Fatigue modeling of marine composites

Fatigue of aerospace-grade composite materials has been a research topic for many years. The vast majority of these studied material systems include various laminate configurations constructed from unidirectional carbon-epoxy, autoclave-cured prepregs. To date, however, no protocols demonstrating N-year service life for these materials have been standardized. Marine composites have generally migrated towards E-glass fibers and polyester, vinyl ester, or epoxy resins processed via wet layup and liquid infusion techniques and out-of-autoclave cure schedules. Although fatigue research of marine composite materials has been increasing, the relative number of databases is small compared to those generated with aerospace-grade composites. Also, the lack of a legacy standard life-prediction protocol for guidance has resulted in composite marine structures employing large safety factors and load-path redundancy in their design. This paper attempts to add to the current research by offering an approach to structural life prediction through fatigue modeling based upon coupon-level characterization, and demonstrated with subelement testing and non-destructive monitoring.