Impact of pre-existing delamination defects on the evolution of buckling in composites
Topic(s) : Material and Structural Behavior - Simulation & Testing
Co-authors :
Swami SUBRAMANIYAN VENKAT (GERMANY), Sven SCHEFFLER (GERMANY), P.M. ANILKUMAR (GERMANY), Emmanuel BARANGER (FRANCE), Raimund ROLFESAbstract :
The structural integrity of wind and aerospace structures encounters significant challenges due to a variety of damage mechanisms, including delamination. Delaminations pose critical threat to safety and reliability of the structure due to challenges in detecting them and the severe detriment they cause to mechanical performance of the structure. Fatigue loads can trigger the initiation of delaminations in a pristine laminate. They may also cause either the growth of interfacial defects introduced during the manufacturing process or the delaminations originated by other events such as impact. With sufficient number of load cycles, these delaminations can evolve to a critical size, potentially resulting in catastrophic buckling failure of the structure. This particular subject has, up to this point, seen relatively limited exploration in the existing research landscape. It therefore necessitates deeper investigation and has the potential to substantially advance our understanding of structural failures in composite materials under cyclic loading. In this study, the focus is laid on the classical case of column buckling as a starting point to explore this issue.
As a preliminary step in this research, a quasi-static 'Effect of Defects' study has been conducted. This first step is a necessity to determine the critical configurations which will be analysed later under fatigue loading conditions. A series of finite element analyses have been carried out using commercially available FE software (ABAQUS 2022). These analyses involved maintaining a constant applied load (matching the specified service load) while progressively increasing the delamination sizes in the models. The investigation systematically evaluates how the location of delamination affects the manner in which the laminate tends to buckle. The assessment of the criticality of each distinct buckling mode observed in the study is reported and discussed. This is done by comparing the out-of-plane displacements for different configurations and determining the critical delamination size associated with the unstable growth across diverse configurations. To account for mixed-mode delamination growth for various buckling modes, a user-defined cohesive zone model [2] has been formulated and employed. The most critical configurations exhibited a sequential progression from sublaminate local buckling to eventual structural collapse which has been comprehensively explored in this study. As a conclusion, the study addresses how the observed behavior can vary in response to the applied load, thereby highlighting the relationship between the applied load and the sublaminate buckling load.
As a preliminary step in this research, a quasi-static 'Effect of Defects' study has been conducted. This first step is a necessity to determine the critical configurations which will be analysed later under fatigue loading conditions. A series of finite element analyses have been carried out using commercially available FE software (ABAQUS 2022). These analyses involved maintaining a constant applied load (matching the specified service load) while progressively increasing the delamination sizes in the models. The investigation systematically evaluates how the location of delamination affects the manner in which the laminate tends to buckle. The assessment of the criticality of each distinct buckling mode observed in the study is reported and discussed. This is done by comparing the out-of-plane displacements for different configurations and determining the critical delamination size associated with the unstable growth across diverse configurations. To account for mixed-mode delamination growth for various buckling modes, a user-defined cohesive zone model [2] has been formulated and employed. The most critical configurations exhibited a sequential progression from sublaminate local buckling to eventual structural collapse which has been comprehensively explored in this study. As a conclusion, the study addresses how the observed behavior can vary in response to the applied load, thereby highlighting the relationship between the applied load and the sublaminate buckling load.