Material instabilities in nematic elastomers

Soft deformation paths and domain patterns in nematic elastomers are analyz ed through the minimization of a nonconvex free-energy recently proposed in the literature. The free-energy density has multiple wells, and is not res tricted to small deformations. The problems of calculating the quasiconvex hull of the energy wells and the quasiconvex envelope of the free-energy de nsity are formulated and solved (the latter only in two spatial dimensions) . This leads to a complete characterization of the set of soft deformations paths available to a given material, and of its effective macroscopic ener gy. (C)2000 Elsevier Science B.V. All rights reserved.