KOMPAP – Energy-efficient construction by composite materials with paper
The use of paper in paper-based composite structures is offering manifold possibilities to enhance the role of regrowing, sustainable and recyclable materials in the building sector and to exploit the benefits, in particular cost-effective rapid production and exceptionally good specific strength properties, of paper structures.
The goal of the KOMPAP project was to develop energy-efficient concepts for the construction of, for instance, external building envelopes from composite materials made of paper, paper structures and mineral building materials. It was envisaged to optimize the composite of paper structure and mineral component by way of functionalization of the bonding interfaces.
Funded by the Federal Ministry for Economic Affairs and Energy within the “Building Energy Transformation” programme.
Project period: » 01/03/2017 – 29/02/2020
PTS worked on the KOMPAP project “Energy– efficient construction by composite materials with paper” together with the coordinator PMV (Paper Manufacture and Mechanical Process Engineering) of TU Darmstadt and 7 other project partners (https://www.pmv.tu-darmstadt.de/forschung_pmv/forschungsschwerpunkte_2/index.de.jsp).
Paper can be manufactured in large amounts at low cost and offers a broad range of properties, which can be adjusted in manifold ways by appropriate raw material selection, additives and modifi cations of the chemically reactive hydroxyl groups of cellulose. Good specific strength properties in combination with good heat insulation properties are just a few out of the many advantages of paper that have so far not been put to use inconstruction and insulation material applications.
Fig. 1: Tensile test unit for paper structures of different thicknesses and compositions
Within the project, a multitude of papers from the industrial partners were characterized under paper technology aspects and assessed with regard to their suitability for being subjected to further investigation. For formability classification purposes, a kraftliner, a greaseproof paper and a paperboard for plasterboard manufacture with different corrugation geometries, feed rates and adhesives were re-formed and their formability assessed.
For the production of paper structures on an industrial scale, sinusoidal honeycomb structures were manufactured at the premises of SWAP Sachsen GmbH using the most promising industrial paper combinations determined on the basis of the laboratory trials and were prepared for demonstrator production. The paper-based honeycomb structures were comprehensively tested and characterized in the premises of PTS.
Poisson’s ratios, elastic moduli (Fig 1) and thermal conductivities (Fig 2), among other, were determined.
The thermal conductivities of the industrially manufactured honeycomb structures were tested on layered structures having the same specimen thickness of 30 mm. A multilayered structure of thinner (6*5 mm) laminated paper honeycombs was found to have a significantly better, i.e. lower thermal conductivity than a single-layered structure (1*30 mm). Contrary to expectations, the structures with the larger sinusoidal core (1S) showed lowest heat conductivities. This may be due to the non-adhesive ultrasonic assembly method and thus due to the absence of adhesive.
Fig. 3: Determined thermal conductivities of paper-based honeycomb structures of industrial papers having different numbers of layers
The characteristic values determined for the material form the basis for the validation of the simulation models and for the design calculation of the demonstrator (refer to Fig 3). The figure shows a sandwich construction composed of 2 layers of laminated honeycomb structures manufactured within the scope of the project and comprising a layer of mineralized foam. This modelled structure was generated at the end of the project (dimensions: 3000x 750 x 360 mm).
In the project, it was shown that the structure had the target properties in accordance with the preliminary investigations and simulations and that the project delivered a benchmark result for future research as well as for the application of such structures .
Dr. Stefan Knohl,