4 August 2016

World’s first biocomposite bridge moves off the drawing board

Dutch students developed building material of hemp and flax fibers embedded in bioresin

Fifty students at the Avans University of Aplied Sciences have completed a 2-meter test section for a footbridge that, in a world first, will ultimately be constructed entirely from biocomposite materials.

The new bridge, when built will have a span of 14 meters and will be installed across the Dommel river, on the grounds of the Technical University in Eindhoven.
To date, while been other bio-based building projects have been realised around the world, these all either related to non-structural elements or included the use of fossil-based building materials.

The planned bridge will be made of a biocomposite produced via vacuum injection technology and composed of hemp and flax fibers embedded in a bioresin, with a core of biobased PLA foam. The vacuum injection composite manufacturing process involves using a vacuum pump to drive the resin into the cavity under lower than atmospheric pressure conditions, which causes the resin to be sucked into the laminate. The students tested a number of different vacuum injection production methods when making the test model. A feasibility study of the proposed production method was also conducted, during which the team looked at the layer thicknesses, adhesive bonds, paints, the heat development during the cure of the biobased resin and the speed of the vacuum injection.

The project was aimed at developing options for a more environmentally friendly, recyclable design solution for footbridges of the kind that are found in natural preservation areas and other (protected) environments. In conventional bridge-design, a pre-set Design Life is used. Often, these bridges are given a protection system to prevent early deterioration. The materials used in the construction and protection of these bridges are harmful to the environment. By designing a biobased footbridge, the project is seeking to demonstrate options for less harmful solutions. In that context, the test model developed and built by the students at the Centre of Expertise Biobased Economy-Biobased Construction Materials lectorate at Spark Rosmalen is an important step in the direction of the realization of the pedestrian bridge.

The project is being carried out within the scope of the 3TU Lighthouse research project “B3: Fully Bio-Based composite pedestrian Bridge”. The 3TU Bouw Lighthouse subsidy program provides seed money for funding leading edge construction projects in an attempt to dispel the industry’s conservative image and to illustrate the innovative potential it offers. The project consortium is made up of TU Eindhoven (project leader), TU Delft, composites specialist NPSP bv and the Centre of Expertise Biobased Economy at Avans.

TU Eindhoven is responsible for the optimization of the structural design. To that end, different fiber directions and material thicknesses were investigated and use was made of new topological optimization technologies. The design has now been finalized and the plans have been submitted to the Eindhoven municipality in support of the applications for approval.

Source: Bioplastics MAGAZINE, 2016-07-01.

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