Postdoc Upscaling Performance of Wrapped Composite Joints

With the increasing size of turbines and the deeper location of wind farms, the monopile foundations of offshore wind turbines increase in size, weight, and costs. Jackets can be an attractive alternative because multi-membered circular hollow section (CHS) support structures are lighter than monopiles. However, the complex welds result in reduced fatigue resistance of structural joints of circular hollow sections, thus higher costs and longer production routes for jackets than for monopiles.

In the project WrapNode-I, TU Delft will lead research with 9 industrial partners that will enable implementation of the innovative, bonded, wrapped composite joint in jackets for offshore wind turbines. We are forming a team of researchers to characterise and understand full-scale and multi-axial behaviour and the influence of the offshore environment on the durability of the joints. The team is led by Dr. Marko Pavlovic, assistant professor of Steel and Composite Structures.

The concept of an innovative bonded joining technology by wrapping composite material (a.k.a. Fibre Reinforced Polymer - FRP) around steel tubes is introduced as an alternative to traditional welded connections. Compared to complex welds, the load is transferred through a dedicated composite wrap and not through the small area of the weld. Fatigue resistance of joints is increased; thus, the tube wall thicknesses of the legs (chords) and brace members can be significantly reduced, resulting in up to 50% lighter jacket structures. In addition, the production time of the jacket is considerably shortened due to the possibility of prefabrication. Compared to monopiles, jackets manufactured with Wrapped Composite Joints offer a potential cost reduction of 25% to 50% for the supporting structures and reduction of CO2 footprint by 30% to 70%.

Your role in the project/team will be to investigate the influence of size effects on static and fatigue performance of wrapped composite joints. The research will rely on:

• Large-scale member/component ultimate failure and cyclic load (fatigue) experiments
• FEA validation and analysis of failure modes interaction and crack propagation in large-scale member/component experiments
• Characterisation of influence of size-effects (bonded surface area) on failure modes and crack propagation in composite materials and bonded interface

The project is realised with the support of the Dutch government, GROW consortium and industrial partners: Shell, Tree Composites bv, Siemens Gamesa Renewable Energy bv, HSM bv, Smulders Projects International bv, Enersea bv, AOC Nederland bv, BÜFA composites Benelux bv and Salzgitter Mannesmann Renewables GmbH.

Visit the project's website here .

You will gain scientific experience by working in a dedicated international team of 4-5 PhD and PostDoc researchers at TU Delft. You will develop professional experience by collaborating with a team of engineers from leading industrial partners who will support the project by developing reference full-scale jacket design, design and production of materials and wrapped composite joints specimens.