Abstract
Delamination is one of the major failure mechanisms for composites and traditionally the simulation requires high expertise in fracture mechanics and dedicated knowledge of the Finite Element Analysis (FEA) tool. Yet, the simulation cycle times are high. Geometrically nonlinear analysis approach, which is based on the Reissner-Mindlin-Von K´arm´an type shell facet model, has been implemented into the Elmer FE solver. Altair ESAComp software runs the Elmer Solver in the background. A post-processing capability, which enables the prediction of the delamination onset from the FEA output, has been implemented into the AltairESAComp software. A Virtual Crack Closure Technique (VCCT) specifically developed for shell elements defining the Strain Energy Release Rate (SERR) related to the different delamination modes at the crack front is used. The onset of delamination is predicted using the relevant delamination criteria that utilize the SERR data and material allowables in the form of fracture toughness. The modeling methodology is presented for laminates including initial through-the-width delamination. Examples include delamination in the solid laminate and debonding of the skin laminate in the sandwich structure. Rather coarse FE mesh has proved to yield good results when compared to typical approaches that utilize the standard VCCT or Cohesive Zone Elements.
Highlights
Layered composite structures exhibit various failure mechanisms namely fiber failure, matrix cracking, buckling and delamination
In this work the focus is in delamination, which is a separation between internal layers of a composite laminate caused by high through-the-thickness stresses, impacts or manufacturing defects
[10] The shell facet model was implemented with the Elmer opensource Finite Element Method (FEM) solver [11, 12, 13] developed by CSC - IT Center for Science (CSC) in collaboration with Finnish universities, research laboratories, and industry
Summary
Layered composite structures exhibit various failure mechanisms namely fiber failure, matrix cracking, buckling and delamination. The motivation of the work was to develop an approach that brings the delamination assessment in to the hands of a typical composites engineer. Virtual Crack Closure Technique VCCT [8] is the choice of this work since it is generally applicable [9] It is based on Linear-Elastic Fracture Mechanics (LEFM). In the simplest form the classic application of the VCCT consists of post-processing the finite element results of a layered structure in which an initial crack is explicitly modeled. ESAComp software [10] The shell facet model was implemented with the Elmer opensource Finite Element Method (FEM) solver [11, 12, 13] developed by CSC - IT Center for Science (CSC) in collaboration with Finnish universities, research laboratories, and industry. Latin indices take their values in the set {1, 2, 3} and Greek indices in the set {1, 2}
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