Assessment of the Impact of Material Selection on Aviation Sustainability, from a Circular Economy Perspective

Verification of the Self-Healing Ability of PP-co-HUPy Copolymers in Epoxy Systems

This work concerns the verification of the self-healing ability of PP-co-HUPy copolymers dispersed in epoxy systems. PP is the acronym for the Poly-PEGMA polymer, and HUPy refers to the HEMA-UPy copolymers based on ureidopyrimidinone (UPy) moieties. In particular, this work aims to verify whether this elastomer characterized by an intrinsic self-healing ability can activate supramolecular interactions among polymer chains of an epoxy resin, as in the elastomer alone. The elastomer includes a class of polyethylene glycol monomethyl ether methacrylate-based copolymers, with different percentages of urea-N-2-amino-4-hydroxy-6-methyl pyrimidine-N'-(hexamethylene-n-carboxyethyl methacrylate) (HEMA-UPy) co-monomers. The self-healing capability of these copolymers based on possible quadruple hydrogen bond interactions between polymer chains has been verified. The formulated epoxy samples did not show self-healing efficiency. This can be attributed to the formation of phase segregation that originates during the curing process of the samples, although the PP-co-HUPy copolymers are completely soluble in the liquid epoxy matrix EP. The morphological investigation highlighted the presence of crystals of PP-co-HUPy copolymers, which are in greater quantity in the sample containing the highest weight percentage (7.8 wt%) of HUPy units. Furthermore, the crystals act as promotors for increasing the curing degree (DC) of the epoxy systems containing HUPy units. DC goes from 91.6% for EP to 96.1% and 95.4% for the samples containing weight percentages of 2.5 and 7.8 wt% of HUPy units, respectively. Dynamic mechanical analysis (DMA) shows storage modulus values for epoxy systems containing PP-co-HUPy units lower than that of the unfilled resin EP. The values of maximum in Tan δ (Tg), representing the temperature at which the glass transition occurs, are 220 for the unfilled resin EP, 228 for the sample containing 2.5 wt% of HEMA-UPy units, and 211 for the sample containing 7.8 wt% of HEMA-UPy units.

A novel life cycle assessment and life cycle costing framework for carbon fibre-reinforced composite materials in the aviation industry

Purpose

Carbon fibre-reinforced composite materials offer superior mechanical properties and lower weight than conventional metal products. However, relatively, little is known about the environmental impacts and economic costs associated with composite products displacing conventional metal products. The purpose of this study is to develop an integrated life cycle assessment and life cycle costing framework for composite materials in the aviation industry.

Methods

An integrated life cycle assessment (LCA) and life cycle costing (LCC) framework has been developed. The displacement of a conventional aluminium door for an aircraft by a composite door is presented as an example of the use of this framework. A graphical visualisation tool is proposed to model the integrated environmental and economic performances of this displacement. LCA and LCC models for composite applications are developed accordingly. The environmental hotspots are identified, and the sensitivity of the environmental impact results to the different composite waste treatment routes is performed. Subsequently, the research suggests a learning curve to analyse the unit price for competitive mass production. Sensitivity analysis and Monte Carlo simulation have been applied to demonstrate the cost result changes caused by data uncertainty.

Results

Energy consumption was the hotspot, and the choice of composite waste treatment routes had a negligible effect on the LCA outcomes. Concerning the costs, the most significant cost contribution for the unit door production was labour. The future door production cost was decreased by about 29% based on the learning curve theory. The uncertainties associated with the variables could lead to variations in the production cost of up to about 16%. The comparison between the two doors shows that the composite door had higher potential environmental impacts and cost compared to the conventional aluminium door during the production stage. However, the composite door would have better environmental and financial performance if a weight reduction of 47% was achieved in future designs.

Conclusions

The proposed framework and relevant analysis models were applied through a case study in the aerospace industry, creating a site-specific database for the community to support material selection and product development. The graphical tool was proved to be useful in representing a graphical visualisation comparison based on the integration of the LCA and LCC results of potential modifications to the composite door against the reference door, providing understandable information to the decision-makers.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11367-023-02164-y.