Investigation of the Mechanisms for the Delamination Resistance Found in Bio-Engineered Composites Found in Nature: Bi-Layered Exoskeleton Fish Scales

The focus of this study was to learn how nature integrates hard and soft materials at each length scale to form a layered composite that better resists delamination. This research provided a detailed description, using novel experiments, to explain how hard and soft materials have been mixedintegrated at each length scale, optimized by volume fractions, which affect the fish scales mechanical response due to external loading. The results from the study showed the following 1. The combination of the hard inorganic minerals and soft organic collagen fibers are integrated instead of being glued at the nano scale. At the micron scale for the two-layered composite, the outer dental enamel hard layered interface uses a saw tooth-shaped joint to connect to the inner bone hard open-like foam layer. At the millimeter scale, the material and mechanical properties are gradually graded through the thickness away from the interface. 2. The outer hard layer has 90 percent hard inorganic minerals and 10 percent collagen fibers by volume. Whereas, the inner bone layer has 60 percent hard inorganic minerals and 40 percent organic collagen fibers by volume. The property variation seems to delocalize stresses, which increase delamination resistance at the interface.