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Hierarchical hexagonal sandwich honeycomb core

Hierarchical sandwich honeycombs are a new class of sandwich core materials. They have the potential to outperform other sandwich cores due to a better mechanical performance per weight to enable lower weight structures and parts.

The exploitation of the economic advantages of weight reduction has become essential for many industries. Honeycomb sandwich construction offers the best mechanical performance per weight. The weight reduction has a positive ecological impact in the full life cycle, mainly by a lower energy consumption during the in-service phase, but also during the production and recycling. The continuous production process of honeycomb cores enables today additional to the weight saving also to utilize the cost advantage of sandwich construction. Within the EUREKA Project E!2796 "New thermoplastic folded honeycomb core for automotive, aerospace and other applications" (http://www.eurekanetwork.org/project/id/2796) from 2002 to 2005 the worldwide first continuous production technology for honeycomb cores had been developed. EconCore N.V. started as a spin-off from KU Leuven, Belgium in December 2005. Due to the high efficiency the technology, developed in the EUREKA Project E!2796, is applied today in mass market applications allowing reductions of product costs and weight and consequently reductions of CO2 emissions. EconCore licensed the technology to industrial partners in different continents and industries. ThermHex Waben GmbH, EconCore’s production site in Germany, produces the ThermHex PP honeycomb core material for composite applications. Today those continuously produced honeycomb cores offer the best performance per cost of all thermoplastic honeycombs. This HiHex EUREKA project targets to develop a new class of sandwich core material. Hierarchical sandwich honeycombs have the potential to outperform conventional honeycomb cores and other sandwich cores due to a better mechanical performance per weight to enable lower weight structures and parts. The thin cell walls of low density honeycomb cores are compression and shear loaded elements, which usually fail due to buckling. Sandwich constructions provide a maximum out-of-plane compression (and out-of-plane shear) buckling resistance at minimal weight. The implementation of sandwich cell walls in honeycomb cores leads to a new class of materials, the hierarchical sandwich honeycombs, patented in 2015 [EconCore, WO2016/184528] and presented first by EconCore on the International Conference on Sandwich Structures ICSS 11 in 2016. EconCore´s continuous production technology allows to produce a very thin sandwich material with high performance composite skins, which can be used to create sandwich cell walls. Initially the cell size of the HiHex honeycombs will be rather large. To avoid the buckling of the skins into the HiHex honeycomb cells sandwich skins can be used. With higher performance thermoplastics and fibre reinforced thermoplastics this secondary hierarchical structuring allows to outperform todays convential aerospace honeycombs from aramid fibre paper and aluminium, to enable that in the future thermoplastic honeycombs will have the best performance per weight. The hierarchical sandwich honeycomb core offers the advantage that the skin material used in the cell walls may be made from very thin layers of materials with high in-plane stiffness and strength, like a carbon fibre reinforced composite, while the cell wall core material could be based on a lower weight and lower cost material, like a thermoplastic polymer. Compared to standard honeycomb core concepts, the hierarchical concept increases the number of geometrical and material design parameters even further. Intensive modelling and optimisation studies will be required to develop the knowledge base for optimizations to reach the performance targets. Developments and tests will be needed to understand the performance advantage and to translate the production concepts into efficient processes and to develop lab-scale equipment to produce samples. In the implementation phase of the project additional partners will be added for the application developments. For aerospace applications the extremely low weight of thick HiHex honeycombs will be beneficial. Developing efficient automated production concepts will allow to transfer knowledge from high performance leading edge applications to large volume applications. Truck side walls require similarly thick cores and are thus an interesting large volume application target for HiHex honeycombs, based on cost efficient thermoplastic polymers.
Acronym: 
HIHEX
Project ID: 
12 679
Start date: 
01-08-2018
Project Duration: 
60months
Project costs: 
6 000 000.00€
Technological Area: 
INDUSTRIAL MANUFACTURING, MATERIAL AND TRANSPORT
Market Area: 
Chemicals and Materials

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