| 1. |
- Aziz, Shazed, et al.
(författare)
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Artificial Muscles from Hybrid Carbon Nanotube-Polypyrrole-Coated Twisted and Coiled Yarns
- 2020
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Ingår i: Macromolecular materials and engineering. - : WILEY-V C H VERLAG GMBH. - 1438-7492 .- 1439-2054. ; 305:11
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Tidskriftsartikel (refereegranskat)abstract
- Electrochemically or electrothermally driven twisted/coiled carbon nanotube (CNT) yarn actuators are interesting artificial muscles for wearables as they can sustain high stress. However, due to high fabrication costs, these yarns have limited their application in smart textiles. An alternative approach is to use off-the-shelf yarns and coat them with conductive polymers that deliver high actuation properties. Here, novel hybrid textile yarns are demonstrated that combine CNT and an electroactive polypyrrole coating to provide both high strength and good actuation properties. CNT-coated polyester yarns are twisted and coiled and subjected to electrochemical coating of polypyrrole to obtain the hierarchical soft actuators. When twisted without coiling, the polypyrrole-coated yarns produce fully reversible 25 degrees mm(-1)rotation, 8.3x higher than the non-reversible rotation from twisted CNT-coated yarns in a three-electrode electrochemical system operated between +0.4 and -1.0 V (vs Ag/AgCl). The coiled yarns generate fully reversible 10 degrees mm(-1)rotation and 0.22% contraction strain, 2.75x higher than coiled CNT-coated yarns, when operated within the same potential window. The twisted and coiled yarns exhibit high tensile strength with excellent abrasion resistance in wet and dry shearing conditions that can match the requirements for using them as soft actuators in wearables and textile exoskeletons.
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| 2. |
- Aziz, Shazed, et al.
(författare)
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Characterisation of torsional actuation in highly twisted yarns and fibres
- 2015
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Ingår i: Polymer testing. - : Elsevier. - 0142-9418 .- 1873-2348. ; 46, s. 88-97
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Tidskriftsartikel (refereegranskat)abstract
- Highly twisted oriented polymer fibres and carbon nanotube yarns show large scale torsional actuation from volume expansion that can be induced, for example, thermally or by electrochemical charging. When formed into spring-like coils, the torsional actuation within the fibre or yarn generates powerful tensile actuation per muscle weight. For further development of these coil actuators and for the practical application of torsional actuators, it is important to standardise methods for characterising both the torsional stroke (rotation) and torque generated. By analogy with tensile actuators, we here introduce a method to measure both the free stroke and blocked torque in a one-end-tethered fibre. In addition, the torsional actuation can be measured when operating against an externally applied torque (isotonic) and actuation against a return spring fibre (variable torque). A theoretical treatment of torsional actuation was formulated using torsion mechanics and evaluated using a commercially available highly-oriented polyamide fibre. Good agreement between experimental measurements and calculated values was obtained. The analysis allows the prediction of torsional stroke under any external loading condition based on the fundamental characteristics of the actuator: free stroke and stiffness.
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| 3. |
- Aziz, Shazed, et al.
(författare)
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Controlled and scalable torsional actuation of twisted nylon 6 fiber
- 2016
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Ingår i: Journal of Polymer Science Part B. - : John Wiley & Sons. - 0887-6266 .- 1099-0488. ; 54:13, s. 1278-1286
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Tidskriftsartikel (refereegranskat)abstract
- Large‐scale torsional actuation occurs in twisted fibers and yarns as a result of volume change induced electrochemically, thermally, photonically, and other means. A quantitative relationship between torsional actuation (stroke and torque) and volume change is here introduced. The analysis is based on experimental investigation of the effects of fiber diameter and inserted twist on the torsional stroke and torque measured when heating and cooling nylon 6 fibers over the temperature range of 26–62 °C. The results show that the torsional stroke depends only on the amount of twist inserted into the fiber and is independent of fiber diameter. The torque generated is larger in fibers with more inserted twist and with larger diameters. These results are successfully modeled using a single‐helix approximation of the twisted fiber structure
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| 4. |
- Aziz, Shazed, et al.
(författare)
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Effect of anisotropic thermal expansion on the torsional actuation of twist oriented polymer fibres
- 2017
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Ingår i: Polymer. - : Elsevier. - 0032-3861 .- 1873-2291. ; 129, s. 127-134
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Tidskriftsartikel (refereegranskat)abstract
- Torsional actuation of twisted polymer fibres is the basis for high performance tensile actuation when these fibres are formed into coils. The thermally-induced torsional actuation of twisted polyamide-6 fibres can be predicted by a single helix approximation when the measured diameter and length direction thermal expansion coefficients are known. The single helix model illustrates the sensitivity of the magnitude of torsional actuation to the volume expansion anisotropy for a given volume change. The applicability of the model has been further assessed by investigating three polymer fibres that display different thermal expansion anisotropies. Commercially available polyethylene, polypropylene and polyamide-6 fibres were twisted to the maximum extent without coiling and then heat treated to fix the twisted structure. Heating the twisted fibres between 26 and 62 °C resulted in a partial untwist which was reversed during cooling. The single-helix model of the twisted fibres was used to accurately predict the torsional stroke based on the measured fibre length and diameter change during heating. Comparative torsional stroke of twisted polyamide-6, polyethylene and polypropylene was explained in terms of materials thermo-physical properties. Generated blocked torques was also correctly predicted by the single-helix model when combined with the measured fibre torsional stiffness. Variances between torsional stiffnesses were found to be dependent of different anisotropic thermal properties of tested fibres.
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| 5. |
- Aziz, Shazed, et al.
(författare)
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Effect of fibre coating and geometry on the tensile properties of hybrid carbon nanotube coated carbon fibre reinforced composite
- 2014
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Ingår i: Materials & Design. - : Elsevier. - 0261-3069. ; 54, s. 660-669
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Tidskriftsartikel (refereegranskat)abstract
- Hierarchically structured hybrid composites are ideal engineered materials to carry loads and stresses due to their high in-plane specific mechanical properties. Growing carbon nanotubes (CNTs) on the surface of high performance carbon fibres (CFs) provides a means to tailor the mechanical properties of the fibre–resin interface of a composite. The growth of CNT on CF was conducted via floating catalyst chemical vapor deposition (CVD). The mechanical properties of the resultant fibres, carbon nanotube (CNT) density and alignment morphology were shown to depend on the CNT growth temperature, growth time, carrier gas flow rate, catalyst amount, and atmospheric conditions within the CVD chamber. Carbon nanotube coated carbon fibre reinforced polypropylene (CNT-CF/PP) composites were fabricated and characterized. A combination of Halpin–Tsai equations, Voigt–Reuss model, rule of mixture and Krenchel approach were used in hierarchy to predict the mechanical properties of randomly oriented short fibre reinforced composite. A fractographic analysis was carried out in which the fibre orientation distribution has been analyzed on the composite fracture surfaces with Scanning Electron Microscope (SEM) and image processing software. Finally, the discrepancies between the predicted and experimental values are explained.
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| 6. |
- Aziz, Shazed, et al.
(författare)
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Experimental evaluation of the interfacial properties of carbon nanotube coated carbon fiber reinforced hybrid composites
- 2015
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Ingår i: Polymer Composites. - : John Wiley & Sons. - 0272-8397 .- 1548-0569. ; 36:10, s. 1941-1950
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Tidskriftsartikel (refereegranskat)abstract
- A floating catalyst chemical vapor deposition (CVD) unit was utilized to grow CNT onto the surface of carbon fiber (CF). The surface morphology of the resultant fibers, CNT population density and alignment pattern were found to be depended on the CNT growth temperature, growth time, and atmospheric conditions within the CVD chamber. In contrast to the neat‐CF reinforced composites, improved interfacial shear strength (IFSS) between CF and matrix were obtained when the surface of CF was coated by CNT. Particularly, CF treatment condition for CNT‐coating with 700°C reaction temperature and 30 min reaction time has shown a considerable increase in IFSS approximately of 45% over that of the untreated fiber from which it was processed. The proper justification of fiber–matrix adhesion featured by composite interfacial properties was explained through IFSS.
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| 7. |
- Aziz, Shazed, et al.
(författare)
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Fast and High-Strain Electrochemically Driven Yarn Actuators in Twisted and Coiled Configurations
- 2021
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Ingår i: Advanced Functional Materials. - : John Wiley & Sons. - 1616-301X .- 1616-3028. ; 31:10
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Tidskriftsartikel (refereegranskat)abstract
- Commercially available yarns are promising precursor for artificial muscles for smart fabric-based textile wearables. Electrochemically driven conductive polymer (CP) coated yarns have already shown their potential to be used in smart fabrics. Unfortunately, the practical application of these yarns is still hindered due to their slow ion exchange properties and low strain. Here, a method is demonstrated to morph poly-3,4-ethylenedioxythiophene:poly-styrenesulfonate (PEDOT:PSS) coated multifilament textile yarns in highly twisted and coiled structures, providing >1% linear actuation in <1 s at a potential of +0.6 V. A potential window of +0.6 V and -1.2 V triggers the fully reversible actuation of a coiled yarn providing >1.62% strain. Compared to the untwisted, regular yarns, the twisted and coiled yarns produce >9x and >20x higher strain, respectively. The strain and speed are significantly higher than the maximum reported results from other electrochemically operated CP yarns. The yarn’s actuation is explained by reversible oxidation/reduction reactions occurring at CPs. However, the helical opening/closing of the twisted or coiled yarns due to the torsional yarn untwisting/retwisting assists the rapid and large linear actuation. These PEDOT:PSS coated yarn actuators are of great interest to drive smart textile exoskeletons.
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| 8. |
- Aziz, Shazed, 1985-, et al.
(författare)
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PEDOT:PSS coated twisted and coiled yarn actuators
- 2021
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Ingår i: EuroEAP 2021.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Commercial yarns can be functionalized with conducting polymers (CPs) todevelop yarn and textile actuators. Here we show a method of functionalizationof commercial polyamide yarns by poly-3,4-ethylenedioxythiophene:polystyrenesulfonate (PEDOT:PSS) coating. Aftercoating, while PEDOT:PSS is drying, it is possible to twist and coil the yarns,resulting in a major improvement of their linear strain and speed of movement.By using a potential window between +0.6 V and -1.2 V vs Ag/AgCl it waspossible to obtain a fully reversible actuation of a coiled yarn providing up to1.62% strain. A strain higher than 1% was achieved in less than 1 second.Compared to the untwisted, regular yarns, the twisted and coiled yarns produce>9× and >20× higher strain, respectively. These results are a step forward towardsthe development of soft, silent and compliant smart textile exoskeletons.
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| 9. |
- Aziz, Shazed, et al.
(författare)
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Plant-Like Tropisms in Artificial Muscles
- 2023
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Ingår i: Advanced Materials. - : WILEY-V C H VERLAG GMBH. - 0935-9648 .- 1521-4095.
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Tidskriftsartikel (refereegranskat)abstract
- Helical plants have the ability of tropisms to respond to natural stimuli, and biomimicry of such helical shapes into artificial muscles has been vastly popular. However, the shape-mimicked actuators only respond to artificially provided stimulus, they are not adaptive to variable natural conditions, thus being unsuitable for real-life applications where on-demand, autonomous operations are required. Novel artificial muscles made of hierarchically patterned helically wound yarns that are self-adaptive to environmental humidity and temperature changes are demonstrated here. Unlike shape-mimicked artificial muscles, a unique microstructural biomimicking approach is adopted, where the muscle yarns can effectively replicate the hydrotropism and thermotropism of helical plants to their microfibril level using plant-like microstructural memories. Large strokes, with rapid movement, are obtained when the individual microfilament of yarn is inlaid with hydrogel and further twisted into a coil-shaped hierarchical structure. The developed artificial muscle provides an average actuation speed of approximate to 5.2% s(-1) at expansion and approximate to 3.1% s(-1) at contraction cycles, being the fastest amongst previously demonstrated actuators of similar type. It is demonstrated that these muscle yarns can autonomously close a window in wet climates. The building block yarns are washable without any material degradation, making them suitable for smart, reusable textile and soft robotic devices.
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| 10. |
- Aziz, Shazed, et al.
(författare)
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Theoretical Prediction of CNT-CF/PP Composite Tensile Properties Using Various Numerical Modeling Methods
- 2013
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Ingår i: Fullerenes, nanotubes, and carbon nanostructures. - : Taylor & Francis. - 1536-383X .- 1536-4046. ; 21:5, s. 411-416
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Tidskriftsartikel (refereegranskat)abstract
- Development of effective models to predict tensile properties of ‘carbon nanotube coated carbon fibre reinforced polypropylene (CNT-CF/PP)’ composites is briefly discussed. The composite taken as the reference is based on the highest growth mechanism of CNTs over carbon fibres. Halpin-Tsai and Combined Voigt-Reuss model has been implemented. Young's modulus for CNT-CF/PP composites has been found 4.5368 GPa and the tensile strength has been estimated 45.367 MPa considering the optimum operating condition of chemical vapor deposition (CVD) technique. Stiffness of the composite is represented through the stress-strain plots; stiffness is proportional to the steepness of the slope. There are slight deviations of results that have been found theoretically over the experimental issues.
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| 11. |
- Aziz, Shazed, et al.
(författare)
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Thermomechanical effects in the torsional actuation of twisted nylon 6 fiber
- 2017
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Ingår i: Journal of Applied Polymer Science. - : John Wiley & Sons. - 0021-8995 .- 1097-4628. ; 134:47
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Tidskriftsartikel (refereegranskat)abstract
- Thermally induced torsional and tensile actuators based on twisted polymeric fibers have opened new opportunities for the application of artificial muscles. These newly developed actuators show significant torsional deformations when subjected to temperature changes, and this torsional actuation is the defining mechanism for tensile actuation of twisted and coiled fibers. To date it has been found that these actuators require multiple heat/cool cycles (referred to as “training” cycles) prior to obtaining a fully reversible actuation response. Herein, the effect of annealing conditions applied to twisted nylon 6 monofilament is investigated and it is shown that annealing at 200 °C eliminates the need for the training cycles. Furthermore, the effect of an applied external torque on the torsional actuation is also investigated and torsional creep is shown to be affected by the temperature and load
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| 12. |
- Bidita, B. S., et al.
(författare)
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Preparation, characterization and engine performance of water in diesel nanoemulsions
- 2016
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Ingår i: Journal of the Energy Institute. - : Elsevier. - 1743-9671 .- 1746-0220. ; 89:3, s. 354-365
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Tidskriftsartikel (refereegranskat)abstract
- Water in diesel (W/D) nanoemulsions were prepared by the aid of high energy emulsification method. The formulation was accomplished in the presence of Triton X-100 surfactant. A wide range of surfactant concentration (0.25%–0.40% v/v) with varying amount of water percentage (0.50%–0.90% v/v) was used in the preparation of W/D nanoemulsion fuels. The droplet size of the nanoemulsions at different water:surfactant:diesel ratio increased as surfactant concentration decreased. High kinetic stability was observed in the nanoemulsions. The stability of nanoemulsions with 0.40% surfactant concentration was persisted more than two weeks without phase separation. The droplet size of the nanoemulsions increased with time proving the influence of breakdown processes such as Ostwald ripening. Combustion characteristics of W/D nanoemulsions were studied in terms of different formulating compositions. An engine test bed of diesel engine was used to combust the nanoemulsions to study the exhaust emission concentrations such as CO, CO2, NH3 and NO, and performance parameters include brake power, thermal efficiency. The highest reduction in the exhaust gas emissions concentrations was notified by using surfactant concentration of 0.40% with 0.90% water content. The lowest calorific value of prepared W/D nanoemulsions was achieved 38.48 MJ/kg by using surfactant concentration of 0.40% with 0.90% water. The highest brake power and thermal efficiency was also obtained with 0.40% surfactant concentration and 0.90% water content. In addition, the characteristic evaluation of W/D nanoemulsions was made on the basis of emission characteristics of neat diesel. It has been observed that the use of W/D nanoemulsions in diesel engine has evidently led to the reduction in exhaust emissions, anticipating its application as an alternative eco-friendly fuel in the internal combustion engine.
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| 13. |
- Foroughi, Javad, et al.
(författare)
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Knitted Carbon-Nanotube-Sheath/Spandex-Core Elastomeric Yarns for Artificial Muscles and Strain Sensing
- 2016
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Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-0851 .- 1936-086X.
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Tidskriftsartikel (refereegranskat)abstract
- Highly stretchable, actuatable, electrically conductive knitted textiles based on Spandex (SPX)/CNT (carbon nanotube) composite yarns were prepared by an integrated knitting procedure. SPX filaments were continuously wrapped with CNT aerogel sheets and supplied directly to an interlocking circular knitting machine to form the three-dimensional electrically conductive and stretchable textiles. By adjusting the SPX/CNT feed ratio, the fabric electrical conductivities could be tailored in the range of 870 to 7092 S/m. The electrical conductivity depended on tensile strain, with a linear and largely hysteresis-free resistance change occurring on loading and unloading between 0 and 80% strain. Electrothermal heating of the stretched fabric caused large tensile contractions of up to 33%, and generated a gravimetric mechanical work capacity during contraction of up to 0.64 kJ/kg and a maximum specific power output of 1.28 kW/kg, which far exceeds that of mammalian skeletal muscle. The knitted textile provides the combination of strain sensing and the ability to control dimensions required for smart clothing that simultaneously monitors the wearer's movements and adjusts the garment fit or exerts forces or pressures on the wearer, according to needs. The developed processing method is scalable for the fabrication of industrial quantities of strain sensing and actuating smart textiles.
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| 14. |
- Kim, Shi Hyeong, et al.
(författare)
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Harvesting temperature fluctuations as electrical energy using torsional and tensile polymer muscles
- 2015
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Ingår i: Energy & Environmental Science. - : Royal Society of Chemistry. - 1754-5692 .- 1754-5706. ; 8, s. 3336-3344
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Tidskriftsartikel (refereegranskat)abstract
- Diverse means have been deployed for harvesting electrical energy from mechanical actuation produced by low-grade waste heat, but cycle rate, energy-per-cycle, device size and weight, or cost have limited applications. We report the electromagnetic harvesting of thermal energy as electrical energy using thermally powered torsional and tensile artificial muscles made from inexpensive polymer fibers used for fishing line and sewing thread. We show that a coiled 27 μm-diameter nylon muscle fiber can be driven by 16.7 °C air temperature fluctuations to spin a magnetic rotor to a peak torsional rotation speed of 70 000 rpm for over 300 000 heating–cooling cycles without performance degradation. By employing resonant fluctuations in air temperature of 19.6 °C, an average output electrical power of 124 W per kg of muscle was realized. Using tensile actuation of polyethylene-based coiled muscles and alternating flows of hot and cold water, up to 1.4 J of electrical energy was produced per cycle. The corresponding per cycle electric energy and peak power output, per muscle weight, were 77 J kg−1 and 28 W kg−1, respectively.
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| 15. |
- Martinez, Jose Gabriel, Dr. 1986-, et al.
(författare)
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Woven and knitted artificial muscles for wearable devices
- 2019
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Diseases of the nervous system, traumas, or natural causes can reduce human muscle capacity. Robotic exoskeletons are forthcoming to support the movement of body parts, e.g. assist walking or aid rehabilitation. Current available devices are rigid and driven by electric motors or pneumatic actuators, making them noisy, heavy, stiff and noncompliant. We are developing textile based assistive devices that can be worn like clothing being light, soft, compliant and comfortable. We have merged advanced textile technology with electroactive polymers. By knitting and weaving electroactive yarns, we are developing soft textile actuators ("Knitted Muscles") that can be used in wearable assistive devices. We will present the latest progress increase the performance and to rationalise the fabrication. In addition we will show some demonstrators of the textile exoskeletons.
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| 16. |
- Md. Aziz, Shazed, et al.
(författare)
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Application of CNT Enhanced Carbon Fibers in Hybrid Composites with Improved Interfacial Properties
- 2014
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Ingår i: Nanoscience, Nanotechnology and Nanoengineering. - : Trans Tech Publications. - 9783037859131 ; , s. 237-242
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Konferensbidrag (refereegranskat)abstract
- Growing carbon nanotubes (CNT) on the surface of high performance carbon fibers (CF) offers a means to tailor the mechanical properties of the fiber-matrix interface of a composite. In the context of this work, a floating catalyst chemical vapor deposition (CVD) unit was utilized to grow CNT onto the surface of CF. The surface and mechanical properties of the resultant fibers, CNT density and alignment morphology were explained to depend on the CNT growth temperature, growth time, and atmospheric conditions within the CVD chamber. Single fiber/Epoxy composite coupons were fabricated by using both neat and CNT-coated CF to conduct single fiber fragmentation test (SFFT). It was observed that the coating of CNT onto CF surface improves the IFSS between CF and matrix when compared with neat-CF. Particularly, CF treatment condition for CNT-coating with 700 °C reaction temperature and 30 minutes reaction time has shown a considerable increase in IFSS approximately of 45% over that of the untreated fiber from which it was processed. The fiber-matrix adhesion was analyzed by using SEM on cryogenically fractured surface of both types of composites. The proper justification of fiber-matrix adhesion featured by composite interfacial properties was explained through IFSS.
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| 17. |
- Mirabedini, Azadeh, et al.
(författare)
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Wet-Spun Biofiber for Torsional Artificial Muscles.
- 2017
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Ingår i: Soft Robotics. - : Mary Ann Liebert. - 2169-5172 .- 2169-5180. ; 4:4, s. 421-430
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Tidskriftsartikel (refereegranskat)abstract
- The demands for new types of artificial muscles continue to grow and novel approaches are being enabled by the advent of new materials and novel fabrication strategies. Self-powered actuators have attracted significant attention due to their ability to be driven by elements in the ambient environment such as moisture. In this study, we demonstrate the use of twisted and coiled wet-spun hygroscopic chitosan fibers to achieve a novel torsional artificial muscle. The coiled fibers exhibited significant torsional actuation where the free end of the coiled fiber rotated up to 1155 degrees per mm of coil length when hydrated. This value is 96%, 362%, and 2210% higher than twisted graphene fiber, carbon nanotube torsional actuators, and coiled nylon muscles, respectively. A model based on a single helix was used to evaluate the torsional actuation behavior of these coiled chitosan fibers.
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| 18. |
- Rahmanian, S., et al.
(författare)
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Carbon and glass hierarchical fibers : Influence of carbon nanotubes on tensile, flexural and impact properties of short fiber reinforced composites
- 2013
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Ingår i: Materials & Design. - : Elsevier. - 0261-3069. ; 43, s. 10-16
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Tidskriftsartikel (refereegranskat)abstract
- Dense carbon nanotubes (CNTs) were grown uniformly on the surface of carbon fibers and glass fibers to create hierarchical fibers by use of floating catalyst chemical vapor deposition. Morphologies of the CNTs were investigated using scanning electronic microscope (SEM) and transmission electron microscope (TEM). Larger diameter dimension and distinct growing mechanism of nanotubes on glass fiber were revealed. Short carbon and glass fiber reinforced polypropylene composites were fabricated using the hierarchical fibers and compared with composites made using neat fibers. Tensile, flexural and impact properties of the composites were measured, which showed evident enhancement in all mechanical properties compared to neat short fiber composites. SEM micrographs of composite fracture surface demonstrated improved adhesion between CNT-coated fiber and the matrix. The enhanced mechanical properties of short fiber composites was attributed to the synergistic effects of CNTs in improving fiber–matrix interfacial properties as well as the CNTs acting as supplemental reinforcement in short fiber-composites.
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| 19. |
- Rahmanian, S., et al.
(författare)
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Mechanical characterization of epoxy composite with multiscale reinforcements : Carbon nanotubes and short carbon fibers
- 2014
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Ingår i: Materials & Design. - : Elsevier. - 0261-3069. ; 60, s. 34-40
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Tidskriftsartikel (refereegranskat)abstract
- Carbon nanotubes (CNT) and short carbon fibers were incorporated into an epoxy matrix to fabricate a high performance multiscale composite. To improve the stress transfer between epoxy and carbon fibers, CNT were also grown on fibers through chemical vapor deposition (CVD) method to produce CNT grown short carbon fibers (CSCF). Mechanical characterization of composites was performed to investigate the synergy effects of CNT and CSCF in the epoxy matrix. The multiscale composites revealed significant improvement in elastic and storage modulus, strength as well as impact resistance in comparison to CNT–epoxy or CSCF–epoxy composites. An optimum content of CNT was found which provided the maximum stiffness and strength. The synergic reinforcing effects of combined fillers were analyzed on the fracture surface of composites through optical and scanning electron microscopy (SEM).
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| 20. |
- Spinks, Geoffrey M., et al.
(författare)
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Using force-displacement relations to obtain actuation parameters from artificial muscles
- 2019
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Ingår i: Sensors and Actuators A-Physical. - : ELSEVIER SCIENCE SA. - 0924-4247 .- 1873-3069. ; 290, s. 90-96
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Tidskriftsartikel (refereegranskat)abstract
- Many different test methods are currently used to characterise the output of artificial muscle materials but few studies report the full range of possible force and displacements that can be generated by a given material when activated with a given input stimulus but when operated against different external loads. The measurement of the loading and unloading force extension curves in tension in both the un-activated and activated states is investigated as a means for efficiently characterising the full range of outputs for three different types of artificial muscles: pneumatically operated braided muscle and thermally operated shape memory alloy spring and twisted / coiled polymer fiber. A graphical method of analysis was applied whereby the force-extension curves obtained before and after actuator activation were plotted on the same axes. By overlaying the external loading conditions, the graphical method provided the equilibrium starting and finishing forces and displacements and successfully predicted the isotonic strokes, isometric forces and combined force and displacement generated when the actuator was operated against an external spring. Complications in the interpretation of the force-stroke curves were encountered as all three artificial muscles displayed a degree of loading-unloading hysteresis and non-ideal mechanical behavior. (C) 2019 Elsevier B.V. All rights reserved.
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