Computed Tomography Informed Composite Damage State Model Generation

Abstract

During an impact event on composite structures a complex damage state is created involving matrix cracking, delamination, and fiber damage. For multi-directional composite laminates, conventional Non-Destructive Evaluation (NDE) techniques such as Ultrasonic C-Scan are generally limited to characterizing damage as a projected overall envelope (through-transmission), or as a series of damage planes that are partially hidden by planes closer to the transducer (one-sided pulse-echo mode). Alternatively, X-ray Computed Tomography (CT) imaging provides non-destructive high fidelity damage information that accurately displays layer-by-layer damage states and matrix damage in a way that can be made compatible with implementation into high fidelity modeling. A method has been developed to convert detailed 3D damage state information into composite relevant delamination, matrix cracking and fiber damage model representation. Based on geometric information, delamination information can be implemented into a computational model by excluding points within the delaminated zone from the initial bonding set in a ply-by-ply model, Matrix damage can be implemented as element sets with degraded initial matrix properties, and fiber breakage can be implemented as element sets with degraded fiber properties. Composite specimens subjected to low velocity metal tip impact were CT imaged and the resulting data were converted to model relevant data. Potential implementable data includes delamination, matrix damage, and measured indentation profile.