Investigation of sandwich crack stop elements under fatigue loading

Abstract

This paper deals with the investigation of crack stop elements for carbon-fibre-reinforced polymer (CFRP)/foam core sandwich structures manufactured by using liquid composite moulding technology under fatigue loading. The novel crack stoppers consist of CFRP and they connect the face sheets. In this way, they are suited to be used as crack stoppers to decrease the face sheet debonding and as load introduction elements. Two types are investigated, a box section and a double-T beam. Quasi-static and cyclic Single Cantilever Beam (SCB) and Cracked Sandwich Beam (CSB) tests are run to evaluate their crack stop capability under global mode I and global mode II loading. The double-T beam shows the better crack stop effect. In the SCB test the box section increases the specimen durability by less than 2%, whereas the double-T beam increases the load cycles to failure by a factor of 2.7 to 447. In the CSB test, both crack stoppers have a significant impact on the crack propagation behaviour. The box section increases the durability by a factor of 11 to 95, and most of the double-T beam sandwich specimens sustained 3 million load cycles without global failure.