On the Saint-Venant torsion of composites bars with imperfect interfaces (Q2748151)

An important extension of Saint-Venant's theory on torsion is the case in which the cross-section of the cylinder is not homogeneous, but contains some subregions of different materials in its interior. Here the classical theory still applies, but with the difference that now the warping function undergoes discontinuities at the interfaces between the matrix and inclusions.NEWLINENEWLINENEWLINEIf, however, the inclusions are not perfectly bonded to the elastic matrix, but separated by an elastic sheet, then the boundary conditions at each interface are more complicated. They are of two types, according to the circumstance that the shear modulus of the interface is low or high. In both cases it is possible to estimate the overall torsional rigidity of the cross-section.NEWLINENEWLINENEWLINEThe paper is interesting, but it is strange that the authors ignore the works by \textit{G. Geymonat} and \textit{F. Krasucki} [e.g. C. R. Acad. Sci., Paris, Sér. II, Fasc. b, Méc. Phys. Chim. Astron. 325, No. 6, 307-314 (1997; Zbl 0894.73051)] on the rigorous definition of an interface in general elasticity.