Micromechanical design of hierarchical composites using global load sharing theory

摘要: Abstract Hierarchical composites, embodied by natural materials ranging from bone to bamboo, may offer combinations of material properties inaccessible conventional composites. Using global load sharing (GLS) theory, a well-established micromechanics model for we develop accurate numerical and analytical predictions the strength toughness hierarchical composites with arbitrary fiber geometries, strengths, interface properties, number levels, N. The demonstrates that two key at each level—a characteristic length—control scalings composite properties. One crucial finding is short- long-fiber behave radically differently. Long-fiber are significantly stronger than short-fiber factor 2N or more; they also tougher because their breaks bridged smaller-scale fibers dissipate additional energy. Indeed, an “infinite” length appears be optimal in However, highest level composite, long localize on planes pre-existing damage, thus short must employed instead achieve notch sensitivity damage tolerance. We conclude providing simple guidelines microstructural design including selection N, lengths, ratio scales successive volume fractions, desired smallest-scale reinforcement. Our enables superior designed rational way, without resorting either simulation trial-and-error-based experimentation.