ANALYTICAL DESIGN METHODOLOGY FOR MULTI-ROW MULTI-COLUMN FASTENER JOINTS IN COMPOSITE STRUCTURES

An analytical tool for the preliminary design of single- and multi-row mechanically fastened joints in composite and FML structures is presented. The two-dimensional load distribution in multi-row and multi-column joints is obtained by superposing the load distributions in row and column direction - each based on a one-dimensional spring model, respectively. The obtained overall transfer and bypass loads at each fastener junction are then transformed into ply loads in order to calculate the 2D stress distribution around a fastener hole. The analytical tool currently allows for a design for ultimate load. On that account, the characteristic curve method is applied in combination with the Yamada-Sun criterion to predict failure in the composite plies while the von Mises yield criterion is used to determine failure in ideally plastic metal plies. Characteristic distances in tension and compression required by the characteristic curve method are determined numerically. The tool predictions are compared to experimental pin-bearing test data and discussed with respect to adaptability and further development