Abstract: During the last decade, novel polymers and composite materials have been developed for applications as micro- and nanodevices. In these applications, conventional mechanical characterization techniques like tensile, compression and bending tests are inapplicable due to the size of the samples. Nanoindentation technique, widely used to characterize the mechanical properties of hard metals and ceramics has started to be used also to characterize polymers and composite materials. Recently, a review has been published by the author comparing mechanical measurement techniques at different scales: “Indentation Hardness Measurements at Macro-, Micro-, and Nanoscale,” Tribology Letters vol 65 (2017) p.23.

In this talk, the application of indentation techniques to measure the hardness, elastic modulus, and creep of polymers and composite materials is discussed. A comparison between nanoindentation results and macroscopic properties is offered. Finally, typical mistakes in the measurements of these materials are also critically examined. Challenges and future perspectives in the application of nanoindentation to characterize mechanical properties of polymers and composite materials are suggested.

Biography: Esteban Broitman holds a Ph.D. in Physics from the University of Buenos Aires (Argentina), and a Docent (Habilitation) degree in Tribology from Linköping University (Sweden). He has been doing research and teaching at the University of Buenos Aires (Argentina), The College of William & Mary (USA), Carnegie Mellon University (USA), Linköping University (Sweden), and Invited Professor at University of Sao Pablo (Brazil), and the Chinese Academy of Sciences (CAS - China). He is presently a Senior Scientist in the area of Coatings at the SKF Research and Technology Development Center in Netherlands. His activities focus on the use of advanced surface engineering to control friction and wear at the macro-, micro-, and nano-scales of coatings like DLC, nanocomposites, and softer materials like soft metals and polymers.

Abstract: In fiber reinforced composites, the fiber/matrix combination produces certain mechanical properties that cannot be achieved by either of the constituents acting alone. Pull-out and micro-bond tests are commonly used to investigate the interface properties by using the average interface stress without considering the singular stress fields (ISSFs). In this talk, therefore, the ISSF at the fiber entry/end points is discussed since the ISSF may control the interface debonding for pull-out and micro-bond tests. It is found that the ISSFs of pull-out test can be predicted from the ISSF of the micro-bond test conveniently used because the ISSF of micro-bond test is about 1.5 times of the ISSF of pull-out test under the same fiber geometry. Suitable testing geometry is proposed for micro-bond test since the ISSF is very sensitive to the knife gap under the small dimension commonly used.

Key words: Fiber reinforced composites, Micro-bond test, Fiber Pull-out, Intensity of singular stress field (ISSF), Fiber/Matrix interface

Biography: Nao-Aki Noda received his Ph.D. degree in Mechanical Engineering from Kyushu University, Japan in 1984. He has been doing research and teaching at Kyushu Inst. Tech., Kitakyushu, Japan, 1984-87, He is an author of Theory of Elasticity useful for engineers and a co-author of Safety Engineering for Workers in Industry and other several books. He is a co-editor of Stress Intensity Factors Handbook, vol. 4 & 5, Advances in Finite Element Analysis for Computational Mechanics. He is a recipient of Outstanding Paper Medal of Japan Soc. Tech. Plasticity, Sokeizai Industry Technology award from the Materials Process Tech. Ctr., a fellow of JSME (Japan Soc. Mech. Engrs.) and a fellow of JSAE (Soc. Automotive Engrs. Japan), JSMS Award for Academic Contribution and JSME Materials and Mechanics Division Award. He Achievements include researches in stress analysis for notched material testing specimens, and development for large ceramics structures used for steel manufacturing machinery and special bolt-nut connection improving anti-loosening and fatigue strength.