When a spacecraft flies at a high speed through a high‐heat flow, the ablative composites suffer from severe delamination and bulging due to their weak interlaminar performance. This will interfere normal operations of spacecraft. To improve the interlaminar performance of ablative composites is of great significance to the ablative structures. This study investigated Z‐pin reinforced quartz‐phenolic composites and reinforcement mechanism. First, a thermogravimetry (TG) test was used to analyze the thermal decomposition process of the phenolic. Second, a series of tests, including a single Z‐pin pull‐out, a single‐lap joint tensile and an oxyacetylene ablation test, were conducted to investigate composites' ablation performance. We also deployed a 3D morphometer and an infrared thermography to reveal the function of Z‐pins. The results demonstrated that Z‐pins can improve composites' ablation performance in both structure and function. In the structure, Z‐pins suppress the interlaminar delamination of composites by enhancing the interlaminar strength. As the ablation time increases, interface bridging between the Z‐pin and laminates contributes increasingly to the interlaminar shear strength of laminates. After 60 s of ablation in a flame of 920°C, the interlaminar shear strength of Z‐pin specimens is 84.66% stronger than that of the normal composites. In the function, the Z‐pins suppress large areas of bulges by providing escape channels for pyrolysis gas, and reduce bulging areas by 60%. Z‐pin technology can effectively suppress mechanical erosion of the ablative surface due to the delamination and bulging. It is an important way to improve ablation performance of ablative structures.

Aiming at the use of glass fiber reinforced poly‐ether‐ether‐ketone (GF/PEEK) with low laser absorbance in laser assisted tape winding/placement (LATW/LATP), a method for dyeing GF/PEEK prepreg with nanoparticle fillers (NFs) is presented. First, the effects of carbon black (CB) and graphite (G) NFs on composites laser absorbance and reflection pattern were quantified, and the complex refractive index model was derived. Next, the effects of NFs on composites transverse thermal conductivity were tested, and the accuracy of four thermal conductivity prediction models were compared. Finally, the effects of NFs on composites interlayer performance were studied. The optical test results showed that NFs could improve laser absorbance while not changing reflection pattern, and the increase rate of absorbance for CB was higher than for G. As calculated by complex refractive index model, GF/PEEK with 1‐layer thickness could achieve complete laser absorption by addition of either 2.74%CB or 3.78%G. The thermal conductivity test results showed that NFs could improve composites transverse thermal conductivity. The increase rate of thermal conductivity for G was higher than for CB. Among the four prediction model, the Lewis‐Nielsen model had correct prediction regularity and was within 10% predict deviation. Based on this model, the transverse thermal conductivity of GF/PEEK/2.74%CB was 0.557 W/m K, and of GF/PEEK/3.78%G was 0.592 W/m K. The mechanical test results showed that the CB loading ≤4% had little effect on interlayer performance, while the G decreased interlayer performance. Consequently, adding CB at a low loading is a better way to realize GF/PEEK application in LATW/LATP.

Aiming to improve safety and stability in manufacturing poly-ether-ether-ketone (PEEK) prepreg by powder impregnation, the aqueous system combined with surfactant and thickener was proposed in this paper. Based on surface tension method, the effects of surfactants and concentration on dispersion efficiency of PEEK powders were studied, and concentration of surfactants was determined. The effect of thickener concentration on suspension stability was analyzed, and ingredients of aqueous system were optimized by mechanical tests. The results show that, dispersion efficiency would reach maximum when surfactant concentration at critical micelle concentration, but not affected by the type of surfactant. Network association mechanism of thickener could improve stability of suspension, which holding time was increased from 40 min to 4 h. The good dispersion effect and long times stable system improved the coefficient variation of resin mass fraction, which was reduced from 7% to 4%. Compared with circulating system, the mechanical test results showed that the tensile strength kept unchanged, but interlayer properties were associated with carbon residue mass, the lower the residue carbon mass, the higher the interlayer strength retention rate, the optimized ingredient was Aerosol OT 75%E solution. Aqueous system has characteristics of safety, green, and low cost, which fits the demands of industrial production of prepreg.

As a key component to ensure the safety and stability of the surface-mounted permanent magnet motor rotor, stress research on the sleeve has long been a subject that has attracted researchers. Fiber-reinforced composite materials have the characteristics of high specific strength, high specific modulus, and low eddy current loss. The use of a fiber-reinforced composite material sleeve that can effectively reduce the thickness of the sleeve and structural weight, and can improve the power density of the motor is an inevitable trend of the development of high-performance permanent magnet motors. This paper summarizes the matching of fibers and resins of composite materials to the sleeve: the stress design criteria, stress calculation method, and stress influencing factors of the composite sleeve; two typical stress-forming methods of the composite sleeve; and the preloading effect of the sleeve, strength, and rotor prototype performance testing. This paper focuses on the application of tension winding technology in sleeve forming. Based on the characteristics of composite material layer synthesis, this method has the advantages of high forming efficiency, small forming damage, easy realization of stress design, and a high preloading effect. This method can meet the sleeve-forming requirements of high-performance, large-scale, high-speed permanent magnet motors. However, the application of the new high-performance material system in the existing research is insufficient, the research on the technological factors in the tension winding process is scarce, and the performance testing method after the sleeve preparation is single, which needs further research.

To improve the performance of thermoplastic composite joints and reduce the weight of joints, glass fiber (GF)/polypropylene (PP) thermoplastic composite rivets (GF/PP rivets) were prepared and tensile test and simulation analysis of GF/PP-riveted single-lap joints were carried out. Based on the tensile test, the optimum extension length of GF/PP rod with different diameters was determined by taking the specific joint strength (the ratio of joint strength to the weight of fasteners) as the evaluation index. The effects of the rivet diameter and the thickness of composite laminates on the specific joint strength and the weight reduction of GF/PP-riveted single-lap joints were studied. The joining mechanism and the failure behavior of GF/PP-riveted joints were analyzed by finite element simulation. The experimental results indicate that the specific joint strength of GF/PP-riveted joints decreased with increasing rivet diameter and laminate thickness. For the same specific joint strength, the weight of fasteners at joints could be reduced by 81.4% and 73.9%, respectively, by using GF/PP rivets instead of steel bolts and aluminum blind rivets. The simulation results show that the change of inclination angle of rivet body would cause the change of failure mode of joints.