3. Continuum micromechanics of inhomogeneous materials
The thermomechanical and thermophysical behavior of materials that contain inhomogeneities of sizes upwards of, say, 1mm, can be studied to advantage by continuum methods, an approach that is often referred to as continuum micromechanics.
This research field aims, on the one hand, at obtaining homogenized responses of inhomogeneous materials from the geometry and properties of the constituents and, on the other hand, at estimating the local stress, strain, temperature and flux fields that are induced at the length scale of the constituents by macroscopic loads. In many cases, intermediate length scales between the constituent and structural levels can also be introduced, leading to hierarchical modeling schemes. At the Institute of Lightweight Design and Structural Biomechanics (ILSB) pertinent research has been mainly targeted on lightweight and highperformance structural materials, such as particle or fiber reinforced composites, laminates, foams, cellular materials and graded materials as well as lightweight compounds such as sandwich shells. In addition, “natural composites” such as bone and functional composites have been studied. The work has been strongly integrated with the institute’s other research fields, viz., lightweight structures, numerical engineering methods and biomechanics. Over the past decade, it has involved the majority of researchers working at the ILSB, among them Franz Rammerstorfer, Philippe Zysset, Heinz Pettermann and Helmut Boehm.
Research in continuum micromechanics offers exciting opportunities for better understanding and, as a consequence, improving inhomogeneous materials, especially structural composites, the properties of which are “tailorable” in many cases. It involves both analytical and numerical approaches, the latter being based on numerical engineering methods such as the Finite Element Method. Work in continuum micromechanics at the ILSB has been instrumental to co-hosting two Christian Doppler Laboratories, to serving as a node of a K net competence center, to participating in EU projects, and to a range of other projects in basic as well as applied research pertinent to materials modeling. Current pertinent research interests of the ILSB research group concentrate on advanced multi-particle unit cell and “windowing” methods for studying composites and on models for simulating damage in laminated composites.
The length scales studied by the ILSB group are the largest within the proposed CompMat grouping. A major requirement of micromechanics are suitable in-situ material models and parameters for describing the thermomechanical behavior at the constituent level (including interfacial properties), which in some cases (e.g., single crystal elastic moduli or coefficients of thermal expansion of pure phases) may be provided by CompMat members carrying out modeling at lower length scales. Another potential field of cooperation are micromechanical studies interacting with microstructural data generated by the thermodynamical models of the Kozeschnik group.