Feather evolution from knotted barbules to hooked and unhooked barbules and its finite element analysis.

Experiments involving scanning electron microscopy of the microstructure of barbules and optical microscopy of knotted barbules were conducted: the behaviour of knotted barbules, and their evolution to form a branch of hooked barbules and unhooked barbules were analysed. A growth model for a feather plume was proposed. MATLAB™ 2-d contour microstructures of sectioned knotted feathers and three-dimensional structural models of barbules were established, moreover, these were analysed using the finite element method. The response under load of different parts of the barbules was obtained. The results showed that there were stress concentrations in feather barbules. The study laid a foundation for finding the internal and external causes of the evolutionary transition of knotted barbules.