Abstract

Composites based on epoxy resin are a class of high performance structural materials with great potential in a wide variety of industrial sectors. However, being thermoset resins, despite their great benefits in lightness and mechanical performance, they present the great disadvantage that once cured they can not be reprocessed, repaired or recycled. This is hindering the rapid growth of composite materials in applications such as automotive.

In order to overcome the disadvantages of thermosetting resins, this paper presents the development of a new generation of dynamic thermoset epoxy resins able to be reprocessed,  repaired and recycled thanks to the incorporation of reversible bonds within its reticulated structure. As resins containing dynamic bonds, the cured material presents new properties previously unthinkable for thermosetting materials. These new resins have been developed for the manufacture of composite materials reinforced with both glass fiber and carbon fiber. It has been shown that these new composites have mechanical properties equivalent to those of conventional thermosetting composites, but unlike the latter, they are recyclable, repairable and reprocessable, which is a step forward and the creation of new opportunities for sectors such as automotive .

Abstract

The objective of the AIRPOXY project is to reduce production and maintenance, repair & operating (MRO) costs of composite parts in aeronautics, by introducing a new family of enhanced thermoset composites that preserve all the advantages of conventional thermosets, while show unprecedented new features such as Re-processability, Repairability and Recyclability. This new generation of composites, called 3R composites, are obtained using dynamic hardeners which create reversible crosslinks in the cured epoxy resin. Once the 3R composite has been produced, the dynamic chemical bonds in the cured resin can be reshuffled under determined external stimulus, such as temperature or exposure to a specific chemical agent.

The study describes the development of a first version of 3R composite that meets the requirements of the aeronautical sector. Firstly the resin has been formulated, then the composite laminates have been produced by Resin Transfer Moulding (RTM) and finally their dynamic and mechanical properties have been studied.

Abstract

Composites based on epoxy resin are a class of high performance structural materials with great potential in a wide variety of industrial sectors. However, being thermoset resins, despite their great benefits in lightness and mechanical performance, they present the great disadvantage that once cured they can not be reprocessed, repaired or recycled. This is hindering the rapid growth of composite materials in applications such as automotive. In order to overcome the disadvantages of thermosetting resins, this paper presents the development of a new generation of dynamic thermoset epoxy resins able to be reprocessed,  repaired and recycled thanks to the incorporation of reversible bonds within its reticulated structure. As resins containing dynamic bonds, the cured material presents new properties previously unthinkable for thermosetting materials. These new resins have been developed for the manufacture of composite materials reinforced with both glass fiber and carbon fiber. It has been shown that these new composites have mechanical properties equivalent to those of conventional thermosetting composites, but unlike the latter, they are recyclable, repairable and reprocessable, which is a step forward and the creation of new opportunities for sectors such as automotive .

Abstract

This work is focus on the development of photocurable resins doped with nanoparticles of very diverse nature, diamond, barium oxide, hydroxyapatite and silver. These nanoreinforcements are being investigated, and even applied industrially, as nanofillers of thermosetting resins, due to the different enhancements and new properties, including increased mechanical, thermal and chemical properties, high electrical and thermal conductivity, improved biocompatibility and antimicrobial properties, among others. The reinforcement of photocurable thermosetting resins can be complex since the added charge can exert shielding to the radiation, limiting to reach high curing degree. For it, it is necessary to use catalysts and sensitizers of UV radiation. In addition, in order to limit this negative effect, a high degree of dispersion of the nanofillers is required, avoiding the presence of micrometric agglomerates. An epoxy system has been selected, whose is commly used for dental applications, and differente contents of nanofillers have been added. Once the dispersion process has been optimized, the effect of the different fillers on the degree of curing of the photocurable resin, measured through its glass transition temperature, has been studied. The degree of curing achieved has been explained through transperance measurements to the visible light of the samples, as well as the morphology of the cured and doped resins.

Abstract

The use of CIDETEC's patented 3R technology allows the development of thermoset composites that are intrinsically Reprocessable, Recyclable and Repairable (3R). These materials are very interesting for sectors as diverse as energy, transport, and construction, as they maintain the high performance of conventional thermoset composites and can be processed using common manufacturing technologies. The use of prepregs is one of the methods used to manufacture thermoset composites, but it is a labour-intensive and cost-intensive process. In addition, the epoxy matrix of prepregs, which is partially cured (called B-phase) and sticky, requires them to be stored cold (refrigerated or frozen) and, once the due date has passed, they cannot be used to form a consolidated laminate because of their lack of adhesion. The dynamic character of the 3R epoxy resin described here makes it possible to manufacture what we have called "enduring prepregs", which are (semi-)cured, non-perishable prepregs, with the advantage that they can be stored at room temperature without losing their adhesion capacity. Moreover, it is possible to process them using techniques as diverse as AFP (automated fibre placing) or thermoforming to manufacture multilayer composite parts. This communication will present the latest advances and the objectives of several European projects funded under the H2020 (CARBO4POWER - GA.953192) and Horizon Europe (BIO-UPTAKE -GA. 101057049 and GENEX -GA. 101056822) frameworks, which are working on the development and optimisation of these "enduring prepregs" for different sectors.

Abstract

In the railway sector, represented by TALGO, there is growing concern about the recyclability and reusability of composite parts at the end of their useful life. To address this concern and comply with Spanish and European directives and legislation, an innovation project (divided into 'PART 1' and 'PART 2') has been carried out in which AITEX, CIDETEC, iTREE, and TALGO have collaborated. The main results of the first part are as follows:

1. Recycling process of the composite material of the first prototype of the Lightweight Running Gear Frame: This process focuses on recovering the carbon fiber contained in the material by combining several chemical-physical steps.
2. Development of a 3R (recyclable) epoxy resin formulation: This resin meets the thermal, mechanical, and FST (Fire, Smoke, and Toxicity) requirements of the railway sector and is suitable for use with prepreg technology.

The results indicate that the recycling process is suitable for producing post-consumer parts and that the formulated resin meets the required standards. The overall conclusions of the project will be revealed in PART 2 of this study.

Abstract

This PART 2 is the continuation of the project: “PART 1: recyclability and revalorisation of railway components made of composite materials”. Following the successful development of the recycling process for the Lightweight Running Gear Frame prototype and the formulation of a 3R epoxy resin suitable for use in the railway sector, the project advances with the following challenges:

1. Revalorisation of Recycled Carbon Fibre (rCF) into new fabrics, by obtaining hybrid rCF and polyamide 6 (PA 6) yarns by adapting and optimising textile processes to incorporate recycled fibres into new intermediate products.
2. Production of a new prepreg and its laminates. The new prepreg and its laminates will be produced using the dry fabric obtained in the previous objective and the 3R epoxy resin, developed in PART 1 of the project.

The overall conclusions of the project are that: the recycling process is suitable for post-consumer components, the spinning and weaving methods are effective for dealing with this type of fibres and the 3R laminates manufactured are of high quality and ready to be evaluated in terms of their properties.