The deviation in wall thickness caused by core shift during the investment casting process significantly impacts the strength and service life of hollow turbine blades. To address this issue, a core shift limitation method is developed in this study. Firstly, a shift model is established based on computational fluid dynamics and motion simulation to predict the movement of the ceramic core in investment casting process. Subsequently, utilizing this model, an optimization method for fixturing layout inside the refractory ceramic shell is devised for the ceramic core. The casting experiment demonstrates that by utilizing the optimized fixture layout, not only can core shift during the investment casting pouring process be effectively controlled, but also the maximum wall thickness error of the blade can be reduced by 42.02%. In addition, the core shift prediction is also validated, with a prediction error of less than 26.9%.

Ultrasonic vibration-assisted drilling (UVAD) has recently been successfully applied in the drilling of carbon fiber reinforced polymer/plastic (CFRP) due to its high reliability. Multiple defects have been observed in the CFRP drilling process which negatively affects the quality of the hole. The carbon fiber/bismaleimide (BMI) composites is an advanced kind of CFRPs with greater strength and heat resistance, having been rapidly applied in lightweight and high temperature resistant structures in the aerospace field. To suppress the defect during the drilling of carbon fiber/BMI composites, it is necessary to comprehensively understand the defect formation and suppression mechanism at different positions. In this study, the defects formation in both conventional drilling (CD) and UVAD were observed and analyzed. The variation trend in the defect factor and thrust force with the spindle speed and feed rate were acquired. The results revealed that the UVAD could significantly enhance the hole's quality with no delamination and burr. Meanwhile, the defect suppression mechanism and thrust force in UVAD were analyzed and verified, where the method of rod chip removal affected the exit defect formation. In summary, UVAD can be considered a promising and competitive technique for drilling carbon fiber/BMI composites.

Interference fit has advantages in improving fatigue behaviors of composite bolted joints; however, interference fit bolt insertion tends to cause damages in laminates weakening joint mechanical properties. Therefore, an experimental study was conducted to investigate bolt insertion damages of Carbon Fiber Reinforced Polymer (CFRP)/CFRP interference fit bolted joints. Mechanical behaviors of joints were also evaluated experimentally under both quasi-static loads and cyclic loads. Scanning Electron Microscope (SEM) and high-resolution X-ray micro-CT scan were used to examine micro damages in laminates. Damage and failure behaviors of joints were characterized. The results demonstrated that the hole entrance in upper laminate and the laminate boundary near the hole wall were the most critical regions for damages during bolt insertions. However, the influence of those damages on quasi-static failure loads and fatigue failure modes of joints was minimal. Delamination and matrix cracking occurred first in laminates following fiber and matrix fracture in quasi-static tensile tests. Interference fit could improve the fatigue resistance of the laminate hole; however, the bolt seemed to suffer a more critical local fatigue loading condition. This paper can contribute to composite structure designs, especially in understanding damage and failure behaviors of composite bolted joints.

The in-situ TiB₂ particle reinforced Al-based metal matrix composites have become a series of promising aeronautical materials due to the advanced properties such as finer evenly-distributed grains, cleaner particle-matrix interface, improved mechanical performance and strength when compared with ex-situ SiC particle reinforced Al-based metal matrix composites. However, over the last 50 years, a significant body of research has been carried out on ex-situ SiC particle reinforced Al-based metal matrix composites from material fabrication process, material property improvement, material mechanical test to machining performance such as machined surface integrity, cutting process simulation and modeling, parameter optimization and fatigue characteristics. For in-situ TiB₂ particle reinforced Al-based metal matrix composites, studies in recent years were mainly focused on the material preparation process and property development and few published works was found on the machining performance of this new kind material. Hence, this article aims to provide a general overview of recent achievement on machining performance of in-situ TiB₂ particle reinforced Al-based metal matrix composites.