Continuum Damage Modeling of Common Feature Test Component Under Constant Amplitude and Block Fatigue Loading

Progressive damage and failure analysis (PDFA) methods have been proposed as an essential tool for reducing the certification costs of primary and secondary composite structures. Successful application of PDFA methods have been demonstrated on test coupons and relatively small composite components; however, to achieve the goal of cost reduction for certification programs, performance of PDFA methods must be verified at larger length scales than typical aerospace allowable tests. The United States Air Force Research Laboratory (AFRL) has been actively investigating the use of these methods for aerospace durability and damage tolerant applications through the Composite Airframe Life Extension (CALE) program. Prior programs have examined applications such as unnotched tension/compression, open hole tension/compression, bearing, filled hole compression and bearing bypass. The Boeing-led CALE Project 4 seeks to build on the previous efforts and assess the tools for durability and damage tolerance of advanced composite structural features. In particular, this program focused on a Common Feature Test Component (CFTC) representative of key aircraft design considerations and failure modes. CFTC advanced structural features include a composite skin made of unidirectional tape, a fabric hat stiffener, and a mechanically fastened aluminum rib. In this work, the authors present an evaluation of fatigue simulations by CDMat – a PDFA software developed at the University of Texas at Arlington, used for the progressive damage and failure analysis of CFTC under static and cyclic loads. Both constant amplitude and block fatigue loading are considered, and residual strength capability of the element is predicted. This work will present comparison of CFTC simulation predictions with tests that have been conducted at AFRL including blind predictions of critical failure loads and fatigue damage growth for the CFTC specimens.