Influence of geometry, elasticity properties and boundary conditions on the Mode I purity in sandwich composites

A review of mode I dominant interfacial fracture toughness test methods of skin-core bonding for thermoplastic composite sandwich structures

“…47,50,54 It is generally agreed that a bi-material interface such as the sandwich skin-core contact leads to the coupling of normal and shear deformations. 47,48,54,55,57 Similar findings were published by Burlayenko et al, 77 who studied the debonding behaviour of sandwich structure with glass fibre reinforced epoxy composite facesheets and PVC foam cores using the DCB and SCB method. Experimental and finite element analysis showed that the SERR were significantly higher using the DCB method, which they attributed to considerable Mode II fractions involved.…”

“…In addition to its Mode I dominance, the SCB method exhibits only a minimal tendency of crack kinking into the core, which was found by several authors. 39,78,83 Burlayenko et al 77 even established a negative shear stress at the crack tip using the SCB method, which would result in a crack propagation towards the actual skin-core interface or even to the facesheet. In order to provide consistent and reproducible GI values using the SCB test method for sandwich composites, Ratcliffe and Reeder 41 proposed specific constraints regarding the specimen and the testing procedure.…”

Numerical and analytical modeling of the end-loaded split (ELS) test specimens made of multi-directional coupled composite laminates

“…The complexity of the FE model and the computational task can be reflected by a number of degrees of freedom (DOFs) equal 82 026. The stress state and strain energy release rate along the initial delamination front were determined based on linear elastic fracture mechanics (LEFM) [14]. Simulations of the ELS test in the case of coupled laminates enabled distinction of the most problematic couplings from the point of view of a proper calculation of SERR in accordance with the ISO 15114 Standard [11]..…”

On the elastic and mixed-mode fracture properties of PVC foam

“…In sandwich panels, the main role of the core is in transferring shear forces between the face sheets when the panel is subject to bending. The intensive loading conditions to which sandwich structures are subjected might produce the skin/core debonding [7][8][9][10][11] and crack kinking propagation in the core region [12][13][14]. Regarding the crack kinking propagation in the core region, the assessment of the elastic and fracture properties of PVC foams is an essential prerequisite to correctly implement a numerical model, which will be able to simulate deviation of crack trajectory from the initial direction.…”