轻质复合材料新型点阵结构设计及其力学行为研究

发布时间：2018-06-02 07:33

  本文选题：轻质结构 + 点阵结构　； 参考：《哈尔滨工业大学》2013年博士论文

【摘要】：为了实现飞行器减轻重量、增加有效载荷的目的,发展先进轻质复合材料结构,实现结构轻量化和多功能化是迫切需要解决的科学问题。碳纤维复合材料格栅结构和点阵结构兼备轻量化和多功能化特点,是当前国际学术界公认的最有前景的新一代超轻质高强结构之一。在本论文中,我们开展了碳纤维复合材料三维格栅结构、碳纤维复合材料金字塔点阵结构、碳纤维复合材料增强型点阵结构、轻质金字塔点阵曲面壳与圆柱壳的设计、制备及力学性能的研究工作。在绪论中回顾和评述了轻质复合材料格栅结构、复合材料点阵结构、轻质夹层曲面壳及圆柱壳力学行为的国内外研究现状,从中提炼出本课题需要解决的关键问题。设计并制备出芯子空间贯通的碳纤维复合材料三维格栅结构,推导了蛋壳型和金字塔型格栅结构在平压、侧压及三点弯曲载荷下的力学性能理论预报公式。考虑到复合材料铺层和芯子拓扑构型可变的特点,绘制出蛋壳型和金字塔型格栅结构在侧压和三点弯曲载荷下的失效机制图。开展了三种不同相对密度试验件的平压试验,得到蛋壳型和金字塔型格栅结构平压模量、平压强度及准静态吸能特性。依据侧压失效机制图,设计了六组典型的侧压试件,观察到了面板起皱、格栅间局部屈曲、面板压溃、剪切型欧拉屈曲、芯子压溃等失效模式。针对三点弯曲失效机制图,设计了四组典型的三点弯曲试验件,观察到面板起皱和面芯脱胶失效模式。面板起皱不能导致弯曲承载能力的急剧下降,但是会诱使面芯脱胶模式提前出现,面芯脱胶是结构主导的弯曲失效模式。设计了具有自主知识产权的组装模具,采用模具热压工艺制备出碳纤维复合材料金字塔点阵结构,使得所有纤维均沿着杆件受载方向,充分发挥杆件中纤维增强的潜力。用扫描电镜观察了杆件典型截面的微观组织结构。开展了三组不同相对密度的平压试验,观察到杆件欧拉屈曲、杆件断裂、杆件分层及面芯脱胶失效模式,并与平压理论预报结果进行比较,发现本文制备的金字塔点阵结构在低密度条件下具有优越的平压比强度。开展了四组不同相对密度的剪切试验,观察到杆件欧拉屈曲、杆件分层及面芯脱胶现象。推导出金字塔点阵结构在侧压载荷下极值的理论预报公式,考虑到面板铺层及芯子密度可变性设计三组典型的侧压试验件,观察到面板起皱、面板压溃及剪切型欧拉屈曲失效模式。推导出金字塔点阵结构在三点弯曲载荷下中心点挠度和极值的理论预报公式,考虑了面板压溃、面板起皱、芯子屈曲、芯子压溃及面芯脱胶可能的失效模式。针对不同铺层的面板及不同相对密度的芯子,绘制了三点弯曲载荷下金字塔点阵结构的失效机制图,并设计了八组典型的试验件验证理论模型及失效机制图的准确性。研究了双层碳纤维复合材料金字塔点阵结构在准静态平压载荷下的力学性能及吸能特性,通过对不同相对密度双层金字塔点阵结构的低速冲击试验揭示其能量吸收机理。针对碳纤维复合材料点阵结构面芯界面性能较弱的瓶颈问题,采用电火花和激光切割工艺制备出碳纤维复合材料增强型点阵结构。研究了激光切割工艺所制备的复合材料直柱和斜柱增强型点阵结构在平压及剪切载荷下的力学性能和失效机理,推导出预报直柱和斜柱增强型点阵结构平压模量、平压强度、剪切模量及剪切强度的理论公式,并对结构尺寸与比强度和比模量之间的内在联系进行深入分析。试验及理论结果发现增强型点阵结构可以明显提高点阵结构剪切性能的瓶颈值。设计并制备出轻质复合材料金字塔点阵曲面壳及圆柱壳。其纵环筋采用7075铝合金线切割批量成型,金字塔芯子通过环筋和纵筋嵌锁而成,而曲面壳和圆柱壳的面板均为碳纤维复合材料。对两种不同厚度面板的金字塔点阵曲面壳,观察结构的失效模式,发现了曲面壳独特的M型失效模式。给出了预报曲面壳弯曲性能的理论公式,并用有限元方法对不同面板厚度的曲面壳进行数值模拟。考虑到圆柱壳可能的轴压失效模式,推导出相应的理论预报公式,并绘制了不同角度铺层面板的金字塔点阵圆柱壳在轴压载荷下失效机制图。设计了三组典型的圆柱壳轴压试验并得到点阵圆柱壳的极限承载能力及应变值,同时观察到筋格间面板局部屈曲和面板压溃失效模式。
[Abstract]:In order to reduce the weight of the aircraft and increase the payload, the development of the structure of advanced lightweight composite materials and the realization of the lightweight and multi-function structure are the urgent needs to be solved. The structure of the grid and the lattice structure of carbon fiber composite materials is the most widely recognized in the current international academic circle. In this paper, we have carried out the three-dimensional grid structure of carbon fiber composites, the Pyramid lattice structure of carbon fiber composites, the reinforced lattice structure of carbon fiber composite materials, the design, preparation and mechanical properties of the light matrix camber shell and cylindrical shell in Pyramid, and the introduction of the mechanical properties. This paper reviews and reviews the domestic and foreign research status of light composite grid structure, composite lattice structure, light sandwich surface shell and cylindrical shell, and extracts the key problems to be solved in this topic. The theoretical prediction formula for the mechanical properties of the Pyramid type grid structure under flat pressure, lateral pressure and three point bending load. Taking into account the variable structure of the composite layer and core topology, the failure mechanism diagram of the shell and Pyramid grid structures under side pressure and three point bending load is drawn. Three different relative density tests have been carried out. The flat pressure modulus, flat pressure strength and quasi static energy absorption characteristics of the shell type and Pyramid type grid structure are obtained. According to the failure mechanism diagram of the side pressure, six groups of typical side pressure specimens are designed. The failure modes, such as panel wrinkling, local buckling between grille, panel crushing, shear type Euler buckling and core crushing, are observed. Three points are also observed. Four typical three point bending tests are designed for the bending failure mechanism diagram. The failure mode of the panel wrinkling and the surface core degumming is observed. The panel wrinkling can not lead to a sharp decline in the bending bearing capacity, but it will induce the appearance of the surface core degumming mode in advance, and the surface core degumming is the bending failure mode of the main guide of the structure. The independent knowledge is designed. The structure of the carbon fiber composite material Pyramid lattice structure was prepared by hot pressing of the mould. All the fibers were loaded along the load direction of the rod, and the potential of fiber reinforced in the rod was fully played. The microstructure of the typical section of the rod was observed by scanning electron microscope. Three groups of different relative density tests were carried out. The failure modes of Euler buckling, rod fracture, member delamination and surface core degumming are observed, and compared with the prediction results of flat pressure theory, it is found that the Pyramid lattice structure has superior compressive strength under low density. The shear test of four groups of different phase density is carried out, and the rod Euler buckling is observed and the rod is observed. A theoretical prediction formula for the extreme value of Pyramid lattice structure under lateral pressure is derived. Considering the three typical side pressure test parts of the panel and core density variability, the failure modes of panel wrinkling, panel crushing and shear type Euler buckling are observed. The structure of Pyramid lattice is deduced at three points. The theoretical prediction formula for the deflection and the extreme value of the center point under the bending load, considering the failure mode of panel crushing, panel wrinkling, core buckling, core crushing and core degumming. The failure mechanism diagram of the Pyramid lattice structure under three point bending loads is drawn for different layers and different relative density cores, and the design of the failure mechanism of the lattice structure is drawn. The accuracy of the theoretical model and failure mechanism diagram of the eight groups of typical test parts. The mechanical properties and energy absorption characteristics of the double carbon fiber composite Pyramid lattice structure under quasi static flat pressure are studied. The energy absorption mechanism is revealed by the low velocity impact test on the double layer lattice structure with different relative density in Pyramid. An enhanced lattice structure of carbon fiber composites was fabricated by electric spark and laser cutting. The mechanical properties and failure of the composite direct and oblique column reinforced lattice structures prepared by laser cutting were studied under the flat and shear loads. The theoretical formulas for predicting the modulus of pressure, the compressive strength, the shear modulus and the shear strength of the reinforced lattice structure of the straight column and the inclined column are deduced, and the internal relation between the structure size and the specific strength and the specific modulus is deeply analyzed. The experimental and theoretical results show that the reinforced lattice structure can obviously improve the shear property of the lattice structure. A lightweight composite Pyramid lattice shell and cylindrical shell is designed and prepared. The longitudinal ring is made by 7075 aluminum alloy wire cutting, and the core of Pyramid is locked through the ring and longitudinal bars. The surface of the curved shell and the cylindrical shell are both carbon fiber composites. The Pyramid dot matrix of two different thickness panels is made. The failure mode of the structure is observed and the unique M type failure mode of the curved shell is found. The theoretical formula for predicting the bending property of the curved shell is given. The finite element method is used to simulate the curved shell of different panel thickness. The corresponding theoretical prediction formula is derived considering the possible axial pressure failure mode of the cylindrical shell, and the corresponding theoretical prediction formula is derived, and the drawing is drawn. The failure mechanism diagram of the Pyramid lattice cylindrical shell with different angles is subjected to axial compression. Three typical cylindrical shell axial compression tests are designed and the ultimate bearing capacity and strain values of the lattice cylindrical shells are obtained. At the same time, the local buckling and the failure mode of the panel collapse are observed.
【学位授予单位】：哈尔滨工业大学
【学位级别】：博士
【学位授予年份】：2013
【分类号】：V214.8
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本文编号：1967946