Strength Prediction for Composite Parts utilizing the Material Modeling Approach

The aerospace industry is increasingly using composites for structural applications. The 787 aircraft, for example, makes extensive utilization of composite materials for the primary structure. This ever-increasing consumption of composite materials in aerospace has caused a corresponding increase in physical testing to ensure parts have sufficient strength. However, extensive physical testing can be very expensive and contribute significantly to the overall cost of a new airplane program.

The ability to predict strength of composite parts and structures provides a significant competitive advantage. Not only can expensive physical tests be minimized but the vast design space of potential composite configurations can be explored far beyond what is capable from physical testing alone.

To enable this predictive capability, composite simulation methods have been developed at the Boeing Company that employ the material modeling approach. In this approach, material properties that can be obtained from simple uniaxial tests are generalized for three-dimensional application using the principles of Continuum Mechanics. Algorithms for failure initiation and propagation are encapsulated into source code (‘material subroutines’) that can be interfaced with commercial Finite Element software such as ABAQUS. Once this is completed, stress analysts can then utilize the modeling capabilities of ABAQUS together with customized material subroutines to predict the strength of any type of composite structure in a highly generalized manner.

The presentation will include details of these methods as well as their applications to new composite material systems under development, with applications ranging from coupons to bolted joint assemblies.