The Predictive Fatigue Behavior of Three Dimensional Composites

摘要

Three dimensional fabrics have seen increasing use lately as composite reinforcements. Advantages over prepreg or chopped fiber processes can include cost, handling, consistent quality, impact behavior, and resistance to delamination. To gain acceptance in the transportation industry it is imperative that its properties including dynamic and fatigue behavior be designable. A Progressive Failure Analysis (PFA) was developed jointly by Alpha Star Corp and NASA to predict fatigue life of composites and determine their damage mechanisms so that the life could be extended. The title of this software package is GENOA. It was discovered through fatigue testing that, as with all composite materials, void content greatly affected fatigue life for three dimensional composites. The challenge for GENOA was to predict this behavior and characterize the accumulation of damage. This paper examines the results of a study on an 11-ply stitched multi-angled composite. First, the S-N curves for resin and fiber were "reverse engineered" to match the composites experimental fatigue life. Calculated S-N curves were then used to predict the fatigue life of the composite with different void content: 2% and 12%. The GENOA simulation accurately predicted the fatigue life for both scenarios and showed the higher void content decreased the fatigue life. Additionally, GENOA demonstrated the damage and failure mechanisms to change depending on the void content. Virtual Testing has the potential to decrease lead times in commercializing composite products by assisting in the design optimization and verifying product durability while reducing or eliminating prototyping and field testing