14 Externe wissenschaftliche Einrichtungen
Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/15
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Item Open Access Micro/nanomechanical measurements on insect and plant cuticles(2005) Barbakadze, Nato; Arzt, Eduard (Prof. Dr. phil.)Head articulation cuticle of the beetle (Pachnoda marginata) designed for friction minimization and wax covered pea (Pisum sativum) plant surfaces adapted for insect attachment prevention have been studied. Both insect and plant cuticles are multilayered fiber-composite materials. All samples were tested in fresh and dry conditions to observe the effect of desiccation. To understand the influence of an outer wax/lipid layer, tribo-mechanical experiments on the gula cuticle were performed as well in a chemically treated condition. Mechanical properties were determined by nanoindentation. Due to the high damping coefficient and high resonant frequency of the indenter it was possible to determine mechanical properties of materials with low contact stiffness and low damping coefficients. Continuous stiffness measurement (CSM) allowed hardness and elastic modulus to be calculated at every data point acquired during the indentation. The mechanical behavior of all samples was found to be greatly influenced by desiccation. However the effect on hardness and elastic modulus were different for insect and plant cuticles. Desiccation made gula cuticle of the beetle harder and stiffer but the plant surface softer and more compliant. Chemical treatment caused further hardening and stiffening of the gula cuticle. All fresh plants exhibited the same mechanical behavior apparently due to the influence of cell walls and especially pressure of the cell-fluid. Dry samples with normal wax layer were softer and more compliant than with reduced waxy bloom. Friction properties of the gula cuticle were influenced by different factors. Fresh samples were smooth, soft and compliant and exhibited higher friction coefficients than dry ones, which were rough, hard and stiff. Chemically treated cuticles showed the lowest friction coefficient. This study is believed to be one of the first for the mechanical testing of insect cuticles and the very first for wax coated plant surfaces in native condition.