“…Here, as a (computationally more efficient) complement, we present a three-step, fully continuum micromechanicsbased macro-to-meso-to-micro (stress and strain) downscaling scheme, linking in the end the quasibrittle failure of single micrometer-or sub-micrometersized hydroxyapatite crystal needles to the overall strength of both millimeter-sized biomaterial scaffolds and composites comprising biomaterial scaffold and bone tissue, respectively. For this purpose, a number of homogenization concepts are adapted, extended, and combined, considering the pioneering contributions of Eshelby (1957), Hill (1963Hill ( , 1965, Laws (1977Laws ( , 1985, Hervé and Zaoui (1993); and also considering more recent contributions of Deudé et al (2002), Dormieux et al (2004), Fritsch et al (2006), Bertrand andHellmich (2009). Following Fritsch et al (2009a, b), we feed the stress of the most unfavorably loaded hydroxyapatite needle into a suitable, Mohr-Coulombtype failure criterion, and deduce then therefrom the corresponding ultimate macroscopic load bearable by the aforementioned granular, hydroxyapatite-based biomaterial (optionally containing ingrown bone tissue).…”