ISSN:
1013-9826
Source:
Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Different sets of silica aerogels (classical aerogels, partially dense aerogels, composite aerogels)have been studied in the objective to understand the mechanical behaviour of these extremelyporous solids. The mechanical behaviour of xerogels and aerogels is generally described in terms ofbrittle and elastic materials, like glasses or ceramics. The main difference compared to silica glass isthe order of magnitude of the elastic and rupture modulus which are 104 times lower. However, ifthis analogy is pertinent when gels are under a tension stress (bending test) they exhibit a morecomplicated response when the structure is submitted to a compressive stress. The network islinearly elastic under small strains, then exhibits yield followed by densification and plastichardening. As a consequence of the plastic shrinkage it is possible to compact and stiffen the gel atroom temperature. These opposite behaviours (brittle and plastic) are surprisingly related to thesame kinds of gel features: pore volume silanol content and the pore size. Both elastic modulus andplastic shrinkage depend strongly on the volume fraction of pores and on the condensation reactionbetween silanols. On the mechanical point of view (rupture modulus and toughness), it is shownthat pores size plays likely an important role. Pores can be considered as flaws in the terms offracture mechanics and the flaw size, calculated from rupture strength and toughness is related tothe pore size distribution
Type of Medium:
Electronic Resource
URL:
http://www.tib-hannover.de/fulltexts/2011/0528/01/57/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.391.27.pdf
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