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Insect wing veins are biological composites of chitin and protein arranged in a complex lamellar configuration. Although these hierarchical structures are found in many ‘venous wings' of insects, very little is known about their physical and mechanical characteristics. For the first time, we carried out a systematic comparative study to gain a better understanding of the influence of microstructure on the mechanical characteristics and damping behaviour of the veins. Morphological data have been used to develop a series of three-dimensional numerical models with different material properties and geometries. Finite-element analysis has been employed to simulate the mechanical response of the models under different loading conditions. The modelling strategy used in this study enabled us to determine the effects selectively induced by resilin, friction between layers, shape of the cross section, material composition and layered structure on the stiffness and damping characteristics of wing veins. Numerical simulations suggest that although the presence of the resilin-dominated endocuticle layer results in a much higher flexibility of wing veins, the dumbbell-shaped cross section increases their bending rigidity. Our study further shows that the rubber-like cuticle, friction between layers and material gradient-based design contribute to the higher damping capacity of veins. The results of this study can serve as a reference for the design of novel bioinspired composite structures.

A genetic algorithm and singular value decomposition (SVD) are deployed simultaneously for optimal design of both connectivity configuration and the values of coefficients respectively involved in group method of data handling (GMDH)-type neural networks, which are used for modelling the explosive cutting process of plates by shaped charges. The aim of such modelling is to show how the depth of penetration varies with the variation in important parameters, namely the apex angle, standoff, liner thickness and mass of charge. It is also demonstrated that SVD can be effectively used to find the vector of coefficiencs of quadratic subexpressions embodied in such GMDH-type networks. Such application of SVD will improve the performance of evolved GMDH-type networks to model the very complex process of explosive cutting of plates by shaped charges.

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Dragonflies are fast and manoeuvrable fliers and this ability is reflected in their unique wing morphology. Due to the specific lightweight structure, with the crossing veins joined by rubber-like resilin patches, wings possess strong deformability but can resist high forces and large deformations during aerial collisions. The computational results demonstrate the strong influence of resilin-containing vein joints on the stress distribution within the wing. The presence of flexible resilin in the contact region of the veins prevents excessive bending of the cross veins and significantly reduces the stress concentration in the joint.

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