Large variable geometry structures in thermoplastic composite

Sirris is finalizing an innovative implementation process for large thermoplastic (TP) composite structures using variable geometry forming.

The two-year Evocomp project funded by the Walloon Region is complete.

Its objective was to develop, optimize and qualify a manufacturing process without moulds to produce large thermoplastic composite structures with variable geometry.

Conventional thermoforming or thermocompression processes involve a long and costly heating/cooling cycle with potential damage to the material, especially when manufacturing large parts where the thermal regulation of a large mould is difficult and expensive. 

The innovative concept, described in an i-DEPOT in 2012, is based on the pultrusion process taking a pre-heated composite sheet through a former. 

Pultrusion is a proven process dedicated to the manufacture of straight sections, but here it is a matter of completing it with a variable geometry former with a view to giving the resulting structure a variable shape according to the required final design. The variable geometry can be programmed from the object's CAD by means of actuators. 


The selected material is fibreglass reinforced polypropylene in the form of consolidated sheets (Tepex from Bond Laminates) with several layers. Other materials can of course be implemented in the same way using another set of parameters. 

The industrial production installation that would enable products to be made without size limitation (length) and from semi-products, whether consolidated (sheets) or not (rollers as illustrated) is the following: 

For space reasons, Sirris has constructed a demonstrator with smaller dimensions in which the heating, forming and cooling units are placed along a pre-consolidated composite sheet to be formed, the latter being held in position by a support frame. 

The installation is 1 m wide with a useable zone 860 mm, length 2 m and total maximum height variation (positive and negative) 200 mm, and provides heating to 250°C. 

The developed process is dedicated to large slim parts whose geometric variations are not too pronounced. 

The potential applications are for large size products (yacht masts, wind turbine blades, signal posts, barriers, etc.), where conventional thermocompression processes cannot be envisaged for thermoplastic composites. 

Another sector is that of the single structural part (or very short runs) for which the design and manufacture of a thermo-regulated mould makes the cost of the part inaccessible. 

Applications can also be in:

  • medicine: personalized supports for patients in IRM for example
  • building: single decorative facing parts
  • transport: design components for prototype vehicles
  • designer furniture

If you have an application for a large variable geometry structure in thermoplastic composite, please don't hesitate to contact Sirris. 

Partner : UCL-CEREM