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Bolted joints are commonly used for assembling carbon fiber/resin composite structures. Since drilling may generate defects at hole edges which affect mechanical properties, it is of great engineering significance to develop proper repair methods to restore the mechanical properties of the defective parts. However, there are few studies on hole edge defects and their repair methods. Therefore, a novelty short fiber filling repair method was proposed to repair defective holes in this study. The mechanical properties of intact, defective and repaired countersunk composite joints were compared and investigated. Experimental tensile tests showed that defective joints had lower initial stiffness and failure loads compared to intact joints, while the mechanical properties were effectively restored after repair. Three-dimensional finite element models were also established to analyze the damage process of the joints. Results of numerical modelling were consistent with the experimental results. The simulations showed that changes in contact behaviors and local deformations caused by hole edge defects led to the low initial stiffness and stiffness transition point of the joint, while this phenomenon was reduced after repair. Additionally, despite different joint types, laminate failure mainly occurred around the hole and countersink.

Highly-performance fogdrop collection is of great practical importance in addressing the worldwide water shortages, especially in arid regions. Although great progresses have been made to solve this problem, there still are challenges in developing high-performance fogdrop collecting systems to satisfy efficient fogdrop capturing and fast transport simultaneously, which are two critical factors that determine the collection efficiency. The well-evolved water-collecting capacity of creatures that adapt to the harsh environment provides a great inspiration for the design of efficient collection systems. Here, inspired by the unique hierarchical structures and the excellent fogdrop collection ability of wheat awn, artificial awn-like hierarchical systems are developed via a precision 3D printing strategy which exhibit excellent fogdrop capture and fast transport. The presence of hierarchical structure composed of conical spine, gradient microgrooves, and oriented thorns enables the fogdrop collection to transform from dropwise mode on the thorns to filmwise one on the spine. Furthermore, the collection efficiency of such a bioinspired system is 5.90 g/cm−2·h, which is higher than individual ones and other bioinspired systems. Through the model of structure–function relationship, the mechanisms of diverse collecting behaviors are explored to address the origin of highly-performance collection. This work opens up new avenues to design systems and devices for dramatic fogdrop collection enhancement.