Evaluating experimentally and numerically different scarf-repair methodologies of composite structures (original) (raw)
2020, International Journal of Adhesion and Adhesives
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A computational analysis of the scarf angle on a composites repair
International Journal of Ocean System Engineering, 2011
This study examined the relationship between the scarf angle and stress distribution, and estimated the strength recovery via a finite element analysis. The following conclusions were drawn from this study. Resin will fracture due to a tensile load with a high scarf angle, which is similar to the patch repair method. An applied stress can be loaded to a repaired laminate if the scarf angle is 5. The Von-Mises stress increases with decreasing scarf angle, with the exception of a scarf angle of 30, where the scarf angle can indicate the rates of shear and normal stresses. Strength recovery can be better if the scarf angle is decreased to a lower angle. However, scarf machining requires more time, a high skill level and considerable expense. Therefore, a scarf angle of 5 is the most effective for a repair. These results may provide a guide for engineers wishing to formulate a standard for repair. The scarf angle needs to be carefully managed for a more efficient composite repair.
Tensile Failure Prediction and Measurement in Composite Scarf Repair (Preprint)
2007
: Oversized quasi-isotropic tensile specimens were manufactured from IM6/3501-6 graphite/epoxy prepreg. Seven specimens were scarfed in the center of the panel, and four of the panels were subsequently repaired. The repair patch consisted of a ply-by-ply replacement of the removed material with a FM-300M095 film adhesive placed between the repair patch and the scarfed specimen. The patch and adhesive were then co-cured. The repaired and unrepaired specimens were strain gaged and tested to failure. A three-dimensional failure analysis was performed. The strength prediction was based on the state of stress in the 0(exp 0) plies by taking into account the redistribution of stress due to adhesive failure. The performed analysis accurately predicted both the strength of the scarfed and repaired panels based solely on properties characterized by testing unnotched standard coupons.
Optimization of a composite scarf repair patch under tensile loading
Composites Part A: Applied Science and Manufacturing, 2009
Mechanics of the composite repair under tensile loading with and without overlay plies was examined for nontraditional patch ply orientations. Three-dimensional nonlinear analysis was performed for repair failure prediction and good baseline comparison for open hole scarfed panels and panels repaired by using standard ply-by-ply replacement patch composition was achieved. Multidimensional optimization was performed to calculate the repair patch ply orientations which minimize the von Mises stresses in the adhesive. These optimal stacking sequences achieved significant reduction of the stress levels and resulted in predicted up to 85% and 90% strength restoration for flush and single ply thickness overply repair. These results are intended to illustrate additional design variables available for efficient composite repair design, namely the composition of the repair patch.
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