Incorporation of Analysis Enhancements of a p-Element Analysis Code Required for Implementing the Strain Invariant Failure Theory

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 atstreamlining the design certification process for laminated composite structures.Phase I activities address the necessary enhancements to StressCheckr, 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.