Controlled energy dissipation in fibrous composites. II: Microscopic failure mechanisms

Abstract

Mechanical properties and microscopic fracture mechanisms of continuous fiber reinforced polymer composites were investigated. Perforated polyimide films (e.g. Kapton@) were added between composite prepreg layers to modify the interlaminar bonding strength. Addition of highly perforated films can increase the toughness of unidirectional glass/epoxy composites without a n appreciable reduction in strength. The fibrous composites studied exhibit two fracture modes (compressive and tensile) when failed by three-point bending. In general, the compressive failure mode preceded the tensile failure mode. Real-time acoustic emission (AE) analysis was found to provide more fracture information which is otherwise not discernible from mechanical testing alone. The crack initiation stress level and the subsequent crack propagation mode were identified by realtime AE during deformation and by post-failure scanning electron microscopy fracture surface analysis.

Acoustic Emission Technique, an Overview as a Characterization Tool in Materials Science

“…Microstructural failure mechanisms are strongly dependant on several factors in any composite material such as the nature of the components, reinforcement/matrix interface, volume fractions, reinforcement geometry etc. Different types of damage mechanisms have been identified for fiber-reinforced composites such as matrix damage (matrix micro-cracking, coalescence of micro-cracks, matrix/matrix friction), interfacial debonding (fiber/matrix, bundle/matrix), fiber/matrix and fiber/fiber friction and fiber and bundle breaks [1][2][3]. The identification and evaluation of damage or fracture stages of polymer composites are extremely complex due to a composite material exhibiting heterogeneous nature, lacking of uniformity in composition owing to its components and, therefore, the assignment may be controversial.…”

Characterization and analysis of the tensile and acoustic emission parameter distributions of single wool fibers

“…These features include the stress level when micro-fracture begins and the fracture mechanisms operating during various stages of a fracture process. 8 Rios-Soberanis et al 9 proved that the architecture/geometry of textiles is an essential factor that influences the mechanical behavior of a composite material and that it is dependent on the loading orientation. AE signals in an epoxy/ polypropylene geotextile composite exhibited higher density in comparison to an epoxy/polyethylene-terephthalate geotextile composite.…”