show the shape memory effect (SME) and superelasticity (SE) were heat-treated to memorize the round shape. The shape-memorized round SMA tapes were arranged facing in the opposite directions and were sandwiched between the SMP sheets. The SMC belt can be fabricated by using the appropriate factors: the number of SMP sheets, the pressing force, the heating temperature and the hold time. (2) The two-way bending deformation with an angle of 56 degrees in the fabricated SMC belt is observed based on the SME and SE of the SMA tapes during heating and cooling. (3) If the SMC belt is heated and cooled by keeping the bent form, the recovery force increases during heating and degreases during cooling based on the two-way properties of the SMC. (4) The development and application of high-functional SMCs are expected by the combination of the SMA and the SMP with various kinds of phase transformation temperatures, volume fractions, configurations and heating-cooling rates.     

A Sensaptic ADAS Device Using Shape Memory Alloy Wires: Design and Control

This paper presents an active accelerator pedal system based on an integrated sensor and actuator using shape memory alloy (SMA) for speed control and to create haptics in the accelerator pedal. A device named sensaptics is developed with a pair of bi-functional SMA wires instrumented in a synergistic configuration function as an active sensor for positioning the accelerator pedal (pedal position sensing) to control the vehicle speed through electronic throttle and as a variable impedance actuator to generate active force (haptic) feedback to the driver. The reaction force emanated from the pedal alerts the driver and takes appropriate control action by slowing down the vehicle, in harmony with the road’s condition. The design is developed as a proof-of-concept device and is tested and evaluated in a real-time common rail diesel system for rail pressure regulation and over speeding tests, and the responses and performances are found to be promising.     

Effect of the Topology of Carbon-Based Nanofillers on the Filler Networks and Gas Barrier Properties of Rubber Composites

The topology of nanofillers is one of the key factors affecting the gas barrier properties of rubber composites. In this research, three types of carbon-based nanofillers, including spherical carbon black (CB), fibrous carbon nanotubes (CNTs), and layered graphene (GE) were chosen to investigate the effect of the topological structures of nanofillers on the gas barrier properties of styrene-butadiene rubber (SBR) composites. Results showed that the structure and strength of the filler networks in SBR composites were closely associated with the topology of nanofillers. When filled with 35 phr CB, 8 phr CNTs, and 4 phr GE, the SBR composites had the same strength of the filler network, while the improvement in gas barrier properties were 39.2%, 12.7%, and 41.2%, respectively, compared with pure SBR composites. Among the three nanofillers, GE exhibited the most excellent enhancement with the smallest filler content, demonstrating the superiority of two-dimensional GE in improving the barrier properties of rubber composites.     

Deformation and Strength Parameters of a Composite Structure with a Thin Multilayer Ribbon-like Inclusion

Within the framework of the concept of deformable solid mechanics, an analytical-numerical method to the problem of determining the mechanical fields in the composite structures with interphase ribbon-like deformable multilayered inhomogeneities under combined force and dislocation loading has been proposed. Based on the general relations of linear elasticity theory, a mathematical model of thin multilayered inclusion of finite width is constructed. The possibility of nonperfect contact along a part of the interface between the inclusion and the matrix, and between the layers of inclusion where surface energy or sliding with dry friction occurs, is envisaged. Based on the application of the theory of functions of a complex variable and the jump function method, the stress-strain field in the vicinity of the inclusion during its interaction with the concentrated forces and screw dislocations was calculated. The values of generalized stress intensity factors for the asymptotics of stress-strain fields in the vicinity of the ends of thin inhomogeneities are calculated, using which the stress concentration and local strength of the structure can be calculated. Several effects have been identified which can be used in designing the structure of layers and operation modes of such composites. The proposed method has shown its effectiveness for solving a whole class of problems of deformation and fracture of bodies with thin deformable inclusions of finite length and can be used for mathematical modeling of the mechanical effects of thin FGM heterogeneities in composites.     

Experimental Investigation on Bending Behavior of Existing RC Beam Retrofitted with SMA-ECC Composites Materials

In order to realize the self-centering, high energy consumption, and high ductility of the existing building structure through strengthening and retrofit of structure, a method of reinforced concrete (RC) beam strengthened by using Shape Memory Alloy (SMA) and Engineered Cementitious Composites (ECC) was proposed. Four kinds of specimens were designed, including one beam strengthened with enlarging section area of steel reinforced concrete, one beam strengthened with enlarging section area of SMA reinforced concrete, beam strengthened with enlarging section area of SMA reinforced ECC, and beam strengthened with enlarging section area of steel reinforced ECC; these specimens were manufactured for the monotonic cycle loading tests study on its bending behavior. The influence on the bearing capacity, energy dissipation performance, and self-recovery capacity for each test specimens with different strengthening materials were investigated, especially the bending behavior of the beams strengthened by SMA reinforced ECC. The results show that, compared with the ordinary reinforced concrete beams, strengthening existing RC beam with enlarging section area of SMA reinforced ECC can improve the self-recovery capacity, ductility, and deformability of the specimens. Finally, a revised design formula for the bending capacity of RC beams, strengthened with enlarging sections of ECC, was proposed by considering the tensile capacity provided by ECC, and the calculated values are in good agreement with the experimental value, indicating that the revised formula can be well applied to the beam strengthening with enlarging section of SMA-ECC Materials.     

Low Stress Mechanical Properties of Plasma-Treated Cotton Fabric Subjected to Zinc Oxide-Anti-Microbial Treatment

Cotton fabrics are highly popular because of their excellent properties such as regeneration, bio-degradation, softness, affinity to skin and hygroscopic properties. When in contact with the human body, cotton fabrics offer an ideal environment for microbial growth due to their ability to retain oxygen, moisture and warmth, as well as nutrients from spillages and body sweat. Therefore, an anti-microbial coating formulation (Microfresh and Microban together with zinc oxide as catalyst) was developed for cotton fabrics to improve treatment effectiveness. In addition, plasma technology was employed in the study which roughened the surface of the materials, improving the loading of zinc oxides on the surface. In this study, the low stress mechanical properties of plasma pre-treated and/or anti-microbial-treated cotton fabric were studied. The overall results show that the specimens had improved bending properties when zinc oxides were added in the anti-microbial coating recipe. Also, without plasma pre-treatment, anti-microbial-treatment of cotton fabric had a positive effect only on tensile resilience, shear stress at 0.5° and compressional energy, while plasma-treated specimens had better overall tensile properties even after anti-microbial treatment.     

Some Inconsistencies in the Nonlinear Buckling Plate Theories—FSDT,S-FSDT,HSDT

Bending and membrane components of transverse forces in a fixed square isotropic plate under simultaneous compression and transverse loading were established within the first-order shear deformation theory (FSDT), the simple first-order shear deformation theory (S-FSDT), and the classical plate theory (CPT). Special attention was drawn to the fact that bending components were accompanied by transverse deformations, whereas membrane components were not, i.e., the plate was transversely perfectly rigid. In the FSDT and the S-FSDT, double assumptions concerning transverse deformations in the plate hold. A new formulation of the differential equation of equilibrium with respect to the transverse direction of the plate, using a variational approach, was proposed. For nonlinear problems in the mechanics of thin-walled plates, a range where membrane components should be considered in total transverse forces was determined. It is of particular significance as far as modern composite structures are concerned.