This study proposes a novel algorithm for generating representative volume elements which mitigate microstructural inhomogeneities in fiber-reinforced composites. The algorithm integrates void characteristics obtained from micro-computed tomography to more accurate microstructure models. Based on these models, the effects of void content, spatial distribution, and void diameter on the mechanical behavior of CF/PEEK composites are systematically evaluated using finite element analysis and experimental validation. The results reveal that void content significantly reduces transverse tensile strength and ductility, while void size further accelerates failure and enhances brittleness. In contrast, void distribution has minimal influence on the transverse mechanical response. These findings not only offer qualitative insights into void-induced damage mechanisms but also provide a theoretical basis for optimizing microstructures to enhance the mechanical performance of CF/PEEK and similar composite systems. Finally, the limitations of this study have been discussed, and directions for future research are proposed.

Due to their unlimited shelf life, high impact resistance, recyclability, and fast processing time, the use of carbon fibers in combination with a thermoplastic matrix promises a fiber metal laminate (FML) with improved properties and potentially automated series production. Accordingly, the formability and performance of fast forming technologies, i.e., the hot stamping of thermoplastic FMLs, are increasingly attracting research interest. In this study, a new one-step hot stamping process is first proposed to produce curved thermoplastic FML beams fabricated by Al sheets, PEEK films, and CF/PEEK prepregs (Al/CF/PEEK). Then, the effects of the forming temperature and punching speed on the formability, as well as on the performances of the curved beams, i.e., their macro- and micro-defects, interlaminate strength and failure, thickness distribution, and spring-back, are experimentally investigated via SEM observations, four-point bending tests, and digital image correlations. It is found that curved Al/CF/PEEK laminate beams with the least spring-back (<0.2°) and thickness reduction (<0.2 mm), the fewest defects, the highest curved beam strength (195 N·mm/mm), and the highest interlaminate strength (16.5 MPa) can be produced under the forming temperature of 380°C and punching speed of 10 mm/s.

The vibration of a swash plate is caused by the piston forces and the control actuator acting on the swash plate. An earlier study of the outlet flow ripple of variable-displacement axial piston pumps assumed a fixed swash plate angle; it ignored the influence of swash plate vibration on the outlet flow ripple of the axial piston pump. In this work, a theoretical model of the outlet flow ripple and pressure pulsation was established in a constant power variable-displacement piston pump. The vibration of swash plate, flow leakage, and valve dynamic characteristics are considered in the theoretical model. The computational results of the theoretical model at different external load pressures are verified by comparison with experimental results. The vibration of the swash plate is strongly influenced by both the piston chamber pressure variation and the control actuator mechanism. The study proved the influence of the swash plate vibration on the outlet flow ripple and the pressure pulsation of an axial piston pump. Compared to the case of a fixed swash plate angle, accounting for swash plate vibration is much more suitable for the accurate determination of the outlet flow ripple and pressure pulsation of an axial piston pump. It is also shown that the vibration of the swash plate affects the valve plate design. Accordingly, valve plate optimization based on the theoretical model of the outlet flow ripple was also studied in this work. The amplitude of the instantaneous outlet flow ripple was considered as the optimization objective function. Finally, the optimized design parameters for a constant power variable-displacement swash plate axial piston pump were evaluated.