International Research Center for Computational Mechanics学术报告
报告题目：Deformation measurements and modelling of polymers on multiple scales: X-ray scattering, DIC and in-situ loading
In this work the deformation of the microstructure of polycarbonate (PC) was studied, especially with respect to permanent deformation on different scales, using X-ray scattering with in-situ loading and simultaneous full-field deformation measurements using 3D-surface DIC. The results from X-ray scattering and DIC with in-situ uni-axial loading has revealed a non-affine relation between the observed deformation on the macro- and meso-scale and the deformation of the microstructure. The experimental results indicate that the reorientation of the chains is a result of the polymer chain segments being stretched to a limit stretch, after which they start to slide past each other. Furthermore, the results show that the polymer chain segments unload elastically with only a small residual deformation, when the macroscopic force is removed, i.e., the intra-chain deformation is predominately elastic.Taking advantage of the experiments, a model is proposed that makes use of a microstructural deformation gradient to incorporate the experimentally obtained deformation of the microstructure, as well as, its evolving deformation. It is shown that this approach is able to predict accurately glassy polymer deformation over a wide range of length-scales, from macroscopic response (mm range) down to the deformation of the microstructure (nm range)
Introductionof Professor Matti Ristinmaa：
Professor Matti Ristinmaa is the head of the department of Construction Sciences since 2015. His main research interests have been related to material mechanics, modeling of coupled fields, mixture theory, smart materials, electro-active polymers, structural optimization andcomputational materials mechanics. Recently, Prof. Ristinmaa has also contributed to the field ofexperimental. He has received a reward for his work on constitutive modeling fiber basedmaterials. In addition to coordinating the activities of the Division of Solid Mechanics, he hasalso led a number of multi-year research projects on fundamental material modeling and coupled fieldproblems as well as on research directly related to industrial applications. He has beensupervisor of several PhD students, which now are active in academia and the industry. Prof.Ristinmaa has been a member as well as the chair of the applied mechanics evaluation panel atSwedish research council for several years.