Maximum Tensile Strain Research Articles

Experimental Research on Impact Resistance Test of Polycrystalline Diamond Compact Based on Digital Image Correlation Method

In this study, the impact resistance of Polycrystalline Diamond Compact (PDC) was studied with DIT drop weight tester and high speed camera. The surface of PDC was analyzed by Digital Image Correlation (DIC). The reason of impact failure of PDC was obtained by using the surface strain field of PDC. The results show that local delamination occurs near the impact point of the polycrystalline layer. The brittle fracture occurs at the maximum tensile strain of the impact resistant composite sheet. The quantitative relationship between the surface strain and the image obtained by DIC can effectively reflect the whole process of PDC composite failure, and can reasonably explain the failure process of PDC composite, and provide scientific research methods for engineering applications.

Investigating the damage to masonry buildings during shield tunneling: A case study in Hohhot Metro

After prolonged service, masonry buildings constructed in the 1970s and 1980s often experienced significant deterioration in strength and stiffness. Excessive ground deformation caused by shield tunneling frequently leads to cracking in adjacent masonry buildings. Most studies have focused on the settlement and tilting caused by shield tunneling on masonry structures, failing to reflect the specific damages caused by shield tunneling. This paper employs a jointed masonry model in numerical simulations to simulate masonry buildings, considering the actual measurement data from the Hohhot Metro Line 1 project. It discusses a thorough investigation into the potential damages and cracking on masonry buildings that may occur during shield tunneling in masonry structures. It provides a detailed study of the specific forms of cracking in masonry buildings. Then, a comprehensive and in-depth analysis is conducted on the impact of bricklaying methods, mortar adhesive strength, and synchronous grouting pressure on buildings in the context of shield tunneling through structures. The results show that using the jointed masonry model can effectively reflect the cracking and damage situation of masonry structures during shield tunneling construction, providing valuable guidance for actual shield tunneling operations. The area of cracking damage caused by shield tunneling construction gradually increases from the top to the bottom of the building. It is concentrated above the doors and windows of the structure. Potential cracks around door and window openings extend from the upper-middle part of the openings towards both sides, forming a regular figure-eight distribution. With changes in the masonry construction method, grouting pressure, and mortar bond strength, the settlement and damage levels of the building also undergo alterations. Specifically, as the mortar bond strength increases from 30 kPa to 50 kPa, the maximum tensile strain of the masonry construction decreases to 0.11 %. Simultaneously, when the construction method of the building bricks transitions from A to B, the damage at the door and window openings on the west wall of the building gradually intensifies, resulting in a rise in the maximum tensile strain to 0.109 %. Furthermore, as the grouting pressure increases from 50 kPa to 300 kPa, the maximum settlement of the building walls decreases by 51 %, and the maximum tilt reduces by 48 %. However, this study did not account for the lintels and sills in the masonry building, which may lead to an overestimation of simulated strain data.

Ultrastretchable Helical Carbon Nanotube-Woven Film.

Helical carbon nanotube (HCNT) is regarded as one of the most promising nanomaterials due to its excellent tensile strength and superhigh stretchability. Here, a novel HCNT-woven film (HWF) is proposed, and its in-plane and out-of-plane mechanical properties are systematically investigated via molecular dynamics (MD) simulation. The MD results show that HWF possesses highly stretchable capability resulting from sliding and straightening of CNT segments, and the maximum tensile strain can reach 2113%. Furthermore, the HWF presents an obvious tensile mechanical anisotropy. The torsion failure is the main fracture mode when the HWF is stretched along the longitudinal direction. However, when the HWF is stretched along the transverse direction, the fracture is mainly caused by intertube compression. On the other hand, the HWF can dissipate large amount of kinetic energy of projectile via sliding and fracture of HCNTs, leading to high specific penetration energy. This work provides a theoretical guidance for designing and fabricating next-generation superstrong two-dimensional CNT-based nanomaterials.

Ultrahigh-Quality Ge-on-Glass with a 3.7% Uniaxial Tensile Strain.

While there have been notable advancements in the quality of epitaxial Ge on Si, the crystal quality of bulk Ge remains much superior, which provides an effective method to study the performance potentials of Ge-based semiconductor devices. This study showcases the development of ultrahigh-quality Ge/poly-Si/SiO2 on glass with a Ge thickness reduced to ≤100 nm (10 μm width) through wafer bonding, thinning, and polishing processes. The minority lifetimes measured for the Ge thin films range between 200 and 1000 ns, surpassing those achieved with epi-Ge on Si by at least 20 to 100 times. The wafer bonding process introduces a desirable tensile strain of 0.1%, attributed to thermal expansion mismatch. A Ge microbridge structure was employed to amplify the tensile strain, reaching a maximum uniaxial tensile strain of 3.7%. The much longer minority carrier lifetime together with the strain-induced band gap engineering holds promise for improving light emission efficiency. This work establishes an economical and convenient method for producing high-quality tensile-strained Ge thin films, a pivotal step in exploring the potential of Ge in light emission applications.

Optimization design of fiber rubber asphalt gravel sealing layer based on fatigue crack resistance test.

Crack is one of the main diseases of pavement structure. In order to improve the anti-reflective crack ability of pavement, fiber rubber gravel sealing layer is proposed as the stress absorbing layer. In view of the shortcoming that Mcleod design method can not be associated with road performance, a sealing layer optimization design method based on fatigue crack test is proposed. Firstly, the reinforcement effect of fiber on rubber asphalt was studied through force ductility testing. Secondly, the optimum dosage of fiber, asphalt and gravel was optimized through fatigue cracking resistance test. Finally, the cracking resistance of fiber rubber gravel seal was verified through fracture energy test. The results show that fibers can significantly increase the maximum tensile force and strain yield energy of rubber asphalt, and basalt fiber has the best reinforcement effect. The most obvious effect on cracking resistance performance in the sealing layer is the amount of fiber, followed by the amount of asphalt, and finally the amount of gravel. The optimized material combination with the best crack resistance is 120g/m2 fiber, 14kg/m2 gravel and 2.4kg/m2 rubber asphalt, and the fatigue resistance times can reach 19532 times. The fracture energy of the composite pavement treated by the optimized sealing layer is nearly double that of the non-treated pavement structure, and it has a good anti-crack effect.

Full-temperature performance characterisation of super tough resin concrete for steel bridge deck paving

ABSTRACT The severe service environment of steel bridges put forward strict requirements for the deck pavement, especially the flexibility of paving materials. In this study, a new super tough resin-based concrete (STRC) was introduced and a comparative study of STRC and epoxy asphalt concrete (EAC) performance was conducted. Specifically, the high-temperature stability, low- and intermediate-temperature flexibility, fracture resistance, and fatigue properties were characterised by the dynamic creep test, beam bending test, semi-circular bending test, and semi-circular fatigue test, respectively. According to the results, at 70°C, the cumulative strain after 10,000 cycles of loading is about 2700μϵ and 900μϵ for STRC and EAC, respectively. At −10°C, the maximum tensile strain of EAC is only 2419 μϵ, which is significantly lower than that of STRC (17000 μϵ). For the cracking resistance, STRC exhibits larger total fracture energy, pre-peak and post-peak fracture energies, which indicates the excellent cracking resistance of STRC. Furthermore, the fatigue life and accumulated dissipated energy of STRC are higher than that of EAC. Besides, the tensile strain growth rate of EAC is significantly greater than that of STRC, which implies a lower crack propagation rate and better fatigue resistance of STRC.

Seismic fragility analysis of nuclear containment structure using Bayesian logistic regression model

Nuclear containment structure serves as the critical shielding structure in nuclear power plants, and must maintain structural integrity under various conditions. Following the Fukushima nuclear accident, seismic safety of nuclear power plant structures has become a significant concern in nuclear engineering community. This study presents seismic fragility analysis of the nuclear containment structure subjected to far-fault ground motion based on Bayesian logistic regression model. A refined finite element model of the nuclear containment structure was developed using layered shell element with considering material nonlinear behavior. The maximum tensile strain and roof drift of the nuclear containment structure were analyzed. MATLAB scripts for the seismic fragility analysis method based on Bayesian logistic regression model were developed. Posterior samples for the parameter of fragility function parameters were obtained using developed scripts. The sensitivity of the proposed Bayesian logistic regression based seismic fragility analysis method was verified. Seismic fragility curves of the nuclear containment structure obtained with the minimized sum of squared error, maximum likelihood estimation and Bayesian logistic regression methods were compared in depth.

Study on the Performance of High Content RAP Recycled Mixture

The performance of RAP material directly affects the engineering effect of pavement recycling technology. In this study, the performance of high content RAP recycled mixture was analyzed. Through the extraction and screening of RAP materials, it was found that the viscosity of old asphalt increased significantly, the softening point decreased, and the coarse aggregate was refined seriously. The high, low temperature and water stability of high content plant mixed recycled ATB-25 mixture were studied through laboratory tests with different regenerants. The results showed that, compared with the control group, the dynamic stability, freeze-thaw splitting strength ratio and the maximum flexural tensile strain increase rate were: Type A regenerant: 27.48%, 29.45%, 35.71%; Type B regenerant: 16.76%, 21.28%, 38.96%. Comparing the effects of the two kinds of regenerants, after adding Type A regenerant, the mixture has the best high-temperature and water stability, and Type B regenerant is better than Type A regenerant in improving the low-temperature performance. The high, low temperature and water stability of the mixture after adding the regenerant can meet the specification requirements.

Highly stretchable, robust, sensitive and wearable strain sensors based on mesh-structured conductive hydrogels

With the rapid development of wearable electronic devices, flexible sensors, as the core components of wearable devices, have received extensive attention. Manufacturing of the strain sensors with excellent mechanical properties, wide working range, and high sensitivity is crucial for the development of wearable devices. Herein, for the first time we proposed a strategy based on mesh-structured conductive hydrogel to sensitively detect the body movement in a large workable strain ranges, and demonstrated the facile fabrication procedure of the sensors by using a direct ink writing 3D printing technique. Low cost conductive hydrogels were prepared by a simple one-pot method of combining dispersant-free carbon nanocolloids with easily synthesized PVA/TA/PAM. The printing of complex mesh-structured hydrogels was optimized with high fidelity. The strain sensor based on the mesh-structured hydrogel exhibited excellent mechanical properties, of which the maximum failure stress of the honeycomb was 1.28 MPa and the maximum failure tensile strain was 704 %, amazing sensitivity (GF = 32.95 for the tensile strain range of 3.5 %-5%, GF = 21.5 for the tensile strain range of 100 %-120 %), wide detection range, good stability and durability (for 500 tensile cycles, the ΔR/R0 value remained unchanged). In addition, the working mechanism during the stretching process of mesh-structured hydrogels was revealed by combining finite element simulation with microscopic morphology observation. At last, the applications of the mesh-structured hydrogel-based sensors to accurately and reliably detect both subtle physiological signals and large joint movements were soundly demonstrated, endowing the ability of achieving all-round detection of human motion. Our work could provide a universe strategy for fabricating highly ventilated, stretchable, robust, sensitive and wearable strain sensors, which would greatly expand the applications of strain sensors in wearable devices.

Preparation and Performance of High Thermal Conductivity Polypropylene-based Composites

Polypropylene-based composites with high thermal conductivity were obtained by pressure injection molding using a hybrid form of PP as the matrix and FG as the thermally conductive filler with a particle size of 37 µm. Microscopic morphologies of the material were examined by SEM to determine the effect of FG content on the thermal conductivity and mechanical properties of the composites. The study found a clear correlation between the thermal conductivity of the composites and the FG content. The research confirmed a direct link between the thermal conductivity of the composites and FG content. At 70 wt%, the material demonstrated the greatest average, axial, and radial thermal conductivity of 7.52 W·m-1·K-1, 12.6 W·m-1·K-1, and 4.50 W·m-1·K-1, respectively. However, any subsequent increase in fractional gradient (FG) content resulted in a decrease in the strength and modulus of the material. The highest tensile and flexural strength values of 34.9 and 63.7 MPa respectively, were achieved when the FG content was 60 wt%. At this particular FG content, the tensile and flexural modulus also reached 9.78 and 10.7 gigapascals (GPa), respectively. As the FG content increased, the strain on the composite material decreased. Note that the maximum tensile and flexural strains were measured at 50 wt% FG content, with values of 0.77% and 0.79%, respectively. The glass fiber sheets in the injection molded composites were uniform and predominantly vertically oriented.

Uniaxial tensile mechanical behavior research of HTPB propellant under wide temperature and confining pressure

To investigate the effects of confining pressure, strain rates, and temperatures on the mechanical properties of the Hydroxyl-terminated Polybutadiene (HTPB) propellant, uniaxial tensile tests were performed utilizing wide-temperature-confining pressure systems. The resulting damage was subsequently analyzed and characterized through scanning electron microscopy and mirco-ct. The results indicate that the stress–strain curves of HTPB at 20 and 70 °C are comparable, and the propellant damage is primarily attributed to de-wetting at 20 and 70 °C with respect to the mechanism. At −50 °C, the maximum tensile strength and ultimate tensile strain at 8 MPa surpass those at 0 and 2 MPa to a significant degree and the damage shifts from de-wetting and ductile fracture of particles to severe particle breakage with the elevated confining pressure. Ultimately, the primary curve of the HTPB propellant's maximum tensile strength was constructed by the curve fitting analysis based on the time–temperature equivalent superposition principle (TTSP) and time–pressure equivalent superposition principle (TPSP). Comparing to the properties of TPSP, TTSP exhibits a wider range of applicability and greater fitting precision in relation to the HTPB propellant. This study mainly serves to establish a fundamental theory and furnish data support for the enhancement of mechanical properties and structural integrity of solid rocket motors.

Thermal-Mechanical Behaviour of Road-Embedded Wireless Charging Pads for EVs

Road-embedded inductive power transfer (IPT) systems have the potential to accelerate the electrification of the transportation sector. For these systems to be economically viable, however, they need to have a similar durability and lifespan to those of asphalt roads. One area that has lacked investigation is thermally induced stresses in a primary IPT pad, which are caused by the increase in the temperature of the pad when it is energized and the differing thermal expansion of the materials within. This paper presents an experimental and a finite element-based methodology for investigating the thermal–mechanical behaviour of a ¼-scale double-D pad, which was energized while suspended in air, as well as energized when embedded in pavement. A focus was placed on the measurement and prediction of strains in the magnetic ferrite cores because of their brittleness. Ferrite strains were measured using a combination of resistive strain gauges and non-metallic fibre Bragg grating (FBG) sensors. Coupled electromagnetic–thermal–structural simulations were conducted to predict temperature and strains in the system, with temperature-dependent properties obtained through physical testing. At an ambient temperature of 50 °C, the temperature in the middle of the copper litz wire coil was predicted to be 100 °C in both the suspended and embedded case. There was an excellent correlation with the experimental results, with a difference of less than 10% for most temperature measurements. When energized, the pad was predicted to experience an upward bow due to its temperature rise, resulting in bending strains in the ferrite cores. At an ambient temperature of 50 °C, the maximum tensile strain in the ferrites of the embedded pad was measured to be 62 microstrains (με), with a root-mean square error that was 18 με across three sensors. The experimental and validated numerical methodology can be applied to full-scale operational IPT pads to analyse and improve their thermal–mechanical performance.

Mechanical Properties of Buried Steel Pipe With Polyurethane Isolation Layer Under Strike-Slip Fault

Abstract Long-distance buried pipelines are one of the most common and economical transportation methods for oil and gas, but the fault movement will pose a threat to the safety of pipelines. The main challenge of pipeline under strike-slip faults is to improve the ability of resistance to fault dislocation, and the main aim of the study is how to improve the critical fault displacement of pipelines with the help of polyurethane isolation layer. Three-dimensional finite element models were proposed for mechanical analysis of X80 buried steel pipe with polyurethane isolation layer under strike-slip fault. The influence of factors on the mechanical properties of pipelines were studied, such as thickness of isolation layer, internal pressure, fault displacement, diameter-thickness ratio, and the angle of pipe and fault line. The simulation results indicate that with the increase of the thickness of the isolation layer, the development of the maximum tensile and compressive strain of the pipeline is significantly reduced for the same fault displacement, resulting in a significant increase in the critical fault displacement corresponding to the three failure modes of the pipeline. As the ratio of diameter to thickness and internal pressure decrease, the critical displacements decrease. When designing and planning the pipeline, pipeline is recommended with the seismic isolation layer, large wall thickness, and the crossing-angle at 70 deg∼80 deg. The research provided a reference for judgment of earthquake resistance, failure analysis, and safety design of pipelines with polyurethane isolation layer crossing strike-slip faults.

Multifunction E-Skin Based on MXene-PA-Hydrogel for Human Behavior Monitoring.

Hydrogels have attracted significant attention in various fields, such as smart sensing, human-machine interaction, and biomedicines, due to their excellent flexibility and versatility. However, current hydrogel electronic skins are still limited in stretchability, and their sensing functionality is often single-purpose, making it difficult to meet the requirements of complex environments and multitasking. In this study, we developed an MXene nanoplatelet and phytic acid-coreinforced poly(vinyl alcohol) (PVA) composite, denoted as MXene-PA-PVA. The strong hydrogen bonds formed by the interaction of the different components and the enhancement of chain entanglement result in a significant improvement in the mechanical properties of the PVA/PA/MXene composite hydrogel. This improvement is reflected in an increase of 271.43% in the maximum tensile strain and 35.29% in the maximum fracture stress. Moreover, the composite hydrogel exhibits excellent adhesion, water retention, heat resistance, and conductivity properties. The PVA/PA composite material combined with MXene demonstrates great potential for use as multifunctional sensors for strain and temperature detection with a strain-sensing sensitivity of 3.23 and a resistance temperature coefficient of 8.67. By leveraging the multifunctional characteristics of this composite hydrogel, electronic skin can accurately monitor human behavior and physiological reactions. This advancement opens up new possibilities for flexible electronic devices and human-machine interactions in the future.

Mechanical, Chloride Permeation, and Freeze–Thaw Resistance of Recycled Micronized Powder Polypropylene-Fiber-Engineered Cementitious Composites

Research on engineered cementitious composites was carried out using recycled micronized powder from waste construction waste as a substitute for cement. Consequently, this paper focuses on the investigation of recycled micronized powder (RMP) as the subject of study. Using RMP-PP-ECCA0 as the control group, we explored the impact of polypropylene fiber content (0.5%, 1%, 1.5%, 2%) and the substitution rate of RMP (10%, 20%, 30%, 40%) on the mechanical properties, resistance to chloride ion penetration, and freeze–thaw durability of recycled micronized powder polypropylene-fiber-engineered cementitious composites (RMP-PP-ECCs). It was found that, with the increase in RMP substitution rate and fiber content, the mechanical, chloride ion permeation, and freeze–thaw resistance of recycled micronized powder polypropylene-fiber-engineered cementitious composites showed a trend of increasing and then decreasing when the RMP substitution rate was 10%, and the fiber content was 1.5%; the compressive, tensile, chloride ion permeation, and freeze–thaw resistance of recycled micronized powder polypropylene-fiber-engineered cementitious composites were most obviously improved. Compressive strength performance increased by 18.8%, tensile strength performance increased by 80.8%, maximum tensile strain increased by 314%, and electrical flux decreased by 56.3%. Meanwhile, when the recycled micronized powder substitution rate was 10%, the fiber content was 1%, with the most obvious improvement in flexural and freeze–thaw cycle resistance, compared with the control group 28 d flexural strength increased by 22%, after 150 freeze–thaw cycles, the mass-loss rate was reduced by 26%, and the relative dynamic elastic modulus was improved by 4%. In addition, the chemical composition of the regenerated microfractions and the defects in the matrix of the fracture surface of the tensile specimens, the distribution of polypropylene fibers, the surface morphology, and the failure mode were analyzed by X-ray diffraction and scanning electron microscopy.

Trench Formation under the Tunable Nanogap: Its Depth Depends on Maximum Strain and Periodicity.

Metallic nanogaps have been studied for many years in the context of a significant amount of field enhancements. Nanogaps of macroscopic lengths for long-wave applications have attracted much interest, and recently one dimensional tunable nanogaps have been demonstrated using flexible PET substrates. For nanogaps on flexible substrates with applied tensile strain, large stress is expected in the vicinity of the gap, and it has been confirmed that several hundred nanometer-deep trenches form beneath the position of the nanogap because of this stress singularity. Here, we studied trench formation under nanogap structures using COMSOL Multiphysics 6.1. We constructed a 2D nanogap unit cell, consisting of gold film with a crack on a PDMS substrate containing a trench beneath the crack. Then, we calculated the von Mises stress at the bottom of the trench for various depths and spatial periods. Based on it, we derived the dependence of the trench depth on the strain and periodicity for various yield strengths. It was revealed that as the maximum tensile strain increases, the trench deepens and then diverges. Moreover, longer periods lead to larger depths for the given maximum strain and larger gap widths. These results could be applied to roughly estimate achievable gap widths and trench depths for stretchable zerogap devices.

Investigation and measurement of old building response to the overlapped shield tunnel of multiple schemes in the sandy cobble stratum

Ground movements due to tunneling are becoming increasingly critical as buildings are located around construction sites. This study proposes a new combined reinforcement method using a foundation grouting oblique pipe roof. The former improves the bearing capacity of the subsoil, and the latter blocks the transmission of soil deformation, which weakens the influence of construction during overlapped tunnel under-crossing. Based on this new method, a case study of the shield tunneling response to an old building in Line 6 of China’s Chengdu Metro is presented. Additionally, three-dimensional numerical models without reinforcement, traditional foundation grouting reinforcement, and the new combined reinforcement schemes were compared. The numerical simulation performance was verified using a set of field instrumentation data, which demonstrated that the old building response to the overlapped tunnels was under control, and the maximum deformation, angular distortion, and principal tensile strain of the building were 5.25 mm, 5.10 × 10–6 rad/m, and 0.0081%, respectively. Compared with the traditional reinforcement scheme, the deformation, angular distortion, and principal tensile strain in the combined reinforcement scheme were reduced by 54.78%, 71.02%, and 70.22%, respectively. These results have important implications for the design and construction of shield tunnels and their response to old buildings.

Effects of species and moisture content on the behaviour of solid wood under impact

The article's main aim is to assess the effects of species and moisture content (MC) on the behaviour of solid wood material under the low velocity of impact and present a pattern for predicting loading vs time curves for these species in different moisture levels. Three groups of samples (300 × 20 × 20 mm) were made from beech, oak, and spruce wood. Each group was subdivided into two groups with low moisture content (LMC) level (10–12%) and high moisture content (HMC) level (40–60%). A drop-weight impact machine did the tests, and high-speed cameras recorded the lateral specimens' surface during the impact. The digital image correlation technique (DIC) determined the strain pattern and the deflection. The timing of the crack initiation was also observed. Also, the force–time charts, the maximum force required for crack initiation, the work needed for crack initiation, and the total work required for the breakage of every specimen were gathered. A general force–time pattern with five identifiable steps was determined for each group. It turned out that the maximum deflection and longitudinal tensile strain of the beams up to crack initiation increase with increased moisture content while maximum force decreases. Unlike beech, the required work for rupture of HMC samples of oak and spruce is higher than LMC group.

Numerically optimized post‐cracking branch of the constitutive tensile model for fiber‐reinforced concrete with natural and recycled aggregates

AbstractThis paper investigates the post‐cracking behavior of glass fiber‐reinforced recycled concrete (FR‐RAC). This was done on eight fiber‐reinforced concrete (FRC) mixtures, with three types of recycled aggregates (RAs), while the used fibers were the CEM‐FIL Minibars™ with a fiber content of 0.50 and 0.75 V%. Based on those investigated mixtures, it was found that the proposed constitutive tensile model of the fib Model Code 2010 and the model of di Prisco overestimate the measured load–CMOD curves. Therefore, the post‐cracking branch of the constitutive tensile model was numerically optimized. This was done by optimizing the ka and kc value in the simplified model (Equations 16 and 17), proposed by Vandevyvere and based on the model of di Prisco. The ka value relates to the tensile strength at serviceability limit state, while the factor kc relates to the tensile strength at ultimate limit state (ULS). The numerically optimized ka and kc value, abbreviated by and , indicates a lower value and a higher value than the model of di Prisco et al. In addition, the extensive test data in this study show an increased post‐cracking behavior for the 0.75 V% mixtures with RAs. However, the and values are 0.325 and 0.710 for NAC‐0.75 V%, and only slightly different and values are obtained for the FR‐RAC mixtures. Therefore, one unified constitutive tensile model is proposed for all FRC mixtures. In addition, the numerically optimized model indicates a lower neutral axis location as well as a higher maximum tensile strain () and compressive strain () for the recycled concrete mixtures. The value at CMOD3 is 0.074‰ for NAC‐0.75 V%, while the nRAC‐0.75 V% mixture indicates a value of 0.100‰. This explains the improved fiber activation of the fiber‐reinforced recycled concrete mixtures (with 0.75 V% glass fibers).

Reconstructed Hierarchically-Structured Keratin Fibers with Shape-Memory Features Based on Reversible Secondary Structure Transformation.

Biocompatible and biodegradable shape-memory polymers have gained popularity as smart materials, offering a wide range of applications and environmental benefits. Herein, we investigate the possibility of fabricating regenerated water-triggered shape-memory keratin fibers from wool and cellulose in a more effective and environmentally friendly manner. The regenerated keratin fibers exhibit comparable shape-memory performance to other hydration-responsive materials, with a shape fixity ratio of 94.8 ± 2.15% and a shape recovery rate of 81.4 ± 3.84%. Owing to their well-preserved secondary structure and crosslinking network, keratin fibers exhibit outstanding water-stability and wet stretchability, with a maximum tensile strain of 362 ± 15.9%. In this system, we investigate the reconfiguration of the protein secondary structure between α-helix and β-sheet as the fundamental actuation mechanism in response to hydration. This responsiveness is studied under force loading and unloading along the fiber axis. Hydrogen bonds act as the "switches" clicked by water molecules to trigger the shape-memory effect, while disulfide bonds and cellulose nanocrystals play the role of "net-points" to maintain the permanent shape of the material. Water-triggered shape-memory keratin fibers are manipulable and exhibit potential in the fabrication of textile actuators, which may be applied in smart apparel and programmable biomedical devices. This article is protected by copyright. All rights reserved.