Historically, the correlation between predicted failure and actual failure of composite aircraft structures has left much to be desired. Current analytical prediction methods often over estimate or under estimate the failure load by 25% or more. Compounding the problem is that the failure location is not consistently identified by the analytical method. The inability to accurately model and predict failure of composite structure has led to a lengthy and costly, test-based certification process. A relatively new failure theory for composites, the Strain Invariant Failure Theory (SIFT), is proving to be far more accurate at predicting failure. SIFT in conjunction with a robust finite element analysis (FEA) tool offer an efficient method aimed at streamlining the design certification process for laminated composite structures. Phase I activities address the necessary enhancements to StressCheck, a parametric p-version FEA tool, to facilitate the use of SIFT methodology during post-processing. Enhancements include: 1) Add a General Shell element and a Transition element that will enable the connection of a shell to a 3D solid element. 2) Add laminated orthotropic material properties that follow the general curvature of a shell or solid element. 3) Add a Contact element and 3D Fastener element with clamp-up simulation.
Benefit: Successful demonstration of the proposed enhancements in combination with SIFT will provide analysts with a tool enabling the design certification of composite structure at a significantly reduced cost compared to certification methods in place to date. StressCheck can be expanded to include new material systems, such as hybrids and exotic materials for use on next generation Naval aircraft. Aerospace OEMs such as The Boeing Company, are expected to incorporate the technical capabilities developed under this project into their design, design certification and test evaluation procedures. Verification and validation of the method will lead to a substantial increase in the number of StressCheck licenses placed and create an increased demand for training and technical services to be provided by ESRD.
Keywords: Global/Local analysis, Global/Local analysis, Shell Element, Laminated Orthotropic Material Properties for General Curvature, 3D Contact, 3D Fastener Element, Composite structures, Strain Invariant Failure Theory (SIFT)., Parametric Handbook, p-Element
