Damage Tolerance of Thick Walled Composites with Wavy Fibers

This paper presents interim results of a collaborative effort between Boeing and Georgia Tech to develop accurate analysis methods to predict failure in thick composite structures that contain wavy fibers. A coupon design is presented that yields repeatable and controllable wrinkle geometry. Static and fatigue test data are presented to illustrate the impact of varying wrinkle geometry (wrinkle height, length, and percentage of wall thickness) on the static and fatigue strength of a glass/epoxy composite system. A finite element based failure model shows that nonlinear interlaminar shear stress-strain relations are required at least for accurate predictions of static strength for a wrinkle coupon. To generate the nonlinear interlaminar stress-strain relations, a full-field strain measurement based technique is developed. The failure model predictions for wrinkle coupons are correlated with test data.