In this work, the PEEK/short carbon fiber (CF) composites were prepared, a new thermodynamic coupling (preheating and impact compaction) process of the FDM method is proposed, and the warp deformation mechanism was obtained by finite element simulation analysis. Results show that a new method could improve the forming quality of an FDM sample. The porosity of FDM samples of the PEEK/CF composite gradually decreased from 10.15% to 6.83% with the increase in impact temperature and frequency. However, the interlayer bonding performance was reduced from 16.9 MPa to 8.50 MPa, which was attributed to the influence of the printing layer height change from the printhead to the forming layer. To explain the above phenomenon, a thermodynamic coupling model was established and a relevant mechanism was analyzed to better understand the interlayer mechanical and porosity properties of PEEK/CF composites. The study reported here provides a reference for improving the forming quality of fabricated PEEK/CF composites by FDM.

To improve the reinforcement effect between a binder and high solid filler in a propellant formula, grafting the bonding group into the binder to form a neutral polymeric is a practically novel approach to improving the interface properties of the propellant. In this work, a glycidyl azide polyol energetic thermoplastic elastomer binder with a –CN bonding group (GAP–ETPE) was synthesized, and the mechanical and thermal decomposition mechanism of GAP–ETPE with Hexogeon (RDX) model propellants were studied. The stress–strain results indicated that the tensile strength and strain of GAP–ETPE/RDX model propellants were 6.43 MPa and 32.1%, respectively. DMA data showed that the storage modulus (E’) of the GAP–ETPE/RDX model propellants could increase the glass transition temperature (Tg) values, those were shifted to higher temperature with the increase in filler RDX percentages. TG/DTG showed the four decomposition stages of the decomposition process of the GAP–ETPE/RDX model propellants, and the thermal decomposition equation was constructed. These efforts provide a novel method to improve GAP–ETPE/RDX propellants mechanical property, and the thermal decomposition behavior of GAP–ETPE/RDX propellants also provided technical support for the study of propellant combustion characteristics.

Flapping flight is an important mode of insect flight, and its unique flapping motion pattern enables it to fly efficiently in complex environments. This paper takes a biomimetic moth flapping-wing aircraft as the research object and proposes a periodic function composed of two sine functions with different frequencies as the flapping function. This paper explores the effect of this flapping function on the flight performance of flapping-wing aircraft and verifies whether it can be applied to the flight control of flapping-wing aircraft. Firstly, through the study of biomimetic mechanisms, the basic structure of the flapping-wing aircraft is roughly designed; then, the flapping motion is simplified, a rigid wing flapping motion model is established, and the key parameters affecting the average lift are determined. Next, a virtual wind tunnel simulation platform is built, and the key parameters of the flapping function that affect lift generation are simulated and calculated. Finally, an experimental prototype of a biomimetic moth flapping-wing aircraft is designed and manufactured. Through flight experiments, the effects of flapping amplitude, flapping frequency, and mid-position angle in the flapping function on the flight performance of the biomimetic flapping-wing aircraft are verified. The key control parameters are clarified, the control strategy of the flapping-wing aircraft is optimized, and the maneuverability and controllability of the aircraft are improved, providing a theoretical basis and practical support for the development of control methods for biomimetic flapping-wing aircraft.