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The composite overwrapped pressure vessel (COPV) with its excellent properties is used for high-pressure storage in aerospace industries. Before they can be reliably incorporated into space flight applications, a significant amount of work has been conducted for better predicting the condition status and residual life of COPVs. A novel MXene film sensor technology that can provide real-time and in situ structural health monitoring of composite structures was proposed in this work. An excellent MXene film sensor can be obtained based on the method proposed in this paper. Before sensor is applied to pressure vessels, coupon tests include tensile loading testing and fatigue loading testing is carried out. For coupon tests, the piezoresistive response of MXene sensor is understood. MXene sensors made on a flexible printed circuit (FPC) have been integrated into a composite pressure vessel, and are used to monitor changes in the hoop and axial strain fields during hydraulic pressure tests. The piezoresistive response of MXene sensor is obtained and the main working mechanism of MXene is explained. The distributed strain measurement of the vessel provides a more efficient process of monitoring structural integrity to further understand the failure mechanisms of the vessel.

Changes in the surface wettability of poly(p-phenylene benzobisoxazole) (PBO) fibers were investigated by thermogravimetric analysis (TGA) following an air dielectric barrier discharge (DBD) plasma treatment. The results were then supplemented and confirmed by scanning electron microscopy (SEM), dynamic contact angle analysis (DCAA), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) measurements. After exposure to the DBD plasma at a pre-determined power level, TGA analysis showed that the residual rates retained by the PBO composites decreased, which meant an increase in the amount of resin coating the PBO fibers in the composites. Observations by SEM confirmed that there was more resin adhering to the treated PBO fibers and the wetting behavior of resin on the fibers was greatly improved. Meanwhile, DCAA for the treated fibers showed a significant enhancement in fiber surface free energy. XPS and AFM were performed in order to reveal any variations in fiber surface activity and surface morphology resulting from the surface treatment. The resulting data showed that increases in oxygen-containing polar groups and surface roughness on the plasma-treated PBO fibers contributed to the above improved wetting behavior. With comprehensive analyses, it was concluded that TGA could be used as a supporting method assessing the surface wettability of PBO fibers before and after air DBD plasma treatment.

A nanocomposite with soluble high-performance poly(phthalazinone ether sulfone ketone) (PPESK) as matrix and multi-walled carbon nanotube buckypaper (MWCNT-BP) as reinforcement was fabricated by hot-press processing. The morphologies, dynamic and static mechanical behavior, thermal stability of the MWCNT-BP/PPESK composites were studied using scanning electron microscope (SEM), dynamic mechanical analyzer (DMA) and thermogravimetric analyzer (TGA). SEM microphotographs revealed a high impregnation degree of the MWCNT-BP/PPESK composites. Dynamic and static mechanical analysis revealed that the nanocomposites possessed high storage modulus, and good retention rate of mechanical strength even at 250 °C, which is mainly attributed to satisfied impregnation and strong interactions between MWCNT-BP and PPESK. Thermogravimetric analysis exhibited that the nanocomposites had excellent thermal stability. These investigations confirm that MWCNT-BP can be effectively used to manufacture high-loading CNT/PPESK composites with improved properties.

The use of novel aromatic diamine containing phthalide structure (BAPP) as curing agent of diglycidylether of bisphenol A (DGEBA) epoxy resin has been studied. BAPP can react with epoxy monomers by an epoxy-amine condensation mechanism, which renders phthalide cardo incorporate into the network structure of the thermoset. The curing behavior and kinetics have been investigated by differential scanning calorimetry (DSC) and the kinetic analysis of non-isothermal cure shows that autocatalytic model is suitable to describe the cure mechanism. The thermal–mechanical properties have been determined with dynamic mechanical analysis (DMA) and the activation energies for relaxation were calculated according to the Arrhenius law. Thermogravimetric analysis exhibits a lower initial decomposition temperature, decreased rate of decomposition and higher char yield compared with DGEBA cured with commercially available 4,4′-diaminodiphenylsulfone (DDS).

Electromagnetic interference ( EMI) originated from radio stations to various electronic appliances and devices is an increasingly serious problem, and there are significant interests in the development of light-weight, high-efficiency materials for EMI shielding. Herein we report novel carbon nanotube (CNT)composite films synthesized by a simple spray and vacuum-filtration method. The film containing 30 wt%single-walled CNTs demonstrates high electrical conductivity up to 20,000 S/m and excellent EMI shielding effectiveness 65 dB, with ~130 μm in thicknesses and 0.011 g/cm² in areal density. The composite films are stiffer, stronger and more ductile than neat MWCNT film, i.e. 17.4 versus 3.3 MPa in tensile strength. Our films are sufficiently smooth, tough and flexible, which allow themselves to attach onto any complex curved surface. SWCNTs play an essential role in achieving such exceptional functional and mechanical performance; both SWCNTS and MWCNTS need to be well disentangled prior to the filtration. The composite films would have a wide range of engineering applications, i.e. production of conventional composite laminates due to their porous structure Refereed/Peer-reviewed

This study develops a facile approach to fabricate adhesives consists of epoxy and cost-effective graphene platelets (GnPs). Morphology, mechanical properties, electrical and thermal conductivity, and adhesive toughness of epoxy/GnP nanocomposite were investigated. Significant improvements in mechanical properties of epoxy/GnP nanocomposites were achieved at low GnP loading of merely 0.5 vol%; for example, Young’s modulus, fracture toughness (K 1C ) and energy release rate (G 1C ) increased by 71%, 133% and 190%, respectively compared to neat epoxy. Percolation threshold of electrical conductivity is recorded at 0.58 vol% and thermal conductivity of 2.13 W m −1 K −1 at 6 vol% showing 4 folds enhancements. The lap shear strength of epoxy/GnP nanocomposite adhesive improved from 10.7 MPa for neat epoxy to 13.57 MPa at 0.375 vol% GnPs. The concluded results are superior to other composites or adhesives at similar fractions of fillers such as single-walled carbon nanotubes, multi-walled carbon nanotubes or graphene oxide. The study promises that GnPs are ideal candidate to achieve multifunctional epoxy adhesives. Refereed/Peer-reviewed

This work developed a facile approach to fabricate highly sensitive and flexible polyurethane/graphene platelets composite film for wearable strain sensor. The composite film was fabricated via layer-by-layer laminating method which is simple and cost-effective; it exhibited outstanding electrical conductivity of 1430 ± 50 S/cm and high sensitivity to strain (the gauge factor is up to 150). In the sensor application test, the flexible strain sensor achieves real-time monitoring accurately for five bio-signals such as pulse movement, finger movement, and cheek movement giving a great potential as wearable-sensing device. In addition, the developed strain sensor shows response to pressure and temperature in a certain region. A multifaceted comparison between reported flexible strain sensors and our strain sensor was made highlighting the advantages of the current work in terms of (1) high sensitivity (gauge factor) and flexibility, (2) facile approach of fabrication, and (3) accurate monitoring for body motions en-aus Refereed/Peer-reviewed

In this study, we developed a buckypaper (BP) composed of a mono-dispersion of multi-walled carbon nanotubes (MWCNTs) via a spray-vacuum filtration method. This highly flexible and sensitive carbon nanotube buckypaper (MWNCTs-BP) sensor can be integrated into complex curved surfaces and at critical stress areas to monitor the dynamic manufacturing process of fibre-reinforced composites in real time. A dynamic heating cure cycle and two revised cure cycles were designed to study the response of the resistance of the buckypaper to resin phase changes during the composite manufacturing process. Dynamic mechanical analysis (DMA) was performed to obtain the cure behaviour of a glass fibre/epoxy composite as a baseline to compare with the MWCNTs-BP sensor output. The experimental results show that the cure behaviour of epoxy/glass composites can be effectively monitored by the relative resistance change of the BP sensor embedded in the composite laminate. The MWCNTs-BP shows that the lowest viscosity point and gelation point of the composite resin were at 78 °C and 125 °C during the dynamic heating cure cycle, which is consistent with the DMA results. The lowest viscosity and gelation point can also be accurately obtained during the revised cure cycles. The MWCNTs-BP system has great potential as a sensor to establish and optimize manufacturing processes and to improve the cure quality of fibre-based resin composites. Refereed/Peer-reviewed

Cost-effective, solution-processable and high-quality nanomaterials have critical roles in the development of advanced polymer composite films which combine mechanical robustness with functional properties such as electrical conductivity for many applications. This study first fabricated 3 nm-thick graphene platelets (GnPs) which have an electrical conductivity of 1460 S/cm; each platelet may contain double or a few layers of graphene whose C/O ratio was measured as 13.2. We then developed epoxy/GnP composite films by a layer-by-layer method through two-step curing. A percolation threshold of electrical conductivity was observed at merely 0.6 vol% GnPs, and the composite electrical conductivity increased to 1298.7 S/cm at 20.0 vol%. The composite films were mechanically strong to be used as the cost-effective electrodes for flexible supercapacitors. Specific capacitance 50.1 F/g was recorded for the 15.0 vol% composite film by two-electrode configuration, in comparison with the specific capacitance 41 F/g for commercial multi-walled carbon nanotubes. More importantly, impressive capacitance was found at a high current density of 20 A/g, which is desired in practical applications. The film electrode demonstrated a capacitance retention rate of 94.7% through 20,000 cycles. At a bending angle of 90°, it exhibited a capacitance of 38.9 F/g at 100 mV/s. Refereed/Peer-reviewed

Buckypapers are free-standing porous mats of entangled CNT ropes cohesively bounded by van der waals interactions, and can be used to monitor the manufacturing process of glass fiber reinforced composite. In this paper, the buckypaper (BP) was fabricated with monodispersion of multi-wall carbon nanotubes via spray-vacuum filtration, and its morphology and pore size distribution were characterized by scanning electron microscope and nitrogen adsorption/desorption. The resistance of the BP sensor was obtained using a four-point probe method, and the resistance changes could be related to phase changes of the resin matrix,. Experimental results show that the BP sensor embedded in the glass/epoxy composite laminates has indicated a relative resistance change from -2.9% to 226.5% during the manufacturing process. In addition, the temperature sensitivity of a pristine BP sensor and a BP sensor embedded in composite were also characterized. The results demonstrate that the effect of resin phase changes on the resistance changes of a BP sensor is greater than that of the temperature during composite manufacturing. Refereed/Peer-reviewed