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Duringthe curingprocess of thick glass/epoxy composite laminates, substantial amounts of temperature lagand overshoot at the center of the laminates is usually experienced due to the large thickness and low thermal conductivity of the glass/epoxy composites, which require a long time for full and uniform consolidation. In this work, the temperature profiles of a 20mm thick unidirectional glass/epoxy laminate duringan autoclave vacuum bag process were measured and compared with the numerically calculated results. For the calculation of distributions of the temperature, degree of cure, resin pressure, exothermic heat and required time for full consolidation by three-dimensional finite element analyses, the effects of convective heat transfer coefficient and geometry of mold and bagging assembly on the temperature profiles were taken into consideration. Based on the numerical results, an optimized cure cycle with the coolingand reheatingsteps was developed by minimizingthe objective function to reduce the temperature overshoot in the composite. From the experimental and numerical results, it was found that the measured temperature profiles were in good agreement with the numerical ones, and conventional cure cycles recommended by prepregmanufacturers for thin laminates should be modified to prevent temperature overshoot and to obtain full consolidation.

In this work, the microstructures of inkjet-printed nanosilver films sintered by intense pulsed light (IPL) were systematically analyzed and correlated with the electrical properties. Nanosilver films with various dimensions were inkjet-printed and sintered at different light intensities to investigate the effects of the film dimension and light intensity on the sintering characteristics. For comparison purposes, the same inkjet-printed films were also thermally sintered at 210 °C for 1 h. Consecutive light pulses from a xenon lamp induced film swelling and the corresponding hollow microstructures of the inkjet nanosilver films. The resistance of IPL-sintered films was inversely proportional to the light intensity, and the resultant conductivity comparable to the thermally sintered one was achieved within just a few tens of ms, without damaging a polymer substrate. While all the thermally sintered patterns experienced shrinkage during the sintering process, the IPL-sintered ones could keep their initial dimension at a certain light intensity.

Surface modification of polyimides (PIs) using electrospinning would significantly improve the performance of TENGs because of the larger surface area of the electrospun friction layer. However, PIs generally have high solvent resistance, so it is complicated to convert them into nanofibers using electrospinning process. This study aims to fabricate PI nanofibers via simple, one-step electrospinning and utilize them as a friction layer of TENGs for better performance. PI nanofibers were directly electrospun from PI ink made of polyimide powder without any additional process. The effect of PI concentration on spinnability was investigated. Uniform and continuous nanofibrous structures were successfully produced at concentrations of 15 wt% and 20 wt%. Electrospun PI nanofibers were then utilized as a friction layer for TENGs. A TENG with 20 wt% produced an open circuit voltage of 753 V and a short circuit current of 10.79 μA and showed a power density of 2.61 W m −2 at a 100 MΩ load resistance. During tapping experiment of 10,000 cycles, the TENG could stably harvest electrical energy. The harvested energy from the proposed TENG is sufficient to illuminate more than 55 LEDs and drive small electronic devices, and the TENGs exhibit excellent performance as a wearable energy harvester. The rapid development of flexible electronics has promoted the wide application of various low power consumption electronic devices. Thus, an effective power source of these devices has gained increasing attention. Nanogenerators are good candidates due to their ability to harvest electrical energy sustainably from environmental sources 1-7. Among various types of nanogenerators such as triboelectric, pyroelectric, thermoelectric, and piezoelectric nanogenerators, triboelectric nanogenerators (TENGs) have gained enormous attention over past few years owing to their simple configuration, low weight, and cost-effective fabrication process. TENG's electrical performance is usually assessed by power density (W m −2), including voltage and current. TENG's power density is relatively small compared to other types of nanogenerators because the current generated by TENGs is insufficient. In order to enhance the performance of TENGs, various approaches have been conducted. Selecting materials of the friction layers according to the triboelectric series is an easy, reliable, and straightforward way. The farther two materials on the triboelectric series table, the higher the amount of charges generated. Many synthetic polymers have the nature of being negatively charged while nylon, cotton, and aluminum are generally used as positive friction layers. Polyimide (PI) has been widely used as a negative friction layer for TENGs due to its highly negatively charged nature 8-11. In addition, PI exhibits excellent stability as a friction layer under repetitive external pressure or deformation due to its outstanding mechanical properties. Some researchers have tried to further improve the performance of TENGs by enlarging the surface area of the friction...