| The effectiveness of repair of damaged fiber reinforced composite laminates was investigated; the effectiveness of repair being assessed by the tensile failure load of the repaired laminate.; First, tests were conducted measuring the failure loads of laminates repaired either by the scarf, the uniform lap, or the stepped lap technique. Data were generated with the following parameters having been varied: type of material of the damaged laminate, type of repair material, scarf angle and number of external plies in scarf repair, length and number of repair plies in uniform and stepped lap repair, moisture content of the laminate prior to repair, moisture content of the laminate after repair, test temperature, roughness of grinding tool used in preparing the repair surface, and the temperature applied during the cure of the repair patch. The aforementioned parameters were varied over wide ranges, and provided systematic sets of data which shed light on the influence of each of these parameters on the effectiveness of the repair.; Second, models were developed for calculating the failure loads of composite laminates repaired by scarf and uniform lap techniques. The models take into account anisotropy of each ply in the laminate and in the repair play and non-elastic behavior of the adhesive or resin interlayer between the laminate and the repair patch. On the basis of the models two computer codes were written for generating numerical values of the failure loads. The first code is for calculating the failure loads of laminates repaired by the uniform lap technique, the second for calculating the failure loads of laminates repaired by the scarf technique. Failure loads calculated by the models and the corresponding computer codes were compared with data, and good agreement was found between the results of the models and the tests. |
