One approach to investigating functional attributes of the central complex is to relate its various elaborations to pancrustacean phylogeny, to taxon-specific behavioral repertoires and ecological settings. Here we review morphological similarities between the central complex of stomatopod crustaceans and the central complex of dicondylic insects. We discuss whether their central complexes possess comparable functional properties, despite the phyletic distance separating these taxa, with mantis shrimp (Stomatopoda) belonging to the basal branch of Eumalacostraca. Stomatopods possess the most elaborate visual receptor system in nature and display a fascinating behavioral repertoire, including refined appendicular dexterity such as independently moving eyestalks. They are also unparalleled in their ability to maneuver during both swimming and substrate locomotion. Like other pancrustaceans, stomatopods possess a set of midline neuropils, called the central complex, which in dicondylic insects have been shown to mediate the selection of motor actions for a range of behaviors. As in dicondylic insects, the stomatopod central complex comprises a modular protocerebral bridge (PB) supplying decussating axons to a scalloped fan-shaped body (FB) and its accompanying ellipsoid body (EB), which is linked to a set of paired noduli and other recognized satellite regions. We consider the functional implications of these attributes in the context of stomatopod behaviors, particularly of their eyestalks that can move independently or conjointly depending on the visual scene.

<p>  </p> <p>The smashing mantis shrimp is a crustacean that uses its dactyl club to defend itself or prey on other animals. This dactyl club is so strong that it can reach accelerations as high as a bullet of a caliber 0.22 gun and impact without breaking. We seek to understand the secrets behind the staggering properties of this club that withstand several high-damage impacts without breaking catastrophically. The dactyl club comprises three parts: the impact region, the periodic region, and the striated region.</p> <p>The first region of interest is the periodic region. This region is made of a helicoidal arrangement of fibers called Bouligand architecture, and in this architecture, cracks only form in the matrix between fibers. The first research project approximates the Bouligand composite with a single helicoidal crack embedded in an isotropic material. The test consists of a disk with a notch under quasistatic biaxial boundary conditions. We found an enhancement of mechanical properties when we increase the pitch angle.</p> <p>In the following section, a coarse-grained model is developed. This model allows multiple crack formation. This approximation tells us that as the initial crack grows, the driving force of crack propagation, the energy release rate, diminishes. The crack stops growing, confining itself, and allowing multiple crack nucleation and delocalization. At the same time, this dissipates more energy as more cracked surfaces appear.</p> <p>Hashin damage model with a cohesive zone model are used under different boundary conditions, geometries, and material properties, to model Bouligand composites. The helicoidal composites outperform the reference ones in peak load and absorbed energy.</p> <p>The next part of this thesis investigates the bicontinuous particles present in the impact surface of the dactyl club. These bicontinuous particles consist of a soft phase (organic) and a hard phase (hydroxyapatite) that can withstand high strain rates. Their stiffness and strength increase with strain rate. On the other hand, preliminary studies suggest that they perform well in cyclic loading.</p> <p>Finally, we proceed to use the helicoidal composites to design structural parts. We introduce a model for simulating the fiber-reinforced composites called LARC05. We verify, validate, and then use models for fiber-reinforced composites.</p>