A synergistic damage mechanics based multiscale model for composite laminates subjected to multiaxial strains. (April 2015) - Montesano, John
Highlights: Developed a multiscale damage model for multidirectional laminates under multiaxial strains. Damage modes due to cracks in multiply oriented off-axis plies are analyzed. Shear deformation response is accounted for by the model; not previously considered. Accurate prediction of nonlinear stiffness degradation for three laminate layups. Prediction model is robust; useful for symmetric laminates with multiple ply cracks. Abstract: A multiscale model based on synergistic damage mechanics is developed for predicting the elastic response of symmetric composite laminates containing matrix cracks in plies of multiple orientations, and subjected to an arbitrary multiaxial strain state. On the micromechanical scale, the proposed multiscale modeling approach invokes three-dimensional finite element analysis to characterize the multiaxial damage state within the cracked multidirectional laminate, and evaluate damage constants required in the damage constitutive model. These damage constants capture the ply constraint effects acting on the surface displacements of the developed matrix cracks in all off-axis and on-axis plies. The representative volume element describing the applied multiaxial stress state within the laminate is developed through finite element models using periodic boundary conditions, which are necessary to accurately represent the physical problem. The developed micromechanical models also allow for prediction of the laminate's shear deformation response. The model is shown to accurately capture the nonlinear stiffness degradation exhibited by cross-ply, quasi-isotropic and angle-ply laminates containing matrix cracks in multiple plies and subjected to various multiaxial stress states. The prediction results are validated by available experimental data and compared with independent three-dimensional finite element calculations. The multiscale model can easily be implemented into a commercial finite element software package in order to predict stiffness degradation in composite structures. This will provide a means to predict the integrity and durability of these structures, and ultimately lead to damage-tolerant designs.