Huntsman Advanced Materials Unveils Novel FST Thermoset Solution for Lightweight Composite Interior Aerostructures

10 September 2013

Huntsman Advanced Materials says it has launched an entirely new high-performance and inherently flame resistant solution for RTM and infusion processing which offers greater strength whilst answering continued demand for weight reduction in interior aerospace designs.

It claims Araldite FST 40002 / 40003 is a radically different development that provides a unique combination of high mechanical, fire, smoke and toxicity (FST) performance alongside high quality, user-friendly composites processing conditions enabling efficient production of interior carbon and glass composites parts with maximised weight savings. 

The mixed two-component system exhibits a low viscosity at working temperatures above 50°C.  The latency range from 50°C to 100°C provides the ability to produce complex parts in small and large dimensions.  In addition, Araldite FST 40002 / 40003 has low reaction energy of about 220 J/g which eliminates bulk exothermic safety issues and enables large thickness composite part production.

In comparison to traditional RTM and infusion systems, its viscosity and reactivity profile shows snap-cure behaviour which allows fast Tg and interlaminar shear strength (ILSS) development.  Also, after pre-cure conditions of approximately one hour at 100°C followed by one hour at 120°C, the system can be de-moulded, resulting in moulding time and mould cost optimisation.  Indeed after the latter pre-cure conditions, the system develops 85-90% of its ultimate ILSS – when measured on carbon fabric reinforcement.

Pre-curing is followed by two-hour post-curing at 180°C, which can be done either in the mould or freestanding, to enable the ultimate performance development.

Araldite FST 40002 / 40003 develops dry and wet Tg of 260°C and 185°C (measured by DMA) with very high ILSS performance of 97 MPa and 55 MPa at 23°C and 120°C respectively – when measured on unidirectional carbon reinforcement.  Surprisingly for a system with such high Tg and high crosslinking density, it also exhibits high tensile elongation and appreciable toughness, enabling the substitution of metal in highly structural applications.

In contrast to other materials used in interiors, Araldite FST 40002 / 40003 is an unfilled system.  The inherent FST properties of the system come from the chemical nature of the network and its high cross-link density.  The new system meets the FAR 25.853 vertical burn, smoke and toxicity requirements with both carbon and glass fibre in all thickness configurations.

The heat release of the system is highly dependent on composite thickness, making it ideally suited for non-visible parts in the interior that do not have direct contact with potential ignition sources as well as cockpit parts that currently do not need to pass heat release. 

Due to the filtration effect, filled systems are processed with open fabric where low fibre content sacrifices composites performance.  With the new Araldite system, the combination of excellent matrix mechanical properties and high fibre volume capabilities maximise performance, meeting industry demand for further weight savings. 

By comparison to phenolic resins which are subject to a polycondensation type reaction and are used for non- and semi-structural applications, Araldite FST 40002 / 40003 undergoes a polyaddition reaction without gas release.  This enables significant weight reduction, improved composites quality, elimination of intensive part production post-operations as well as a cleaner and healthier manufacturing solution for operators, supporting closed mold processes and VOC emissions free system exposure.

Olivier de Verclos, Technical Support, Composites & Tooling Team Leader, summarised:  “Advanced composites processes and materials are essential for high-performance fibre reinforced composites to penetrate the aerospace market to their full potential.  With Araldite FST 40002 / 40003, we are taking RTM and infusion processing into a new dimension to provide improved strength for lighter and mechanically superior parts which can be cost-effectively produced for the first time.

This innovative high-performance solution creates a radically new and much improved value proposition for aerospace designs, providing a preferred alternative to metal in structural applications 

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