Enhanced Analytical Modeling of Crack Propagation in Through-Thickness Reinforced Composite Laminates
Topic(s) : Material and Structural Behavior - Simulation & Testing
Co-authors :
Albrecht RADTKE (GERMANY), Philipp WEISSGRAEBER (GERMANY)Abstract :
Several measures to counteract laminated fibre-reinforced composites' vulnerability to delamination with a transverse reinforcement have been thorougly researched. These include 3D-weaving and stitching of dry layups prior to the impregnation as well as z-pinning, a technique involving the insertion of pins, either composite or metal, in the through-thickness direction of an impregnated laminate layup laminate typically before curing [1].
In all of these reinforcements the interface between the composite layers is bridged, thoughening the laminate in the through-thickness direction, thus hindering inter-laminar crack propagation. Several studies have demonstrated their capacity to enhance fracture behavior by implementing deliberate crack bridging [2] , underscoring the importance of accurate analytical models to be able to predict and design the resulting delamination behaviour.
The mode-I crack propagation in general as well as the effectivness of through-thickness reinforcements in FRP-composites are typically investigated through double-cantilever-beam (DCB) tests. In this study a new enhanced model describing the delamination through DCB tests based on beam theories is introduced. The new approach takes into account the cantilever beams' transverse compliance near the crack tip through an incorporation of a Winkler elastic foundations in the analytical model. Also the model introduces first order shear deformation [3] in the beam kinematic in order to also allow realistic delamination behaviour predictions for setups with non-neglible shear compliance.
To be able to easily easily investigate inter-laminar crack propagation in different composites featuring different through-thickness reinforcements, an effective parametric iterative solving following the approach of Song [4] is implemented. This takes into account the crack growth in both an unreinforced and a reinforced zone, whose behaviour gets characterized by an applicable linear bridging law accoring to the reinforcement technique used.
The results are then compared with finite element simulations featuring a cohesive zone in the crack plane and distributed or individual non-linear spring elements representing the different kinds of transveral toughening measures as well as results from literature. The improved agreement of the results of this novel analytical model with experimental and numerical studies, marks an important advancement in prediction of delamintion in through-thickness reinforced composite laminates. The refined analytical model offers valuable insights for the design of composite laminates with enhanced resistance to delamination. It shows the significance of accurately characterizing the transverse compliance and shear deformation of the beams in modeling the crack bridging behavior achieved by through-thickness reinforcement techniques.
In all of these reinforcements the interface between the composite layers is bridged, thoughening the laminate in the through-thickness direction, thus hindering inter-laminar crack propagation. Several studies have demonstrated their capacity to enhance fracture behavior by implementing deliberate crack bridging [2] , underscoring the importance of accurate analytical models to be able to predict and design the resulting delamination behaviour.
The mode-I crack propagation in general as well as the effectivness of through-thickness reinforcements in FRP-composites are typically investigated through double-cantilever-beam (DCB) tests. In this study a new enhanced model describing the delamination through DCB tests based on beam theories is introduced. The new approach takes into account the cantilever beams' transverse compliance near the crack tip through an incorporation of a Winkler elastic foundations in the analytical model. Also the model introduces first order shear deformation [3] in the beam kinematic in order to also allow realistic delamination behaviour predictions for setups with non-neglible shear compliance.
To be able to easily easily investigate inter-laminar crack propagation in different composites featuring different through-thickness reinforcements, an effective parametric iterative solving following the approach of Song [4] is implemented. This takes into account the crack growth in both an unreinforced and a reinforced zone, whose behaviour gets characterized by an applicable linear bridging law accoring to the reinforcement technique used.
The results are then compared with finite element simulations featuring a cohesive zone in the crack plane and distributed or individual non-linear spring elements representing the different kinds of transveral toughening measures as well as results from literature. The improved agreement of the results of this novel analytical model with experimental and numerical studies, marks an important advancement in prediction of delamintion in through-thickness reinforced composite laminates. The refined analytical model offers valuable insights for the design of composite laminates with enhanced resistance to delamination. It shows the significance of accurately characterizing the transverse compliance and shear deformation of the beams in modeling the crack bridging behavior achieved by through-thickness reinforcement techniques.