航空材料学报

2022, 42(2)

[Abstract](61) [PDF 10085KB](24)

Abstract:

Research progress of helicopter noise suppression technology based on materials/structures

LI Wenzhi, CAO Yaoqin, HE Zhiping

2022, 42(2): 1-10.

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Abstract:
Helicopter has achieved rapid development and wide application in various fields, due to its unique flight mode. However, the noise is also a particular feature of the helicopter, which people cannot bear without protection. With the requirements of helicopter comfort and low noise pollution, its noise has become an urgent problem that must be solved. According to the main sources and propagation ways of external noise and internal noise of the helicopter, the current situation of material and structure-based helicopter noise control in domestic and international scope was reviewed. The noise control characteristics and effects of conventional sound absorbing materials, intelligent piezoelectric control materials, acoustic super material/structure and damping material were introduced in this paper. Traditional materials are no longer suitable for the current lightweight requirements of the helicopter. Intelligent composite materials, new sound-absorbing structures, and acoustic super material/structure have become potential selections of noise suppression. Finally, combined with the current development status of helicopter vibration and noise reduction materials, the development trend of helicopter noise reduction material/structure in the future such as active noise reduction technology, resonance sound absorption, metamaterial acoustic band gap, damping material noise reduction and so on, is proposed, and feasible research ideas for the development direction of helicopter noise suppression materials/structures are put forward.

Analysis of hot deformation behavior of TB9 titanium alloy after friction correction and establishment of processing map

WANG Chunyang, WANG Yuhui, LI Ye, ZHANG Wangfeng

2022, 42(2): 11-19.

[Abstract](184) [FullText HTML] (147) [PDF 1732KB](43)

Abstract:
The hot compression tests of TB9 titanium alloy sample were carried out on Gleeble-1500 thermal simulator at the temperature range of 750-1000 ℃ and the strain rate range of 0.01-10 s⁻¹. The stress-strain curves obtained by the experiment were subjected to friction correction and the processing map was drawn according to the corrected stress-strain curve .The results show that the stress-strain curve after friction correction is obviously lower than that before correction, and the stress difference between them increased with the increase of strain. The corrected stress−strain curve is $ \sigma {\text{ = }}\frac{{\arcsin h{{[\frac{{\dot \varepsilon \exp (\frac{Q}{{RT}})}}{A}]}^{\frac{1}{n}}}}}{\alpha } $, and can used to predict the stress of TB9 titanium alloy under different strain rates at 750 ℃ to 1000 ℃. Instable deformation of TB9 titanium alloy leads to localize the deformation bands which is about 45° to the compression direction appeared, resulting in the inhomogeneous microstructure. Stable deformation during hot working in suitable process window can bring dynamic recrystallization and recovery in the alloy, which can improve the microstructure and properties of the alloy. According to the processing map, the suitable thermal deformation process parameters of TB9 titanium alloy are obtained as follows: deformation temperatures of 850-1000 ℃ at deformation rates of 0.01-1 s⁻¹.

Interfacial reaction between mullite-based inclusions and PM superalloy FGH96

ZHANG Yibo, ZHENG Liang, XU Wenyong, LI Zhou, ZHANG Guoqing

2022, 42(2): 20-28.

[Abstract](118) [FullText HTML] (47) [PDF 5403KB](29)

Abstract:
The morphology and chemical composition evolution of mullite based refractory inclusions in FGH96 PM superalloy with powder state, hot isostatic pressing (HIP) and hot deformation (HF) were studied by means of artificial implantation of inclusions, optical microscopy (OM), scanning electron microscopy (SEM) and electrolytic etching. The mechanism of interfacial reaction between mullite based refractory inclusions and alloy matrix was revealed. The results show that in the powder state, the artificial mullite based inclusions are irregular particles, and there is no obvious change of morphology and composition in the inclusions after HIP process at high temperature and high pressure. A complex reaction layer is formed at the interface between inclusions and alloy matrix. The reaction layer is consisted of Al and Ti oxides. After thermal deformation of 1080 ℃/0.0004 s^-1 under the condition of 25% deformation rate, the main morphology and composition of the inclusions are not changed obviously. The reaction layer coated on the inclusion began to peel and elongate from the inclusion with the deformation of the superalloy matrix, and aggregated on the side close to the elongation direction with the flow deformation of the matrix. When the deformation degree is 50%, mullite inclusions and the externally coated reaction layer are broken and deformed to form an inclusion fragments and reaction layer. The inclusions in the composite form are distributed linearly, and the long axis is perpendicular to the compression direction. When the reaction layer coated outside the inclusion is stripped and the mullite inclusion is broken to form a new surface exposed to the superalloy matrix, the reaction continues to form a new reaction layer. The crushed mullite inclusion is still dominated by O, Al and Si, but it also contains a small amount of element in the superalloy such as Ni, Cr, Ti, Co and Mo.

High temperature oxidation behavior of DD406 SX superalloy film cooling holes with different laser drilling processes

YANG Yizhe, YANG Zhao, ZHAO Yunsong, PEI Haiqing, LI Meng, YANG Yanqiu, WEN Zhixun, YUE Zhufeng

2022, 42(2): 29-40.

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Abstract:
Turbine blades of long-life civil aircraft and gas turbines are affected by high temperature oxidation during service, which greatly reduces the surface strength under complex working conditions and significantly shortens the service life. Therefore, oxidation resistance is one of the most specific properties that must be considered in the application of turbine blades. The influence of the different drilling processes for cooling holes on the oxidation behavior of Ni-based SX (single-crystal) superalloy at 980℃ and 1100 ℃ was investigated. The difference in the oxidation mechanism of the cooling holes under different drilling processes provided a basis for the establishment of the blade life model under service conditions. The results indicate that the film cooling holes processed by millisecond laser exhibit poor oxidation performance, and all oxidation kinetic curves basically obey the parabolic or linear law. In the initial oxidation stage of the millisecond laser specimen, the oxidation reaction is primarily determined by the growth pattern of outer NiO. Subsequently, a three-layer oxide layer（(Ni, Co)O-Spinel phase layer-α-Al₂O₃） gradually formed around the hole. There are relatively micro-holes under the internal α-Al₂O₃ layer and the γ'-free zone, which makes the oxide layer easy to exfoliate. Discontinuous α-Al₂O₃ is rapidly formed in the initial oxidation stage of the picosecond laser specimen, and then connected to each other to form the dense α-Al₂O₃ layer.

Interlaminar fracture toughness of carbon/flax fiber hybrid composite

YUAN Weike, LI Yan, ZHAO Jian

2022, 42(2): 41-46.

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Abstract:
The application of carbon fiber reinforced composites (CFRP) was limited by their poor delamination resistance. However, the hierarchical microstructure of flax fibers could help to improve the interlaminar properties of the composite. Therefore, the interlaminar fracture toughness of CFRP composites can be improved by hybridized flax with carbon fibers. In this study, the carbon/flax fiber hybrid composites (CFFRP) were manufactured by moulding process. The mode Ⅰand mode Ⅱ interlaminar fracture toughnesses of CFFRP composites were studied by double cantilever beam (DCB) and end-notched flexure (ENF) tests, and were compared with those of CFRP composites. The results show that the Mode Ⅰinterlaminar fracture toughness of CFFRP composite is 1.29 kJ/m², which is about 3.5 times higher than that of CFRP composites (0.37 kJ/m²). The Mode Ⅱinterlaminar fracture toughness is 1.09 kJ/m² and is about 23.86% higher than that of CFRP composites (0.88 kJ/m²). The interlaminar fractured surfaces of CFRP and CFFRP composites are observed with the aid of scanning electron microscopy (SEM). From the microscopies of the fractured CFRP specimens it can be seen that pure delamination by the peeling of carbon fibers from epoxy resin is obtained for CFRP composites. The surfaces of carbon fibers were relatively clean and few epoxy resin fragments attached. The weak interfacial properties between carbon fiber and epoxy resin cause a lower G_Ⅰc for CFRP composites. On the contrary, from the observation of SEM photographs of flax fiber layers in the interlaminar fractured CFFRP composites, fiber breakage, fiber peeling and fiber entanglement are founded. On the fractured carbon fiber layer, there are some flax fibers tangling with carbon fibers. These multi-scale failure modes due to the unique microstructure of the flax fibers may make the crack propagation become difficult and thus lead to the G_Ⅰc and G_Ⅱc increased for CFFRP composites than those of CFRP composites.

Mechanical behavior and modification of poly-ether-ether-ketone using a molecular dynamics method

ZHANG Ke, YAO Chongyang, LI Dongyu, NIU Fei, WANG Bo, LI Tong

2022, 42(2): 47-56.

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Abstract:
The molecular dynamics method was employed to predict the tensile mechanical properties of polyether-ether-ketone (PEEK). Non-equilibrium tensile simulation with anisotropic pressure control was employed to obtain the stress-strain curve of PEEK, and to calculate the elastic modulus, yield strength and other mechanical properties. The influences of the strain rate and temperature on the mechanical properties, free volume, mean square radius of gyration (R_g), and energy for PEEK were investigated to explain the relationship between PEEK chain characteristics and macro mechanical properties. The results indicate that the elastic modulus and yield strength of PEEK significantly increase with the increase of strain rate, and significantly decrease with the increase of temperature. In the elastic and yield stage, free volume linearly increases, and R_g of PEEK chains remains steady, and the non-bonded energy results in the amount of the total potential energy increase. The interchain non-bonded interactions play a dominant role in the elastic and yield performance. Therefore, the amino modification strategy is investigated to improve the mechanical property of PEEK. It is found that the elastic modulus and yield strength of PEEK modified by amino are increased by 21% and 34% respectively than that of PEEK.

Effect of span-thickness ratio on bending properties of high-strength glass fiber reinforced composite unidirectional plate

BAI Xin, WANG Yunying, WANG Yana, CHEN Xinwen, HE Yuhuai

2022, 42(2): 57-63.

[Abstract](148) [FullText HTML] (104) [PDF 762KB](45)

Abstract:
Based on the three-point bending test, the bending performances of S6C10-800/AC318 composite unidirectional plates with different span-thickness ratios (hereinafter referred to as unidirectional plates) were tested, and the effect of span-thickness ratio on the bending strength and bending modulus of unidirectional plate was studied. The influence and fracture mode of the specimens with different span-thickness ratios were analyzed to obtain the bending failure mechanism, and the critical span-thickness ratio of three-point bending test of unidirectional plate was determined. The results show that the bending strength of the unidirectional plate increases with the increase of the span-thickness ratio, and the bending modulus first increases and then decreases with the increase of the span-thickness ratio. The fracture mode of the unidirectional plate changes when the span-thickness ratio α＝20, and the degree of delamination damage of unidirectional plate gradually decreases with the increase of span-thickness ratio, but the degree of splitting increases. When α≤20, the stress-strain curve conforms to the linear relationship with the increase of the span-thickness ratio, but when α＞20, the stress-strain curve does not conform to the linear relationship. Therefore, the predicting formula of bending strength of unidirectional plate under arbitrary span-thickness ratio and a failure criterion for three-point bending test of unidirectional plate are obtained. It is recommended that the critical span-thickness ratio of the three-point bending performance test of unidirectional plate is 20. This is of great significance for optimizing the three-point bending test method of glass fiber composite materials to more accurately test the bending performance of composite materials.

Static compression and compression-compression fatigue properties of plain woven composite laminates

ZHANG Tiechun, YANG Chenchen, WANG Xuan, ZHOU Chunping

2022, 42(2): 64-72.

[Abstract](164) [FullText HTML] (73) [PDF 1911KB](34)

Abstract:
The static compression and compression-compression fatigue tests of glass fiber plain woven composite laminates were carried out on an electro-hydraulic servo fatigue testing machine. The stress ratio was R=10, and the S-N curve was fitted. The fatigue damage evolution was characterized by stiffness degradation, energy dissipation, cyclic creep and cyclic softening during fatigue tests. The fracture morphology was observed by scanning electron microscope. The results show that the conditioned fatigue limit is 66.3% of the static compressive strength. The S-N curve fitted by the double-weighted least square method has high reliability. With the increase of the number of cycles, the stiffness of the test piece decreases gradually, and the energy dissipation under each peak load increases gradually. At the initial stage of cyclic loading, the test pieces exhibit strong cyclic creep phenomenon, and the test pieces under the peak load exhibit strong cyclic softening behavior. The resistance to deformation of the test piece is enhanced after cyclic loading. Four failure modes including matrix cracking, fiber/matrix interface debonding, fiber fracture and delamination are observed. Compared with fatigue fracture, the static compression fracture shows larger delamination damage.

Micromechanical FE analysis on thermal residual stress and shrinkage behavior of 2.5D woven C_f/Al composites

TONG De, CAI Changchun, WANG Zhenjun, LIU Yanwu, ZHANG Yihao, YU Huan, XU Zhifeng

2022, 42(2): 73-82.

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Abstract:
2.5D woven C_f/Al composites were fabricated by vacuum-assisted pressure infiltration method. Thermal shrinkage behavior and residual stress of the composites were investigated using micromechanical analysis and experimental method. The thermal expansion properties of yarn along longitudinal and transverse direction were evaluated by analytical method. Based on the yarn’s structural characteristic, the micromechanical finite element models of composites were established. The calculated macroscopic thermal strain-temperature curve from micromechanical simulation agrees well with the thermal shrinkage curve from the experiments. The simulation results indicate that the warp and weft yarns are in compressive stress state, and the residual stress on weft yarns are higher than that on the warp yarns. However, the matrix alloy is mainly in tensile stress state, and the maximum tensile stress occurs in the matrix alloy near warp yarn’s surface. The over high residual stress between the warp and weft yarns lead to local interface debonding. It is an important technical approach to reduce the residual stress in order to improve the mechanical properties of composites.

Effect of thermodynamic coupled simulation condition on microstructure and stress rupture properties of DZ406 alloy

JIA Xinyun, ZONG Cui, GUO Jing, CHEN Shengping, ZHENG Zhen, ZHAO Wenxia, HUANG Zhaohui

2022, 42(2): 83-90.

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Abstract:
There is a problem about microstructure evolution and properties degradation for the superalloy turbine blades in long term service conditions. DZ406 alloy samples were pre-loaded to simulate the high temperature service environment of turbine blades. The thermodynamic coupling simulation conditions were 980 ℃/70 MPa, 980 ℃/110 MPa, 980 ℃/140 MPa and 980 ℃/180 MPa respectively. And then the samples were subjected to stress rupture property test at 980 ℃/275 MPa. The microstructure and 980 ℃/275 MPa rupture life of the samples under different service loading conditions were observed and analyzed. The results show that the heat treatment microstructure of DZ406 alloy is composed of carbides, residual γ +γ´ eutectic and regular γ´ phase. The morphology and size of carbides and eutectic have no obvious change with the increase of loading stress under simulated service conditions. The γ´ phase of the sample parallel to [001] direction presents different degrees of rafting, and the size of γ´ phase perpendicular to [001] direction obviously increases. The residual stress rupture life of the sample declines rapidly with the increase of service stress.

Charge accumulation and dissipation characteristics of rGO / CNTs / EP composite coating

ZHAO Xin, XING Yilong, LI Meng, HUANG Chengchao, ZHAO Haodong, YANG Huarong

2022, 42(2): 91-98.

[Abstract](77) [FullText HTML] (20) [PDF 1019KB](15)

Abstract:
The process of charge accumulation and dissipation on the surface of rGO / CNTs / EP composite coating was analyzed theoretically, and the fitting analysis was carried out according to the experimental data. The rationality of the theoretical model and the factors affecting the charge dissipation were discussed. On this basis, three kinds of charge dynamic change models were adopted to fit the measured data analysis, revealed the fitting curve and charge accumulation and dissipation process parameters such as time constant, fitting coefficient, and compared with the theoretical change curve, verified the charge and time constant, the relationship between the changes of the rationality of the evaluation model with a coating of charge dissipation effect. The results show that: compared with the accumulation model, the complex model better reflects the change process of charge accumulation process. With the increase of rGO / CNTs content in the coating, the ratio of accumulation time constant to dissipation time constant increases, the peak value of accumulated charge decreases and the dissipation effect increases. The dissipation model is basically consistent with the actual trend of charge dissipation process. With the increase of rGO / CNTs content, the dissipation time constant decreases and the dissipation effect increases.

2022 Vol. 42, No. 2