DURABILITY AND DAMAGE TOLERANCE TESTING AND ANALYSIS OF STARSHIP FORWARD WING WITH LARGE DAMAGES

摘要

A methodology synthesizing the life factor, load enhancement factor, and damage in compositesrnis proposed to determine the fatigue life of a damage-tolerant composite airframe. Thisrnmethodology further extend the current practice during damage-tolerance certification to focusrnon the most critical damage locations of the structure and interpret the structural and load detailsrninto the most representative repeated load testing in element level to gain information on thernresidual strength, fatigue sensitivity, inspection methods and inspection intervals during fullscalerntest substantiation. The proposed methodology was validated with several full-scale testrnexamples of the Beechcraft Starship forward wings with large impact damages on the front andrnaft spars. Full-scale durability and damage tolerance (DaDT) test conducted with category 2rndamage (that can be detected by scheduled or directed field inspection at specified intervals) onrnthe aft spar using the updated LEFs based on the design details of Starship forward wingrnstructure demonstrated the repeated life requirements according the proposed load-life-damagernhybrid approach, and the post-DaDT residual strength requirements. The Starship forward-wingrnDaDT test article with category 3 damage (that is obvious and can be detected within a fewrnflights by walk-around inspection) on the front spar demonstrated the capability of therncumulative fatigue reliability model to predict the damage growth in terms of reliability and therncapability of the model to determine the inspection levels. Although it is not a one-to-onerncorrelation for the damage propagation or its size, the cumulative fatigue reliability modelrnhighlighted load segments that resulted in gradual progression of local damage, such as possiblernmatrix cracks, and the global impact of high loads that resulted in evident damage growth.