浆砌复合结构形式的材料与结构力学行为

发布时间：2018-08-09 19:58

【摘要】：自然界的生物历经亿万年优胜劣汰演变,形成了具有优异性能的天然生物材料,其中贝壳珍珠层以其高强度和强韧性性质受到了研究者的广泛关注。研究表明,其优异的性能来源于珍珠层独特的结构形式:即碳酸钙片层与有机质交替排列的多级“砖—浆”结构,使得脆性碳酸钙具有70—180MPa的拉伸强度及高达1%的断裂应变,其强韧性还由于其复杂的矿物桥、多边形晶粒、纳米突起等与浆砌组合形成的精巧多级结构形式,这些因素的存在使得人们很难全面的解释其力学机理,但也极大的启发了人们对于高性能材料的设计与构造。基于此,本文对浙江渔场养殖的三角帆蚌的珍珠层进行了显微结构观察及力学行为研究,以探索珍珠层具体强韧机理,并以此为基础构建浆砌层合结构形式的板、壳元件,研究其细观结构对宏观力学性能的影响,为该材料在结构防护等领域的应用提供有益的探索和技术支持。研究的内容主要包括以下几个方面:1、珍珠层显微结构观察以及力学性能测试;利用扫描电子显微镜对三角帆蚌珍珠层微观结构进行观察,给出其细观结构形貌;利用纳米压入测试系统测试珍珠层不同方向的硬度、刚度、以及弹性模量,并分析加载深度、加载速率等因素对测试结果的影响;对珍珠层进行拉伸、压缩、三点弯曲实验,测试其抗拉压性能以及断裂性能,并分析水中浸泡对珍珠层性能的影响。实验结果表明:珍珠层材料呈各向异性且对应变率敏感,其弹性模量与硬度随应变率的增加而增加;但各个方向对应变率敏感程度不同,其厚度方向的性能对应变率更敏感;水的浸润会提高珍珠层的强度与韧性,且随着浸泡时间的增加而增加。2、构造珍珠层弹性模量的简化分析模型。依据珍珠层微观近似周期分布的结构形式,结合串并联思想构建简化的分析模型计算珍珠层不同方向的等效弹性模量。在此基础上,分析了浆体材料性能与尺寸对等效弹性模量的影响。结果表明:浆体的弹性模量对整个材料的弹性模量影响很大。随着浆体弹性模量的减小,浆砌结构的等效模量减小;当浆体弹性模量减小到低于砌体弹性模量的20%时,等效弹性模量减小的趋势急剧增加。因此在浆砌结构复合材料中,砌体中填充的浆体材料弹性模量应不小于砌体材料的20%,此时的整体结构依然能够保持良好的性能。3、构建浆砌结构有限元模型,研究其基本力学性能及板壳结构受冲击作用下的动力响应与抗侵彻能力。根据珍珠层微结构形式建立规则六边形与不规则随机多边形浆砌结构层状复合板与壳的模型,利用abaqus有限元软件对浆砌结构层状复合板、壳在子弹冲击作用下的结构响应进行了数值模拟。板的模拟结果表明:浆砌结构形式可有效提高复合板的韧性,相同载荷下陶瓷板呈圆台形破坏形式,而浆砌结构复合板呈圆柱形破坏形式,且挠度大,变形程度高;浆砌结构复合板的抗冲击性能优于单一材料的陶瓷板,在相同条件的子弹冲击作用下,浆砌结构形式构件的损伤程度小,开孔直径小,高速碎片少,子弹残余速度低等;其中,不规则浆砌结构复合构件的性能优于规则浆砌结构复合构件,且增加层内砌体体积分数,或减小层间砌体体积分数,能有效提高复合板的吸能特性。圆柱壳的模拟结果表明:与纯陶瓷圆柱壳相比,浆砌结构复合圆柱壳的刚度较低,其弹道极限速度较低,但陶瓷圆柱壳受到子弹冲击后全局多处发生严重失效,而浆砌结构复合圆柱壳只产生局部失效,结构完整性保持较好;其中,规则浆砌结构复合圆柱壳比不规则浆砌结构复合圆柱壳的抗冲击性能更好,主要体现在损伤程度小,子弹残余速度低,产生碎片少等。
[Abstract]:Natural biological materials have evolved over hundreds of millions of years and formed a natural biological material with excellent properties. The shell pearl layer is widely concerned by the researchers for its high strength and toughness. The study shows that its excellent performance comes from the unique structure of the pearl layer, that is, the alternate arrangement of the Calcium Carbonate Tablets layer and the organic matter. The multilevel "brick - slurry" structure makes brittle calcium carbonate have 70 - 180MPa tensile strength and up to 1% fracture strain, and its strength and toughness are also due to its complex mineral bridge, polygon grain, nano protruding and so on. The existence of these factors makes it difficult for people to explain its force in an all-round way. Learning mechanism, but also greatly enlighten people on the design and construction of high performance materials. Based on this, this paper studies the microstructure and mechanical behavior of the pearl layer of Hyriopsis cumingi cultured in Zhejiang fishing ground, in order to explore the concrete strength and toughness of the pearl layer. The influence of the microstructure on the macroscopic mechanical properties provides useful exploration and technical support for the application of the material in the field of structural protection. The main contents of the study include the following aspects: 1, the microstructure observation of the pearl layer and the mechanical properties test, and the microscopic structure of the pearl layer of Hyriopsis cumingii by scanning electron microscopy. The microstructure and morphology were observed and the hardness, stiffness and elastic modulus of different directions of pearl layer were tested by nano pressure entry test system, and the effects of loading depth and loading rate on the test results were analyzed. The tensile, compression and three point bending experiments were carried out to test the tensile and fracture properties of the pearl layer and the fracture properties were measured and divided into two parts. The effect of water immersion on the performance of pearl layer was analyzed. The experimental results showed that the material of nacre was anisotropic and sensitive to strain rate, and its modulus and hardness increased with the increase of strain rate, but the sensitivity of each direction to variation rate was different, the performance of its thickness direction was more sensitive to the variation rate, and the infiltration of water would increase the strength of the pearl layer. The simplified analysis model of the elastic modulus of the pearl layer is constructed with the increase of the immersion time and the increase of the soaking time. According to the structure of the approximate periodic distribution of the pearl layer, the equivalent elastic modulus of the different directions of the pearl layer is calculated by a simplified analysis model combined with the series parallel connection idea. On this basis, the properties of the slurry are analyzed. The effect of the size on the equivalent elastic modulus shows that the modulus of elasticity of the slurry has a great influence on the elastic modulus of the whole material. With the decrease of the modulus of elasticity of the slurry, the equivalent modulus of the masonry structure decreases, and the decrease of the equivalent elastic modulus increases sharply when the modulus of elasticity of the slurry decreases to less than 20% of the elastic modulus of the masonry. In the masonry composite material, the elastic modulus of the slurry filled material in masonry should not be less than 20% of the masonry material. The overall structure of the masonry can still maintain good performance.3. The finite element model of the masonry structure is constructed. The basic mechanical properties and the dynamic response and anti penetration ability of the plate and shell structure under the impact of the shell and shell structure are studied. The model of regular hexagonal and irregular random polygon laminated composite plates and shells is established in the microstructural form of the pearl layer. The structural response of the laminated composite plate and shell under the impact of bullets is simulated by the ABAQUS finite element software. The simulation results show that the structure of the mortar can be effectively improved. The toughness of the plywood plate is in the form of circular failure under the same load, and the mortar structure composite plate has a cylindrical failure form, and the deflection is large and the deformation degree is high. The impact resistance of the masonry composite plate is better than that of the single ceramic plate. Under the impact of the same condition, the damage degree of the structural members is small. The diameter of the hole is small, the high-speed debris is few, and the residual velocity of the bullet is low. Among them, the performance of the irregular slurry structure composite member is better than that of the regular masonry structure composite member. It can increase the volume fraction of the masonry in the layer, or reduce the volume fraction of the interlayer masonry. The simulation results of the cylindrical shell show that the cylindrical shell is with the pure ceramic cylinder. Compared to the shell, the stiffness of the composite cylindrical shell is lower and its ballistic limit speed is low, but the ceramic cylindrical shell is severely damaged in many places after the impact of the bullets, and the composite cylindrical shell of the mortar structure only produces local failure and the structural integrity is better, in which the composite cylindrical shell is more than the irregular slurry. The impact resistance of cylindrical shell is better, which is mainly manifested in the small degree of damage, low residual velocity of bullet and less fragments.
【学位授予单位】：太原理工大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O34

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