The concept of an innovative bonded joining technology where welding is not required is presented as an alternative to traditional welded connection for steel circular hollow section (CHS). Wrapped composite joints have potential to greatly improve fatigue endurance when applied in multi-membered truss structures, e.g. offshore jackets for wind turbines. This paper focuses on characterization of influence of chemical bonding resistance, fracture toughness of resins, and steel yielding on debonding of wrapped composite joints. Uniaxial splice joints (A-joints) are made with GFRP composite material wrapped around steel sections, and tested under static tensile loading conditions until failure. Different chemical bonding properties by application of bonding primer, different types of polymer resins and steel grade are used during the wrapping procedure. Debonding on the bonded interface are identified by surface strain measurements through 3D digital image correlation (DIC) technique. Testing results indicate that steel yielding limits full utilization of the resistance of the bonded interface. Wrapped composite A-joints with high-strength steel exhibits 75% larger ultimate load where yielding is prevented. Larger fracture toughness of toughened vinyl-ester resin contributes to 30% larger displacement of the joints at failure compared to regular vinyl-ester and polyester resins.
FundingThis research is supported by NWO (Netherlands Organization for Scientific Research) under Demonstrator project “Fatigue resistant Wrapped FRP joints of structural hollow sections”, proj. no. 16949. The first author would also like to express his gratitude for the financial support from China Scholarship Council (CSC) under grant number of 201806260242. The authors are grateful for the acknowledge provision and fabrication of the wrapped composite joints by Tree Composites b.v., Versteden b.v.and Ask Romein b.v. The authors are very grateful for the assistance of technicians from Steven Lab II of TU Delft.
- 3D DIC
- Fracture toughness
- Steel yielding
- Wrapped composite joints