In recent years a few footbridges were made of FRP (Fibre Reinforced Polimer) composites - glass and carbon fibers, surrounded by synthetic resin. One of the most visible examples of using composite materials is the program of building a hybrid (concrete-composite) road bridge Com-bridge, financed by The National Centre for Research and Development’s funds from “Demonstrator+” program. The bridge made of composites has been officially opened in Błażowa, February the 9^th, 2016. 

What is so special about FRP composites?

FRP composites interest engineers and architects regarding their high specific tensile strength (high strength while being relatively light).  They are prone to forming different shapes of constructive elements. They are also characterized by visual appearance, low thermal conductivity, and low emission of carbon dioxide during the whole life cycle .

Fibers (in this case glass and carbon) give toughness and rigidity. The warp made of thermosetting polymer (epoxy resin in this case) joins fibers, carries the load from fiber to fiber,and at the same time provides protection against the influence of environment.

Many times those materials proved their exceptional indestructibility and corrosion resistance in comparison to conventional construction materials using in building trade. RFP composites do not succumb to natural decomposition like wood and do not succumb to corrosion – like steel, and they are also resistant to the chemicals factors.  The fact that they are very commonly used in yachts and boats manufacturing, shows their effectiveness in environment, where others typical materials (like metals) would not be useful, exploitable. RFP composites should also be flameproof to provide construction safety in case of fire.

Using proven solutions

The common knowledge concerning RFP composites, formed during their design and manufacture  for aviation and shipbuilding industries allows the researchers picking the right methods and implementing them into bridge engineering. The team led by Rafał Molak PhD focused on analysis of  the influence of a size of composite samples on mechanical properties.

However challenging may be the fact that bigger constructions are more likely to be found  critical defects in determining resistance then the small laboratory samples.  Academic Research Center “Functional Materials” operating within Warsaw University of Technology have carried out laboratory tests of samples of starting materials and constructional elements under actual conditions, designed by Promost Consulting Company and manufactured by Mostostal Warszawa. Mechanical properties of RFP composites, crucial to design a bridge and evaluate the resistance, based on standards and guidelines guaranteeing construction’s safety have been determined based on the laboratory researches. Thanks to the results of laboratory tests of construction elements in a real scale, engineers could verify the amounts set amounts of computational resources. They were checking if the production process led to getting the same amounts, as expected.

A wide range of materials’ tests including: strength tests in extremely low and high temperatures (static tests of stretching, squeezing and curdling), computed tomography (CT), scanning electron microscopy (SEM) and other methods from non-destructive testing group (NDT) like: acoustic emission (AE) and ultrasound tests (UT), were conducted during scientific researches.

Starting materials (just after manufacturing), used in tests, were affected by environmental degradation impacts (e.g. UW radiation, temperature gradient, water, salt, tensions and others).

Experiments were supported by numerical simulations of standard endurance tests (stretching, squeezing and curdling) and set construction elements under the laboratory or usable bias. 

High time to change the attitude

Solutions initiated by researchers from Warsaw University of Technology are the “novum” for composite constructions on the national market. Due to the length of the leaf - 21 meters – the longest in the world, this is also the amazing structure on a global scale. The most common countries using such innovative solutions are: the United States, Canada, Japan, Spain, China and France. Expectations concerning overburdened structure are still growing, especially in a building trade. Researchers are looking for materials which are light, tenacious and solid. FRP composites have all those assets.

Researchers from Warsaw University of Science admit that other constructors and designers are more skeptical about applying composites to such serious constructions. Other researches such as endurance and creeping test, combustibility, and influence from other environmental factors are planning to implement within the Com-bridge project.

The project became a source of one thesis and two doctoral dissertations. The aim of one of the doctoral dissertation is development of composite constructions in civil engineering.

In this project took part:

Rafał Molak Ph.D., D.Sc., Wojciech Spychalski Ph.D., D.Sc, Łukasz Gołębiowski M.Sc., Radosław Karczewski M.Sc., Katarzyna Balke MA , Edyta Granica Eng.

The author: Łukasz Gołębiowski M.Sc. – member of the research team.

Contact: Rafał Molak, Rafal.Molak@wimpw.edu.pl, tel. 8724

Monika Bukowska