Shazed Aziz

Knitted Carbon-Nanotube-Sheath/Spandex-Core Elastomeric Yarns for Artificial Muscles and Strain Sensing

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 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 wearers 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.

Harvesting temperature fluctuations as electrical energy using torsional and tensile polymer muscles

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.

Theoretical Prediction of CNT-CF/PP Composite Tensile Properties Using Various Numerical Modeling Methods

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. Youngs 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.

Application of CNT Enhanced Carbon Fibers in Hybrid Composites with Improved Interfacial Properties

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.