Cumulative energy demand analysis in the current manufacturing and end-of-life strategies for a polymeric composite at different fibre-matrix combinations

Fibre Reinforced Polymers (FRPs) are finding more applications in different industrial sectors. From a sustainability point of view, a component made of FRPs reduces energy consumption and CO2 emissions during its usephase due to the material’s lightweight nature. However, the production of these materials impacts the global energy demand significantly. To mitigate this impact, circular economy strategies are essential. This study focuses on a Cumulative Energy Demand (CED) analysis for different End-of-Life (EoL) strategies of FRPs components. Three EoL routes were evaluated: i.e., combustion, recycling and reforming of continuous fibres reinforced thermoplastics. Different fibres and matrices and three Fibre Volume Fractions (FVF) were taken into account. Specifically, Glass Fibres, Carbon Fibres, Polypropylene, and Polyether ether ketone were examined while FVF of 11%, 23% and 45% were evaluated. A Life Cycle Inventory data was built combining literature review and CES Edupack database. The results provided some guidelines for optimising the product’s EoL phase in terms of CED reduction underlining the advantages and high competitiveness of the reforming strategy especially if high-performance matrices and/or fibres are processed. Recycling results to be a valuable EoL alternative if FRPs made by high-performance fibres and high FVF are employed while combustion is the more advisable option if low-performance matrices and fibres are used

An insight into friction stir consolidation process mechanics through advanced numerical model development

Friction stir consolidation (FSC) is a solid-state process adopted to recycle machining scraps with aim to reduce the adverse impact of obtaining metals from their primary source. FSC was also applied to offer plausible new routes for alloying and upcycling from powder and scrap metal and thus drew the attention of many researchers. During FSC process, a rotating tool with a certain force is applied to a given chips batch enclosed in a die chamber turning it into a consolidated billet. It is assumed that favorable process conditions for chips bonding are acquired by the combined effect of friction, stirring action, and pressure of the tool. However, the real process is quite complex, and it can be understood only by developing proper solid bonding criteria through numerical modeling that can forecast the consolidation process. Therefore, in this research, an attempt was made to implement different existing bonding criteria. Some of these were good enough to predict favorable conditions for sound bonding of particular case studies, however a uniform criteria with a single threshold value that is applicable to all case studies could not be achieved. Therefore, this study suggests for a new approach to accurately predict the bonding integrity of the FSC process

Investigation of the reshaping process by hydroforming using magnetorheological fluids

The reshaping of End-of-Life (EoL) components is considered a promising approach to put in practice one of the virtuous strategies of the Circular Economy. The heterogeneity in a EoL part, the alternation of deformed/undeformed regions resulting from the manufacturing process, may hinder an effective reshaping into a brand new geometry. Therefore, the proper selection among the sheet metal forming processes to overcome such a limitation is of utmost importance. The present work, based on a full numerical approach, investigates the reshaping process of a discshaped EoL by hydroforming using a Magneto Rheological Fluid (MRF) as the forming medium. The basic idea is to combine the advantages coming from the flexibility of the hydroforming process with those from the MRF whose behavior (i.e. its viscosity affecting the shear stresses at the contact with the blank) can be tailored by adjusting the applied magnetic field. The reshaping approach is investigated according to two separate routes, differentiated by a different target geometry. A factorial plan of numerical simulations allowed to investigate the effect of the MRF behaviour as well as the geometry of the EoL component on the quality of the reshaped part, expressed in terms of accuracy in the final shape and thickness distributio

Geometrical deviation of end-of-life parts as a consequence of reshaping by single point incremental forming

Putting in place circular economy strategies is an urgent challenge to face. In this scenario, manufacturing processes play a relevant role as efficient material reuse enabler. Scientists have to make an effort either to find new process or to rethink old process to reprocess end-of-life (EoL) component to recover both material and functions. In this paper, single point incremental forming (SPIF) process is used for reshaping sheet metal EoL components. The entire process chain was replicated including both deep drawing process (to imitate the end-of-life component) as well as SPIF operations (to obtain the reshaped components). The geometrical deviation as a consequence of SPIF operations was studied; two different SPIF directions (named inwards and outwards) were analyzed. A wide experimental campaign along with statistical analyses was developed to analyze effects of some geometrical parameters on the observed geometrical deviation. The results are promising as limited distortions were observed and sound components were obtained in all the analyzed process configurations. Despite that, some research is still needed to better standardize the reshaping process and bring it closer to an industrial applicability

Optimization of the sheet hydroforming process parameters to improve the quality of reshaped EoL components

The reshaping of End-of-Life (EoL) components by means of sheet metal forming process has been considered largely attractive, even from the social and economic point of view. At the same time, EoL parts can be often characterized by non-uniform thicknesses or alternation of work-hardened/undeformed zones as the results of the manufacturing process. Such heterogeneity can hinder a proper reshaping of the EoL part and residual marks on the re-formed blanks can be still present at the end of the reshaping step. In a previous analysis, the authors evaluated the effectiveness of reshaping a blank with a deep drawn feature by means of the Sheet Hydroforming (SHF) process: it was demonstrated that residual marks were still present if the deep drawn feature was located in a region not enough strained during the reshaping step. Starting from this condition and adopting a numerical approach, additional investigations were carried out changing the profile of the load applied by the blankholder and the maximum oil pressure. Numerical results were collected in terms of overall strain severity and residual height of the residual marks from the deep drawn feature at the end of the reshaping step. Data were then fitted by accurate Response Surfaces trained by means of interpolant Radial Basis Functions, subsequently used to carry out a virtual optimization managed by a multi-objective genetic algorithm. Optimization results suggested the optimal value of the output variables to reduce the marks from the deep drawn feature without the occurrence of rupture

Progresses in multi-materials billet manufacturing out of metal scraps through friction stir consolidation

The evolution of Friction Stir Consolidation (FSC) from recycling towards upcycling technique proved to be one of the excellent solid-state methods for manufacturing functionally graded billets. Multi-material Functional Graded Materials (FGMs) represent a novel class of materials characterized by a gradual change in properties and functions which can be tailored to enhance components performance. Manufacturing techniques play a critical role in achieving the designed compositional and microstructural distribution. Specifically, FSC allows the manufacturing of FGM billets out of metallic chips; the mixing of different metallic chips offers mutually exclusive mechanical properties like high hardness and good ductility in a single FSC billet with excellent formability. The present research further explores some challenges while combining dissimilar aluminum alloys chips in different percentages and spatial order, especially in the radial direction. The mechanical and metallurgical properties were assessed through the Vickers hardness measurements and microstructure analysis. The results revealed that new strategies are needed for a better exploitation of FSC as a solid-state method for fabrication of Functionally Graded Materia

Understanding formability and geometrical accuracy of SPIF process used as reshaping approach

Putting in place Circular Economy strategies is an urgent action to be undertaken. Manufacturing processes play a relevant role as efficient material reuse enabler. Scientists have to make an effort either to find new process or to rethink old process to reprocess End-of-life (EoL) components to recover both material and functions. In this paper, Single Point Incremental Forming (SPIF) process is used for reshaping sheet metal EoL components. Deep drawing process as well as uniaxial pre-straining (to imitate the End-of-Life component) followed by SPIF operations (to obtain the reshaped components) are set- up and implemented to form and reform aluminum sheet metal components. As the authors have already proved the technical feasibility of such an approach, the present paper aims at a better understanding of the formability and geometrical accuracy performance of SPIF process as used to reform components. Specifically, an experimental campaign varying kind and extent of restraining is developed and the formability and geometrical accuracy of the subsequent SIPF operations is analyzed. Results proves that SPIF process is a promising approach for reshaping purpose

Fabrication of Billet from Aluminum Alloys AA 2011-T3/7075 Chips through Friction Stir Consolidation

Recently evolving Solid-State Recycling (SSR) techniques have shown promising features to recycle metals scraps more efficiently compared to remelting-based approaches. Among these SSR methods, Friction Stir Consolidation (FSC) has been successfully tested to transform metals chips directly into semi or final solid products. Therefore, researchers explored FSC critical process parameters and their subsequent effects on quality in terms of the mechanical and metallurgical properties of the billet. All the previous studies of FSC were limited to developing billet of mono materials. Therefore, in this research, an attempt was made to go beyond the idea of recycling; in fact, a billet of two dissimilar aluminum alloys AA 7075 and AA 2011-T3 out of chips was obtained. The mechanical and metallurgical properties were assessed through the Vickers hardness measurements and microstructure analysis. The experimental results of this research illustrate that the FSC process is a feasible approach to develop a billet of dissimilar materials with achieving quality closer to the corresponding billet of mono-material