Torque Levels Research Articles

Harmonic Vibration Analysis in a Simplified Model for Monitoring Transfemoral Implant Loosening.

A simplified axisymmetric model of a transfemoral osseointegration implant was used to investigate the influence of the contact condition at the bone-implant interface on the vibrational response. The experimental setup allowed the degree of implant tightness to be controlled using a circumferential compression device affixed to the bone. Diametrically placed sensors allowed torsional modes to be distinguished from flexural modes. The results showed that the structural resonant frequencies did not shift significantly with tightness levels. The first torsional mode of vibration was found to be particularly sensitive to interface loosening. Harmonics in the vibrational response became prominent when the amplitude of the applied torque increased beyond a critical level. The torque level at which the third harmonic begins to rise correlated with implant criticality, suggesting a potential strategy for early detection of implant loosening based on monitoring the amplitude of the third harmonic of the torsional mode.

Sound Sensing: Generative and Discriminant Model-Based Approaches to Bolt Loosening Detection.

The detection of bolt looseness is crucial to ensure the integrity and safety of bolted connection structures. Percussion-based bolt looseness detection provides a simple and cost-effective approach. However, this method has some inherent shortcomings that limit its application. For example, it highly depends on the inspector's hearing and experience and is more easily affected by ambient noise. In this article, a whole set of signal processing procedures are proposed and a new kind of damage index vector is constructed to strengthen the reliability and robustness of this method. Firstly, a series of audio signal preprocessing algorithms including denoising, segmenting, and smooth filtering are performed in the raw audio signal. Then, the cumulative energy entropy (CEE) and mel frequency cepstrum coefficients (MFCCs) are utilized to extract damage index vectors, which are used as input vectors for generative and discriminative classifier models (Gaussian discriminant analysis and support vector machine), respectively. Finally, multiple repeated experiments are conducted to verify the effectiveness of the proposed method and its ability to detect the bolt looseness in terms of audio signal. The testing accuracy of the trained model approaches 90% and 96.7% under different combinations of torque levels, respectively.

Implant Stability After Graftless Motor-Driven Crestal Sinus Elevation: A Cohort Study.

Graftless motor-driven crestal sinus elevation may be a preferable alternative to conventional methods due to the reduction of postsurgical complications and lower cost. This prospective cohort study evaluated the stability of implants installed using this technique. Twenty-nine Straumann BLT (bone level tapered) implants in 29 patients were included in the sample. Average implant stability quotients (ISQ) were measured immediately after surgery (mean: 73.5 ± 9.2) and after a period of healing (mean: 77.1 ± 4.5) using resonance frequency analysis (RFA). There was a significant increase in implant stability after healing (P = .035). The healing duration did not significantly influence how implant stability increased (P =.373). The mean ISQ after healing was significantly higher than the clinically acceptable stability value of 65 ISQ (P < .001). Implant length and width were not significantly correlated with ISQ increase (P = .764 and P = .085, respectively). In addition, there were no significant differences in average ISQ values measured immediately postsurgery (at baseline) or after healing between implants with and without registered perforations during surgery (P = .118 and P = .366, respectively). The posthealing stability of 4 implants that did not achieve primary stability was not significantly less stable after the healing period than those that had achieved primary stability (P = .086). Moreover, the level of insertion torque significantly impacted implant stability immediately postsurgery (P < .001), but the ISQ values measured after healing were not significantly different based on the initial insertion torque values (P = .131). This study suggests that implants installed using graftless motor-driven crestal sinus elevation may achieve clinically acceptable stability as measured by RFA.

Bicortical Compression and Construct Stability With Variable Pitch Locking Screws in Cadaveric Specimens.

A variable pitch locking screw is intended to provide interfragmentary compression combined with fixed angle stability of locking plate constructs. The objective of this study was to compare variable pitch locking screws (3.5-mm KreuLock Ti locking compression screws, Arthrex Inc., Naples, FL) with standard locking screws (from the same manufacturer) in bicortical fixation scenarios in cadaver bone by assessing (1) interfragmentary compression and plate-bone compression and (2) construct biomechanical stability. Nine matched pairs of fresh-frozen cadaveric specimens with an average age of 67.2 years (range, 37-83) were used. Interfragmentary compression and plate-bone compression associated with insertion of single bicortical screws were compared between the variable pitch and standard locking screws at increasing levels of torque. The specimens tested were distal tibiae having a simulated longitudinal fracture. Additionally, fibulae were osteotomized to create a stable longitudinal fracture pattern and were fixed with a 5-screw plate construct with either all variable pitch or all standard locking screws. One of the 5 screws was placed across the osteotomy without lagging. Fibulae were tested cyclically with axial with torsional loading to compare displacements, rotation, and loads at failure or tested in 4-point bending to compare construct stiffness and maximum force to failure. Interfragmentary and plate-bone compression forces in the distal tibia model varied across specimens but were significantly higher with variable pitch locking screws compared with standard locking screws [512 N (SD = 324 N) vs. 79 N (SD = 64 N), P = 0.002, and 242 N (SD = 119 N) vs. 104 N (SD = 123 N), P = 0.028, respectively]. In cyclic loading of fibula constructs, no significant differences were detected in construct axial displacement or angular displacement (P > 0.05). In 4-point bending, no differences were detected in maximum force or bending stiffness (P > 0.05). Variable pitch locking screws produced interfragmentary compression between cortices and plate-bone compression that was greater than that produced by standard locking screws. In a stable bicortical fibula fixation scenario under external loading, the stability of variable pitch locking screw constructs was similar to constructs with standard locking screws.

Descending motor drive does not interact with muscle metaboreflex for ventilation regulation during rhythmic exercise in healthy humans.

The muscle metaboreflex effect on pulmonary ventilation (V̇E) regulation is more apparent during rhythmic exercise than rest, possibly because this reflex interacts with other mechanisms regulating V̇E during voluntary contractions, such as central command. Therefore, we tested whether one part of central command, the descending component of motor execution (i.e., descending motor drive), and the muscle metaboreflex interact synergistically to regulate V̇E. Thirteen healthy adults (9 men) completed four experiments in random order under isocapnia. The muscle metaboreflex was activated by rhythmic handgrip exercise at 60% maximal voluntary contraction (MVC) force with the dominant hand. Then, the muscle metaboreflex remained active during a 4-minute recovery period via post-exercise circulatory occlusion (PECO), or it was inactivated, maintaining free blood flow to the dominant upper limb. During the last 2-minutes of the handgrip exercise recovery, participants either performed rhythmic voluntary plantar flexion with the dominant leg at 30% MVC torque to generate descending motor drive or the dominant leg's calf muscles were involuntarily activated by electrical stimulation at a similar torque level (i.e., without descending motor drive). V̇E increased to a similar level during handgrip exercise in all conditions (≈22 L/min, P = 0.364). PECO maintained V̇E elevated above recovery with free blood flow (≈17 L/min vs. ≈13 L/min, P = 0.009). However, voluntary and involuntary plantar flexion with or without PECO evoked similar V̇E responses (∆ ≈ 4 L/min, P = 0.311). Therefore, an interaction between descending motor drive and muscle metaboreflex is not ubiquitous for V̇E regulation during rhythmic exercise.

Assessment of the Effectiveness of Vibration Therapy and Passive Rest on the Recovery of Muscular Strength and Plasma Lactate Levels in the Upper Limbs after Intense Anaerobic Exercise in Elite Boxers and Kickboxers

Background: High-intensity anaerobic physical training frequently leads to muscle fatigue among boxers and kickboxers. Vibrational therapy (VT) and passive rest (PR) have been employed as methods to enhance muscular recovery and performance. This study evaluates the effectiveness of these two recovery methods on upper limb muscle strength and lactate levels in plasma after high-intensity exertion. Methods: Eighteen elite boxers and kickboxers, aged 19–32 years, underwent tests employing VT and PR as recovery methods in a controlled, crossover study. Muscle performance was assessed via isokinetic dynamometry, and lactate levels were measured pre-exercise, post-exercise, and post-recovery. The study adhered to the Declaration of Helsinki guidelines and was approved by the relevant bioethics committee. Results: The results showed that VT led to a faster recruitment of muscle fibers and improved muscle endurance as indicated by decreased fatigue work indices compared to PR. However, no significant differences were observed in peak torque or lactate levels between the two recovery methods. The VT group exhibited quicker recovery times in torque generation and better performance in fatigue resistance. Conclusions: VT appears to provide superior muscular recovery compared to PR following intense anaerobic effort, particularly in terms of muscle strength endurance and activation speed. These findings support the potential of VT in sports recovery protocols, although similar lactate response suggests that metabolic recovery rates are not significantly affected.

Greenhouse gas emission prediction and impact analysis of dual-fuel engine

This study explored the profound influence of greenhouse gas (GHG) emissions on global climate change by introducing an innovative prediction model. Utilizing a backpropagation (BP) neural network with dual-hidden layer, optimized through simulated annealing particle swarm optimization (SA-PSO), the model predicted emissions from a diesel/natural gas dual-fuel engine at 1500 rpm across four torque levels: 400, 800, 1200, and 1600 N·m. The inputs included engine torque, injection timing, pressure, excess air coefficient, and natural gas substitution ratio, with CO2 and CH4 as outputs. Evaluation metrics—the coefficients of determination (R²) of 0.9975 for CO2 and 0.9951 for CH4, the root mean square error (RMSE) of 0.062 % and 278.04 ppm, and the mean relative error (MRE) of 0.82 % and 5.35 %, respectively—demonstrated the model’s accuracy. A quantitative analysis using the Mean Influence Value (MIV) algorithm showed engine torque’s pivotal role in emissions at a medium engine speed with contribution rates of 48.5 % and 40.3 % for CO2 and CH4 emissions, respectively. Notably, at a lower load condition (engine torque = 400 N·m), the natural gas substitution ratio was identified as having the most substantial impact on emissions. This study presents a novel approach to predicting and reducing GHG emissions from dual-fuel engines.

The reliability assessment method for sealing structure of subsea horizontal clamp connector based on sealing and strength

The reliability assessment of the Subsea Horizontal Clamp Connector (SHCC) sealing performance faces a challenge due to the lack of characteristic dimension evaluation methods. Hence, this paper develops the Comprehensive Sealing Reliability Evaluation (CSRE) method. This approach allows for the simultaneous analysis of failure in two dimensions: structural sealing and structural strength, incorporating the uncertainty of fuzzy stress in the evaluation. The CSRE method is based on Bayesian networks, using contact stress as a critical parameter to establish structural sealing failure nodes with gasket coefficients combined with the API standards for acceptance. Simultaneously, it establishes structural strength failure nodes using an improved stress interference model. When applying the CSRE method, this paper, through Monte Carlo simulations combined with torque transmission mechanics and finite element contact models, analyzes the reliability variations of the developed SHCC under different torque levels. The results indicate that the sealing reliability of SHCC is related to sealing pressure and structural strength, with excessively high or low torque affecting its sealing reliability. At an input torque of 2400 N·m, its reliability reaches the maximum value, which is 0.9912. The presented CSRE approach, validated through experimentation and method comparison, demonstrates greater alignment with engineering practicality.

The Contralateral Ankle Joint Is a Reliable Reference for Testing Syndesmotic Stability Using Bilateral External Torque CT.

Subtle chronic or latent instabilities are difficult to delineate with currently available diagnostic modalities and do not allow assessment of ligamentous functionality. The noninvasive bilateral external torque computed tomography (CT) was able to reliably detect syndesmotic lesions in a cadaveric study. The aim of the study was to test the external torque device in young, healthy subjects at 3 different torque levels and to demonstrate comparability with the contralateral side. Ten healthy subjects without history of injury or surgery to the ankle joint were enrolled in this cross-sectional study. Four CT scans were performed. During the scans, the lower legs and feet were placed in an external torque device with predefined external rotation torques of 0, 2.5, 5, and 7.5 Nm. Five different radiographic measures of syndesmotic stability were measured: anterior distance (AD), tibiofibular clear space (TCS), posterior distance (PD), external rotation (ER), and β angle. With increasing external torque, slight increases in AD, ER, and β angle were observed, whereas TCS and PD decreased slightly. Large absolute differences were found between the healthy subjects for all measured parameters, regardless of the external torque applied. Differences from the contralateral side using the same external torque were minimal for all parameters, but smallest for AD with a maximum difference of 0.5 mm. Using the healthy contralateral ankle joint is appropriate for assessing syndesmotic stability based on minimal intraindividual side differences using the external torque device. Side differences >0.5 mm in AD and >0.9 mm in PD may be considered abnormal and may indicate significant instability of the syndesmosis. However, future studies are needed to define definitive cutoff values for relevant side differences in acute and chronic syndesmotic instability to guide clinicians in their treatment decisions.

Human-Exoskeleton Coupling Simulation for Lifting Tasks with Shoulder, Spine, and Knee-Joint Powered Exoskeletons.

In this study, we introduce a two-dimensional (2D) human skeletal model coupled with knee, spine, and shoulder exoskeletons. The primary purpose of this model is to predict the optimal lifting motion and provide torque support from the exoskeleton through the utilization of inverse dynamics optimization. The kinematics and dynamics of the human model are expressed using the Denavit-Hartenberg (DH) representation. The lifting optimization formulation integrates the electromechanical dynamics of the DC motors in the exoskeletons of the knee, spine, and shoulder. The design variables for this study include human joint angle profiles and exoskeleton motor current profiles. The optimization objective is to minimize the squared normalized human joint torques, subject to physical and task-specific lifting constraints. We solve this optimization problem using the gradient-based optimizer SNOPT. Our results include a comparison of predicted human joint angle profiles, joint torque profiles, and ground reaction force (GRF) profiles between lifting tasks with and without exoskeleton assistance. We also explore various combinations of exoskeletons for the knee, spine, and shoulder. By resolving the lifting optimization problems, we designed the optimal torques for the exoskeletons located at the knee, spine, and shoulder. It was found that the support from the exoskeletons substantially lowers the torque levels in human joints. Additionally, we conducted experiments only on the knee exoskeleton. Experimental data indicated that using the knee exoskeleton decreases the muscle activation peaks by 35.00%, 10.03%, 22.12%, 30.14%, 16.77%, and 25.71% for muscles of the erector spinae, latissimus dorsi, vastus medialis, vastus lateralis, rectus femoris, and biceps femoris, respectively.

Investigating the impact of magnetic air gap variations on short circuit characteristics of partially high temperature superconducting generator

Partially high-temperature superconducting generators (PHTSGs) feature large magnetic air gaps imposed by using cryostats for HTS field windings. This increased air gap significantly affects end winding inductance and can lead to elevated fault torque levels. This study investigates the influence of magnetic air gap variation on generator design and end winding inductance and its implications for short-circuit faults in PHTSGs. Through a combination of numerical simulations and analytical analysis, the study explores how changes in the magnetic air gap affect end winding inductance and subsequently influence short-circuit fault behavior. The results reveal a direct correlation between magnetic air gap length, end winding inductance, and key short-circuit parameters such as stator current, field currents, and electromagnetic torque. Notably, an increase in the magnetic air gap is observed to elevate stator and field currents and electromagnetic torque during short-circuit events. These insights underscore the importance of considering magnetic air gap variation and its impact on end winding inductance and its relationship with short circuit characteristics in the design and operation of PHTSGs, providing valuable insights for enhancing the resilience and performance of high-temperature superconductor-based generator systems.

A Stereo-Microscopic Study: In-Built Torque Comparison using MBT Prescription Brackets of Different Companies

Torsion in an "archwire" that forms a pair when it interacts with a "bracket slot" produces torque. The archwire moves the tooth through the torsional tension created in the activated state, depending on the degree of torsion, the size and quality of the wire, and the deformability of the bracket. The dimensions of the bracket hole may unintentionally vary when brackets are made. Therefore, the purpose of this study was to evaluate the accuracy of built-in torque from various manufacturers.  Objective:- To measure and analyse the built-in torque of the maxillary right canine brackets, maxillary right lateral canines, and maxillary right central incisors from commercially available bracket systems (JJ Orthodontics, American Orthodontics, Koden Orthodontics, Desires - Ozone series). The brackets will be measured in 0.022 inches.  Material and Method:- The sample was made up of three brackets from each company (maxillary central incisor, lateral incisor, and canine), the torque of which was measured in a dimension of 0.022 inches. Using a stereomicroscope, images were captured, measurements were made following operator calibration with IMAGE PROPLUS, and a digital readout was generated.  Results:- In practically every bracket, the built-in torque mean values were lower. The built-in torque levels were most similar to the American Orthodontics standard values.

EXPERIMENTAL FAILURE OF HIP ARTHROPLASTY UNDER TORSION LOADING

Polymethylmethacrylate (PMMA) bone cement is strong in compression, however it tends to fail under torsion. Sufficient pressurisation and subsequent interdigitation between cement and bone are critical for the mechanical interlock of cemented orthopaedic implants, and an irregular surface on the acetabular cup is necessary for reasonable fixation at the cup-cement interface. There is limited literature investigating discrepancies in the failure mechanisms of cemented all-polyethylene acetabular cups with and without cement spacers, under torsional loading.In vitro experimental comparison of three groups of polyethylene acetabular prosthesis (PAP) cemented into prepared sawbone hemipelvises:* PAP without PMMA spacers maintaining an equal cement mantle circumferentially. (Group 1 n=3)* PAP without PMMA spacers cemented deliberately ‘bottoming-out’ the implant within the acetabulum. (Group 2 n=3)* PAP with PMMA spacers. (Group 3 n=3)The constructs were tested to torstional failure on a custom designed setup, and statistical analysis done by a one-way ANOVA and Tukey-Welsh test.Group 3 demonstrated superior torsional resistance with a statistically significant torque of 145Nm (SD±12Nm) at failure, compared to group 2 (109Nm, SD±7Nm) and group 1 (99Nm, SD±8Nm). Group 3 experienced failure predominantly at the bone-cement interface, in contrast, Groups 1 and 2 exhibited failure predominantly at the cup-cement interface. There was no significant difference between Group 1 and 2. Qualitative analysis of the failure mode indicates the efficient redistribution of stress throughout the cement mantle, consistent with the greater uniformity of cement.PMMA spacers increase the resistance to torsional failure at the implant-cement interface. Acetabular components without spacers (Groups 1 and 2) failed at the implant-cement interface before the cement-bone interface, at a statistically significantly lower level of torque to failure. Although the PMMA spacers may reduce cement interdigitation at the cement-bone interface the torsional forces required to fail are likely supraphysiological.

Torque Calculation and Dynamical Response in Halbach Array Coaxial Magnetic Gears through a Novel Analytical 2D Model

Coaxial magnetic gears have piqued the interest of researchers due to their numerous benefits over mechanical gears. These include reduced noise and vibration, enhanced efficiency, lower maintenance costs, and improved backdrivability. However, their adoption in industry has been limited by drawbacks like lower torque density and slippage at high torque levels. This work presents an analytical 2D model to compute the magnetic potential in Halbach array coaxial magnetic gears for every rotational angle, geometry configuration, and magnet specifications. This model calculates the induced torques and torque ripple in both rotors using the Maxwell Stress Tensor. The results were confirmed through Finite Element Analysis (FEA). Unlike FEA, this analytical model directly produces harmonics values, leading to faster computational times as it avoids torque calculations at each time step. In a case study, a standard coaxial magnetic gear was compared to one with a Halbach array, revealing a 14.3% improvement in torque density and a minor reduction in harmonics that cause torque ripple. Additionally, a case study was conducted to examine slippage in both standard and Halbach array gears during transient operations. The Halbach array coaxial magnetic gear demonstrated a 13.5% lower transmission error than its standard counterpart.

Clustering index analysis on EMG-Torque relation-based representation of complex neuromuscular changes after spinal cord injury

Spinal cord injury (SCI) resulting in complex neuromuscular pathology is not sufficiently well understood. To better quantify neuromuscular changes after SCI, this study uses a clustering index (CI) method for surface electromyography (sEMG) clustering representation to investigate the relation between sEMG and torque in SCI survivors. The sEMG signals were recorded from 13 subjects with SCI and 13 gender-age matched able-bodied subjects during isometric contraction of the biceps brachii muscle at different torque levels using a linear electrode array. Two torque representations, maximum voluntary contraction (MVC%) and absolute torque, were used. CI values were calculated for sEMG. Regression analyses were performed on CI values and torque levels of elbow flexion, revealing a strong linear relationship. The slopes of regressions between SCI survivors and control subjects were compared. The findings indicated that the range of distribution of CI values and slopes was greater in subjects with SCI than in control subjects (p < 0.05). The increase or decrease in slope was also observed at the individual level. This suggests that the CI and its sEMG clustering-torque relation may serve as valuable quantitative indicators for determining neuromuscular lesions after SCI, contributing to the development of effective rehabilitation strategies for improving motor performance.

Performance Analysis of Permanent Magnet BLDC Motor for Reducing Cogging Torque Using Taguchi Method

An electric motor is an electromagnetic machine commonly utilized across various industries and automotive products. One prevalent type of electric motor employed in electric vehicles is the Permanent Magnet Brushless DC Motor (PM-BLDC), a brushless motor employing permanent magnets. However, despite its efficiency, permanent magnet motors often experience vibrations that can disrupt their performance. This research aims to optimize the existing BLDC motor design, with a specific focus on reducing the existing cogging torque. Initially, the existing design exhibited a cogging torque level of 0.21482 Nm. The optimization process involved modifications to several key design parameters, such as air gap, magnet thickness, magnet type, and slot opening width. In previous research, only comparisons were made between stator slot designs, which proved to be less effective as significant differences were not evident in the results of the comparative analysis of BLDC motor designs. So, in this research, the Taguchi method was utilized for the optimization process due to several advantages it offers. Through an analysis of means and variance, the optimization process successfully achieved a significant reduction in cogging torque by 0.099744 and an increase in efficiency by 0.6%. The results of the optimized permanent magnet BLDC design indicated a cogging torque value of 0.115072 Nm and an efficiency of 86.64% at an operational motor speed of 1500 rpm. This research provides a substantial contribution to the development of more efficient electric motors suitable for various applications.

Skeletal Muscle Heat Shock Protein Content and the Repeated Bout Effect.

The "Repeated Bout Effect" (RBE) occurs when a skeletal muscle is preconditioned with a few lengthening contractions (LC) prior to exposing the muscle to a greater number of LC. The preconditioning (PC) results in significantly less damage and preservation of force. Since it takes only a few LC to increase muscle heat shock protein (HSP) content, it was of interest to examine the relationship between HSPs and the RBE. To do this, one tibialis anterior (TA) muscle from Sprague-Dawley rats (n = 5/group) was preconditioned with either 0, 5, or 15 lengthening contractions (LC) and exposed to a treatment of 60 LC 48 h later. Preconditioning TA muscles with 15 LC, but not 5 LC, significantly elevated muscle αB-crystallin (p < 0.05), HSP25 (p < 0.05), and HSP72 content (p < 0.001). These preconditioned TA muscles also showed a significantly (p < 0.05) reduced loss of active torque throughout the subsequent 60 LC. While there was a trend for all preconditioned muscles to maintain higher peak torque levels throughout the 60 LC, no significant differences were detected between the groups. Morphologically, preconditioned muscles appeared to show less discernible muscle fiber damage. In conclusion, an elevated skeletal muscle HSP content from preconditioning may contribute to the RBE.

Stochastic uncertain lubrication in gear transmission subjected to tribodynamic loading

A stochastic uncertain tribodynamic model is established for a spur gear pair for the first time. The stochastic uncertainty of pinion rotation speed propagated to lubrication performance is investigated. The probability density function of the minimum lubricant film thickness hmin evolves over time periodically at interval of an engagement process. Correspondence between abrupt increase in meshing force and amplification of hmin uncertainty is found. Robust and reliable lubrication performance can be achieved by suppressing the hmin uncertainty and decreasing the lubrication failure probability. This can be done by increasing lubricant viscosity, and decreasing input torque and uncertainty level of input rotation speed. This work lays a solid foundation for robust and reliability based optimization for tribodynamic gear system.

Development of Quasi-Passive Back-Support Exoskeleton with Compact Variable Gravity Compensation Module and Bio-Inspired Hip Joint Mechanism.

The back support exoskeletons have garnered significant attention to alleviate musculoskeletal injuries, prevalent in industrial settings. In this paper, we propose AeBS, a quasi-passive back-support exoskeleton developed to provide variable assistive torque across the entire range of hip joint motion, for tasks with frequent load changes. AeBS can adjust the assistive torque levels while minimizing energy for the torque variation without constraining the range of motion of the hip joint. To match the requisite assistance levels for back support, a compact variable gravity compensation module with reinforced elastic elements is applied to AeBS. Additionally, we devised a bio-inspired hip joint mechanism that mimics the configuration of the human hip axis to ensure the free body motion of the wearer, significantly affecting assistive torque transmission and wearing comfort. Benchtop testing showed that AeBS has a variable assistive torque range of 5.81 Nm (ranging from 1.23 to 7.04 Nm) across a targeted hip flexion range of 135°. Furthermore, a questionnaire survey revealed that the bio-inspired hip joint mechanism effectively facilitates the transmission of the intended assistive torque while enhancing wearer comfort.

Biopolymer composites based on ultrasound/plasma‐modified fiber waste and polybutylene adipate terephthalate (PBAT): Physicochemical and functional performance

AbstractA strategy for a circular economy is to reuse and modify agricultural wastes through green methodologies, which can be employed as high‐value raw materials to produce sustainable materials. Thus, polybutylene adipate terephthalate (PBAT) composites containing plasma (P) and ultrasound/plasma (UP) modified Agave fibers (AF) were prepared by the melt mixing process. The effect of content (10% and 20%) and type of fiber on the processing, structural, mechanical, and water barrier performance of PBAT composites was assessed. FTIR analysis exhibited the presence of O‐Si‐O groups in all composites containing modified AF, indicating the presence of nanometric hexamethyldisiloxane (HMDSO) coating on the fiber surface. The addition of modified AF into PBAT polymer promoted higher torque levels and specific energy during the composites processing, indicating higher matrix‐fiber interactions that hindered the free flow of the polymeric chains. Nevertheless, SEM, DSC, and crystallinity results revealed that PBAT‐AFUP composites exhibited more homogeneous surfaces and ordered structures that promoted higher entanglement between modified fibers and the PBAT matrix and restricted the binding sites for water interaction as changes in tensile modulus (from 90 to 163 MPa) and water contact angle (from 63 to 77°) indicated. These findings show that modified Agave fibers are a sustainable raw material that can be easily processed to produce soft and hydrophobic PBAT‐based composites.Highlights The fiber type determined the functional performance of the PBAT composites The modified fibers increased the entanglement of composite chains UP‐modified fibers improved the water barrier performance of the PBAT matrix