[en] Broadening knowledge about future materials and manufacturing processes will serve to develop high value-added products that respond to major societal challenges. Additive manufacturing (AM) is one such process and demonstrates great potential to contribute to enhanced product customization, digitalization of manufacturing, and the circular economy (EC). Sustainable design is currently one of the criteria in the development of automotive components; with lightweight design, energy savings and efficient use of raw materials the subject of much research. In parallel with environmental concerns, safety remains a critical factor, and manufacturers must strive to ensure or improve the safety of vehicle occupants in impact situations. To satisfy both these requirements, the increase of energy absorption properties by means of complex structure design and non-conventional fibre orientations in cFRTP composite materials is the main objective of the present thesis. To this end, new concepts of structures and metamaterials with predefined or programmable properties addressing specific needs/functionalities within the vehicle structure were analysed and developed using composite AM technologies. 3D printing - FFF of continuous fibre permits greater design freedom and flexibility in terms of fabrication of cFRTP structures, since the fibre can be oriented in the direction of the load, increasing performance and material utilization. The present work focuses on broadening knowledge in three fundamental blocks: The first block investigates increasing the energy absorption properties of fabricated structural components through geometric profile design and selection of continuous fibre printing trajectories. For this purpose, microstructural characterization and identification of printing defects due to the FFF process was carried out, and the relationship between geometry (Fold profile), fibre printing pattern, and the nature of the reinforcement filament (cCF/PA, cGF/PA and cKF/PA) in the generation of these defects was analysed. At the same time, the fracture mechanisms that induce stable collapse modes of printed profiles were identified, analysing the position and typology of the defects and their relationship with the load direction. This work facilitates the conversion of a weakness/discontinuity in the structure (printing defects) into initiators of stable collapse. The cCF/PA profiles achieved an axial and radial static SEA of 30.1 kJ/kg and 9.0 kJ/kg, respectively. In the second block, the response of printed materials reinforced with continuous fibre cFF (carbon, glass, and Kevlar©) at different test speeds was studied. The results proved that there are differences in the nature of the PA matrices that cover the fibres, which explains their greater sensitivity to the strain rate and improvement of their impact resistance (Kevlar©). It was also demonstrated that poor impregnation of the fibres or lack of consolidation of the printing material causes certain failure mechanisms based on fibre fracture, delamination, and friction between the layers and the printing beads. The cGF/PA profiles shown an axial and radial dynamic SEA of 20.0 kJ/kg and 12.8 kJ/kg, respectively. Moreover, the strain-hardening effect enhanced impact resistance of cCF/PA material, whereas in cCF/PA not. The third block was centred on the identification and characterization of auxetic filling structures that improve the transverse behaviour of tubular profiles, and that produces a synergistic effect on the absorption capacity of the profile-core. The results of this study also showed that the collapse mode of the RSH auxetic core (star-shape re-entrant) increases the load capacity of the profile and controls of the profile progressive collapse mode during its densification. A synergetic effect has been observed for every profile filled with the RSH auxetic core. The cKF/PA filled profile achieved the highest radial impact SEA value (20.6 kJ/kg). 3D printing is one of the Industry 4.0 enabling technologies identified in the RIS3 smart specialization strategy of Euskadi. It was selected because it easily integrates into the circular economy through the use of recycled materials (filament or pellet), however it remains underutilised because of its high cost and long manufacturing time. Hybridization in thermoplastic composite manufacturing technologies responds to these challenges by: (i) achieving high levels of lightweighting and material utilization, (ii) reducing the operational cost of parts, and (iii) increasing productivity.

[eu] Etorkizuneko materialei eta fabrikazio prozesuei buruzko ezaguera sortzeak gizarteak dituen erronka nagusiei erantzungo dizkieten balio erantsi handiko produktuak garatzeko balio izango du. Produktuen pertsonalizatzea, fabrikazioaren digitalizazioa edo ekonomia zirkularra (EC) fabrikazio gehigarriak (AM) erantzun diezaiekeen erronka horietako batzuk dira. Gaur egun, diseinu jasangarria da ibilgailuetako osagaien garapenean, ildoetatik bat eta diseinu arinak, energia aurrezteak eta lehengaien erabilera eraginkorrak ikerketa anitz izan dituzte. Dena den, ingurumenaren aldeko kezkarekin batera, segurtasunak faktore kritikoa izaten jarraitzen du eta talkak diren egoeretan ibilgailuko bidaiarien segurtasuna bermatu edo hobetzen saiatu behar dute fabrikatzaileek. Horregatik, diseinu geometriko konplexuaren bidez, energia xurgatze propietateak gehitzea eta cFRTP material konposatuko egitura zuntzen orientabide ez konbentzionalak tesi honen helburu nagusi dira. Horretarako, konposite-ko AM teknologien bidez, aurretik definituta dituzten propietateak edo programatu daitezkeen egituren eta metamaterialen kontzeptu berriak aztertu eta garatu dira, ibilgailuaren egituraren barruan berariazko beharrak/funtzionaltasunak betetzen dituztenak. cFRTP (cCF/PA, cGF/PA y cKF/PA) egituren fabrikazioari dagokienez, zuntz jarraituzko 3D – FFF inprimaketak diseinuaren askatasun eta malgutasun handiagoa ematen du, kargaren norabidean zuntza bideratzeari aukera ematen baitio. Beraz, lan honek funtsezko hiru bloketan ezaguera sortzeari ekin dio: Lehen blokea ondorengo honetan ardaztu da: profil diseinu geometrikoaren bidez fabrikatutako egitura-osagaien energia xurgatzeko propietateen gehikuntzan eta zuntz jarraituzko inprimaketa ibilbideak hautatzen. Horretarako, karakterizazio mikroestrukturala eta FFF prozesua dela bide inprimaketa akatsen identifikazioa burutu dira eta baita aztertu ere geometria-erlazioa (Fold perfila), zuntzaren inprimaketa patroia eta errefortzu zuntz mota (karbonoa, beira eta Kevlar©) aipatutako akatsen sorreran. Halaber, inprimatutako profilen kolapso egonkor moldeak eragiten dituzten haustura mekanismoak identifikatu dira, kokapena, akatsen tipologia eta kargaren norabidearekin duen zerikusia aztertuz. Hori guztia, egituraren ahultasuna/etenaldia (inprimaketa akatsak) kolapso egonkorraren abiarazleetan bihurtzeko xedez. cCF/PA perfil baterako 30,1 eta 9,0 kJ/kg-ko SEA balioak lortu dira norabide axialean eta erradialean hurrenez hurren. Bigarren blokean cFF zuntz jarraiez (karbonoa, beira eta Kevlar©) indartutako inprimaketa materialen erantzuna aztertzen da saiakuntza abiadura ezberdinetan eta zera frogatu da: zuntzak estaltzen dituzten PA matrizen izaeran ezberdintasunak daudela, deformazio abiadurarekiko bere sentsibilitate handiagoa eta talkarekiko bere erresistentzia hobea azaltzen dutenak. Frogatu da ere zuntzen inpregnazio txarrak edo inprimaketa materialaren sendotze gabeziak hutsegite mekanismo ziurrak eragiten dituela, zuntzen hausturan, delaminazioetan eta geruzen eta inprimaketa kordoien arteko marruskaduran funtsatzen direnak. cGF/PA profilek sentsibilitate handiagoa erakutsi dute deformazio-abiadurarekiko. Hau dela eta, inpaktuarekiko erresistentzia eta zurruntasuna hobetu direla ikusi da. Inpaktuaren araberako SEA baloreak 20 kJ/kg axialean eta 12,8 kJ/kg erradialean dira. Hirugarren blokea, azkenik, nukleo auxetikoren egiturak identifikatu eta karakterizatzeari dago bideratuta, profil tubularraren zeharkako portaera hobetzeko eta, profil eta nukleo binomioari esker, xurgatze ahalmenean ondorio sinergetikoa eragiteko. Frogatu da ere RSH nukleo auxetiko kolapso moduak (izar motatako errentrantea) profilaren zamaedukiera gehitzen duela eta, loditzearekin batera, bere kolapso progresibo modua kontrolatzen duela. Efektu sinergiko bat hauteman da nukleo auxetiko eta profilen artean, eta inpaktu erradialeko SEA balorerik altuena cKF/PA profilerako lortu da (20,6 kJ/kg). 3D motatako inprimaketa 4.0 Industry-a bideratzen duen teknologietako bat da eta RIS3 Euskadi espezializazio adimendun estrategian identifikatzen da, gai birziklatuen erabileraren bidez, ekonomia zirkularraren integratze errazari aukera ematen diona. Dena den, berez ez da erakargarria bere kostu handiagatik eta fabrikazio denborak luzeak direlako. Beraz, material konposatu termoplastikoen fabrikazio teknologietako hibridazioak materialaren arintze eta ustiatze maila altuagoak lortzeko beharrari ez ezik, piezen operazio-kostuak murriztekoari erantzuten dio eta baita produktibitate gehitzearenari ere.