Repair of Thin Face Sheet Sandwich Structure with Small Holes and Impact Damage

Abstract

This manuscript presents experimental results of compression tests of repaired sandwich structure typical of a launch vehicle Payload Adapter Fitting (PAF) that is being considered for the National Aeronautics and Space Administration’s (NASA) Space Launch System (SLS) launch vehicle. Specimens with 8-ply quasi-isotropic carbon/epoxy face sheets and aluminum honeycomb core were damaged with representations of misdrilled holes, barely visible impact damage (BVID) or visible impact damage (VID). A patch repair technique not requiring removal of any material is presented and assessed for residual in-plane compressive load-carrying capability on each of the three types of damage. Edgewise compression tests on specimens demonstrated the repairs could recover all measured undamaged compressive load-carrying capability of the misdrilled hole and BVID specimens. For the specimens with VID, an average of about 91% of the average measured undamaged compressive load carrying capability was recovered indicating that larger patches, or perhaps removal and replacement of the damaged material, may be needed for more severe damage if all the measured undamaged compression strength needs to be regained.