The effects of shear and near tip deformations on interface fracture of symmetric sandwich beams

TL;DR

This paper develops semi-analytic models to analyze how shear and near tip deformations influence interface fracture behavior in symmetric sandwich beams, aiding fracture characterization in various engineering applications.

Contribution

It introduces new semi-analytic expressions for shear effects on energy release rate and mode mixity, incorporating near tip deformations for general loading and geometries.

Findings

Derived explicit formulas for shear components of energy release rate.

Validated models with finite element analyses across diverse configurations.

Applicable to fracture testing of sandwich composites in multiple industries.

Abstract

The effects of shear on energy release rate and mode mixity in a symmetric sandwich beam with isotropic layers and a debond crack at the face sheet/core interface are investigated through a semi-analytic approach based on two-dimensional elasticity and linear elastic fracture mechanics. Semi-analytic expressions are derived for the shear components of energy release rate and mode mixity phase angle which depend on four numerical coefficients derived through accurate finite element analyses. The expressions are combined with earlier results for three-layer configurations subjected to bending-moments and axial forces to obtain solutions for sandwich beams under general loading conditions and for an extensive range of geometrical and material properties. The results are applicable to laboratory specimens used for the characterization of the fracture properties of sandwich composites for civil, marine, energy and aeronautical applications, provided the lengths of the crack and the ligament ahead of the crack tip are above minimum lengths. The physical and mechanical significance of the terms of the energy release rate which depend on the shear forces are explained using structural mechanics concepts and introducing crack tip root rotations to account for the main effects of the near tip deformations.