WrapNode-I project aims to investigate the use of wrapped composite joints in offshore wind turbine support structures to reduce costs, weight, and production time.

Complex welds in the joint region of jacket foundations can reduce fatigue resistance, but using composite joints can increase resistance and reduce the amount of steel needed.

This project involves full-scale joint tests and performance validation to demonstrate the technical and economic feasibility of using wrapped composite joints.

          The first full-scale Composite Joint (TC-joint)

Tree Composites produced the first full-scale Tree Composites Joint (TC-joint) within the WrapNode-I project, which is supported by the Netherlands Enterprise Agency (RVO) and TKI Wind op Zee

With a height of 2.6 meters and a length of 10 meters, and a total weight of around 6 tons, it is the largest joint that Tree Composites has produced so far. The full-scale joint will be tested to validate the performance of the full-scale wrapped composite joint under cyclic loading. The joint dimensions and testing loads are based on a jacket design with wrapped composite joints that was performed in the Wrap Node-I project. Next to the cyclic load test also, two full-scale wrapped composite joints will be tested in static loading, and we will witness its performance together with our partners AOC, BUEFA, Enersea, GROW, HSM Offshore Energy, Salzgitter, Shell, Siemens Gamesa, Smulders, TU Delft and Vattenfall

WrapNode-I started in May 2021 and by the time it is completed it will validate the wrapped composite joint to be used in offshore jackets. It supports the step towards implementation in a Jacket structure planned in the follow-up project called WrapNode-II.


The project is supported by a Take Off-1 grant of the Dutch Research Council (NWO). WrapFly aimed at assessing the commercial feasibility of implementing the TC-joint, a composite joint technology developed by Tree Composites, as an alternative to complex welded joints in multi-membered fatigue-prone structures. 

The project showed that the TC-joint offered added value to onshore, nearshore and offshore structures. Tree composites decided to focus on these 4 primary markets:

  • Bottom Fixed Offshore Wind
  • Floating Offshore Winds
  • Ocean Energy
  • Offshore Aquaculture


This selection is in line with the anticipated growth of offshore renewable energy projects in the coming decades.

              Potential markets in TC – joint application

The TC-joint was shown to increase production capacity, decrease total costs of offshore wind structures, reduce steel consumption by over 40%, and decrease the carbon footprint of structures by 30% to 70% compared to welded jackets and monopile structures.

The WrapFly project, which began in September 2020 and ended in May 2021, was instrumental in the start of the WrapNode research project.