The objective is to develop resin systems exhibiting extended shelf/pot-life to enable wider utilisation of the out of autoclave process for large or complex parts. This shall be an optimisation between extended pot-life as well as minimisation of curing temperature for a variety of target applications.

 

 

Composite and adhesive resin systems form a cornerstone for the manufacture of any modern spacecraft however both the manufacturing and procurement processes are often limited by the pot and/or shelf life of the prepreg/resin materials. A longer shelf life could mean a reduction of the amount of scrappage which occurs from any typical spacecraft composite system manufacturing line. Typically, it can be necessary to scrap and re-procure significant quantities of unused prepreg or resin materials simply because the shelf life is shorter than any recurrent manufacturing. Improved shelf life could significantly reduce both the cost of manufacture and the environmental footprint of composite processes. Secondly, the extension of pot life for resin systems could allow for extended manufacturing cycles for both larger and more complex smaller composite artefacts particularly seen as part of out of autoclave processing. A brief review of available literature indicates some interest in approaches to extend both the pot and shelf life of commonly used resin systems.

 

The use of CFRP out-of-autoclave technologies is utilised for increasing number of applications for improved automation, either for large structures or smaller complex geometries. The production of large structures require long layup times at room temperature that can reach the order of a week. But also smaller structures can require significant out-time of the prepreg, many of which are required to be stored in low temperature freezers to prevent curing. The limitation of prepreg resins is therefore more fundamental, depending on required layup time and ultimate curing temperature. Extended processing times at room temperature can limit the spectrum of possible applications or compromise the final mechanical performance of the CFRP.

 

Any study shall consider both the composite and adhesive resin system as a mated pair, which shall be tailored for compatibility towards each other.

 

Following the initial analysis a trade-off of the significance of both the pot life and shelf life shall be performed to assess the relative potential benefits of improving either property. Any activity shall preferentially identify chemical modifications to extend both properties.

 

Phase 1 (350K?/14 months)

The following tasks will be performed:

 

• Review of current space applications for out of autoclave processes and available resin/prepreg systems, including a mid-term technology trend. Selection of applications processes that requires resin performance improvement in terms of extended pot-life.

• Procurement, quantification and laboratory materials assessment of candidate resin systems properties and capabilities.

• Preliminary trade-off of candidate systems. Selection of candidate systems.

• Development and test plan for two resin systems.

• Small scale testing and resin optimisation, definition of breadboard demonstrator for phase 2.

 

Phase 2 (250K?/ 10 months)

The following tasks will be performed:

 

• Up-scaling of optimised resin systems and prepreg production.

• Manufacturing and testing of breadboard demonstrator.

• Critical revision, ROM costs for full qualification, spin-off potential.