Accelerated aging test on composite boat hulls produced by infusion process

Abstract

The use of composite materials in the naval industry has been increasing especially over the last decades. The shipbuilding industry tends to use composite materials due to their low weight and good mechanical properties, typically in the construction of ship hulls. Since 2015, Arsenal do Alfeite, SA has been developing and building composite materials vessels, such as the construction of the Fiberglass Reinforced Polymer (FGRP) Coastal Patrol Boats. Thus, arise the need to understand the variation of the properties of the material during the lifespan and to study its degradation. In this study, the part of the hull considered the zone of interest was the one subject to the most severe conditions in the marine environment. Thus, the aim of this dissertation is to study the effect of the most critical factors on material degradation by comparing three distinct conditions: as currently produced, with and without paint coating, and the proposal for improvement through the addition of silica nanoparticles to the resin on the interface between composite material and PVC core. The most critical parameters for degradation were identified, namely ultraviolet radiation and humidity. The addition of silica nanoparticles to the resin aims to reduce the permeability of the interface layer and improve the material performance with respect to UV absorption in order to increase the material life. The set of specimens, produced by infusion, consisted on simulating the characteristics of the currently produced hull, the addition of 2 wt% nano-silica and the addition of nano-silica together with a layer of silicone paint. Monolithic specimens with original characteristics and nano-silica addition were also made. These specimens were tested in the accelerated aging chamber for 1000 hours. After the aging process, the degree of degradation of the specimens was identified and compared by visual and microscopic analysis of the areas of interest, and 3-point bending tests were performed to identify changes in the mechanical properties. A lower degradation level and improved mechanical properties were observed in the specimens with nano-silica addition. It was concluded that the addition of nano-silica increases the mechanical properties and marine life of glass fibre reinforced polymers which can be considered a competitive advantage in the marine industry.