Plenary Session - Wednesday, July 16, 9:00 am

Scaling of Failure of Particulate and Fiber Composites: Overview of Recent Advances

Abstract: In contrast to fluid mechanics, the problems of scaling and size effect in solid mechanics have not come to the forefront of attention until late in the last century. The classical view that any observed size effect was statistical was reversed during the 1980s. It is now widely accepted that major size effects on the mean structural strength are deterministic, caused mainly by stress redistribution and energy release associated with stable propagation of large fractures or with formation of large zones of distributed cracking, typical of both particulate brittle composites such as concrete and polymer-fiber composites. The lecture begins by reviewing the basic asymptotic properties of size effect implied by the cohesive crack model or crack band model and highlights the use of asymptotic matching techniques as a means of obtaining scale-bridging size effect laws representing a smooth transition between two power laws. Applications to the deterministic (energetic) size effect in various types of brittle failure of reinforced and unreinforced concrete structures, in sea ice fractures, and in dry snow slab avalanches, are reviewed. Attention is then focused on fiber-polymer composites failing by either tensile fracture or propagation of compression kink bands with fiber microbuckling. The size effects in polymeric foams and sandwich structures are also discussed. A nonlocal model for incorporating the Weibull-type statistical size effect due to local strength randomness into the energetic size effect theory is outlined next. The problem of size effect on failure loads of extremely small probability, needed to be solved for design, is reviewed and a possible way of adapting to it the stochastic finite element method is discussed. The lecture closes with a brief mention of some famous structural catastrophes in which the size effect must have contributed to the ruin.

Zdenĕk P. Bažant

Born and educated in Prague (Ph.D. 1963), Bažant joined Northwestern University in 1969, became Professor in 1973, and served as Director of Center for Geomaterials (1981-87). Since 1972 he has been W.P. Murphy Professor of Civil Eng. and Materials Science and since 2002 simultaneously McCormick School Professor. He has authored over 430 refereed journal articles and six books (Scaling of Structural Strength, Inelastic Analysis, Fracture and Size Effect, Stability of Structures, Concrete at High Temperature, and Concrete Creep). He was inducted to the National Academy of Sciences, National Academy of Engrg., Austrian Academy of Sciences, Academia di Scienze e Lettere (Italy) and Academy of Engrg. of Czech Rep. He served as Editor of ASCE J. of Engrg. Mechanics and is Regional Editor of Int. J. of Fracture; was president of Soc. of Engrg. Science, founding president of IA-FRAMCOS and of IA-CONCREEP; Division Director in IA-SMiRT; is a member of US Nat. Comm. on Theor. & Appl. Mech.; and chaired various committees in ASCE, RILEM, ACI, SES and IA- SMiRT. He is an Illinois Registered Structural Engineer. Among his honors: 4 honorary doctorates (Colorado, Milano, Karlsruhe, Prague); SES Prager Medal; ASME Warner Medal; ASCE Newmark Medal, Croes Medal, Huber Prize, Lin Award and Lifetime Achievement Award; RILEM L’Hermite Medal; Am. Ceramic Soc. Roy Award; Torroja Medal (Spain); Šolín and Stodola Medals (Czech Rep., Slovakia); ICOSSAR Lecture Award; Medal of Merit (TU Prague); SEAOI Meritorious Paper; Best Engrg. Book of the Year (SAP); ISI Highly Cited Scientist (www.ISIhighlycited.com); and Guggenheim, Humboldt, NATO, JSPS, Kajima and Ford Fellowships.

E-mail questions and inquiries to em03@ce.washington.edu.