| dc.description.abstract | Understanding how advanced composites behave under critical conditions is necessary for effective im- plementation of these materials in aerospace structures. Common design involves advanced laminated carbon- fiber reinforced polymer (CFRP) configurations with fiber orientations tailored for expected load conditions such as flight maneuvers or landing. Among the characteristics of CFRP laminates, compression strength is a critical weakness. The compression behavior is complicated due to the presence of multiple failure mechanisms which may interact during the loading process. Among the failure mechanisms, kink bands are typically driving ultimate failure, while splitting, matrix cracking, and delaminations may additionally be present and affecting the overall behavior. Additional complications such as existing regions of material failure, or damage, due to an impact event weaken the structural response. Under compression-after-impact (CAI) test conditions, interlaminar properties are a crucial weakness and associated with delamination-driven failure. Technologies proposed to arrest delamination growth and increase the CAI strength include through- thickness reinforcements called z-pins. Delamination and other CAI failure mechanisms in the presence of z-pins are not yet fully understood. This dissertation presents multiscale investigations of the compression response of laminated CFRP composites with and without z-pins undertaken using state-of-the-art compu- tational damage analysis models and experimental methods. Physics-based prediction of the composite re- sponse is accomplished by integrating state-of-the-art multiscale and cohesive zone models in finite element analyses. Experimental campaigns are used to support the development, calibration, and validation of the computational models. Damage progression predictions supplement experimental results and demonstrate advancements in modeling capabilities to predict compression failure in laminates with and without z-pins. | |
