Development of Design and Analysis Methodology for Composite Bolted Joints

This paper summarizes work performed at the Helicopters Division of Boeing Defense and Space Group to develop composite joint design methodology for use on rotorcraft primary structure. The purpose of this work was to determine joint characteristics which affect joint bearing and bypass strength and to develop analytical methods for predicting the effects of such characteristics in structural joints. Experimental results have shown that bearing-bypass interaction allowables cannot be defined using a single continuous function due to variance of failure modes for different bearing-bypass ratios. Fatigue testing has shown that hole wear effects can be significant at moderate stress levels and should be considered in the development of bearing allowables. A computer program, BEARBY, has been developed and has successfully predicted bearing-bypass interaction effects for the (0/±45/90) family of laminates using filled hole and unnotched test data.