?? JEC Lab - Vitrimers offer new possibilities for aerospace composites

Vitrimers offer new possibilities for aerospace composites - episode 4

Vitrimers combine the advantages of thermoset and thermoplastic polymers and offer new possibilities in the processing and application of composites. In the EU-funded AIRPOXY project, a new generation of vitrimer-based carbon fiber composite is being developed by a multidisciplinary team of 11 partners from six countries. The aim is to reduce the production and maintenance costs of composite aerospace parts by introducing a novel family of thermoset composites that preserve all the advantages of conventional thermosets, but can also be easily processed and repaired, and even recycled.

The best of both worlds ?

Processes with high output rates and short cycle times are required for the efficient production of high-performance carbon fiber reinforced polymer (CFRP) components. The choice of materials, especially the matrix material, has a decisive influence on the design of the processes. In recent years, there has been an increased use of high-performance thermoplastic polymers. Semi-finished products manufactured using thermoplastic matrices can be formed or welded in the molten state and it’s also possible to recycle end-of-life components as composites or even to separate fiber structure and polymer. Despite these advantages, thermoset matrix systems are still the standard in the production of structural components due to advantages such as high stiffness, high glass transition temperatures (Tg), low creep and good chemical resistance. In addition, unlike thermoplastics, uncured thermoset resins have a low viscosity, which is a benefit for the impregnation of complex fiber structures. In the production of primary aircraft structures, low raw material prices and low processing temperatures are additional arguments in favour of thermosets.

Vitrimers are based on thermoset polymers and therefore show the same properties at room temperature in terms of stiffness and chemical resistance. They consist of covalent networks, which can change their topology by thermally-activated bond-exchange reactions. At high temperatures, they can flow like viscoelastic liquids and in this state vitrimer-based CFRP can be formed, joined and recycled – similar to a thermoplastic material. Below the material’s Tg, the bond-exchange reactions are frozen and the resin behaves like standard thermosets.

Repairable, reprocessable, recyclable?

The AIRPOXY project is researching the newly-developed 3R vitrimer resin. “3R” stands for the three decisive properties of the material: repairable, reprocessable, recyclable. The project is investigating thermoforming, joining and repairing of 3R CFRP and is focusing on the development of a new class of aviation materials by drastically reducing costs in all areas – starting with manufacturing, maintenance, repair and operating costs of CFRP, and ending with material recycling for end-of-life components. The potential of 3R CFRP will be demonstrated by two sub-components: a fan cowl and a wing. Early investigations with fiber-reinforced 3R vitrimers have shown their enormous potential in terms of thermoforming, repair and recycling.

3R CFRPs show great potential for the production of high-strength structural components. They make it possible to use the advantages of thermosets while accessing efficient automated processes that were previously reserved for thermoplastic polymers.

3R CFRP offers:

·??????High production rates through adapted thermoforming processes;

·??????Weight-neutral welding and bonding technologies;

·??????Production of complex parts by resin transfer molding (RTM) processes;

·??????Potential for cost-efficient repairs;

·??????Recycling of end-of-life and production waste.

This results in efficient process chains that support the objective of a far-reaching cost reduction and contribute to the development of 3R CFRP high-performance components for the aerospace industry.

Interested in learning more about the AIRPOXY project? Take a look at the feature article Fiber reinforced composites with a vitrimer matrix in the latest issue of JEC Composites Magazine. Register for your copy here : https://www.nxtbook.fr/newpress/jeccomposites/jcm211_143/index.php

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