【直播】【力学交叉融合系列】Steve Bull院士 学术报告

报告题目：

Viscoelasticity and hyperelasticity  in thin organic semiconductor coatings

报告时间：

2023年4月17日（周一）17:00

报告嘉宾：

Steve Bull 院士

主办单位：

重庆大学国际合作与交流处、重庆大学航空航天学院

直播通道

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Steve Bull教授，英国皇家工程院院士，现任职于英国纽卡斯尔大学。他在薄膜、涂层结构与性能关系的研究方面拥有三十多年的经验，在同行评议期刊上发表了超过230篇论文。
Professor Steve Bull (MA PhD FIMMM FInstP FREng CEng) is Cookson Group Chair of Engineering Materials in the School Engineering at Newcastle. He has over thirty years experience in research on structure-property relationships in thin films and coatings having spent eight years at AEA Technology, Harwell running coating activities before moving to Newcastle University in 1996. His current research is focussed on the relationship between functional properties (e.g. electrical or optical) and the mechanical response of sub-micron multilayered and porous coating systems. He has published over 230 papers in refereed journals and is regularly invited to present his work at International conferences.

报告摘要

A wide range of organic semiconductor coatings have been developed for optical and electronic applications and have been extensively characterised for their electronic and optical properties. What mechanical measurements have been made are focused on assessing the average properties of a film (e.g. using buckling to assess elastic moduli) but are not suitable to assess point-to-point variation in mechanical response which may be related to changes in coating microstructure due to crystallisation and/or phase separation or to understand the deformation mechanisms occurring; this is where contact mechanics is most useful. The assessment of non-linear elasticity and time-dependent mechanical response is also lacking.
This presentation will address the strain and time-dependent mechanical properties of 100-300nm thin films of a range of organic semiconductors on a glass substrate using nanoindentation at very low loads (peak loads less than 50μN) with a relatively blunt indenter (500nm tip radius). Although a well-defined indentation is produced in many cases it is not clear that plastic deformation occurs (and by what mechanism) but viscoelastic deformation is significant in making the observed indent. The use of load and displacement control during a hold period to determine the relaxation modulus for very thin films is helpful to understand deformation mechanisms. Finite element modelling of the load-displacement curves reveals that including both viscoelasticity and hyperelasticity (rather than simple linear elasticity) is necessary to explain the measured load-displacement curves in for several different organic semiconductor materials.

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编辑：黄琦

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