With the rapid development of aviation science and technology, the application of new materials and advanced technology, the modern aircraft structures are becoming more and more complicated. Traditional structural damage monitoring and structural reliability design face the new challenges. The structural health monitoring technology obtains structural response through advanced sensor on-line monitoring. The structural response information will be used to access structural health status and assess the residual life of the structure, and further develop the aircraft structure maintenance decision. This technology can be taken at the appropriate period of time to ensure the safety and service of structures to achieve maximum economic benefits. The state of structural health monitoring technology for aircraft structures is reviewed in this paper, including components of structural health monitoring system, Lamb wave based global damage detection technology, optical fiber based global condition perception, local damage detection method, multi-sensor fusion detection technology and structural health assessment technology. The development trend and challenges of structural health monitoring of aircraft structures are also discussed.

As the barely invisible damages are often induced during the manufacturing processes or in-service applications, the material strength will degenerate and the performance of structure will decrease. Lamb wave based damage detection method can be used to identify the damages effectively. However, due to the complicated amplitude modulation, the distribution of energy spectrum will shift which brings challenge to group velocity determination. As the group velocity often determined by the center frequency of the excitation, the error will be induced when the distribution of energy spectrum is changed. In this paper, on the basis of amplitude modulation curves, its influence on energy spectrum shifting is investigated through simulation and experiment. Furthermore, the group velocity correction method is proposed to improve the damage localization accuracy. The experiment is carried out on a T300/3231 composite laminates. The imaging result shows higher accuracy when using corrected velocity, which verifies the efficiency of the proposed method.

The identification of early partial damage in critical parts is of great significance for the safety of the structure. The early detection of the damage can provide basis and support for the use and maintenance of the structure. The dynamic strain of the structure is tested by fiber Bragg grating sensor. At the same time, the dynamic strain response characteristics of the structure are extracted by using the strain modal identification technique. A damage identification index is proposed based on strain response characteristics to identify the damage degree and location. The experimental results show that the dynamic strain response is sensitive to the local damage, and the damage identification index can reflect the degree and location of damage, which can achieve the purpose of structural early damage identification.

In-situ monitoring manufacturing process of polymer matrix composite to develop and optimize the curecycles, is the key to enhance the reliability and performance of composite parts. A review of in-situ manufacturing industry monitoring techniques is presented for composite cure. A comparison is presented for strain gauge, acoustic, ultrasonic and fibre optic monitoring methods. This review highlights the need for further development in this area, with potential savings to manufacturing time and reductions in cost through quality control measures.

The recent research status of 3D braided composite technology and its application in the field of aerospace are introduced. Firstly, the classification, braiding techniques and mechanical properties of three-dimensional braided composite are introduced; Secondly, the analysis model and mechanical analysis method of three-dimensional braided composite in recent years are reviewed; Finally, the problems in the application of three-dimensional braided composites are discussed, and the advantages of three-dimensional braided materials and their possible improvement in structure and applicationfields are discussed.

Finite element simulation combined with BP neural network is applied to predict the machining deformationof titanium alloy hollow fan blade, which is caused by residual stress and milling load. The empirical formula of cuttingforce was obtained by orthogonal experiment of cutting force. The simulation of milling leading and tailing edge wasperformed by applying the model change technology. Combined with the BP neural network model for milling deformationforecast, wide chord hollow fan blade milling deformation forecast was realized both in stroke milling and ring-cut milling.The simulation results show that ring-cut milling deformation is much larger than that of the stroke milling. The relative errorbetween the deformation results which were predicted by BP neural network and the measured value is less than 10%. The efficiency of deformation prediction is higher than simulation prediction, and the accuracy of deformation prediction is as good as simulation prediction.

Based on autoclave molding simulation software, the flow field and temperature field of autoclave were investigated by the finite element method. The research demonstrated that distribution of flow field and temperature fieldwere optimized, the proper position of parts and tools in autoclave were determined. The study isnot only improving the efficiencyof technological design but also monitoring curing process, and increasing mass of parts.

The technological principle and control difficulties of vacuum differential pressure casting have been introduced.Taking the typical precision casting of aeroengine exhaust end housing for example, the key technologies such asgating system, mould development and pouring temperature selection in the vacuum differential pressure casting of integralthin-wall aluminum alloy casting parts were studied. Then, the existing technical problems are put forward to solve theways and means of control. The results show that, when using double pass structure of mould casting system, mixing systemusing furan resin sand casting sand, at (730±10)℃ pouring temperature, aeroengine loose, pores, inclusions and otherdefects of thin wall casting products overall aluminum alloy basically eliminated. The sample is compact and the elongation is up to 3.6%.

Glass fiber composite material is composed of glass fiber and resin, with high mechanical properties, low density, low cost characteristics. However, in the use and maintenance of aircraft, the moisture absorption of composite materials is inevitable, and can not be simulated well. This article analyzes moisture diffusion process through Tencate 7781 Glass fiber composite specimens conditioned in hygrothermal environment when effective moisture equilibrium is achieved. It indicates that mechanical property and glass transition temperature of wet composite would decline to different extent by contrasting with dry material, and the reason for descending is also analyzed preliminarily.

During the heating process of hot air anti-icing cavity, the temperature difference between the inner and outer skin is large, which will result in the changes of the gap between the two skins due to the thermal expansion deformation andinfluence anti-icing effect, even block anti-icing passageway. This paper is focused on the hot air anti-icing system of a certainengine inlet aspect. In order to solve the thermal deformation of double skin anti-icing cavity, the method of adding the numberof shims between the two skins is chosen. The finite element method was used to analyze anti-icing cavity’s thermal deformation,and obtained the maximum thermal deformation area and the change law of thermal deformation the anti-icing cavity of under different number of shims conditions, which provides the design foundation of the double skin anti-icing cavity.