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New thermoplastic folded honeycomb core for automotive, aerospace and other applications

Development of new thermoplastic honeycomb sandwich core materials and their production process. The innovative new folded honeycomb core enables a fast core production from a thermoplastic sheet.

Sandwich constructions with honeycomb core materials are widely used in areas where low weight and maximum stiffness are asked for. The main area of application is, traditionally, the aerospace industry. In other areas, such as the automotive and construction industries, honeycombs are less often used due to the high production costs of the core material. Today, honeycomb cores are produced in batch-wise production processes by cutting the core from a block which has either been expanded from stacked and glued sheets of foil material or which consists of stacked and glued corrugated sheets or tubes. The new folded honeycomb material developed and patented by the K.U.Leuven is produced from a single thermoplastic sheet by successive in-line operations: cell thermoforming, web folding, core bonding and skin lamination. This concept allows the continuous and cost efficient manufacturing of thermoplastic honeycomb sandwich panels and parts. All the production steps can be performed successively by rotational operations in one production line. The option of rotational movements makes a core output speed of 10 m/min or more possible. The input material is one endless thermoplastic foil, which is transformed by successive steps: (1) forming of half-hexagonal shapes either by deep drawing or by vacuum thermoforming (2) folding the half-hexagonal web into a honeycomb (3) relaxation and welding of the honeycomb core. Skins, preferably from the same thermoplastic material, can be welded onto the honeycomb directly in-line after the production of the core. The thermoplastic folded honeycomb core has closed skin strips, which allow a strong bonding of the skins onto the core. The possibility of using the same thermoplastic material for core and skin leads means that the sandwich part is readily recyclable. In automotive applications, sandwich materials are used in the interior, such as parcel shelves or headliners. The demands on cost efficiency of panels and light-weight structures are becoming more stringent. For those applications and for the packaging industry, the new sandwich material will be developed from polypropylene (PP) and polyethyleneterephthalate (PET) foils. Optionally, the foil can be reinforced by glass or natural fibre mats. In ground transportation and aircraft interior applications the reduction of the production costs of today's phenol coated aramide paper honeycomb panels becomes possible, due to the cost efficient continuous production of folded honeycomb panels from non-flammable thermoplastic foils, e.g. polyetherimide (PEI). The continuous lamination and the forming of all-thermoplastic panels in a press to complex curved parts will be investigated. Keywords: honeycomb, sandwich, production.
Acronym: 
THERMHEX
Project ID: 
2 796
Start date: 
01-04-2002
Project Duration: 
44months
Project costs: 
2 000 000.00€
Technological Area: 
Plastics, Polymers
Market Area: 

Raising the productivity and competitiveness of European businesses through technology. Boosting national economies on the international market, and strengthening the basis for sustainable prosperity and employment.