Abstracts Category : Other

An efficient virtual testing framework to simulate the progression of damage in notched composite laminates

by Mina Shahbazi

The progression of damage in composite laminates is influenced by the interactions of several failure/damage mechanisms including matrix cracking, fibre breakage, splitting and delamination. In capturing detailed prediction of various damage modes, it is important to maintain the efficiency of the computational models so that they can be readily used by engineers for damage tolerant design of composite components. Continuum damage models are commonly employed to simulate the smeared response of certain failure modes such as matrix cracking and fibre failure due to their higher numerical efficiency in comparison with discrete damage models. However, application of continuum damage based models for accurate prediction of the onset and propagation of macro-discrete damage modes (i.e. splitting and delamination) and their interactions with other failure modes is limited. This work presents an efficient methodology to capture the interacting effect of discrete and smeared cracks based on a combination of the continuum and discrete approaches. Here, delamination is the only damage mode captured by a discrete approach (cohesive zone interface), while all intra-laminar forms of damage including splitting are modelled using the non-local composite damage model (CODAM2) in a mesoscopic context. Through placement of discrete delamination interfaces and synchronizing the onsets of delamination and matrix cracks, the computational effort is markedly reduced. The effect of ply thickness and constraints imposed by neighbouring plies on initiation of intra-laminar matrix damage modes is also considered. A novel methodology involving a combination of physical and virtual tests on notched laminates is proposed to calibrate the in-situ fracture energies of intra-laminar damage modes.The numerical simulations are conducted using an enhanced version of CODAM2, implemented in the explicit finite element software, LS-DYNA, as a user-defined model (UMAT), together with a built-in tie-break cohesive interface in LS-DYNA to model delamination. The proposed approach is validated using various layups and notched specimen geometries under tensile loading. The reasonable agreement of the predictions with experiments in terms of global behaviour and detailed damage patterns proves the efficiency and applicability of the presented methodology for damage tolerant assessment of composite laminates.