A new multiscale fracture mechanics methodology is being developed at TU Delft for composite materials. This methodology aims to unlock the use of hierarchical multiscale frameworks to link sub-ply fracture processes to laminate failure. In this thesis, this methodology is extended to 3D, both in terms of its analytical formulation and the numerical implementation of the pre-processing segment. Suitable conditions for three-dimensional periodicity were developed considering cases that do not appear in the two-dimensional case. Algorithms for three-dimensional crack identification were laid out. A series of representative loading cases were studied, including uniaxial and biaxial stretch, for an unidirectional ply and for a [0,90,0] laminate. Only a small number of analyses were carried out, due to the high computational cost compared to the two-dimensional case. A roadmap for further implementation is laid out, including a discussion of computational challenges for the implementation of three-dimensional multiscale fracture.