Experimental Investigation of Four-Point Bending Test Results of GFRP and CFRP Composites Used in Wind Turbine Blades

YALÇINKAYA S., Yoldaş M. F., MERTGENÇ YOLDAŞ D.

Polymers, cilt.17, sa.17, 2025 (SCI-Expanded) identifier identifier

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 17 Sayı: 17
  • Basım Tarihi: 2025
  • Doi Numarası: 10.3390/polym17172412
  • Dergi Adı: Polymers
  • Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Academic Search Premier, Aerospace Database, Chemical Abstracts Core, Communication Abstracts, Compendex, Food Science & Technology Abstracts, INSPEC, Metadex, Directory of Open Access Journals, Civil Engineering Abstracts
  • Anahtar Kelimeler: adhesively bonded joints, composite materials, elastic modulus, four-point bending test, mechanical properties
  • Marmara Üniversitesi Adresli: Evet

Özet

The depletion of fossil fuels and the rise of environmental concerns have increased the importance of renewable energy sources, positioning wind energy as a key alternative. Modern wind turbine blades are predominantly manufactured from composite materials due to their light weight, high strength, and resistance to corrosion. In offshore applications, approximately 95% of the composite content is glass fiber-reinforced polymer (GFRP), while the remaining 5% is carbon fiber-reinforced polymer (CFRP). GFRP is favored for its low cost and fatigue resistance, whereas CFRP offers superior strength and stiffness but is limited by high production costs. This study investigates the durability of adhesively bonded GFRP and CFRP joints under marine exposure. Seven-layer GFRP and eight-layer CFRP laminates were produced using a 90° unidirectional twill weave and prepared in accordance with ASTM D5868-01. Specimens were immersed in natural Aegean Sea water (21 °C, salinity 3.3–3.7%) for 1, 2, and 3 months. Measurements revealed that GFRP absorbed significantly more moisture (1.02%, 2.97%, 3.78%) than CFRP (0.49%, 0.76%, 0.91%). Four-point bending tests conducted according to ASTM D790 showed reductions in Young’s modulus of up to 9.45% for GFRP and 3.48% for CFRP. Scanning electron microscopy (SEM) confirmed that moisture-induced degradation was more severe in GFRP joints compared to CFRP. These findings highlight the critical role of environmental exposure in the mechanical performance of marine composite joints.