Surface tension and the Mori-Tanaka theory of non-dilute soft composite solids.

Eshelby's theory is the foundation of composite mechanics, allowing calculation of the effective elastic moduli of composites from a knowledge of their microstructure. However, it ignores interfacial stress and only applies to very dilute composites-i.e. where any inclusions are widely spaced apart. Here, within the framework of the Mori-Tanaka multiphase approximation scheme, we extend Eshelby's theory to treat a composite with interfacial stress in the non-dilute limit. In particular, we calculate the elastic moduli of composites comprised of a compliant, elastic solid hosting a non-dilute distribution of identical liquid droplets. The composite stiffness depends strongly on the ratio of the droplet size, , to an elastocapillary lengthscale, . Interfacial tension substantially impacts the effective elastic moduli of the composite when [Formula: see text]. When <3/2 (=3/2) liquid inclusions stiffen (cloak the far-field signature of) the solid.