• <tr id="yyy80"></tr>
  • <sup id="yyy80"></sup>
  • <tfoot id="yyy80"><noscript id="yyy80"></noscript></tfoot>
  • 99热精品在线国产_美女午夜性视频免费_国产精品国产高清国产av_av欧美777_自拍偷自拍亚洲精品老妇_亚洲熟女精品中文字幕_www日本黄色视频网_国产精品野战在线观看 ?

    Prediction of Compressive and Shear Moduli of X-cor Sandwich Structures for Aeronautic Engineering

    2015-03-21 05:09:15張向陽(yáng)李勇李俊斐范琳gang譚永剛肖軍
    關(guān)鍵詞:李勇李俊向陽(yáng)

    (張向陽(yáng)), (李勇), (李俊斐), n(范琳), gang(譚永剛), (肖軍)

    College of Material Science and Technology, Nanjing University of Aeronautics and Astronautics,Nanjing 210016, P.R. China (Received 18 November 2014; revised 2 April 2015; accepted 12 May 2015)

    Prediction of Compressive and Shear Moduli of X-cor Sandwich Structures for Aeronautic Engineering

    ZhangXiangyang(張向陽(yáng)),LiYong(李勇)*,LiJunfei(李俊斐),FanLin(范琳),TanYonggang(譚永剛),XiaoJun(肖軍)

    College of Material Science and Technology, Nanjing University of Aeronautics and Astronautics,Nanjing 210016, P.R. China (Received 18 November 2014; revised 2 April 2015; accepted 12 May 2015)

    The so-called ″X(qián)-cor sandwich structure″ is a highly promising novel material as an alternative to honeycomb used in aircraft. Although much work has been conducted on the performance of the X-cor sandwich structure, the gap is still hardly bridged between experimental results and theoretical analyses. Therefore, a method has been innovated to establish semi-empirical formula for the prediction of compressive and shear moduli of X-cor sandwich structure composites, by combining theoretical analyses and experimental data. In addition, a prediction software was first developed based on the proposed method, of which the accuracy was verified through confirmatory experiments. This software can offer a direct reference or guide for engineers in structural designing.

    X-cor sandwich structure; moduli prediction; compressive; shear

    0 Introduction

    Considering the increasing demand of light materials in aerospace industries, more attentions have been drawn to the research and development of sandwich structure composites. However, the de-bonding problem between the core and the panel directly limits their applications in the main load-bearing structural components in aircraft. Recently, a novel technology, called Z-pin, has been reported to significantly improve the through-thickness properties of composite laminates, making it possible for composites to be used in structural components[1]. Fig. 1 illustrates the X-cor sandwich structure made up of embedded fibrous composite rods (pin) and the traditional sandwich structure. As shown, the tips are stitched into the uncured prepreg skins. By means of co-curing effect, the pins are bonded to the foam core and the skins simultaneously to improve the delamination resistance between the skins and the form core. Sikorsky Aircraft demonstrated that X-cor sandwich structures exhibited equivalent mechanical performance to 48 kg/m3biased glass honeycomb core while saving nearly 10% weight[2]. It was also reported that X-cor sandwich structure material was a potential alternative to the traditional honeycomb material thanks to their high specific strength and modulus.

    Fig.1 Cross-section of X-cor sandwich structure

    Marasco et al.[3]and Partridge et al.[4]conducted specific experiments to explore the effects of the pin-insertion angle (the angle between the axle of pins and the tangential direction) on the out-of-plane tensile, compressive and shear properties of X-cor sandwich structure materials. The results showed that with increasing the insertion angle, the modulus and the strength of both tensile and compressive results increased correspondingly, with the decrease of shear modulus and strength. Meanwhile, Mouritz et al.[5]proved that, the out-of-plane compressive strength and modulus went up as the density of inserted pins ascended.

    Throughout reviews on X-cor sandwich structure materials, most of the work was accomplished by samples within specific parameters[6-10]. Meanwhile, most theoretical models built in literature have not been verified by large amount of tests. Considering the industrial applications, it is inconvenient to calculate the material constants by traditional theoretical models. Therefore, a common and convenient method is urgently in need. Aiming at this, the reinforcement of pins were homogenized over the whole volume of sandwich and the semi-empirical formula was built for prediction of X-cor sandwich structure properties by data fitting method. Then, the prediction software was developed to verify the practicability and versatility for the structural design of X-cor.

    1 Analysis Model

    The X-cor sandwich structure present outstanding improvement of the performance in through-thickness direction. In this section, the prediction of the out-of-plane compressive and shear modulus were presented, on account of the dispersion and complexity of the strength analysis. Two kinds of composites widely used in aircraft were discussed: CF/Epoxy with Rohacell?31IG form core, and CF/Bimaleimide (BMI) with Rohacell?51 WF foam core, to meet the demand of thermal property.

    1.1 Compressive model

    Fig.2 Single cell of the X-cor sandwich structure

    As the X-cor truss plays a significant role in the load-bearing, the quotient of foam core could be left out of consideration to simplify the model. As shown in Fig. 2, a single cell of X-cor structure was selected including two pins inserted at ±θ.

    Hao et al.[7]have regarded the pins as beam-column on Winkler elastic foundation and deduced the compressive strength and modulus. Given the pin′s axial compressive modulusEpinand the foam compressive modulusEf, the compressive modulus of the X-cor structureEXis presented as

    (1)

    whereθandVpinrepresent the pin insertion angle and the volume density of pins, respectively.

    Ref.[11] demonstrated that traditional equation cannot match the experimental results well with the structure buckling and with the pin′s length discreteness. The deduced formula was modified by the stiffness discount coefficientM1caused by the structure buckling andM2caused by the pin′s length discreteness as

    (2)

    The design parameters, primarily determining the compressive modulus, are the insertion angle and the volume fraction. Ref.[10] proved that the influence of pin′s diameter and insertion density on the modulus is equivalent to that of the volume fraction. Not only Eq. (1) but also the modified model (Eq.2) indicate that the compressive modulus is proportional to sin4θ, as well asVpin. Therefore, numerous experimental results (Appendix A) of compressive module are analyzed utilizing the linear regression model in Matlab. The semi-empirical equations are deduced as

    (3)

    whereEeXandEbXrepresent the compressive moduli of CF/Epoxy and CF/BMI X-cor sandwich structure. Since the fitting was based on the experimental data tested on specimens of particular materials, including T300/FW125 epoxy and T300/NHZP-1 BMI for Z-pins, the predictor formula specifically verifies the structures made from such materials, and shear module prediction is brought about.

    1.2 Shear model

    Several models have been proposed for the shear property calculation of X-cor structure by now. In Ref.[12], X-cor structure was considered as the space truss frame. Utilizing the equivalent inclusion method, the shear modulusGXof X-cor is calculated by

    (5)

    whereEsis the tensile modulus of the pin,Gethe equivalent shear modulus which can be developed by the equivalent mingle method expressed by a complex matrix.

    Shear stiffness is directly proportional to the volume rateVpin. If shear stiffness is evenly divided into each 1% volume rate pin,GXcan be concisely expressed as

    (6)

    wherekis the shear stiffness contribution of 1% volume rate pins, andG0the fitting constant. Referring to Eq. (5), it can be assumed thatkis a function of the insertion parameterγ,γ=sin2(2θ). Then the expression ofGXshould be

    (7)

    wherea,bandcare fitting constants. With the help of Matlab, the regressive fitting results of the shear modulus of Epoxy/CF and BMI/CF X-cor sandwich composite areGeXandGbX.

    (9)

    The assumption of Eq. (6) has attributed the whole structure stiffness to the pins′ insertion. Although non-considering stiffness of foam core can simplify the process, it leads to a divitation from the testing results, which will be discussed later. In addition,G0here is only a fitting constant without explicit physical meaning whose value and sign are meaningless.

    1.3 Boundary conditions

    The fitting equations derived above can predict the results precisely, only if the parameters are selected in proper range. Thereby, the boundary conditions for this prediction method as well as for the structure design discipline should be clear after all.

    (1) Insertion angle. Knowing that the pultruded pins are anisotropic materials whose axial stiffness is much better than that in the transverse direction, the pins embedded close to the vertical direction are prone to present better load-bearing property. As a result, the recommended design insertion angle of pins is 45°—90°.

    (2) Volume rate of pins. The linear relationship between the stiffness and the volume rate is valid in a specific range. The volume fractions of pins are calculated as a function of the insertion intervals at the longitudinal and the latitudinal directions, as well as the diameter depicted as

    (10)

    whereDis the diameter of Z-pin,xandyare the insertion intervals in the longitudinal and the latitudinal directions, respectively. Based on the inspection of experimental data, on one hand, pins of diameter smaller than 0.4 mm can barely penetrate the rigid PMI foam core. On the other hand, pins of large diameters (≥1 mm) can lead to over-damaged skins, resulting in the declination of structural performance. Moreover, if the number of pins is surplus, pins would function as the defects rather than reinforcement. That is to say, if the space between two adjacent pins are very small (≤3 mm), the foam core will collapse and can hardly support the X-cor truss.

    Summarily, the suitable pin insertion parameters should be set as insertion angle of 45°—90°, the diameter of 0.4—1 mm, and the insertion interval of 3—10 mm.

    2 Software Development

    2.1 Software programming

    On the basis of the compressive and shear stiffness calculation of Eqs. (3, 4, 8, 9), the prediction software was programmed by VB 6.0. The algorithm process is briefly shown in Fig.3. With data input and material selected, the system checks whether the parameters satisfy the boundary conditions. If the answer is no, a warning window will appear to inform the users what should be noticed and corrected. Otherwise, the stiffness will be calculated, according to the choice of compressive modulus or the shear modulus. The limitation of the work is that the program database contains only two kinds of materials.

    Fig.3 The algorithm of the prediction software

    The software provids a clear and simple platform for the X-cor sandwich structural designers, especially for those without expertise. It is not necessary to explore the calculating models of X-cor sandwich structure engineering constants.

    2.2 Prediction results

    The curved surface of the compressive and shear prediction results are shown in Figs. 4, 5, when the insertion angle ranges from 45° to 90° and the volume rate is in common scale. In spite of the differences between the specific values of the CF/Epoxy and the CF/BMI X-cor sandwich structure properties, the dependency of their moduli on insertion angle and volume rate remains similar.

    Fig.4 Prediction results of X-cor sandwich compressive module

    Fig.5 Prediction results of X-cor sandwich shear module

    From the above results, several rules indicated are consistent with the research findings: (1) Along with the increase of insertion angle, the compressive modulus increases and the shear modulus decreases. When the pins are inserted at 45°, the enhancement of the compressive property is not obvious. In other extreme conditions, the pins can hardly improve the shear property of X-cor sandwich when inserted in the angle of 90°. Then, the pins insertion angle should be designed based on the loading environment. (2) Within specific limits, both the compressive and the shear modulus are proportional to the pins volume rate, which agrees well with the mixture theory of the composite modulus, despite that the slope differs when the pin insertion angle changes. However, to some extent, pin insertion is harmful to the skin and the form core of sandwich structure, then pins of high density will lead to the collapse of the skin material and the foam core.

    3 Experiments and Results

    3.1 Experiments

    The compressive modulus was measured on the NEWSANS electronic universal testing machine, and the axial cross-head movement rate imposed on the specimen was set as 1 mm/min. Tests were designed referring to the standard test method GB 1453—87. The specimens for compression test were prepared in the size of 60 mm×60 mm×12.5 mm. The underlying half jig could adjust by itself to maintain the specimen horizontal by means of the semi-globular bottom, at a preload of about 200 N (Fig.6). As the load was ascending, a series of crackle sound could be heard. At last, the fractures in pins led to the overall failure of the specimen. During the experiments, the load-displacement curves were recorded so as to obtain the stress-stain relationship by taking the specimen dimension into consideration.

    The shear test of the X-cor sandwich structure was conducted on the NEWSANS electronic universal testing machine with the constant loading rate of 1 mm/min, according to the standard test method GB 1455—88. As shown in Fig.7, two metal jigs ensured that the shearing stress was spread uniformly on the specimen. An extensometer sensing the shearing deformation was attached onto the specimen as well. To be clarified, the specimens were prepared in the size of 120 mm×60 mm×12.5 mm.

    Regularly, the crack emergeds in the foam core at the very beginning. Nevertheless, the crack propagation was obstructed by pins later then. When the load ascended to the peak, the structure failed because of the pullout and rotation of pins.

    3.2 Results and verification

    The compressive/shear stress were calculated by means of dividing the load by the dimension of each specimen. And the strain data were recorded by the extensometer. Given the stress-strain curves by the experiments mentioned above, the compressive and shear moduli of the X-cor sandwich specimen could be calculated. The experimental results and their contrast to the predicted outcome are listed in Tables 1—2.

    Table 1 Experimental results of compressive moduli

    The experimental verification were conducted for both epoxy and BMI systems within a wide range of pin diameter and density. And most of the deviations of the predicted data were less than 10%. It is well known that the properties of X-cor largely depend on the manufacturing process. Influencing factors, such as pin angle offset, pin/skin bonding conditions and pin length fluctuations, lead to a large variation of the muduli. Thus the deviation of confirmatory experiments (Tables 1, 2) had larger range than that of original data (Tables A1, A2). Similarly, the prediction of X-cor structure based on epoxy, with more stable manufacturing maturity, showed lower deviation and higher accuracy, compared to those on BMI matrix.

    However, it is noticed that the predicted compressive modulus of T300/BMI X-cor was far more than the experimental results when the volume fraction was as high as 2.4%, which means the prediction was invalid at that point. The main reason lies in two aspects. One is the different failure mode. Densely inserted pins introduce serious damage to the foam core, which weakens the lateral support for pins under compression. In this case, the truss architecture of pins could destabilize as a whole and pins failed buckling rather than fracture. The other explanation comes from the length variation of pins. According to the theory of Shan[13], the contribution of pins to the compressive modulus is limited by statistical distribution of pin length. Acturally, only a certain amount of pins are active under compression even though a large amount are inserted. Thus, large density of pins is not recommended for compression load bearing X-cor structures.

    4 Conclusions

    In conclusion, the semi-empirical formulae for prediction of X-cor sandwich compressive and shear moduli are derived through the combination of experimental data and theoretical models. The data fitting method is innovatively employed for the mechanical properties prediction of X-cor structures based on the homogenization of pins.

    (1) The agreement between the predicted properties with the experimental results is demonstrated by confirmatory tests on X-cor sandwich structure with different insertion parameters. And the fitting method based on experiments is proved to be feasible for composite engineering constant prediction.

    (2) The two crucial parameters determining the X-cor sandwich structure performance are the pins insertion angle and the volume rate. Both the compressive and shear moduli ascend with the increase of the pins volume rate. However, with the increase of pin density, the prediction model becomes ineffective for compressive modulus. Moreover, the density higher than 1.5% is not recommended for X-cor under compression considering the reinforcement efficiency. On the other hand, as the pins being inserted closer to theZ-direction, the compressive modulus keeps rising, while the shear modulus decreases.

    (3) The prediction software provides a concise and visualized platform for structural designing. For curtain, its universality and practicability will greatly promote the X-cor structure′s engineering applications.

    Appendix A: The original data and fitting deviations

    Table A1 Raw data and deviations of compressive module fitting

    Table A2 Raw data and deviations of shear module fitting

    Acknowledgements

    This work was supported by the Aviation Science Fund of China(Nos.2015ZE52049,2015ZE521049).

    This research was based on the theoretical models built in the prior study. The authors are grateful to Hao Jijun, Du Long, etc.

    [1] Mouritz A P. Review of z-pinned composite laminates[J]. Composites Part A: Applied Science and Manufacturing, 2007,38(12):2383-2397.

    [2] Carstensen T, Cournoyer D, Kunkel E. X-CorTMadvanced sandwich core material[C]∥33rd International SAMPE Technical Conference. Seattle, WA, USA: Society for the Advancement of Material and Process, 2001:452-66.

    [3] Marasco A I, Cartie D R, Partridge I K, et al. Mechanical properties balance in novel Z-pinned sandwich panels: Out-of-plane properties[J]. Composites Part A, 2006,37(2):295-302.

    [4] Partridge I K, Cartie D R, Bonnington T. Manufacturing and performance of Z-pinned composite[M]. Boca Raton Florida, USA: CRC Press, 2003: 103-138.

    [5] Mouritz A P. Compression properties of Z-pinned sandwich composite[J]. Material Science, 2006,41(17):5771-5774.

    [6] Denis D C, Fleck N A. The effect of pin reinforcement upon the through-thickness compressive strength of foam-cored sandwich panels[J]. Composite Science Technology, 2003,63(16):2401-2409.

    [7] Hao J J, Zhang Z G, Li M, et al. Compression property analysis of X-cor sandwich composites[J]. Acta Aeronautica et Astronautica Sinica, 2008,29(4):1079-1083. (in Chinese)

    [8] Li Y, Xiao J, Tan Y G, et al. Study on compressive property of X-cor sandwich structure[J]. Acta Aeronautica et Astronautica Sinica, 2009,30(3):557-561. (in Chinese)

    [9] Dang X D, Zhang H S, Wang X L, et al. Experimental study on mechanical properties of X-cor sandwich[J]. Material Review, 2011,25(5):54-58. (in Chinese)

    [10]Dang X D, Tan Y G, Xiao J, et al. Finite element modeling analysis of compressive modulus about X-cor sandwich[J]. Journal of Materials Engineering, 2009(1):50-54. (in Chinese)

    [11]Shan H Y, Xiao J, Shang W, et al. Experiment and analysis on compressive modulus of X-Cor sandwich[J]. Journal of Aerospace Power, 2012,27(4):782-788. (in Chinese)

    [12]Du L, Jiao G Q, Huang T, et al. Shear property of X-Z-pinned reinforced foam core sandwich[J]. Acta Materiae Compositae Sinica, 2007,24(6):140-146. (in Chinese)

    [13]Shan H Y, Xiao J, Li N, et al. Compressive properties of X-cor Sandwich[J]. Journal of Nanjing University of Aeronautics and Astronautics, 2012,44(2):251-256. (in Chinese)

    (Executive editor: Zhang Bei)

    TB332 Document code:A Article ID:1005-1120(2015)06-0646-08

    *Corresponding author: Li Yong, Professor, E-mail: lyong@nuaa.edu.cn.

    How to cite this article: Zhang Xiangyang, Li Yong, Li Junfei, et al. Prediction of compressive and shear moduli of X-cor sandwich structures for aeronautic engineering[J]. Trans. Nanjing U. Aero. Astro., 2015,32(6):646-653. http://dx.doi.org/10.16356/j.1005-1120.2015.06.646

    猜你喜歡
    李勇李俊向陽(yáng)
    小天使·一年級(jí)語(yǔ)數(shù)英綜合(2021年11期)2021-11-23 02:48:57
    新年話(huà)“?!?/a>
    組圖:豐收中國(guó)
    吹畫(huà)
    字海拾“貝”
    李勇作品選
    齊魯藝苑(2019年5期)2019-11-09 02:57:58
    李俊彥
    A Brief Analysis On How To Improve Students’ Participation Enthusiasm In Classroom
    Sunny Side Up 向陽(yáng)而生
    紅向陽(yáng)
    亚洲中文日韩欧美视频| 黄片小视频在线播放| 亚洲第一av免费看| 麻豆乱淫一区二区| xxx96com| а√天堂www在线а√下载 | 国产区一区二久久| 午夜老司机福利片| 国产av又大| 超色免费av| 亚洲五月天丁香| 日本黄色日本黄色录像| 两个人免费观看高清视频| 日韩成人在线观看一区二区三区| 欧美 日韩 精品 国产| 国产亚洲一区二区精品| 在线观看66精品国产| 老司机亚洲免费影院| 色播在线永久视频| 国产激情欧美一区二区| 午夜成年电影在线免费观看| 国产熟女午夜一区二区三区| 日韩视频一区二区在线观看| 免费黄频网站在线观看国产| 欧美日韩av久久| 久久久久久久久免费视频了| 男人操女人黄网站| 女人久久www免费人成看片| 国产欧美日韩一区二区三区在线| 成人永久免费在线观看视频| 搡老乐熟女国产| 自拍欧美九色日韩亚洲蝌蚪91| 精品熟女少妇八av免费久了| 高清毛片免费观看视频网站 | 精品一区二区三卡| 国产在线一区二区三区精| a级毛片黄视频| 国产精品一区二区在线不卡| 成人国语在线视频| 国产精品九九99| 亚洲第一欧美日韩一区二区三区| av中文乱码字幕在线| 久热爱精品视频在线9| 自线自在国产av| 国产精品久久久人人做人人爽| 久热这里只有精品99| 亚洲av日韩精品久久久久久密| 国产亚洲精品第一综合不卡| 老司机靠b影院| 国产精品一区二区精品视频观看| 老熟女久久久| 色老头精品视频在线观看| 免费在线观看视频国产中文字幕亚洲| 亚洲欧美日韩高清在线视频| 首页视频小说图片口味搜索| 首页视频小说图片口味搜索| 夜夜夜夜夜久久久久| 99在线人妻在线中文字幕 | 侵犯人妻中文字幕一二三四区| 亚洲中文日韩欧美视频| 久久久久精品国产欧美久久久| 免费不卡黄色视频| 91国产中文字幕| 久久久久久久精品吃奶| 五月开心婷婷网| av视频免费观看在线观看| 久久人人97超碰香蕉20202| 久久国产精品影院| 欧美人与性动交α欧美软件| 亚洲 欧美一区二区三区| www.熟女人妻精品国产| 两人在一起打扑克的视频| 欧美精品一区二区免费开放| 99国产精品一区二区蜜桃av | 黄色a级毛片大全视频| 法律面前人人平等表现在哪些方面| 精品久久久久久电影网| 十八禁人妻一区二区| 天堂中文最新版在线下载| 人人妻人人澡人人看| 高清毛片免费观看视频网站 | 午夜福利乱码中文字幕| 丝瓜视频免费看黄片| 午夜两性在线视频| 妹子高潮喷水视频| 国内久久婷婷六月综合欲色啪| 日韩熟女老妇一区二区性免费视频| 亚洲精品美女久久av网站| 狠狠狠狠99中文字幕| 夜夜夜夜夜久久久久| 高潮久久久久久久久久久不卡| 下体分泌物呈黄色| 国产精品免费视频内射| 欧美成人午夜精品| 国产精品98久久久久久宅男小说| 亚洲av电影在线进入| av一本久久久久| 国产在线观看jvid| 国产主播在线观看一区二区| 国产精品亚洲一级av第二区| 欧美人与性动交α欧美软件| 午夜91福利影院| 久久这里只有精品19| 亚洲五月天丁香| 91国产中文字幕| 女性生殖器流出的白浆| 涩涩av久久男人的天堂| 午夜福利欧美成人| 男女午夜视频在线观看| 亚洲精品在线美女| 欧美乱码精品一区二区三区| 中文字幕精品免费在线观看视频| 50天的宝宝边吃奶边哭怎么回事| 久久 成人 亚洲| 窝窝影院91人妻| 黄色毛片三级朝国网站| 黄色怎么调成土黄色| 国产成人精品久久二区二区免费| 午夜91福利影院| 丁香六月欧美| 亚洲欧洲精品一区二区精品久久久| 亚洲国产中文字幕在线视频| 国产片内射在线| 色婷婷av一区二区三区视频| 老司机午夜福利在线观看视频| 熟女少妇亚洲综合色aaa.| 制服人妻中文乱码| 久久久久久免费高清国产稀缺| 欧美亚洲日本最大视频资源| 精品久久久久久久久久免费视频 | 人成视频在线观看免费观看| 午夜免费观看网址| 老司机靠b影院| 自线自在国产av| 少妇被粗大的猛进出69影院| 男女床上黄色一级片免费看| av视频免费观看在线观看| 五月开心婷婷网| 午夜福利在线观看吧| 亚洲一区高清亚洲精品| 日日摸夜夜添夜夜添小说| 变态另类成人亚洲欧美熟女 | 成人精品一区二区免费| 欧美性长视频在线观看| 12—13女人毛片做爰片一| 国产无遮挡羞羞视频在线观看| av天堂在线播放| 亚洲片人在线观看| 18禁观看日本| 国产成人精品久久二区二区免费| 欧美日韩亚洲国产一区二区在线观看 | 天堂√8在线中文| 亚洲av日韩在线播放| 老司机午夜十八禁免费视频| 国产成人av激情在线播放| 午夜两性在线视频| 久久中文看片网| 男女下面插进去视频免费观看| 日韩一卡2卡3卡4卡2021年| 淫妇啪啪啪对白视频| 日本黄色视频三级网站网址 | 精品第一国产精品| 国产无遮挡羞羞视频在线观看| 99re6热这里在线精品视频| 91国产中文字幕| 国产精品欧美亚洲77777| 99久久99久久久精品蜜桃| 成人av一区二区三区在线看| 捣出白浆h1v1| 麻豆国产av国片精品| 人人澡人人妻人| 真人做人爱边吃奶动态| a级毛片黄视频| 色在线成人网| 亚洲性夜色夜夜综合| 国产成人精品久久二区二区91| 99热国产这里只有精品6| 欧美久久黑人一区二区| 日日爽夜夜爽网站| 飞空精品影院首页| 免费在线观看完整版高清| 亚洲五月婷婷丁香| 国产激情久久老熟女| 久久 成人 亚洲| 999精品在线视频| 国产欧美日韩一区二区三| 久久精品人人爽人人爽视色| 又大又爽又粗| 久久久久国内视频| 欧美成人免费av一区二区三区 | 亚洲欧美激情综合另类| 欧美日韩视频精品一区| 麻豆av在线久日| 久久久久久久午夜电影 | 亚洲精品国产精品久久久不卡| 国产精品国产av在线观看| 好男人电影高清在线观看| 国产精品免费视频内射| 免费在线观看视频国产中文字幕亚洲| 成人精品一区二区免费| 两个人看的免费小视频| 国产精品 欧美亚洲| 校园春色视频在线观看| 成人永久免费在线观看视频| 国产一区有黄有色的免费视频| 国产一区二区三区在线臀色熟女 | 久久精品91无色码中文字幕| 日本vs欧美在线观看视频| 看免费av毛片| 国产免费男女视频| 黄色毛片三级朝国网站| xxxhd国产人妻xxx| 黄色丝袜av网址大全| 久久久国产一区二区| 操美女的视频在线观看| 亚洲欧美日韩高清在线视频| 最近最新中文字幕大全电影3 | 18在线观看网站| 欧美精品人与动牲交sv欧美| 久久精品人人爽人人爽视色| 国产欧美亚洲国产| 亚洲av成人av| 久久中文字幕一级| 麻豆国产av国片精品| 亚洲在线自拍视频| 激情视频va一区二区三区| 亚洲欧美激情在线| 亚洲国产欧美日韩在线播放| 亚洲片人在线观看| 日韩欧美免费精品| 日韩有码中文字幕| 夫妻午夜视频| 久久国产精品影院| 欧美av亚洲av综合av国产av| 精品国产一区二区三区四区第35| 在线看a的网站| 欧洲精品卡2卡3卡4卡5卡区| 九色亚洲精品在线播放| 国产av一区二区精品久久| а√天堂www在线а√下载 | 一a级毛片在线观看| 1024视频免费在线观看| xxx96com| 每晚都被弄得嗷嗷叫到高潮| 日韩三级视频一区二区三区| 精品一区二区三区四区五区乱码| 又黄又粗又硬又大视频| 美女视频免费永久观看网站| 亚洲,欧美精品.| 男人的好看免费观看在线视频 | 丰满的人妻完整版| 又大又爽又粗| 国产高清国产精品国产三级| 在线观看66精品国产| av视频免费观看在线观看| 麻豆av在线久日| 亚洲欧洲精品一区二区精品久久久| 国产一区二区三区视频了| 国产男女超爽视频在线观看| 人人澡人人妻人| 国产一区有黄有色的免费视频| 国产av又大| 欧美 亚洲 国产 日韩一| 日韩欧美三级三区| 午夜久久久在线观看| 久久人人97超碰香蕉20202| 1024视频免费在线观看| 免费在线观看视频国产中文字幕亚洲| 90打野战视频偷拍视频| 久久青草综合色| 精品视频人人做人人爽| 欧美丝袜亚洲另类 | 免费观看人在逋| 人妻丰满熟妇av一区二区三区 | 日韩欧美免费精品| 欧美中文综合在线视频| 国产视频一区二区在线看| 他把我摸到了高潮在线观看| 波多野结衣一区麻豆| 国产精品永久免费网站| 午夜两性在线视频| 欧美激情极品国产一区二区三区| 久久香蕉激情| 怎么达到女性高潮| 国产精品综合久久久久久久免费 | 99香蕉大伊视频| www日本在线高清视频| 女性生殖器流出的白浆| 久久草成人影院| 亚洲五月色婷婷综合| 成人国产一区最新在线观看| 国产三级黄色录像| 黄色视频,在线免费观看| 亚洲人成电影免费在线| 黑人欧美特级aaaaaa片| 精品高清国产在线一区| 欧美乱色亚洲激情| 变态另类成人亚洲欧美熟女 | 亚洲欧洲精品一区二区精品久久久| 久久久久久免费高清国产稀缺| 国产精品自产拍在线观看55亚洲 | 丰满的人妻完整版| 国产欧美日韩综合在线一区二区| 欧美性长视频在线观看| 一本一本久久a久久精品综合妖精| 精品一区二区三区四区五区乱码| 美女国产高潮福利片在线看| 男女床上黄色一级片免费看| e午夜精品久久久久久久| 精品少妇久久久久久888优播| 日韩免费高清中文字幕av| 欧美不卡视频在线免费观看 | 国产欧美日韩一区二区精品| 精品熟女少妇八av免费久了| 国产单亲对白刺激| 亚洲第一欧美日韩一区二区三区| 欧美另类亚洲清纯唯美| 欧洲精品卡2卡3卡4卡5卡区| 丰满饥渴人妻一区二区三| 国产有黄有色有爽视频| 久久热在线av| 下体分泌物呈黄色| 精品国产一区二区三区四区第35| 亚洲一区二区三区欧美精品| 国产成人啪精品午夜网站| 国产精品98久久久久久宅男小说| 久久狼人影院| 日韩大码丰满熟妇| 国产人伦9x9x在线观看| 亚洲午夜精品一区,二区,三区| 国产主播在线观看一区二区| 岛国毛片在线播放| 亚洲av欧美aⅴ国产| 欧美人与性动交α欧美精品济南到| 亚洲第一欧美日韩一区二区三区| 日日夜夜操网爽| 精品电影一区二区在线| 国产精品.久久久| av片东京热男人的天堂| 一级a爱视频在线免费观看| 久久这里只有精品19| 国产在视频线精品| 黄片小视频在线播放| 欧美黄色淫秽网站| 亚洲欧美日韩另类电影网站| 久久久国产精品麻豆| 黄色丝袜av网址大全| av中文乱码字幕在线| 久久精品亚洲av国产电影网| 国产成人免费观看mmmm| av天堂久久9| 欧美乱色亚洲激情| 三上悠亚av全集在线观看| 深夜精品福利| 久久久久久久久久久久大奶| 国产国语露脸激情在线看| 午夜成年电影在线免费观看| 一级毛片精品| 欧美精品亚洲一区二区| 99国产精品免费福利视频| 夜夜爽天天搞| 色婷婷av一区二区三区视频| 久久久久久久久免费视频了| 国产免费男女视频| 国产一区有黄有色的免费视频| 在线观看免费日韩欧美大片| 下体分泌物呈黄色| 国产精品一区二区在线观看99| 搡老乐熟女国产| 搡老岳熟女国产| 操出白浆在线播放| 久久精品亚洲熟妇少妇任你| 精品乱码久久久久久99久播| e午夜精品久久久久久久| 欧美精品亚洲一区二区| 人人妻人人爽人人添夜夜欢视频| 国产成人欧美在线观看 | 国产三级黄色录像| 免费看十八禁软件| 国产精品一区二区免费欧美| 亚洲专区中文字幕在线| 久久天堂一区二区三区四区| 久久精品成人免费网站| 自拍欧美九色日韩亚洲蝌蚪91| 久久 成人 亚洲| 黑人巨大精品欧美一区二区蜜桃| 天堂动漫精品| 99riav亚洲国产免费| 制服人妻中文乱码| 水蜜桃什么品种好| videos熟女内射| videosex国产| 免费观看a级毛片全部| av一本久久久久| 少妇 在线观看| 国产精品香港三级国产av潘金莲| 亚洲av美国av| 99国产精品一区二区蜜桃av | 身体一侧抽搐| 一本一本久久a久久精品综合妖精| 老司机福利观看| 亚洲欧美色中文字幕在线| 精品一区二区三区四区五区乱码| 悠悠久久av| 中国美女看黄片| 国产精品国产高清国产av | 国产精品一区二区在线不卡| 精品久久久久久,| 69精品国产乱码久久久| 欧美精品啪啪一区二区三区| 十八禁网站免费在线| 婷婷丁香在线五月| 麻豆成人av在线观看| 99精品欧美一区二区三区四区| 三级毛片av免费| 国精品久久久久久国模美| 国产成人欧美| 十八禁网站免费在线| 国产熟女午夜一区二区三区| 50天的宝宝边吃奶边哭怎么回事| 午夜精品国产一区二区电影| 国产精品自产拍在线观看55亚洲 | 99久久人妻综合| 国产av精品麻豆| 亚洲一区高清亚洲精品| 伊人久久大香线蕉亚洲五| 欧美精品一区二区免费开放| 久久国产精品影院| 亚洲一码二码三码区别大吗| 国产成+人综合+亚洲专区| 视频区欧美日本亚洲| 99热网站在线观看| 欧美乱码精品一区二区三区| 久久久久久久久免费视频了| 亚洲精品在线观看二区| 视频在线观看一区二区三区| 精品久久久精品久久久| 国产欧美亚洲国产| 制服人妻中文乱码| 新久久久久国产一级毛片| 男人的好看免费观看在线视频 | 大香蕉久久网| 精品久久久久久电影网| 欧美国产精品va在线观看不卡| 亚洲片人在线观看| 中文欧美无线码| 真人做人爱边吃奶动态| 日韩欧美一区视频在线观看| 色综合欧美亚洲国产小说| 免费黄频网站在线观看国产| 极品人妻少妇av视频| 精品电影一区二区在线| 69精品国产乱码久久久| 国产无遮挡羞羞视频在线观看| 这个男人来自地球电影免费观看| a级毛片黄视频| 久久99一区二区三区| 不卡av一区二区三区| 极品教师在线免费播放| 91大片在线观看| 久久久久久久国产电影| 成在线人永久免费视频| 色综合欧美亚洲国产小说| 精品少妇一区二区三区视频日本电影| 十八禁网站免费在线| 国产区一区二久久| 中文字幕精品免费在线观看视频| 国产真人三级小视频在线观看| 欧美亚洲 丝袜 人妻 在线| 久久国产亚洲av麻豆专区| 他把我摸到了高潮在线观看| bbb黄色大片| 国产精品国产高清国产av | 国产99久久九九免费精品| 亚洲视频免费观看视频| xxx96com| 高清视频免费观看一区二区| 亚洲精品久久午夜乱码| 精品人妻熟女毛片av久久网站| 黑人欧美特级aaaaaa片| 亚洲片人在线观看| 首页视频小说图片口味搜索| 黑人巨大精品欧美一区二区蜜桃| 麻豆国产av国片精品| 亚洲专区国产一区二区| 高清黄色对白视频在线免费看| 欧美精品啪啪一区二区三区| 狠狠狠狠99中文字幕| 国产亚洲精品一区二区www | 中文字幕精品免费在线观看视频| 中文字幕人妻丝袜制服| 成人永久免费在线观看视频| 黄频高清免费视频| 中文字幕精品免费在线观看视频| 老司机影院毛片| 欧美乱码精品一区二区三区| 啦啦啦 在线观看视频| 最近最新中文字幕大全电影3 | 在线十欧美十亚洲十日本专区| 亚洲av成人av| 美女扒开内裤让男人捅视频| 日韩制服丝袜自拍偷拍| 一级,二级,三级黄色视频| 91在线观看av| 丝袜美腿诱惑在线| 亚洲色图综合在线观看| 在线观看免费视频网站a站| 成人三级做爰电影| 一a级毛片在线观看| 欧美国产精品一级二级三级| 午夜福利一区二区在线看| 在线播放国产精品三级| 亚洲精品一二三| 夜夜躁狠狠躁天天躁| 亚洲熟妇中文字幕五十中出 | 成年人午夜在线观看视频| 人成视频在线观看免费观看| 国产精品免费视频内射| 狠狠婷婷综合久久久久久88av| 一本综合久久免费| 亚洲久久久国产精品| www.精华液| tube8黄色片| 国产精品秋霞免费鲁丝片| 亚洲三区欧美一区| 交换朋友夫妻互换小说| 757午夜福利合集在线观看| 久久天躁狠狠躁夜夜2o2o| 久热爱精品视频在线9| 丝袜人妻中文字幕| 亚洲三区欧美一区| 69精品国产乱码久久久| 男人舔女人的私密视频| e午夜精品久久久久久久| 婷婷精品国产亚洲av在线 | 韩国精品一区二区三区| 免费在线观看亚洲国产| 涩涩av久久男人的天堂| 色综合欧美亚洲国产小说| 日韩欧美一区视频在线观看| 丰满迷人的少妇在线观看| 中文字幕人妻丝袜一区二区| 高潮久久久久久久久久久不卡| 国产又色又爽无遮挡免费看| 99久久精品国产亚洲精品| 久久久久久久国产电影| 久久九九热精品免费| 欧美日韩av久久| 狠狠婷婷综合久久久久久88av| 在线国产一区二区在线| 岛国毛片在线播放| 久久青草综合色| 在线免费观看的www视频| 国产成人啪精品午夜网站| 亚洲片人在线观看| 亚洲综合色网址| 波多野结衣av一区二区av| 成年女人毛片免费观看观看9 | 成年人黄色毛片网站| 国产欧美日韩一区二区三区在线| av片东京热男人的天堂| 日韩 欧美 亚洲 中文字幕| 丰满迷人的少妇在线观看| 99国产精品免费福利视频| 精品第一国产精品| 久久久水蜜桃国产精品网| 丝袜美足系列| 18禁美女被吸乳视频| 下体分泌物呈黄色| 男女之事视频高清在线观看| 国产精品国产高清国产av | 老司机深夜福利视频在线观看| 亚洲性夜色夜夜综合| 亚洲av片天天在线观看| 精品国产一区二区三区久久久樱花| 看黄色毛片网站| 成人免费观看视频高清| 日日爽夜夜爽网站| 国产三级黄色录像| 美女福利国产在线| 国产一区二区激情短视频| 久久国产亚洲av麻豆专区| 亚洲av日韩精品久久久久久密| 久久 成人 亚洲| 国产精品.久久久| 热re99久久国产66热| 国产有黄有色有爽视频| 国产精品一区二区精品视频观看| 香蕉国产在线看| 新久久久久国产一级毛片| 欧洲精品卡2卡3卡4卡5卡区| 欧美黑人欧美精品刺激| 中文字幕高清在线视频| 欧美在线一区亚洲| 久久婷婷成人综合色麻豆| 免费不卡黄色视频| 亚洲欧美色中文字幕在线| 日韩欧美在线二视频 | 亚洲第一欧美日韩一区二区三区| 精品国产一区二区三区四区第35| 美女扒开内裤让男人捅视频| 国产免费av片在线观看野外av| 久久午夜综合久久蜜桃| 免费在线观看完整版高清| 看免费av毛片| videosex国产| 国产免费男女视频| 精品福利永久在线观看| 国产亚洲精品久久久久久毛片 | 成人精品一区二区免费| 免费在线观看完整版高清| 午夜久久久在线观看| 午夜影院日韩av| 精品国产一区二区久久| 身体一侧抽搐|