Nanoscaled elementary components and their mechanical interaction in biological and man-made composite materials: bone, wood, and concrete

Title: Nanoscaled elementary components and their mechanical interaction in biological and man-made composite materials: bone, wood, and concrete
Author(s): Christian Hellmich, Karin Hofstetter, Peter Pivonka
Paper category : conference
Book title: NICOM 2: 2nd International Symposium on Nanotechnology in Construction
Editor(s): Y. de Miguel, A. Porro and P.J.M. Bartos
Print-ISBN: 2-912143-87-X
e-ISBN: 2912143888
Publisher: RILEM Publications SARL
Publication year: 2006
Pages: 49 - 56
Total Pages: 8
Nb references: 55
Language: English

Abstract: Reliable serviceability and safety assessment of civil and bioengineering structures by means of structural numerical (bio-chemo-)mechanics requires decent knowledge of the material properties prevailing in the structural component under investigation. Material properties of many natural composites, be they man-made or of biological origin, are extremely diverse at the classical macroscopic observation scale considered normally in engineering laboratory experiments. In addition, they are often inhomogeneous and anisotropic. Hence, their comprehensive experimental identification at the macroscopic scale would become very expending, sometimes impossible. This situation motivates to examine lower scales of such materials, looking for material properties of microstructural components which are universal, i.e. valid for whole classes of materials, such as bone, wood, or concrete. Indeed, such universal building blocks and mechanical interaction patterns could be identified, by evaluation of large physically and statistically independent data sets, in the theoretical framework of continuum micromechanics. We give a review on related recent developments: The bones of all vertebrates turn out to be hydroxyapatite foams reinforced, within an representative volume element of some microns characteristic length, by collagen strands, and perforated, at an observation scale of several hundred microns, by prolate pores. Wood elasticity of different tree species can be predicted by a multistep homogenization scheme, where cellulose fibers reinforce, at the level of some microns, a lignin-based polymer matrix, which is perforated at the micrometer to millimeter-level by lumen and vessel pores. The universal chloride diffusivity in the capillary porosity of cement pastes is one order of magnitude lower than that of a bulk water solution, probably due to structuring of water through the electrical charges at the pore surfaces.

Online publication: 2005-11-17
Publication type : full_text
Public price (Euros): 0.00