Advanced design methodologies enable lighter and more reliable composite structures or components. However, efforts to include fatigue delamination in the simulation of composites have not yet been consolidated. Besides that, there is a lack of a proper categorization of the published methods in terms of their predictive capabilities and the principles they are based on. This paper reviews the available experimental observations, the phenomenological models, and the computational simulation methods for the three phases of delamination (initiation, onset, and propagation). It compiles a synthesis of the current state-of-the-art while identifying the unsolved problems and the areas where research is missing. It is concluded that there is a lack of knowledge, or there are unsolved problems, in all categories in the field, but particularly in the category of computational methods, which in turn prevents its inclusion in the structural design process. Suggested areas where short-term and midterm research should be focused to overcome the current situation are identified.
The analysis of large-scale fracture processes, such as those involved in the fracture of adhesive joints, falls outside the scope of Linear Elastic Fracture Mechanics (LEFM). However, experimental data produced in testing adhesive joints are usually reduced with LEFM methods. The consequent error has not yet been evaluated. In this work, an experimental characterization under pure-mode loading of an FM-300 epoxy film adhesive is presented for different adhesive and adherend thicknesses. The experimental data is analyzed using both LEFM-based and J-integral-based data reduction methods in order to study their suitability to analyze adhesive joints. LEFM-based data reduction methods are shown to entail a relevant deviation in the fracture toughness results that heavily depends on the size of the fracture process zone. It is concluded that LEFM methods are not suitable to characterize adhesive joints and that their use is restricted, at best, to the measurement of initiation values. The effect that the adhesive and the adherend thicknesses have on the fracture toughness and the R-curve of the material is studied. Adhesive and adherend thicknesses are shown to have a significant influence on the bond fracture toughness and the source of such influence is discussedThe first author would like to acknowledge the FPU programgrant AP20100977 from the Spanish Ministerio de Educación,Cultura y Deporte. The authors also acknowledge the support of the Spanish government through the Ministerio de Economía y Competitividad under the contracts DPI2012-34465 and MAT2012-37552-C03-0
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