Volume 3, issue 1 | Copyright
Wind Energ. Sci., 3, 427-438, 2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research articles 20 Jun 2018

Research articles | 20 Jun 2018

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

Jake D. Nunemaker, Michael M. Voth, David A. Miller, Daniel D. Samborsky, Paul Murdy, and Douglas S. Cairns Jake D. Nunemaker et al.
  • Mechanical and Industrial Engineering Department, Montana State University, Bozeman, MT 59717, USA

Abstract. Fiber-reinforced-polymer composites (FRPs) possess superior mechanical properties and formability, making them a desirable material for construction of large optimized mechanical structures, such as aircraft, wind turbines, and marine hydrokinetic (MHK) devices. However, exposure to harsh marine environments can result in moisture absorption into the microstructure of the FRPs comprising these structures and often degrading mechanical properties. Specifically, laminate static and fatigue strengths are often significantly reduced, which must be considered in design of FRP structures in marine environments. A study of fiberglass epoxy unidirectional and cross-ply laminates was conducted to investigate hygrothermal effects on the mechanical behavior of a common material system used in wind applications. Several laminates were aged in 50°C distilled water until maximum saturation was reached. Unconditioned control and the saturated samples were tested in quasi-static tension with the accompaniment of acoustic emission (AE) monitoring. Cross-ply laminates experienced a 54% reduction in strength due to moisture absorption, while unidirectional laminate strengths were reduced by 40%. Stress–strain curves and AE activity of the samples were analyzed to identify changes in damage progression due to aging.

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Short summary
This paper presents an experimental investigation of the tensile strength of fiberglass–epoxy composites before and after water saturation. The strengths of [0], [90], and [0/90] layups all show a drop in tensile strength. However, investigation of the data, damaged coupons, and acoustic emission events illustrates a change in the mechanism governing final failure between the dry and saturated coupons. This illustrates the complexity of strength prediction of multiple layups after saturation.
This paper presents an experimental investigation of the tensile strength of fiberglass–epoxy...