利用顆粒模擬探討以深海玻璃海綿啟發之高強度和輕量仿生結構與力學行為

Abstract

自然界中的生物為適應環境發展出許多特殊結構，以實現各種功能。近年來，透過解析與模仿生物結構設計為工程領域提供不同以往的設計理念。生物體內的多孔的細胞狀結構(cellular structure)使結構同時兼具高強度、輕量和高韌性等機械性質，尤其是深海玻璃海綿(Euplectella aspergillum)以特殊棋盤結構聞名，憑藉輕量、高承重和容易加工的週期性晶格特性，適合發展於航太、橋樑工業中。本研究針對深海玻璃海綿啟發之仿生晶格和工程上常見方形晶格，用於桁架和晶格套筒結構，固定重量下施以單軸向壓縮並更換材料，討論不同結構的抗壓行為。我們使用顆粒模擬方法，將晶格結構的桁架等效成顆粒和彈簧組成的模型，藉由諧和彈簧(harmonic spring)和諧和扭轉彈簧(harmonic torsion spring)串接，實現受負載之機械行為，得以探索仿生結構的變形機制與能量分布等機械性質。並且搭配視覺化諧和彈簧的長度伸縮量與諧和扭轉彈簧角度變化資訊，了解應力集中與變形之關係。首先，結果顯示，在二維的桁架結構中，仿生結構封閉和開放交錯排列的晶格具有優異的機械性質，依靠特殊的對角線排列幫助吸收更多能量。並且顯示沒有對角線支撐的方形結構出現單邊側向變形，具有不抗壓和不穩定性質。在三維晶格套筒結構中，我們比較對角線支撐的結構，仿生結構具有最大的線彈性區域，使其擁有最高的強度。我們接著對比不同硬度材料，較硬的材料線彈性區變小、結構破壞猛烈。綜合上述結果，仿生結構在固定材料使用量下，擁有最好的抗挫曲性質，放大結構挫曲發生前的彈性區域，達成高強度重量比目標。最後，顆粒模擬方法有效指出應力集中於彈簧長度、角度變化大的位置。利用彈簧斷裂特性，擷取結構中的破壞機制，顯示顆粒模擬用於仿生結構變形的優勢。

To achieve various specific functions, animals and plants in nature have developed multiple structures to adapt to the environment. In recent years, through the analysis and mimic of biological structures, structural designs have provided different design concepts for the engineering field. For instance, porous cellular structure in organisms possesses mechanical properties such as high strength, lightweight and high toughness. In particular, Euplectella aspergillum, known for its special checkerboard arrangement structure, it is suitable for development in the aerospace and bridge industries due to its lightweight, high load-bearing, and periodic lattice properties for easy manufacturing. This study focuses on the design of bionic lattice inspired by deep-sea glass sponge and its comparison to common square lattice in engineering. Using all design in truss and lattice tube structures, and with a constant weight, uniaxial compression, and material replacement, this study aims to discuss the compressive response of the different structures. By using a particle simulation method, the lattice structure is converted into a model formed by particles and springs. The mechanical behavior under loading is achieved by connecting harmonic springs in series with harmonic torsion springs. Therefore, it is possible to explore the mechanical properties of the bionic structure such as deformation mechanism and energy distribution, and to understand the relationship between stress concentration by visualizing the information on the length extension of the harmonic spring and the angular change of the harmonic torsion spring. The results show that in the two-dimensional truss structure, the bionic structure with closed and open alternating arrangement of lattices has excellent mechanical properties, relying on the special diagonal arrangement to improve energy absorption. Moreover, it is shown that the square structure without diagonal support does not perform well under compression, and the resulting single lateral deformation indicates an undesirable structural instability. In 3D lattice tube structures, the bionic structure has the largest area of linear elastic zone compared to the diagonally supported structure, giving it the highest strength. In comparison with materials of different hardness, the linear elasticity zone of the harder material decreases and the structure failure occurs rapidly and prematurely. In summary, under the premise of fixed material usage, the bionic structure can achieve the highest strength-to-weight ratio by enlarging the elastic region of the structure before the buckling occurs. Finally, the results show that the stresses are concentrated on the locations where the change of spring length and angle is significant. As the structural damage in hard materials is showcased by the characteristics of spring breakage, it demonstrates the advantage of utilizing particle simulation in predicting the deformation of bio-structure.