Specialized carnivory is relatively uncommon across mammals, and bats constitute one of the few groups in which this diet has evolved multiple times. While size and morphological adaptations for carnivory have been identified in other taxa, it is unclear what phenotypic traits characterize the relatively recent evolution of carnivory in bats. To address this gap, we apply geometric morphometric and phylogenetic comparative analyses to elucidate which characters are associated with ecological divergence of carnivorous bats from insectivorous ancestors, and if there is morphological convergence among independent origins of carnivory within bats, and with other carnivorous mammals. We find that carnivorous bats are larger and converged to occupy a subset of the insectivorous morphospace, characterized by skull shapes that enhance bite force at relatively wide gapes. Piscivorous bats are morphologically distinct, with cranial shapes that enable high bite force at narrow gapes, which is necessary for processing fish prey. All animal-eating species exhibit positive allometry in rostrum elongation with respect to skull size, which could allow larger bats to take relatively larger prey. The skull shapes of carnivorous bats share similarities with generalized carnivorans, but tend to be more suited for increased bite force production at the expense of gape, when compared with specialized carnivorans.

An FEA model for understanding the effectiveness of fastener as crack arrest mechanism has been constructed. The effect of the fastener in the sliding direction (Mode II) is modeled using fastener flexibility approach. The FEA results show that the fastener provides significant crack retardation capability in both Mode I and Mode II conditions. The analyses provide insights into the problem of disbond/delamination arrest using fastener or similar mechanisms. An analytical model for the problem is developed. The model consists of a splitbeam with a fastener attached; the fastener is modeled as a system of springs. An elastic layer is placed between the beams on the cracked faces to resolve contacts. The problem is solved using energy principles. The mode-decomposed strain energy release rates (SERR) at the crack tip are solved analytically 11-13. The primary goal of the current work is to enhance the safety of bonded composite structures by providing analysis methods for arrest mechanism.

A FEA model for analyzing effectiveness of fastener as crack arrest mechanism has been established. The effect of the fastener is modeled using fastener flexibility approach consisting of linear springs. It is shown that the fastener provide significant crack retardation capability in Mode I, but has limited resistance for Mode II propagation. The development of analytical solution for the crack arrest problem is important to the design of bonded/co-cured/co-bonded composite aircraft structures. A procedure for assessing the reliability of the fastener arrest mechanism has been demonstrated. A probabilistic approach is used because traditional damage tolerance methods for metallic structures are not generally applicable to composite structures. Probabilistic method can provide a more quantitative evaluation of reliability and safety of a structure. Analytical method for analyzing the crack arrest problem is being developed. The method consists of two parts: 1) crack-tip stress analysis; and, 2) nonlinear split-beam analysis with fastener. The analytical method makes possible accurate and efficient solution of crack arrest problems and is useful for structural design and optimization.