Performance of Composite Materials Subjected to Salt Water Environments

Abstract

This paper presents the recent trends in the mechanical characterization of composite systems under consideration for Marine Hydro Kinetic (MHK) applications exposed to salt water environments. First, a testing protocol for environmental effects has been developed for resin infused in-house fabricated laminates. Unidirectional ([0] and [90]) mechanical test samples were submerged in synthetic sea water at 40°C and 50°C, with the weight recorded at time intervals over the entire period. Additional witness coupons were submerged to monitor effects of fiber orientation and cure temperature. Next, after conditioning to both full saturation and partial saturation, static compressive and tensile strength properties at temperatures of 0°C, 20°C and 40°C were collected. These results show trends of reduced tensile and compressive strength with increasing moisture and temperature in the 0° (longitudinal) direction. In the 90° (transverse) direction, compression strength decreases but tensile strength is little affected as temperature and moisture increase. Finally, both mechanical and chemical analysis results are presented for samples conditioned in a Salt Fog Chamber for unidirectional, [0] and [90], samples.

Immersed Fatigue Performance of Glass Fibre-Reinforced Composites for Tidal Turbine Blade Applications

“…On the other hand, there are relatively few investigations of fatigue testing water-saturated GFRP and fewer still which report fatigue life comparisons between the wet and dry conditions. Those reports show up to a 20 % reduction in tension-tension (R = 0.1) fatigue strength of water-saturated unidirectional laminates [10] and up to 40 % reduction in bending fatigue strength [23]. This work therefore complements those studies by reporting on fatigue testing of multi-directional laminates (QI) in both dry and watersaturated conditions.…”

“…While seawater is much more corrosive to many metals than fresh water, studies with SEM on the fracture surfaces of GFRP have found no evidence of salt ions inside the composite material and conclude that the salt ions do not migrate into the composite [10]. Other studies have shown that seawater is slower to diffuse into the matrix but otherwise has similar effects to fresh water [11][12][13].…”

“…Barrier layers may also suffer from either abrasion by sand and grit suspended in the water or from surface cracking at strain levels likely to be experienced by marine renewable energy devices. Finally, it should be noted that it is very difficult to produce a barrier that can actually prevent diffusion of the small amount of moisture (1-2 %) required to saturate GFRP over the [10][11][12][13][14][15][16][17][18][19][20] year lifetime of these devices. Certainly the standard isophthalic polyester gelcoat is not capable of this level of performance [3].…”

Effects of moisture absorption on damage progression and strength of unidirectional and cross-ply fiberglass-epoxy composites

“…Past research has shown significant reductions in both static and fatigue performance due to moisture absorption (Mourad et al, 2010;Miller et al, 2012;Liao et al, 1999;Komai et al, 1991;Siriruk and Penumadu, 2014;Nunemaker, 2017Nunemaker, , 2016.…”

Technological Cost-Reduction Pathways for Axial-Flow Turbines in the Marine Hydrokinetic Environment.

“…The Composite Material Fatigue Database, developed at Montana State University, is being updated to include fatigue response for composite coupons that have been submerged in water. 44,45 Researchers there have shown that significant water uptake can occur; this increases material weight and reduces its strength. Metal blades and components can be manufactured, but will result in high material and fabrication costs, and corrosion of metal in a marine environment is inevitable.…”