1. EM A ,U ni versi t at der B undesw ehr H am burg,H ol stenhofw eg 85,22043 H am burg 2. M ax-Pl anck-Insti tut f ur Pol ym erforschung,Postfach 3148,55021 M ai nz 3. Insti tut f ur T heoreti sche Physi k,U ni versi t at H annover,30167 H annover 4. T heoreti sche Physi k III,U ni versi t at B ayreuth,95440 B ayreuth,G erm any (PR L 84,3223,(2000)) In the l i m i t ofi n ni te yi el d ti m e for stresses,the hydrodynam i c equati ons for vi scoel asti c,N on-N ew toni an l i qui ds such as pol ym er m el ts m ust reduce to that for sol i ds. T hi s pi ece of i nform ati on su ces to uni quel y determ i ne the nonl i near convecti ve deri vati ve, an ongoi ng poi nt of contenti on i n the rheol ogy l i terature. A l lvi scoel asti c non-N ew toni an ui ds behave as N ewtoni an onesatl ow frequenci es,and assol i dsathi gherfrequenci es. A consi stent hydrodynam i c descri pti on needs to re ect thi s fact and m ust therefore contai n, as speci al cases, both the hydrodynam i c theory for i sotropi c l i qui ds and sol i ds. T he l i qui d l i m i t i s wel lheeded i n the pol ym erl i teratureand uni versal l y correctl y i m pl em ented [ 6,7] . T he sol i d l i m i t i s probl em ati c,as we shal lsee,and com pati bi l i ty especi al l y i n the nonl i near regi m e ofl arge di spl acem ents and rotati ons has so far proven el usi ve. T he reason behi nd i t i s probabl y the l ack ofa consi stent hydrodynam i c theory for sol i ds.T hel astsentencem ay com easa surpri se,butthepoi nt we are m aki ng here i s:A l though both the nonl i nearel asti ci ty theory [ 6] and the l i neari zed hydrodynam i cs for crystal s [ 1,8,9]are wel lknow n and establ i shed,a consi stent hydrodynam i c theory that i ncl udes both nonl i near and i rreversi bl e term s i s not { i n spi te ofsom e i nsi ghtful papers [ 10] . O ne of the obstacl es i s that such a theory necessari l y em pl oysa strai n tensordi erentfrom the one custom ari l y used [ 8] . T he usualstrai n tensor i s of the Lagrange type,deri ved from equati ons ofm oti on for m ass poi nts,w hi l e a fram ework to set up hydrodynam i c equati ons i ncl udi ng di ssi pati ve term s onl y exi sts i n the Eul eri an descri pti on { w hi ch consi ders evol uti on of el d vari abl es at spati al poi nts. C onsi stency forbi ds a m i xi ng ofboth descri pti ons and requi res an Eul eri an strai n tensor [ 11] . (W e note that the l i near hydrodynam i c theory m ay m i x both descri pti ons,as the sm al l ness of the di spl acem entsensuresthatthe di screpancy i snegl i gi bl e. )T he presentati on ofthe nonl i near hydrodynam i c theory for sol i ds i s w hat we shal ldo rst. T hen these equati onsare general i zed fornon-N ew toni an ui ds by addi ng rel axati on-type term s to account for a ni te yi el d ti m e ofthe stresses,such that i n the hi gh frequency l i m i t the theory i s unchanged,but i n the l ow frequency l i m i t onl y the term s ofthe i sotropi c l i qui d hydrodynam i cs rem ai n. So, by ensuri ng the val i d l i qui d and sol i d l i m i t...

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Actuators based on carbon nanotubes (CNT) have the potential to generate high forces at very low voltages. The density of the raw material is just 1330 kg/m3, which makes them well applicable for lightweight applications. Moreover, active strains of up to 1% can be achieved-due to the CNTs dimensional changes on charge injection. Therefore the nanotubes have to be arranged and electrically wired like electrodes of a capacitor. Immersing the nanotubes in an electrolyte increases the capacity of the system by allowing electro-chemical double layers to be built around the CNT. For the experimental investigation of the strain generation, carbon nanotube sheets are manufactured by vacuum filtration. The in-plain strain response is being examined, when applying a voltage to the system. This paper presents experimental investigations of the systems response in dependence of varying system parameters like capacity and resistance. Dependencies of the actuator system were formulated from these experimental results. A guideline of how to improve a CNT based actuator is derived from these dependencies.