Department Seminar of Oleg Peri - Progressive damage models for multi-layered laminates under low-velocity impact, compression and fatigue after impact
School of Mechanical Engineering Seminar
Wednesday, November 03, 2021, at 14.00
Wolfson Building of Mechanical Engineering, Room 206
Progressive damage models for multi-layered laminates under low-velocity impact, compression and fatigue after impact
Oleg Pery
M.Sc. student of Prof. Rami Haj-Ali
Multilayer composites can have pronounced nonlinear stress–strain behavior under axial shear and during multi-axial strain-softening damage. Accurate constitutive modeling combined with efficient computational algorithms are crucial to generate effective simulation tools for laminated composite materials and structures.
This study investigates and extends the formulation of the progressive damage model based on the Schapery theory. A particular emphasis of the Schapery theory is its treatment of the nonlinear behavior of a unidirectional layer in the pre-peak stage due to the continuous accumulation of micro-cracks in the matrix. A new numerical implementation is proposed for this model in 3D explicit finite-element. The damage model is integrated into both layer-by-layer and sublaminate methods. The first explicitly recognizes each layer in the thickness direction, while the sublaminate approach provides a meso-scaled effective nonlinear continuum for a through-thickness periodic stacking sequence. Interface cohesive elements are used at the material and structural levels to simulate the initiation and progression of distributed delamination systems.
The proposed computational framework has been first applied for low velocity impact (LVI) of laminated plates. The same framework is also used to analyze compression after impact (CAI) and predict the residual compression strength of laminated plates.
The fatigue model was developed based on the Kinetic Theory of Fracture (KTF). The KTF is integrated into an implicit commercial FE code. Thus, it can be used separately or with the LVI framework to simulate the entire life cycle of the structure with and without prior impact events.
The LVI analysis results correlate well to data from tests designed jointly and conducted by the University of Michigan and the U.S. Air Force Research Laboratory. A demonstration analysis of an impact event and then fatigue was performed and compared to non-impacted fatigue.
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