Interacting Damage Mechanisms in Laminated Composites Subjected to High Amplitude Fatigue

Abstract

1 This manuscript provides a combined computational-experimental investigation of the 2 interaction of damage mechanisms in carbon fiber reinforced polymer (CFRP) laminated 3 composites subjected to fatigue loading. The investigations particularly focus on [60,0,-4 60] 3S laminates, whose behavior demonstrates strong interactions between the relevant dam-5 age modes. Numerical investigations are performed using a spatio-temporal computational 6 homogenization-based multiscale life prediction model. The computational approach relies on 7 a model order reduction methodology to develop a meso-model that can capture the relevant 8 failure mechanisms in a computationally efficient manner. The model was calibrated using a 9 suite of experimental data from the static and fatigue response of simple laminates made of the 10 same constituents. The calibrated model along with experimental observations from acoustic 11 emission and X-ray computed tomography were employed to understand the relative roles of 12 delamination and splitting, and their interactions in controlling fatigue failure processes in 13 CFRPs. 14 The state of damage in laminated composite structures subjected to fatigue loading has a sig-18 nificant effect on the remaining life and the residual strength. Early works on fatigue modeling 19focused on identification of damage markers or characteristic states of damage that correlate 20 well with the prediction metrics such as life, residual strength or residual stiffness (e.g., [25]). 21While this approach provides accurate predictions for some laminate layups and geometries, 22 damage markers may significantly differ from one laminate configuration to another, and there-23 fore the approach does not generalize to arbitrary laminate configurations. The difficulty is 24 largely due to the interactions between various damage mechanisms that depend on the consti-25 tutive and failure properties of the composite constituents, laminate stacking, ply thicknesses, 26 loading profile, and structural geometry. In the context of carbon fiber reinforced polymers 27 (CFRPs) subjected to tension-tension fatigue, understanding and modeling of the interactions 28 between the transverse matrix cracks, longitudinal splits, fiber fracture and delaminations are 29 critical to achieving reliable predictive capability when subjected to cyclic loading. 30 Damage mechanisms and their evolution under fatigue loading conditions of notched and 31 unnotched specimens have been traditionally investigated separately. While the damage mech-32 anisms in both types of specimens are typically the same, damage in unnotched specimens orig-33 inates at edge singularities, whereas stress concentrations at the notch tip initiates damage in 34 notched specimens. Mohandesi and Majidi [17] investigated the fatigue damage mechanisms of 35 quasi-isotropic unnotched specimens. Off-axis matrix cracking and delamination between 90 36 degree and 45 degree plies at the exterior edges of the specimens constituted the initial dam-37 age. The propagation of d...

Recent Advances in Computational Methods in Engineering Mechanics

“…They employ the asynchronous spacetime discontinuous Galerkin (aSDG) method and show various advantages of this approach. Bogdanor et al (2019) provide a combined computational-experimental investigation of the interaction of damage mechanisms in carbon fiberreinforced polymer (CFRP) laminated composites subjected to fatigue loading. A computational homogenization-based multiscale life prediction model, which relies on a model order reduction methodology, is employed.…”