Materials

This study investigates the effects of flame-retardant fillers, mesh electrode geometry, electrode material, propellant thickness, and applied voltage on the ignition and combustion performance of a perchlorate-based Electrically Controlled Solid Propellant (ECSP). Resistivity measurements show that phenolic resin (BS) increases resistivity by 82.8% (to 78.33 Ω·m), whereas decabromodiphenyl ether (BW) decreases it by 32.3% (to 29.04 Ω·m), relative to the base formulation (42.9 Ω·m). Finite element simulations reveal that current density concentrates at electrode–propellant contact points and decreases with increasing wire diameter and mesh number, whereas average current density exhibits a non-monotonic trend with mesh number. Thermal stress analysis indicates that pore size affects interfacial stress more significantly than wire diameter, and larger pores increase the risk of debonding. Ignition experiments demonstrate that asymmetric electrode configurations generate current density disparities that override polarity effects in determining the ignition sequence. The influence of electrode material follows the order Ti > SS > Cu and is independent of polarity. Ignition delay increases with propellant thickness, whereas thicknesses below 3 mm are prone to uncontrolled combustion. Under the present electrode configuration and test method, ignition proceeded very slowly at applied voltages below 60 V, whereas ignition occurred readily above 70 V. These findings provide practical guidance for electrode design and operational optimization in electrically controlled solid propulsion systems.

The emergence of water-borne polyurethane solid–solid phase-change materials (PCMs) has overcome the problems of core material leakage in solid–liquid phase-change materials. However, water-borne polyurethane solid–solid phase-change materials also have issues such as poor heat storage performance and limited temperature regulation range. This study used polycaprolactone diol (PCL-diol) and poly(ethylene glycol) (PEG) as the composite soft segments, and selected dicyclohexylmethane-4,4′-diisocyanate (HMDI) and glycerol (GL) as the hard segments, to prepare a PEG-PCL-HMDI PCM. By adjusting the ratio of the composite soft and hard segments, the content of the soft segment, and the molar ratio of the monomers, the phase-change temperature was precisely controlled and the heat storage performance was synergistically improved. After the PEG-PCL-HMDI PCM had finished being applied onto the surface of cotton fabric, the temperature-regulating fabric exhibited a significant temperature-buffering effect in the 25–35 °C human activity temperature range, with the heating rate reduced and the cooling rate delayed. This study provides a new material system and process scheme for the development of intelligent textiles with both efficient energy storage and precise temperature regulation functions.

Air plasma cutting technology is widely used for high-speed profiling of electrically conductive materials. The cut quality of surface and thermal effects is highly influenced by gas composition and process parameters. This study aims to systematically optimise and comparatively evaluate conventional compressed-air plasma cutting and an oxygen-assisted compressed-air plasma cutting process for 10 mm thick C-20 carbon steel plates. The investigation was conducted in two sequential stages using statistical Design of Experiments (DoE). First, a full-factorial design comprising 20 experiments was performed using compressed air to establish baseline process parameters and optimum operating ranges. Subsequently, a Central Composite Design (CCD) based on Response Surface Methodology (RSM) was employed for 20 additional experiments to model and compare pure compressed air with an oxygen-compressed air mixture. Cut quality was evaluated in terms of kerf width, dross height, bevel angle, surface roughness, maximum cutting temperature, and heat-affected zone (HAZ) length. The results demonstrate that the addition of oxygen improves plasma arc characteristics and produces substantial reductions in kerf width from 2.3 to 2.1 mm, dross height from 0.3 to 0.2 mm, bevel angle from 1.6 to 1.4 Radian, Avg.surface roughness from 1.2 to 0.2 µm, Max.surface roughness from 8.2 to 1.6 µm, Max. surface temperature from 1719.3 to 1607.8 °C and HAZ from 38 to 23.2 µm compared with conventional compressed-air cutting. Furthermore, microstructural analysis of the cut surfaces revealed a significant reduction in HAZ length when the oxygen-assisted gas mixture was employed. Overall, the findings demonstrate the potential of oxygen-assisted compressed-air plasma cutting to improve cutting efficiency and surface quality while reducing thermal effects, providing practical guidance for the optimisation of plasma-assisted manufacturing processes.