| Popis: |
As part of the NASA Advanced Composites Project, several progressive damage analysis methods (PDA) have been applied toward predicting the responses of increasingly large and complex validation test articles. Ultimately, the project seeks the prediction of damage onset and evolution in post-buckled multi-stringer panels subjected to static compression loads. Several smaller specimens were designed and tested to assess specific capabilities of analysis methods in less computationally intensive settings. A three-point bend (3PB) doubler-stiffened coupon and a hatstiffened seven-point bend (7PB) panel are two lower-level validation test articles with which assessments of the PDA methods were made. The 3PB and 7PB specimens were designed to exhibit stable damage growth, with damage fronts containing interacting matrix cracks and delaminations at multiple interfaces. While the 3PB damage front propagates along the length of the specimen, similar to typical interlaminar material characterization coupons, damage in the 7PB initiates away from the panel edges while the panel is in a post-buckled-like deformed shape. A comprehensive data set was collected to measure the structural response and characterize damage. Load, strain, full-field displacement, acoustic emission, and passive thermography data were collected during testing. Most tests were interrupted during loading to characterize damage evolution in the specimen. Upon detecting any indication of damage growth, loading was stopped and ultrasonic and X-ray computed tomography scans were performed before reloading. A ply-by-ply fiber-aligned meshing strategy is employed to predict matrix cracks using a continuum damage mechanics method. Delaminations are represented using layers of cohesive elements between layers of solid elements. Test/analysis correlations are made using various metrics, including load/displacement histories |
