Growth form orthotropic

Second, the growth process allows a variety of routes to the formation of fibers but there are no simple way s to form a dense isotropic plastic. Thus, even essentially isotropic materials will have a fibrous composite microstmcture. Weiner et al. (2000) have argued that many biological structures can be viewed as a search for isotropic properties, or at least orthotropic properties (strong in two dimensions), from fibrous materials. This would reflect the unpredictability of stresses encountered by a structure in a dynamic environment. 

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