New peel stopper concept for sandwich structures

Abstract

The paper addresses the damage tolerance of sandwich structures, where the prevention and limitation of delamination failure are highly important design issues. Due to the layered composition of sandwich structures, face-core interface delamination is a commonly observed failure mode, often referred to as peeling failure. Peeling between the sandwich face sheets and the core material drastically diminishes the structural integrity of the structure. This paper presents a new peel stopper concept for sandwich structures. Its purpose is to effectively stop the development of debonding/delamination by rerouting the delamination, and to confine it to a predefined zone in the sandwich structure. The suggested design was experimentally tested for different material compositions of sandwich beams subjected to three-point bending loading. For all the tested sandwich configurations the suggested peel stopper was able to stop face-core delamination and to limit the delamination damage to restricted zones.

Fracture behaviour at tri-material junctions of crack stoppers in sandwich structures

“…The basic principle of the so-called 'peel stopper' is to deflect the crack away from the face sheet/core interface into the core, so that the crack path follows the boundary of the peel stopper. The functionality of the crack stopper was validated experimentally using three-point bend tests in which sandwich beams with aluminium or GFRP face sheets and Divinycell H60 PVC foam core were studied [5,6]. It was shown that interfacial cracks that were initiated by core shear failure were successfully deflected and arrested by the peel stopper.…”

“…A different concept was proposed by Jacobsen et al [5][6][7][8], where the crack stopper was manufactured from a PolyUrethane (PU) material with stiffness properties similar to those of the foam core materials. A key element in the design was to confine and arrest the growth of the interfacial crack.…”

“…The purpose of the present paper is to further explore the peel stopper concept. In particular two considerations emerge from the peel stopper design proposed in [5,6]. Firstly, the loading conditions at the debond tip in [5] and [6] were mixed mode with significant contribution in mode II.…”

“…In particular two considerations emerge from the peel stopper design proposed in [5,6]. Firstly, the loading conditions at the debond tip in [5] and [6] were mixed mode with significant contribution in mode II. However, many realistic loading situations are mode I dominated, hence there is a need to assess the ability of the peel stopper to deflect propagating interfacial cracks under this condition.…”

“…However, many realistic loading situations are mode I dominated, hence there is a need to assess the ability of the peel stopper to deflect propagating interfacial cracks under this condition. Secondly, the bulky design of the peel stoppers accompanied by the high density of the PU material suggests that the use of the peel stoppers described in [5] and [6] will incur a serious weight penalty.…”