Alloy Fibers Research Articles

Latent heat effects in inductive heating of shape memory alloy fibers

AbstractMotivation of the present work is an inductive heating process, used in manufacturing a new kind of improved ultra‐high performance concrete. In this novel material, fibers made out of shape memory alloys are used to increase the maximum possible fiber volume fraction, or to create an internal state of compressive stress. In contrast to other works, the underlying microstructure transformation from martensite to austenite is highlighted based on thermal analysis. Dynamic scanning calorimetry measurements are adapted as basis for development of a phenomenological phase transformation model. It relates local temperature and temperature rate to the rate of change of the phase indicator, modeling the transformation of martensite to austenite. Latent heat is considered by an enthalpy method, the inductive heating process is considered by a phenomenological model. Study results for a purely thermodynamic process of heating a single fiber embedded in concrete are presented. They show that latent heat effects delay phase transformation and the process of fiber activation is very sensitive to the induced heat. Furthermore, it is discovered that latent heat causes a strongly inhomogeneous state of transformation in radial direction of the fiber, which is of great importance for thermomechanical processes and the interpretation of experimental results.

Development of shape memory alloy fiber reinforced debondable adhesive

This study introduces an innovative debondable adhesive approach by incorporating shape-memory alloy (SMA) fibers within an epoxy adhesive matrix. Employing meticulous techniques, such as winding machinery and other apparatuses, exceedingly thin Nitinol SMA fibers have been successfully integrated into the adhesive layer. Notably, this adhesive exhibits the dual functionality of a fiber-reinforced composite at operational temperatures, conferring heightened joint strength. Upon disassembly at elevated temperatures, the shape-memory effect of the fibers induces stress concentration within the adhesive layer, thereby facilitating effortless debonding and significantly enhancing the recycling efficacy.Various configurations of fiber volume fractions (2.5 %, 5.0 %, 10.0 %) and orientations (0°/0°, 0°/90°, 90°/90°) were explored to assess their impact on joint strength across ambient and elevated temperatures. The investigation reveals that the 0°/0° fiber orientation yields optimal debondable adhesive characteristics. Additionally, higher volumetric percentages generally correlate with improved adhesive strength and debonding capability. This study further elucidates the underlying mechanisms governing the observed effects on joint debonding strength.

Theoretical evaluation of nonlinear thermomechanical deflection characteristics of damaged (cracked) layered composite structural panel bonded with shape memory alloy (SMA) fibre and experimental verification

Thermomechanical deflections of the cracked multi-layered composite panels were investigated numerically using full-scale geometrical nonlinearity and higher-order deformation kinematics. The panel is embedded with shape memory alloy (SMA) fiber to improve the structural strength and integrity under thermomechanical loadings. The theoretical model for the SMA-reinforced cracked laminated composite shell panel is derived considering the material and geometrical nonlinearity. The numerical and experimental cases were performed for the intact and damaged cylindrical panels by varying the environmental conditions. Additional examples of structural and geometrical parameters have been conducted, including SMA-related data.

In-situ precipitation of ultrafine Mg2Ni particles in Mg-Ni-Ag metal fibers and their hydrogen storage properties

The intermetallic compound Mg2Ni shows improved hydrogen de-/absorption kinetics and a lower desorption temperature compared to pure Mg. However, the coarse Mg2Ni phase and its limited hydrogenation capacity restrict the application of the Mg2Ni alloy. In this study, an attempt was made to prepare Mg-Ni alloy fibers with a higher Mg content and a well-distributed Mg2Ni catalytic phase using the melt extraction (ME) method, and a unique metallic glass fiber was formed. With pre-annealing at 350 °C in a vacuum, uniformly dispersed Mg2Ni nanoparticles are in-situ formed, the phase transition is revealed to be metallic glass → Mg6Ni → Mg2Ni + Mg. About 1.5 wt% of hydrogen can be absorbed by the Mg-Ni fibers at 50 °C, and it is completely released in 8.8 min at 225 °C. Both the JMA and Kissinger models were utilized to accurately characterize the dehydrogenation activation energy, and the values of 90.4 and 95.8 kJ/mol were obtained, respectively. The hydrogen desorption process involves two distinct processes, the decomposition of Mg2NiH4 nanoparticles and MgH2 hydride in sequence, with dehydrogenation enthalpy changes of 64.5 and 78.2 kJ/mol, respectively. After hydrogen absorption and desorption cycles, a loose structure forms around the Mg2Ni nanoparticles. This structure serves as an efficient nucleation site for hydrides and provides diffusion paths for H atoms.

Experimental Investigation of Cumulative Damage and Self-Healing Properties of Smart Cementitious Composite under Continuous Compression Load.

This study investigated the effect of sustained loading on the cumulative damage of a newly developed smart cement-based self-healing composite material (SMA-ECC). SMA-ECC is composed of engineered cementitious composite (ECC) and shape memory alloy (SMA) fibers. A uniaxial compressive test with five predefined loading levels (0%, 30%, 40%, 50%, and 60% of compressive strength) was conducted on SMA-ECC hollow-cylindrical specimens and ECC control hollow-cylindrical specimens. The cumulative damage was mainly determined by changes in the total water absorption of different groups of specimens during three different periods (not loaded, at a predefined loading level, and after unloading). A normalized water content index was proposed to couple the effects of self-healing, sustained loading, and cumulative damage. The test results indicate that the cumulative water absorption of SMA-ECC was 35% lower than that of ECC, which may indicate less irreparable damage. In addition, the self-healing ability of SMA-ECC specimens under different compression load levels was evaluated through normalized water content analysis. SMA-ECC exhibited a 100% repair rate at load levels of 30% and 40%. At a higher load level of 60%, the repair rate of SMA-ECC was 76%. These results collectively emphasize the significant impermeability and self-healing performance of SMA-ECC after unloading.

Monitoring of Allowable Bending Stress Overload in Glass‐Fiber‐Reinforced Polymer Composites Using Magnetostrictive Fe–Co Fibers

For the safe operation of glass‐fiber‐reinforced polymer (GFRP) laminates, evaluating the applied stress and the health of composite structures is crucial. Magnetostrictive materials are functional materials that can be applied to structural health monitoring as sensor materials. Herein, a method for detecting whether the maximum stress of GFRP laminates under bending exceeds the allowable stress using magnetostrictive fibers is proposed. First, magnetostrictive Fe–Co alloy fibers are embedded in GFRP laminates. Then, four‐point bending tests are conducted. Magnetomechanical coupled modeling based on the composite beam theory is then applied to the experimental results. The effects of the position of Fe–Co fibers on the magnetostrictive behavior and mechanical properties of the prepared composites are evaluated. A concept for monitoring the relationship between the maximum bending stress and the allowable stress of the composite materials is proposed.

Configurations Manipulation of Electrospun Membranes Based on High‐Entropy Alloys–Enabled High‐Performance Solar Water Evaporation

Solar‐driven interfacial steam technology converts photons into heat energy directly and therefore realizes the effective removal of environmental pollutants, which presents huge potential in seawater desalination and freshwater production. To realize efficient and rapid solar‐driven water evaporation, developing and designing efficient photothermal conversion materials is of great significance. Herein, a high‐entropy alloy (HEA) fiber membrane with rapid heating and wide spectral response is synthesized via adjusting high‐entropy metals diffusion on the surface of carbon nanofibers by an electrospinning technology. Benefiting from the low equivalent evaporation enthalpy and high solar spectrum capacity of HEA fibers, the HEA (FeCoNiCuMn)‐carbon nanofiber‐5S2 achieves a rapid steam‐generation rate of 2.74 kg m−2 h−1 with a solar‐to‐vapor conversion efficiency of 99.4% under 1 sun illumination. In addition, the evaporator presented a stable seawater desalination and wastewater purification performance. Therefore, the HEA‐based solar evaporator can be an alternative photothermal material for efficient solar steam generation.

The Effect of Fiber End on the Bonding Mechanical Properties between SMA Fibers and ECC Matrix

In order to investigate the effect of fiber end on the bonding mechanical properties between shape memory alloy (SMA) fibers and Engineered Cementitious Composites (ECC), this study designed and fabricated five groups of specimens with variations in SMA fiber end shape, diameter and depth-to-diameter ratio. Direct tensile tests were conducted on these specimens under displacement control. The failure modes, stress–strain curves and various performance indicators were analyzed to evaluate the bonding mechanical properties and the effects of different factors. The results revealed that for straight-end SMA fibers, increasing the diameter and depth-to-diameter ratio both led to a decrease in bonding strength. On the other hand, the N-shaped end provided sufficient anchorage force for SMA fibers, resulting in a maximum pull-out stress of 926.3 MPa and a fiber strength utilization of over 78%. Increasing the fiber diameter enhanced the maximum pull-out stress and maximum anchorage stress for N-shaped-end SMA fibers but reduced the fiber strength utilization. These research findings provide a solid theoretical basis and data support for achieving a synergistic effect between SMA fibers and the ECC matrix.

The Effect of SMA Fiber Content on the Bending and Self-Recovery Performance of ECC Beams.

The addition of superelastic shape memory alloy fibers (SMAF) into engineering cementitious composites (ECC) can create a new type of SMAF-ECC composite material with good self-recovery and energy dissipation performance, which is very suitable for seismic structures. In this study, 10 groups of beam specimens with different volume contents of SMAF were fabricated, and the bending performance, deflection recovery and energy dissipation ability of these beams were studied through three-point bending cyclic loading tests. The failure mode, peak load, load-deflection curve, crack width and other indicators of the specimens were analyzed, and the relationship expression between fiber content and bending strength was established by fitting analysis. The results show that adding SMA fibers can significantly improve the peak load of ECC beams, with a maximum increase of 48.31%. The knotted SMA fibers can fully exert their superelasticity, providing the beam specimens with crack self-closing and deflection recovery ability. When the volume content of SMA fibers is 0-0.6%, the bending strength, energy dissipation ability and deflection recovery ability of the composite material beams increase with the increase in fiber content. When the volume content of SMA fibers is 0.6-1.0%, the above indicators decrease with the increase in fiber content. The suggested equations can well reflect the relationship between fiber content and beam bending strength. The research results of this paper provide theoretical support for the engineering application of SMAF-ECC composite materials.

Nonlinear vibration of SMA hybrid composite beams actuated by embedded pre-stretched SMA wires with tension-bending coupling effect

Theoretical and numerical analyses for nonlinear vibrations of the shape memory alloy hybrid composite(SMAHC) beam actuated by the pre-stretched shape memory alloy(SMA) fibers with tension-bending coupling effect are presented in this paper. Under the sudden action of thermal temperature, a recovery force and moment are caused in the SMAHC beam due to the phase transition in the SMA fibers, exciting the nonlinear vibration of the SMAHC beam. The one-dimensional Brison constitutive model was adopted to express the influence of the phase transition temperature, initial volume fraction of martensite, and pre-strain on the phase transition in the shape memory alloy. On this basis, the constitutive law of the SMAHC beam is built by considering the tension-bending coupling effect and the phase transition in the SMAHC beam. The equation of motion for nonlinear vibration of the SMAHC beam with geometric nonlinearity and material nonlinearity is derived from the Hamilton principle and is discretized into matrix form using the Galerkin method. According to the algorithm of the NewMark-β method, numerical solutions are computed by developing Matlab program and are compared with the results from ABAQUS analysis. It shows that the frequencies and amplitudes of the theoretical calculations are very consistent with those obtained from ABAQUS analysis. In addition, both the theoretical study and ABAQUS simulation indicates that the high frequency for longitudinal vibration is not observed in the spectrum diagram of transverse vibration, while the low frequencies for transverse vibration are captured in the longitudinal vibration. With the established Matlab program, parametric study is carried out to investigate the effect of the temperature and the location of the SMA fibers on the vibration responses of the SMAHC beam. The results from this study indicate that the transverse vibration of SMAHC beams is characterized as one of low frequency, while the longitudinal vibration has the characteristics of high frequency. Especially in the case of nonlinear vibration, not only the vibration of high frequency but also the vibration of low frequency observed in the transverse vibration will occur in the longitudinal direction of the SMAHC beam. Furthermore, the double and triple fundamental frequencies of the transverse vibration are excited in the nonlinear vibration of the SMAHC beam. The results of this paper can provide a theoretical basis for the evaluation of the safety and stability of smart composite structures.

Experimental Research on the Bond Performance between SMAF-ECC Composites and Steel Bar.

Combining Engineered Cementitious Composites (ECC) with shape memory alloy (SMA) fibers can form SMA fiber reinforced ECC (SMAF-ECC) that has excellent deformation recovery and energy dissipation capabilities. Substituting some of the tensioned concrete with this new composite material, along with steel bars, is expected to significantly improve the seismic energy dissipation and self-recovery capabilities of traditional reinforced concrete components. However, a reliable bond between steel bars and SMAF-ECC is critical to ensure their synergistic performance. In this paper, the failure mode and bond strength of steel bars and SMAF-ECC were studied through direct tensile tests, and the influence factors such as steel bar diameter, bond length, and SMAF volume fraction were analyzed. A bond-slip constitutive model for steel bars and SMAF-ECC was proposed. The results show that the failure mode of the tensile test specimens is mainly steel bar pull-out failure; the incorporation of SMAF significantly enhances the bond strength between the steel bar and matrix; increasing the steel bar diameter and bond length both lead to a decrease in bond strength while increasing the SMAF volume fraction can significantly increase the bond strength. Among them, the specimen with a steel bar diameter of 12 mm, bond length of 70 mm, and SMAF volume fraction of 0.5% has the largest increase in bond strength, reaching 52.96%. The proposed improved bond-slip constitutive model is in good agreement with the bond-slip curve obtained in the experiments, with a determination coefficient of 0.99. The research results of this paper provide an important theoretical basis for promoting the engineering application of SMAF-ECC materials.

Analysis of low velocity impact response of glass fiber reinforced epoxy resin composite with shape memory alloy incorporation

The current article investigates about degradation of lightweight materials in aircraft structural components resulting from low-velocity impacts, a common cause of failure. Although subsonic collisions do not cause immediate external damage to the structure, they significantly reduce the material's stiffness and impact strength. The study explores the performance of intelligent hybrid thermoplastic composite plates subjected to low-speed impacts, both numerically and experimentally. Particularly, the behavior of laminated composites with integrated shape memory alloy (SMA) fibers is discussed in this study. SMA wires are inserted into the composite laminate fabric layer located on the intermediate planes. The study revealed that incorporating SMA fibers increases the damage tolerance and stiffness of the laminated composites compared to standard composite structures. The compounds exhibit a noticeable increase in hardness and energy levels before failure.

Study on the self-recovery performance of SMAF-ECC under cyclic tensile loading

The incorporation of superelastic shape memory alloy (SMA) fibers into engineered cementitious composites (ECC) has led to a novel composite material, SMAF-ECC, which possesses excellent deformation, energy dissipation, and self-recovery capabilities. To understand the self-recovery performance of this new composite material under tensile loading, this study conducted uniaxial cyclic tension tests on SMAF-ECC specimens to investigate stress, strain, crack width, strain recovery rate, and crack recovery rate, while also considering the primary influencing factors such as SMA fiber diameter and content. The results indicate that the addition of SMA fibers improves the ultimate strain and ultimate tensile strength of ECC; increasing fiber content effectively enhances the strain and crack recovery rates of SMAF-ECC specimens, with the maximum strain recovery rate and crack recovery rate of the tested specimens reaching 69% and 77%, respectively. Both too large and too small SMA fiber diameters lead to reduced recovery rates. In this experiment, when the fiber diameter was 0.5 mm, the strain and crack recovery rates of the specimens were the highest, with a crack recovery rate of 53%, approximately 1.7 times that of specimens with 1 mm and 0.2 mm diameter SMA fibers. These findings provide a reliable basis for establishing a theoretical model of the tensile mechanical properties of SMAF-ECC composite materials.

Shape memory alloy fiber reinforced concrete/mortar- A review

Shape memory alloy (SMA) is a smart material that responds to external non-mechanical stimuli like temperature or magnetic field by changing its underlying microstructural composition. SMA has two key characteristics, the superelastic effect and the shape memory effect, that make them suitable for civil engineering constructions, particularly in designs for earthquake resistance. Its ability to experience significant deformations and return to its original shape after removing the applied stress is known as superelasticity. The capacity to distort and restore its form after heating is known as the shape memory effect. SMA in the form of fibers can be utilized as a fiber-reinforcing material in concrete, commonly termed SMA fiber-reinforced concrete (SMAFRC). They can enhance the ductility and re-centering property of the matrix. Unlike steel fibers, SMA fibers are free from corrosion, thus making the system durable and improving its life span. Studies on SMAFRC show that the high cost of SMA prevents their widespread usage in this field. Notwithstanding this, their features may have to be exploited to significantly improve the safety of structures. This paper provides an in-depth analysis of the existing literature on the studies and investigations on SMAFRC and examines their various applications in earthquake-resistant systems. This paper discusses the various types and forms of SMA fibers available and their utility. Also, the literature available is grouped into the different engineering properties of SMAFRC, which include compressive strength, flexural strength, tensile strength, and impact resistance. The literature review reveals that SMA is anticipated to become a vital material in the construction sector, necessitating considerable study in this area.

Bonding Mechanical Properties between SMA Fiber and ECC Matrix under Direct Pullout Loads.

SMAF-ECC material composed of shape memory alloy fiber (SMAF) and engineered cementitious composite (ECC) has good bending and tensile properties, as well as good crack self-healing ability, energy consumption, and self-centering ability. The bond behavior between fiber and matrix is crucial to the effective utilization of the superelasticity of SMAF. The experimental study considered three variables: SMA fiber diameter, fiber end shape, and bond length. The pullout stress-strain curve of SMAF was obtained, and the maximum pullout stress, maximum bond stress, and fiber utilization rate were analyzed. Compared with the straight end and the hook end, the maximum pullout stress of the specimen using the knotted end SMAF is above 900 MPa, the fiber undergoes martensitic transformation, and the fiber utilization rate is above 80%, indicating that the setting of the knotted end can give full play to the superelasticity of the SMAF. Within the effective bond length range, increasing the bond length can increase the maximum anchorage force of the knotted end SMAF. Increasing the fiber diameter can increase the maximum pullout stress and maximum anchoring force of the knotted end SMAF but reduce the utilization rate of SMA fiber. This study provides a reliable theoretical basis for the bonding properties between SMAF and ECC.

Effect of microstructure and stress ratio on fatigue crack propagation behavior of A7N01 aluminum alloy fiber laser-VPTIG hybrid butt welded

In this paper, the fatigue crack growth rates of A7N01 aluminum alloy welded joint in weld zone (WZ) and heat affected zone (HAZ) are compared under the stress ratio of 0.1. At the same time, the fatigue crack growth rate of WZ under different stress ratios is studied. The results show that the difference of microstructure leads to different fatigue crack growth rates in different areas of welded joints. The HAZ shows better fatigue crack growth resistance and slower fatigue crack growth rate. However, due to the burning loss of Zn element in the WZ, the precipitation of strengthening phase after solidification in the molten pool is less, and the fatigue crack propagation resistance is weak. After 60 days of natural aging, the number of precipitated phases in the WZ and HAZ increased, and the fatigue crack propagation resistance is improved compared with that in the welded condition. Compared with grain boundary strengthening, precipitation strengthening is more important. With the increase of stress ratio, the fatigue crack closure effect in WZ gradually weakens, and the fatigue crack propagation rate increases.

Microstructure characterization and mechanical properties of the 304SS-(NiTif/FeAl) metal-intermetallic laminate composites

In this work, a novel continuous NiTi Shape Memory Alloy Fiber Reinforced (SMAFR) B2-FeAl based metal-intermetallic laminate (MIL) composite was prepared via two-step vacuum hot pressing combined with “multi-thin foils” stacking configuration. The microstructure characterization of the composite was conducted by using X-ray diffractometer, scanning electron microscopy, electron backscattered diffraction and transmission electron microscopy. The compressive and tensile properties of the composites were measured. Results indicated that the SMAFR MIL composite exhibits multi-layer structure consisting of residual stainless steel layer, newly-formed intermetallic layer and intermediate transition layer. The intermetallic layer is composed of several sublayers with the boundaries of centerlines, and B2-FeAl phase is the main phase in this layer. NiTi fibers locate at the centerlines in the intermetallic layer and show a uniform distribution. A metallurgical interfacial bonding between NiTi fiber and FeAl matrix was obtained through the inter-diffusion of Ni, Ti and Al elements across the interface. In the intermediate transition layer, B2 phase was also the dominant phase, and a large amount of fine Al-rich precipitates dispersed in the matrix. Compared with the MIL composite without NiTi fibers, the SMAFR MIL composite possesses superior compressive and tensile properties, which are mainly attributed to (Ⅰ) high tensile properties of NiTi fiber, (Ⅱ) a good interfacial bonding of NiTi/B2-FeAl, (Ⅲ) strong interfacial reaction products, and (Ⅳ) pullout effect of NiTi fibers.

Displacement recovery and energy dissipation of crimped NiTi SMA fibers during cyclic pullout tests

Abstract This study examines the cyclic pullout behavior of two types of cold-drawn NiTi shape memory alloy fibers, such as paddled and crimped fibers. For this, two diameters of 1.0 and 0.7 mm are considered. The experimental cyclic pullout results show that the deep crimped fibers produce a higher maximum pullout resistance than the shallow crimped fibers. When heated, the shallow crimped fiber increases the diameter more significantly than the deep crimped fiber, whereas the fiber wave depth decreases more than the deep crimped fiber. Thus, the maximum pullout resistance increases for the heated shallow crimped fiber and decreases for the heated deep crimped fiber. The displacement recovery ratio (DRR) reduction with an increasing slip is significant for the fiber with a low anchoring bond. The high anchoring bond fiber also introduces a higher average DRR than the fiber with a relatively low anchoring bond. Under heating treatment, the average DRR increases due to the prestressing in the fiber due to the shape memory effect. However, the anchoring bond of the fiber is enough to produce prestressing in the fiber. The anchoring bond of the fiber and the prestressing also influence the energy dissipation (ED). The higher anchoring bond results in a higher ED value, and the prestressing in the fiber contributes more to the increased ED values.

Numerical thermal frequency prediction of smart composite structure and experimental validation

Thermal eigenvalue characteristics of layered composite panels are obtained numerically utilizing the higher-order deformation kinematics, and the exactness of the solution has been verified with in-house experimentation. The laminated panel configuration bonded with and without shape memory alloy (SMA) fibres is modelled mathematical using the equivalent single-layer theory and third-order displacement kinematics. The functional composite structural properties under the elevated temperature are introduced in the current model for the necessary activation via the marching technique (to include the material nonlinearity due to SMA). The structural governing equation of motion is obtained by Hamilton’s principle and discretized using the isoperimetric finite element steps. Further, the computational modal responses are predicted using the in-house MATLAB computer code. The numerical solutions’ accuracy and stability have been compared with the earlier research data, including a few experimental verifications of thermal/ambient frequencies for laminated composite without SMA fibre. Further, a few numerical experiments have been carried out to show the significance of SMA fibre on the frequency responses of the parent structure, including temperature-dependent properties. The structural/material inputs, i.e., geometrical shapes, properties, geometrical parameters, and SMA-relevant data (volume fractions, VSMA; pre-strain, and recovery stress), are utilized for the computation of new results. The final insights have shown a significant improvement of frequency values, i.e., 4 %, 6 %, and 8 % of the laminated composite, while the volume fractions of SMA increase VSMA = 10 %, 15 % and 20 % for 3 % prestrain, respectively.

Plastic deformation behavior of aluminum alloy fiber porous body and its filled tube under impact loading

The size of aluminum alloy fiber wire with a short side of 5mm, a long side of 10mm and an arc radius of 1mm were prepared from the raw material of 6061 aluminum alloy fiber with diameter of 0.15mm by Spring machine cutting, namely the structure size of 5×10mm bending aluminum alloy fiber. The aluminum alloy fiber porous body with different porosity were prepared by vacuum hot pressing sintering furnace, and it was sleeved with 6063 aluminum alloy round tube to prepare aluminum alloy fiber porous body filled tube. The impact test was carried out with drop hammer impact testing machine, The plastic deformation behavior of aluminum alloy fiber porous body and its filled tube under impact loading with different porosity was studied. The results show that the impact process of aluminum alloy fiber porous body can be divided into three stages: plastic platform stage, densification stage and unloading stage, the filled tube with aluminum alloy fiber porous body can be divided into four stages: elastic deformation stage, progressive buckling stage, densification stage and unloading stage. Low porosity will make more fibers, and more benefit the generation of the sintering necks, the plastic deformation strength increases with the porosity decrease. The coupling effect of the aluminum alloy tube and the aluminum alloy fiber porous body makes the filled tube absorb the same energy with shorter impact displacement, and has stronger impact resistance and better mechanical properties.