Effect of skin-core debonding on the dynamic behaviour of GFRP composite beams

摘要

Composites are materials made by combining two individual materials where one material forms the matrix while the other provides the reinforcement. A novel composite sandwich made up of glass fibre reinforced polymer (GFRP) face sheets and modified phenolic core has been developed recently. Although perfect bond between the skin and the core is a common assumption, an important issue that needs to be considered in using a composite beam is the development of debonding between the skin and the core. Debonding may arise during fabrication or under service conditions, which causes changes to the dynamic behaviour in addition to the strength degradation. This paper focuses on the effect of debonding on dynamic characteristics of sandwich beams of different debonding sizes and end conditions. Strand7 software is used for 3D finite element simulation. Free vibration behaviour reported in the literature for composite beams will first be used to compare the analytical results with the fully bonded and debonded beams. Study is extended to depict the effect of debonding on free vibration behaviour of novel composite beams. It is revealed that the decrease in natural frequency with the increase in the extent of debonding is more dependent on the width of debonding across the beam than the length along the beam. It is also perceived that full width debonding leads to increased participation of twisting modes in comparison to half-width debonding in clamped-clamped end condition. End conditions of the beam are a governing factor dictating which modes are more affected.