Tree Composites Joints (TC-joints)

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Composite joints for offshore structures

Page last modified
October 31 2023

TC-joints replaces the traditional welding in TKY joints delivering a lightweight structure with higher fatigue resistance, reduced steel volume (up to 60%) and an increased lifetime. This innovation originates from the faculty of Civil Engineering of the TU Delft. Since 2017 over 120 wrapped composite joints have been manufactured and tested on various sizes of joints at the Stevin Lab of Tu Delft and at OCAS Belgium. The results of these test conclude that the wrapped composite joint outperforms welds in fatigue resistance, maximum load resistance and joint stiffness.

The improvement of the TC-joint compared to welding is that the load is transferred through a dedicated composite wrap and not through the small surface of the weld. The brace members (diagonals) are bonded to the chord members (legs) through a coupling formed by composite wrapping. 

The composite wrap is tailored (length and thickness) to deal with static and dynamic loads transferred by the joint. The optimized, nature-like, shape of the composite wrap, with increasing thickness towards the root of joint, reduces the stress concentration in the composite material and bonded interface, thereby solves issues in fatigue prone/driven design. The substantial improvement of the fatigue resistance of the Circular Hollow Section (CHS) joints is achieved by 1) completely circumventing stress concentrations in steel that normally are present due to local wall bending, and 2) avoiding residual stresses, embrittlement and notch effects due to welding.

A TC-joint is made by the application (lamination) of glass fibres on the non-welded steel tubes. This provides outstanding bonding strength and flawless quality.


Short assembly time
Up to 60% steel reduction
Cost effective
Higher fatigue resistance
Limited track record as a result of being a new technology


TC-joint A TC-joint is a replaces the traditional welding in TKY joints by delivering a dedicated composite wrap to transfer the load. It has a higher fatigue resistance, reduced steel volume, increased lifetime and reduced price.
Integrated corrosion protection The composite functions as a corrosion protection system to the steel next to its load transfer function. This allows for a faster production lead time of structures as the coating of complex joints is integrated.
Eliminating fatigue issues The fatigue resistance of the TC joints are so superior to welded joints that structures can have a 3 to 4 times longer lifetime and being lighter.
Full composite lightweight civil structures With TC-joints full composite structures are enabled providing options to provide lightweight structures, eliminate corrosion and reduce maintenance.
Designs of structures are ULS dominated The improved faitgue resistance of the complex joint leads to reducing in design time as structures can be design to cope with maximum load with fatigue no longer being an issue.

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Technology Readiness Level


Development Technology demonstration Mature / Proven
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Tree Composites offer design and manufacturing of Composite joints for lattice structures. Out composite joint can connect circular hollow tubes of steel, aluminium and even combination. The currently present issues with fatigue prone welds are hereby omitted resulting in up to 60% of weight reduction compared to steel welded structures. 

We are a company that is redefining the use of composite materials in civil application with our innovative approach. Our team of experts is dedicated to developing cutting-edge solutions for a range of applications, from aerospace to renewable energy. We are committed to pushing the boundaries of what is possible with composites and finding new ways to leverage their many benefits.



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