SBIR-STTR Award

An improved understanding of the structural behavior of a composite bolted joint can yield weight and cost savings by enabling the designer to eliminate any unnecessary conservatism.Software tools for the design and analysis of large scale structural bolted joint assemblies of composite laminates are required to be robust, accurate and computationally efficient models to be useful in a military or commercial design environment.The proposed approach applies multi-fidelity modeling to manage the computational expense of solving these complex and challenging problems. A set of validated analysis tools will be developed by the investigators, combining various simulation approaches such as 3D FEA models, shell-based models with spring and gap elements to replace bolt connections and calibrated analytical models for nonlinear spring and gap element type models. Damage induced compliance changes in the laminate and its effect on the load redistribution among the fasteners will also be captured in the modeling toolset. In addition these analytical tools will be utilized to investigate the use of metallic foil reinforcements around bolt holes for predicting the failure behavior of multi-row bolted composite joints of hybrid materials such as carbon fiber laminates with interspersed stainless steel or titanium foil layers.Bolted composite joint,Multi-fidelity modeling,Hybrid metal and composite laminate,Bolted joint failure modes,surrogate model

An improved understanding of structural behavior of a composite bolted yield can yield weight and cost savings by enabling the designer to eliminate unnecessary conservatism. Software tools for the design and analysis of large scale structural bolted joint assemblies of composite laminates are required to be robust, accurate and computationally efficient models to be useful in military or commercial design environments. The high anisotropy of Carbon fiber reinforced polymer composites, the high stress concentrations at load transfer point at the bolted joints and the brittle nature of the composites lead to a reduction in bearing capacity. Proposed solutions have involved the addition of metal plies into the laminate to improve bearing performance. The proposed approach builds on current developed software to automate the generation of realistic and complex finite elements model for composite hybrid joint designs. Multi-fidelity modeling will be used to manage the computational expense of solving these complex and challenging problems. The results of these modeling efforts will be validating by a set of tests of single and multibolt joint configurations.