ABSTRACT
Growth is an irreversible process, metabolism and catabolism being associated with distinct pathways. Energy provided by metabolism is used to grow the mass and improve the mechanical properties of the tissue constituents. This chapter discusses multiplicative decomposition of the deformation into a growth transformation and an elastic transformation for a growing constituent of a mixture. The incompressibility of a single species of a mixture does not introduce a constraint. A constraint arises only if all species are incompressible. The chapter is devoted to build growth laws for the mixture constituents using the notion of convex homeostatic surfaces as an extension of the developments for a single solid. It also describes several aspects that contribute to the evolution of the stiffness of the collagen network during growth, as well as asymptotic properties of the growth law.
