Huntsman Advanced Materials’ commitment to innovation and process improvement was tested to the full on a recent lighthouse project led by ACCIONA Infraestructuras.  Working in collaboration with various partners an outstanding result was achieved which went on to win one of the prestigious 2016 JEC World Innovation Awards.

Here, Philippe Christou, Head of European Technical Support, Huntsman Advanced Materials, and Anurag Bansal, Head of Manufacturing-Composites, ACCIONA Infraestructuras, take a look at how the partnership delivered the world’s first-ever all-composite lighthouse - now installed at the port of Valencia in Spain. Composites are now commonly regarded as the ‘go-to’ material of choice for many design engineers. It’s therefore no surprise to learn that this particular project symbolises another world first for these materials in the construction and civil engineering industries.

Having emerged from the price prohibitive ‘space-age’ materials of the past, composites influence many different aspects of our everyday lives. From helping to safely extract and distribute energy to our homes and delivering better performing and lightweight vehicle designs through to featuring in various items of clothing accessories and sports equipment, composites have become ubiquitous.

They can be formed into any shape and deliver stiffness, strength and lightweight to different structural designs, all facilitated through the latest technologies which make the fast production of high quality composite materials more commercially viable and attractive than ever before.

Innovation in the spotlight
The lighthouse project has also overcome any perceived limitations for composites and opened the way for other applications requiring light, tall structures to benefit from using the latest, proven material innovations.

Developed as a first prototype by ACCIONA Infraestructuras at the beginning of January 2013, this tower structure is testament to the advances in materials engineering that occurred in the short time the project took to complete in February 2015. For example, following the design and process selection, all the composite components were manufactured within the period of a working month at ACCIONA’s composite workshop in Madrid.

Fulfilling the vision
Combinations of hybrid, CFRP and GFRP composites were selected for the tower’s principal components, calling for the development of new material systems and processes to fulfil the design engineer’s vision for the 35m tall tower structure.

To construct the tower’s structural column - made of eight 35m long CFRP pultruded tubes with an outside diameter of 250mm and 20mm thickness - ACCIONA developed a special pultrusion process that produced high quality, very thick pultruded profiles combining carbon tows and heavy carbon fabrics.

The epoxy-compatible glass fibre supplied by Owens Corning for the GFRP tubes was specified for its ease of impregnation, faster pulling speed and better chemical resistance.

Optimising processes for complex needs
Architectural requirements stipulated that while the lightweight GFRP floors were subject to certain aesthetics and chemical resistance factors, they should also not exceed 20cm thickness.

Due to the constraints of cost, time, dimensional tolerance surface finish and ease of molding, ACCIONA decided to develop a resin infusion process to create the floors. As manufacturing needed to be fast, a resin system with low viscosity, long pot life and low exotherm, which could also meet the necessary chemical and mechanical properties, was developed by Huntsman Advanced Materials.

The project also required the production of slip-free, light weight (<25Kg), chemically and mechanically resistant, GFRP stairs that would not exceed 20cm thickness. Composites made by resin transfer molding (RTM), using resin from Huntsman, were identified as providing the optimum solution.

Progressive approaches to strengthening and joining
To join the pultruded CFRP and GFRP tubes, and in order to achieve the low weight, low maintenance, smooth surface, chemical resistance and aesthetics required, the use of metal fasteners were ruled out and a new system was designed that could also meet the complex structural, geometric and budgetary requirements. As part of this new system, carbon and glass fibre stiffeners were designed and produced using a user-friendly and low exotherm resin developed by Huntsman.

ACCIONA also selected ARALDITE® adhesives to bond the lighthouse’s composite components together, chosen in preference to mechanical fastenings, which would detract from the look and add unnecessary weight to the final structure.

Combining a long pot life with fast curing, and thixotropic properties that facilitated easy application on the tower’s vertical surfaces, the ARALDITE® epoxy based structural adhesive specified for this project delivered significant cost and production time savings. It also added to the strength of the composite structure, contributing to its lightweight and aesthetic appeal.

Fast and easy installation
Before the lighthouse was commissioned, final tests were conducted to ensure it met load and wind requirements.

Whereas concrete builds typically take 28 days to be fully cured and a further 21 to install, the all-composite lighthouse was completed in less than 20 days – six hours of which involved its installation, using a lightweight crane due to its advantageous size-to-weight ratio.

Opening new markets and applications
The lighthouse project focused on short and efficient manufacturing cycle times of CFRP and GFRP composites. This was achieved using innovative materials, form factors and processing technologies. It also exemplified the advantages of cross-industry collaboration in action. When companies share research, technologies and ideas, success in innovation is an inevitable outcome.

The technologies developed and proven for the lighthouse project are currently under consideration in numerous other projects including towers for wind energy, columns for bridges and mobile antennas. Other partners involved in this project working with ACCIONA Infraestructuras S.A. and Huntsman Advanced Materials included Autoridad portuaria de Valencia, Siegrist & Moreno S.L, Aimplas, Dow, Saertex and Owens Corning.