Abstract modelling of the nonlinear mechanical response of joints in fiber reinforced composite assemblies

• Applicant: Professor Dr.-Ing. Raimund Rolfes
• Subject Area: Mechanics
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 455924282

Models for the numerical analysis of large scale assemblies in the aerospace and automotive industry may comprise hundreds, or even thousands, of joints.This makes a numerically efficient representation of the joint in the model, while maintaining sufficient accuracy, an issue of paramount importance.In particular, this applies to simulations concerned with the prediction crash-worthiness or service life time of an assembly.For these purposes an accurate representation of the nonlinear response of joints is essential.Detailed modeling approaches featuring a faithful representation of the actual connector properties and geometry, typically as a solid, allow reliable predictions regarding the nonlinear response.However, this generally results on a very high degree of freedom, i.e. total number of unknowns, even for individual connectors.This renders this approach infeasible for the analysis of large scale assemblies.As an alternative to detailed modeling, strategies that is not based on a faithful representation of the actual geometry or physical properties of the joint.In that case the joint is reduced to a low number of nodes, typically only two, and their load-displacement relation is adjusted to be equivalent to the macroscopically apparent load-displacement relation of the actual joint.This approach is referred to as abstract modeling here, it is generally associated with a low degree of freedom and is, hence, suitable for large assembly models.Abstract modeling of joints in finite element analysis is already a wide spread tool in industrial applications, however, typically limited to linear analysis and isotropic materials.Recently, the application of fiber reinforced composites has become more wide spread.This development prompts an extension of existing methods, due to the particular properties of these materials. The most prominent property of these materials is their anisotropy which can not be handled by existing approachesFurthermore, the failure response of various joints in composites is more complex, e.g. bolt connectors in laminates may fail in a pseudo ductile or brittle manner.This motivates the present proposal which is concerned with the development of abstract joint-modeling strategies accounting for failure modes and anisotropy of composites.

• DFG Programme: Research Grants