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Biological materials combine antagonistic properties like toughness and strength with a low density as a consequence of a continuous optimization during billions of years. We investigate the mechanical properties of biological and biomimetic materials at the nano- and microscale using a combined experimental, analytical, and computational approach. Our research interest focuses on understanding the complex mechanical behavior and deformation mechanisms of hierarchical materials at different length scales. Probing locally microscopic volumes allows investigating microstructure-mechanical property relationships and the influence of interfaces on the mechanical response of biological nanocomposites.
Microscale investigation of the ageing skeleton
The rising number of bone fractures poses a challenge to ageing societies worldwide. A large portion of physiological loading is carried by cortical bone which motivates the need to understand its structure-property relationships on several length scales. We investigate whether micromechanical measurements may be combined with compositional, morphological, and proteome information to predict macroscopic bone strength in a donor- and site-matched manner. This will help to form a better un-derstanding of the mechanisms of ageing in bone and lead to an improved personalized fracture risk prediction in the future. (Bone 2016
Strength and deformation mechanisms of bone extracellular matrix
Bone is a natural composite material that features a hierarchical architecture combining both toughness and strength. In order to better understand the mechanisms leading to this advantageous combination, we analyze its post-yield and failure behavior under uniaxial loading on the microscale. Experimental setups for micropillar compression and microtensile testing inside a scanning electron microscope or under liquid immersion are developed to measure bone’s microscale yield properties under physiological conditions. Transmission electron microscopic analysis allows identifying deformation mechanisms and linking them to the underlying microstructure. Analytical and numerical modeling of the observed deformation patterns allows assessing nanoscale properties. This leads to an improved understanding of the nanoscale processes underlying bone deformation, which may be used to enrich multiscale models of whole bone strength for an improved fracture risk prediction in the future. (Nature Materials 2014, Acta Biomaterialia 2017)
Nanomechanics of yielding in the wood cell wall
The hierarchical microstructure of wood necessitates understanding its mechanical behavior at the characteristic length scales of individual cellulose fibrils, the cell wall composite, as well as the macroscale. By combining uniaxial micromechanical experiments with analytical modeling of the secondary cell wall, nanoscale properties of the polymer matrix can be assessed as a function of composition and microfibril angle. This demonstrates a new approach for validating multiscale models predicting yield properties with uniaxial experiments at the microscale or identifying nanoscale properties based on the combination of microscale experiments and modeling. (Philosophical Magazine 2016