Experimental and numerical investigation of cavitation erosion damage in FRP composites

Abstract

The application range of fibre reinforced polymer (FRP) composites in different industries is constantly growing due to their high strength and stiffness, low weight and relatively easy manufacturing. In some applications, FRP composites can be exposed to cavitation erosion. This work presents an experimental and numerical investigation into the behaviour of glass and carbon FRP composites subjected to cavitation erosion. The experimental programme started with a serious of tests aimed to identify several properties of FRP composites including elastic modulus, tensile strength, acoustic impedance and surface hardness. Surface impact resistance of FRP composites was examined using a needle impact rig and different types of indenter (needle) tips. FRP composites were exposed to a cavitation field created using an ultrasonic transducer. The mechanisms of cavitation erosion in the FRP composites were studied through weight loss measurements, postprocessing of specimen images and analysis of erosion imprint topography with a micro computed tomography system. Pits induced by cavitation on composite surfaces were studied with high magnification microscopes and scanning probe microscopy, which allowed to identifying material behaviour and damage mechanisms under highly localised microjet impacts. Further research was focused on finding factors affecting the resistance of FRP composites to cavitation erosion. The effects of water absorption of FRP composites, internal layup of fibres in composites, content of dissolved gas in a testing liquid, specimen thickness and backing material on cavitation erosion of FRP composites were studied. The ultrasonic cavitation field was tested using polyvinylidene difluoride (PVDF) sensors (which were manufactured and calibrated in the university laboratories) and analysed using nonlinear computational fluid dynamics (CFD) modelling. The experimental and numerical data were used in developing nonlinear finite element analysis (NLFEA) models for simulating single microjet impact on FRP composite surface. Different methodologies for modelling a highly localised impact were analysed and the most promising was selected. A NLFEA model of FRP composite surface was validated against the indentation test data obtained using the needle impact rig with different indenter tips. The validated NLFEA model was further extended to include highly nonlinear FRP composites behaviour and applied for prediction of FRP surface response to a localised microjet impact.

Date of Award	2021
Original language	English
Awarding Institution	University of Dundee
Supervisor	Leon Chernin (Supervisor)