Paper number 449

MODELING THE INFLUENCE OF STITCHING ON DELAMINATION GROWTH IN STITCHED WARP-KNIT COMPOSITE LAP JOINTS

E.H. Glaessgen¹, I.S. Raju² and C.C. Poe, Jr.²

1National Research Council
2Mechanics of Materials Branch
NASA Langley Research Center, Hampton, VA, 23681

Summary

The effect of stitches on the failure of a single lap joint configuration was determined in a combined experimental and analytical study. The experimental study was conducted to determine debond growth under static monotonic loading. The stitches were shown to delay the initiation of the debond and provide load transfer beyond the load necessary to completely debond the stitched lap joint. The strain energy release rates at the debond front were calculated using a finite element-based technique. Models of the unstitched configuration showed significant values of modes I and II across the width of the joint and showed that mode III is zero at the centerline but increases near the free edge. Models of the stitched configuration showed that the stitches effectively reduced mode I to zero, but had less of an effect on modes II and III.

Keywords

virtual crack closure technique, plate finite elements, textile composites, stitching, debonding, lap joints.