Experimentation and Analysis of Composite Scarf Joint

Composite bonded scarf repairs were examined by experimentally measuring and analytically predicting the residual curing strains and strains due to mechanical loading. To accomplish this a three prong approach was used: a full strain field through a repaired laminate's thickness was measured for both a loaded specimen and a specimen with the residual strain released, models were developed for comparison to both states, and data was collected for large tensile test specimens at various stages of being scarf repaired. A ~14:1 straight scarfed one-inch wide specimen was used to collect Moir interferometry data to calculate a full strain field due to mechanical loading and strain release. A three-dimensional thermo mechanical linear elastic analysis using an Air Force Research Laboratory in-house stress analysis program B-Spline Analysis Method (BSAM) results were correlated to the Moir interferometry test results. Three large tensile test specimens were tested as manufactured, three were tested with a scarfed hole in the center, and the remaining were tested with a scarf repair centered on a hole in the center. The strain gage results from the panels are presented. An additional feature of this work was to document each of the difficulties present in the given methods incorporated in this research.