BONDED REPAIR SIZE LIMIT (BRSL) STUDY FOR HONEYCOMB SANDWICH STRUCTURES

According to Federal Aviation Administration (FAA) Policy Statement (PS-AIR-20-130-01), all critical aircraft structure must have a bonded repair size limit no larger than what is allowed for it to maintain limit load capability even if the repair failed between arresting features. It is particularly challenging for honeycomb sandwich principal structural elements (PSE) to meet this requirement due to the lack of stiffening elements to redistribute the load. This paper covers the test and analysis study from a joint Boeing-FAA Collaborative Research & Development project. Both closed-form analysis and advanced finite element analysis (FEA) methods are used to determine local peak strains and final residual strength of a honeycomb sandwich panel with a scarfed hole in the facesheet. This represents a conservative assumption that an entire bonded repair has failed. A series of tests conducted at FAA Technical Center showed good correlation with analysis results.