EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Fibre-reinforced composites have been proposed for a range of applications, including deep-sea pipes. The tensile properties and strength to weight ratio of these composites is advantageous compared with classic materials. However, the compressive properties of such composites are poorly understood and difficult to quantify. Compression testing indicates substantial interfacial failure between the matrix and fibres. This implies that interfacial properties are very important to overall performance under compression. Fibre push-off testing has been proposed as a method to characterise the failure of the interface. Recovering useful information from these tests remains challenging.
The aim of our investigation is to formulate a mathematical model of a fibre push-in experiment. The fibre and matrix are assumed to be linearly elastic and a homogeneous plate bending problem is derived for the matrix. This problem is equipped with clamped plate boundary conditions and perfect bonding for the fibre-matrix interface. The solution is obtained in the form of a layer potential, by the boundary element method. The perfect interfacial bonding is then replaced with a coupled damage-friction model, introducing nonlinearity. We again seek a solution by a layer potential, which satisfies a nonlinear set of integral equations. Applying the Nystrom discretization results in a nonlinear algebraic system. This system is then solved by an optimization procedure. Our results and assumptions are finally validated against experimental data.
The novelty and advantage of our model is that boundary nonlinearity is very straightforward to include. This allows the model to capture the debonding process in good detail. Additionally, by formulating the problem as a boundary integral equation we gain access to a wealth of highly efficient methods for small, dense systems of equations.