Caglar Oskay delivered an invited lecture at the Army Research Laboratory
Lecture Title: Multiscale Response and Life Prediction of Composite Materials and Structures.
Location: Vehicle Technology Directorate, US Army Research Laboratory, Aberdeen Proving Ground, MD.
Abstract:
We will present a multiscale simulation-based failure and life prediction approach for composite materials and structures subjected to static and fatigue loads. The multiscale methodology we employ considers the presence of multiple time scales, to account for the size disparity between loading periods and characteristic times associated with damage accumulation, as well as multiple spatial scales, to account for the size disparity between the characteristic lengths of the composite structure and the constituent materials of the microstructure. The methodology is a space-time generalization of the computational homogenization method. The primary issue of computational complexity (i.e., the tyranny of scales) is addressed by reduced order modeling approaches applied at both space and time. The multiscale approach is also coupled with a probabilistic (Bayesian) parameter calibration strategy, which allows for quantification of uncertainty associated with life predictions.
We present the results of a recent study on prediction of the fatigue stiffness degradation, damage progression and residual strength after fatigue of carbon fiber reinforced composite materials. The study is the assessment of the state of the art in predictive capabilities of the composite failure prediction methods and models, as a part of a larger program on the assessment and quantification of applying damage tolerant design principles to aerospace composite structures. A suite of experimental data for a carbon fiber reinforced epoxy (i.e., IM7/977-3) generated at the AFRL was employed in this study. The calibration experiments were initially provided to us (in addition to a number of other teams). The calibration of the computational model was performed and the calibrated model was exercised to predict the response of various laminated composite layups. The proposed approach was found to be accurate in predicting the fatigue properties and damage propagation characteristics of complex layup and specimen configurations (notched and unnotched). Based on the blind prediction results, the model improvement strategies are devised and employed to further improve the predictive capability of the composite damage and failure model.