Investigating Core Gaps and the Development of Subcomponent Validation Methods for Wind Turbine Blades: Preprint

Research output: Contribution to conferencePaper


Core gaps are a common manufacturing defect observed in wind blade composite sandwich constructions, which occur when sheets of core material are not properly butted up against each other in the mold. The aim of this study was to characterize core gaps in composite sandwich constructions at the coupon scale. This was to gain an initial understanding of the defect before developing appropriate methodologies for more complex subcomponents as part of a much broader wind blade structural validation and damage tolerance program. Long beam flexure in 4-point-bending was chosen as the most appropriate loading scenario. Beam specimens were characterized with and without 10 mm core gaps in fiberglass/balsa sandwich beams. The core gaps were characterized with two separate resin systems; a Hexion epoxy and Arkema's Elium resins system (a novel, infusible thermoplastic). Results showed that the Elium beams without the core gaps were had a 15% lower static strength than their epoxy counterparts. The introduction of the core gap to the epoxy beams reduced their static strength by 35%. The Elium beams, however, exhibited negligible strength reductions with the inclusion of the core gap. Overall, this characterization study provided pertinent information with regards to core gaps as a manufacturing defect to allow for continued development of damage tolerance and subcomponent validation methodologies with the inclusion of manufacturing defects.
Original languageAmerican English
Number of pages15
StatePublished - 2020
EventAIAA SciTech Forum and Exposition - Orlando, Florida
Duration: 6 Jan 202010 Jan 2020


ConferenceAIAA SciTech Forum and Exposition
CityOrlando, Florida

Bibliographical note

See NREL/CP-5000-78284 for paper as published in proceedings

NREL Publication Number

  • NREL/CP-5000-75249


  • core gaps
  • subcomponent validation methods
  • wind energy
  • wind turbine


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