Abstract
In this study, the fatigue behaviour of sandwich composites was investigated in both, air and seawater. S–N curves were obtained for different stress levels. 3-point bending (3PB) tests were also performed to investigate strength degradation during the fatigue test. Finite element analyses were carried out to determine the stress distribution in the test coupons used in bending tests. These were used to predict the failure of the composite and to interpret the experimental results. There is good agreement between finite element analysis and experimental results at lower loads. Small deviations were observed at higher loads due to the influence of defects. The typical failure modes observed under quasi-static 3PBT were debonding, fibre pull-out and matrix cracking.
Highlights
Due to their light weight and their relatively, high specific modulus and strength composite materials are ideal candidates in various applications such as in marine energy conversion systems
Sandwich composites are multi-layered materials used as a single structure which is divided in three main constituents: two external thin and stiff face sheets and a central soft and thick core mat
From visual observation of the test, beyond the point of fracture crushing of the face sheets associated with the distortion of the PVC core mat is observed
Summary
Due to their light weight and their relatively, high specific modulus and strength composite materials are ideal candidates in various applications such as in marine energy conversion systems. In order to use composite materials in such applications, knowledge of their mechanical behaviour is required and a better understanding of the different failure modes under various loading conditions is essential. Sandwich composites are multi-layered materials used as a single structure which is divided in three main constituents: two external thin and stiff face sheets and a central soft and thick core mat. The face sheets are bonded to the core mat to allow the transfer of loads between constituents [2]. By placing the stiff material between the faces far from the neutral axes, a high bending stiffness is obtainable. The faces endure most of the normal and bending stresses, while the core carries the shear stresses [3, 5]
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