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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - SSUCHY (Sustainable structural and multifunctional biocomposites from hybrid natural fibres and bio-based polymers)

Teaser

Summary

Interest in composites from renewable and sustainable resources is expanding rapidly. Even if research and innovation in plant fibre composites (PFCs) is growing fast, in particular in well-established application sectors (such as automotive and plastic industries, building and construction), the development of structural PFCs is still a result expected but not yet fully achieved. The penetration of PFCs in the market of structural composite is low. Until now, most of the effort has been devoted to the development of short-fibre and non-woven based composites, which are not suitable for structural applications. The main challenges are related to the development of sustainable methods to expand purpose-grown biomass, service-life and long-term durability, design and engineering of bio-based materials that can exhibit tolerance against various external factors. Beyond this, there is also a strong need to develop all-green composites (i.e. 100% bio-based) with a good durability and cost efficiency.
In such a context, SSUCHY aims at exploiting the intrinsic and differentiating properties of plant fibres (in particular, hemp) and biopolymers derived from lignocellulosic feedstock to develop fully bio-based composites with high structural properties and advanced functionalities. The main driver behind this project is not only to substitute conventional fossil-based materials with more sustainable bio-based ones but also to achieve improved functionalities that surpasses those of fossil-based ones. Enhanced functionalities are, in addition to load-bearing resistance and weight reduction of structures, enhanced durability, vibration damping, vibro-acoustic control and fire retardancy while retaining an essentially recyclable character for certain applications. Such developments would provide to the composite industry a significant value and functions added products with high socio-economic impacts and minimized environmental impact. It will create opportunities to expand market applications for bio-based composites to semi-structural and functional applications in transportation along with new opportunities in high added value niches. In addition to the use of renewable constituents, this project also proposes to measure and minimize the environmental impact and energy consumption of the processes. A complete Life Cycle Analysis of the developed products will be provided. The proposed methodology is implemented within the framework of a multi-level eco-efficiency approach which covers experimental aspects, as well as process optimization, modelling and design. It comprises three main research axis:
(i) development and optimization of a competitive hemp fibre reinforcements for composite applications,
(ii) development and optimization of two fully bio-based polymers with advanced functionalities, a thermoplastic aliphatic polyester and a thermoset epoxy mainly synthetized from lignin-derived building blocks,
(iii) implementation of advanced functionalities in plant-based materials and structures to prove the concept at the scale of demonstrators.

Work performed

During the first period, a large part of the activities were dedicated to the development and optimization of the bio-based constituents for the targeted composite applications.
Regarding the reinforcement, it has been demonstrated that European hemp, when the varieties are finely selected and the primary processing steps optimized, can be successfully transformed into slivers of quality in line with the requirements for the production of textile fabrics. The feasibility of weaving, braiding and knitting low-twisted hemp rovings has been demonstrated at the lab scale. Specific woven fabrics made with hemp roving wrapped by a thermoplastic monofilament have also been developed. All these hemp-based half-products are optimized for structural composite applications.
On the biopolymer side, the main achievement is the formulation of a thermoset epoxy approaching 100% bio-based. Based on a combination involving diepoxides of lignin-derived phenypropenes, this formulation answers the thermo-mechanical requirements for structural composite applications. These all-green epoxy was used with hemp fibres to produce fully bio-based composites. The preliminary results show that this material is really promising for structural applications. The synthesis of a new efficient bio-based flame retardant, derived from eugenol and acting as a copolymer, has been also developed. It opens the way to ground and air transportation applications. New bio-based aliphatic polyesters were also synthesized and their thermal properties were increased when compared to the solutions available on the market. Work is still ongoing to keep their recyclability.
In the meantime, several activities have been started in the upper segments of the value chain, in particular in conjunction with the engineering of bio-based composites. Part of the work has been realized using constituents (reinforcements and polymers) already available on the market, trying to improve their durability and better understand and assess their long-term behaviour in their service conditions (including high-cycle fatigue and creep behaviour). Encouraging progress has been made in this area. The proof of concept that durability of plant fibre composites is enhanced when manufactured at equilibrium moisture content (EMC) of their targeted application has been provided. Metal based catalysts for polyester resins, permitting the use of non-dried fibres, whilst still giving excellent cure, were also successfully developed. A strong focus is also put on the damping capacity of PFCs. Indeed, beyond the density which plays an important role for the inertial effects in the dynamic behaviour, the stiffness and the damping properties are also key points that must be correctly estimated for the design of structures. A multiscale analysis of bio-based composites is thus under investigation in order to understand the vibro-acoustic performance of these materials.
Based on the data and knowledge collected during the first period, the design and Finite Element Analysis of the demonstrator products and prototypes has started. It includes electric aircraft interiors, sound cabinets, automotive trunk floors and bio-scooters.

Final results

For the materials and process technologies developed in SSUCHY, the aim is to increase the sustainability and the competitiveness of Europeâ€™s industry through engagement in the bio-based composite sector. The main expected impacts are: (i) to set the basis and validate new bio-based constituents for composites (hemp-based reinforcements, aliphatic polyesters and fully bio-based epoxy resin) and (ii) to propose new composite structures and products based on these bio-based constituents and demonstrate their advanced functionalities at the scale of demonstrators. The whole work packages aims at developing prototypes of demonstrator products and prototypes at TRL4-5. At this stage, the readiness level of most of the technologies developed within the SSUCHY project (harvesting and primary and secondary processing of hemp, wood fractionation and synthesis of fully bio-based polymers from the lignin-derived synthons, durability improvement of bio-based compositesâ€¦) has significantly increased and has been validated at a scale of the laboratory.