Composite Structural Mechanics of Dorsal Lamella in Remora Fish
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Composite Structural Mechanics of Dorsal Lamella in Remora Fish Michael Culler1 and Jason H. Nadler2 1 Woodruff School of Mechanical Engineering, Georgia Institute of Technology; Atlanta, GA 2 Electro-Optical Systems Laboratory, Georgia Tech Research Institute; Atlanta, GA ABSTRACT Remora fish have evolved a unique dorsal pad capable of fast, reversible adhesion to a large range of natural and artificial surfaces. The effectiveness of adhesion is due in part to the pad’s ability to dynamically conform and adapt to the geometry of its host. Simulations based on measured material properties and geometry can provide useful design metrics for biologically inspired design, and furthermore, serve as platform for virtual experiments. The pad itself consists of a lamellar, composite structure composed of mineralized and soft tissue. In this work, finite element models based on μCT scans and measured viscoelastic material properties elucidate the pad’s complex moduli frequency spectrum and response to different loading configurations. INTRODUCTION Remoras, commonly known as sucker fish, belong to the teleost family Echeneidae, and have a distinct dorsal pad proficient at attaching to an extensive assortment of marine hosts including sharks, sea-turtles, whales, and man-made vessels [1]. Three distinct features of the pad that contribute to attachment are shown in Figure 1 and include spinules, a fleshy lip, and lamellae compartments [2]. The lamellae are comprised of both hard and soft tissue. Several important roles played by the lamella include removal of fluid from within the pad followed by application of a restorative force against the host to maintain suction, and also delivery of the spinules to the host surface which serve to increase the “friction” or resistance to drag forces [2, 3]. Fleshy Lip
5mm Lamellar Compartments
2.5mm Spinules
Figure 1: (Left) Photograph of live remora suction pad (photograph courtesy of Brooke Flammang); (Right) Photograph of detached "suction pad" with highlighted structural features of interest In this work, two finite element models (FEM) will be discussed to estimate and quantify the lamella’s ability to eliminate fluid volume in response to contact with a host, and the complex structural stiffness of the lamellar array. These criteria are useful in both biological and
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engineering contexts as they further understanding of the remora behavior and can be used as design criteria for biologically inspired devices. THEORY The functions of lamellae within the remora pad, namely their ability to remove or “sweep away” fluid volume from within the pad and its structural response to oscillatory loading, are quantified by combining measured geometric and material properties in computer simulations. In order to simplify computational requirements, a periodic, 2D tre