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Z-pinned joints prepared by chemical vapour infiltration are widely used in ceramic matrix composite components. Excellent fatigue behaviour is important for structural safety. In this study, 2D C/SiC Z-pinned joints were loaded in axial direction of the pins under static and cyclic loading. Internal damage was monitored in situ by an acoustic emission system. The binding force between pin and hole is relatively strong. Meanwhile, the joints exhibite promising resistance to fatigue. The residual strength increased first with the fatigue cycles then decreased after 105 cycles. Microstructural analysis indicated that full-developed cracks and local stress redistribution resultes in the increase in the strength of the joints. The acoustic emission analysis also provides a supplementary understanding of the damage mechanism. The results show that damage fully develops at the early stage of fatigue. When the specimen is reloaded, less AE events are collected before the fatigue maximum stress.

A flying of a wild Haliaeetus Albicilla was recorded with extraordinary maneuvering abilities, which was quite rare in bird flights. In order to estimate the control strategy to resist the deep stall, a 2D simplified model is proposed and the aerodynamics are predicted using a traditional lift theory. A proportion-integration-differentiation (PID) method is used to estimate the control strategy. However, the dynamics system always results in differential-algebraic equations or ordinary differential equations which are implicit and high-coupled. Then a quasi-Newton method was proposed and integrated into the proposed method based on BFGS formular. Thus, a Neural Network PID control based on the BFGS method is established. Results show that the proposed method can estimate the perching sequence well.

Feather can morph in a quite convenient and effective way, which enables a bird with excellent flight abilities. Bird feathers have attracted the attention of researchers to reveal underlying physical mechanism of drag reduction or lift production. To investigate the microstructures and the mechanical behaviors of barbs, a series of barbs were manually cut from an eagle's primary feather to observe the cross-sections. How the barb was changed along both the rachis and barb was investigated in this research, and a "λ"-like cross-section with a tiny hook was observed at the right feet at each section. Afterwards, a measurement set-up system was developed to evaluate the leakage ratio of a feather followed by a numerical predicting approach based on CFD method. It is found that the air leakage increased linearly against the pressure and the predicted results coincide well with the experimental results. Finally, the influences of leakage of the flight feather on both steady and unsteady aerodynamics were studied.

The key to high manoeuvre ability in bird flight lies in the combined morphing of wings and tail. The perching of a wild Haliaeetus Albicilla without running or wing flapping is recorded and investigated using a high-speed digital video. A shape reconstruction method is proposed to describe wing contours and tail contours during perching. The avian airfoil geometries of the Aquila Chrysaetos are extracted from noncontact surface measurements using a ROMBER 3D laser scanner. The wing planform, chord distribution and twist distribution are fitted in convenient analytical expressions to obtain a 3D wing geometry. A three-jointed arm model is proposed to associate with the 3D wing geometry, while a one-joint arm model is proposed to describe the kinematics of tail. Therefore, a 3D bird model is established. The perching sequences of the wild eagle are recaptured and regenerated with the proposed 3D bird model. A quasi-steady aerodynamic model is applied in the aerodynamic predictions, a four-step Adams–Bashforth method is used to calculate the ordinary differential equations, thus a BFGS based optimization method is established to predict the perching motions.