Progressive Failure-Based Composite Durability Model Navy SBIR FY2005.1 Sol No.: Navy SBIR FY2005.1 Topic No.: N05-035 Topic Title: Progressive Failure-Based Composite Durability Model Proposal No.: N051-035-0756 Firm: Rhombus Consultants Group, Inc. 1121 San Antonio Road Suite B-100 Palo Alto, California 94303-4311 Contact: Charles Rankin Phone: (650) 691-1142 Web Site: www.rhombuscgi.com Abstract: The proposed program builds on prior development, implementation and validation of models for progressive failure of monotonically loaded composite structures to derive a durability model for predicting fatigue lifetime of composite structures. The durability model incorporates a model for fatigue damage accumulation in composites based on a generalized Paris' Law, and a composite residual-strength model based on progressive failure analysis methods. Finite-element models will be used in conjunction with coupon-level laboratory tests to calibrate fatigue- and residual-strength models with respect to material characteristics and definition of local load-intensity (stress- or strain intensity) and damage-accumulation functions. Several candidate composite strength models will be evaluated analytically to determine the best predictors of load intensity and damage accumulation to match damage growth measured under cyclic loadings. The product of the Phase I effort will be a unified model for composite durability analysis. This model will be refined and applied to analyze results of actual component durability tests in Phase II as a means to speed industrial application of the model. Benefits: The chief benefits accruing to the availability of a tractable and accurate durability model for composite structures are (a) reduction of cost to design and qualify composite primary structures, and (b) improved life-cycle management of composite structures owing to application of well-founded, safe-life operational strategies. The commercialization plan proposed would result in the availability of the new durability model in commercial finite-element analysis programs and stand-alone software for commercial distribution. Return