Plant Stems: Functional Design and Mechanics
ABSTRACT Plant stems are one of nature's most impressive mechanical constructs. Their sophisticated hierarchical structure and multifunctionality allow trees to grow more than 100 m tall. This review highlights the advanced mechanical design of plant stems from the integral level of stem structures down to the fiber-reinforced-composite character of the cell walls. Thereby we intend not only to provide insight into structure-function relationships at the individual levels of hierarchy but to further discuss how growth forms and habits of plant stems are closely interrelated with the peculiarities of their tissue and cell structure and mechanics. This concept is extended to a further key feature of plants, namely, adaptive growth as a reaction to mechanical perturbation and/or changing environmental conditions. These mechanical design principles of plant stems can serve as concept generators for advanced biomimetic materials and may inspire materials and engineering sciences research.
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ABSTRACT: Cellulose whiskers were obtained by means of sulfuric acid hydrolysis of curauá fibers. Before hydrolysis, the natural fibers were treated with an alkaline solution to remove the non-cellulosic content. Fiber degradation evolution and cellulose whisker formation were analyzed by structural and morphological analysis. The original fiber structure underwent a fragmentation mechanism after being exposed for 3 min to sulfuric acid. Cellulose whiskers were lixiviated from the fiber surface after 10 min of hydrolysis, developing two scenarios: one where the whiskers became unattached from the original fiber, and the other which remained attached. The cellulose whiskers presented a needle-like geometry with an approximate diameter of 11 nm and average length of 185 nm, after 30 min of acid hydrolysis. Based on microscopic characterization, a schematic representation of the morphological evolution of the cellulose fibers submitted to acid hydrolysis is proposed.Cellulose 19(4). · 3.48 Impact Factor