This study aims to improve the energy absorption and mechanical properties of auxetic structures by optimizing their design and analyzing the influence of different resin matrices in composite fabrication. Auxetic materials exhibit unique deformation behavior due to their negative Poisson’s ratio, making them promising for energy absorption applications. However, their practical implementation is often constrained by their intrinsic mechanical properties, particularly their strength under realistic loading conditions. This research investigates the effect of resin matrix selection on the energy absorption capacity, Young’s modulus, and yield strength of auxetic composites. A systematic experimental campaign was conducted, subjecting auxetic structures reinforced with various resin matrices to compressive loading. The results indicate that embedding the auxetic structure within a resin matrix significantly enhances energy absorption compared to pure resin samples. Notably, vinylester resin composites exhibited the highest Young’s modulus, yield strength, and energy absorption capacity. This superior performance is attributed to the synergistic interaction between the auxetic structure, which efficiently distributes stress, as well as the intrinsic toughness and load-bearing capacity of the vinylester resin. These findings contribute to the optimization of auxetic composites for energy absorption applications and the development of high-performance materials for impact mitigation in aerospace and automotive industries.

This study investigates the mechanical behavior and energy absorption capacity of a novel metamortar composite, developed by embedding re-entrant auxetic cellular structures into a cementitious mortar matrix. Auxetic materials, which exhibit a negative Poisson’s ratio, offer distinct advantages in impact resistance and stress dissipation. Despite their promising properties, their integration into cement-based systems remains limited. In this work, auxetic cells were fabricated using different 3D printing filaments and combined with mortar to form hybrid composites. The specimens were subjected to quasi-static compression tests to evaluate their Young’s modulus, yield strength, and energy absorption capacity. Results indicate that the auxetic inclusions substantially improved the mechanical performance of the mortar, particularly in the case of PLA-based cells, which achieved the highest values across all tested parameters. The enhancements are attributed to the synergistic deformation mechanisms of the auxetic geometry and the surrounding matrix, promoting efficient load distribution and delayed crack propagation. These findings contribute to the advancement of cementitious metamaterials and establish a foundation for scaling toward metaconcrete systems with improved energy dissipation for use in protective, seismic, and infrastructure applications.

The structural performance of engineered timber products is strongly governedby the behavior of their adhesive interfaces. This study investigates theMode I fracture behavior of one-component polyurethane (1C-PUR) bondedChilean Pinus radiata D. Don using Double Cantilever Beam (DCB) testsand cohesive zone modeling within an equivalent Linear Elastic Fracture Mechanics(LEFM) framework, in which an equivalent crack length derived fromspecimen compliance implicitly accounts for the fracture process zone (FPZ).Crack propagation was analyzed in the tangential–longitudinal (TL) andradial–longitudinal (RL) planes, considering two crack propagation paths:adhesive-dominated (AD) and timber-dominated (TD). Experimental load–displacement responses and equivalent R-curves were used to identify trilinearcohesive laws through the compliance-based methodology based onLEFM. Both plane orientations and crack propagation paths strongly influencedthe response. TD crack propagation path exhibited significantly higher critical strain energy release rate, with average GIc values of 535.56 [N/m](TL-TD) and 428.05 [N/m] (RL-TD), compared with 338.92 [N/m] (TL-AD)and 274.04 [N/m] (RL-AD) for AD crack propagation path. The TL planeconsistently showed higher strain energy release rate and more stable propagationthan the RL plane. Relative to previous results for solid timber (ST)of Chilean Pinus radiata D. Don, AD crack propagation path produced onlymoderate increases in strain energy release rate, whereas TD crack propagationpath nearly doubled the critical strain energy release rate values relativeto solid specimens. The adopted methodology circumvents the experimentaldifficulties associated with crack-front tracking in bonded timber. Moreover,the calibrated cohesive parameters together with Hillerborg’s characteristiclength, revealed substantial differences in critical opening displacement,cohesive tensile strength, and strain energy release rate contributions associatedwith microcracking and fiber bridging, providing a useful basis forfuture numerical simulations of bonded laminated and cross-laminated timberstructures.

The structural performance of engineered timber products depends strongly on the behavior of bonded interfaces. This study investigates Mode I fracture of Chilean Pinus radiata D. Don bonded with a one-component polyurethane (1C-PUR) adhesive through Double Cantilever Beam (DCB) tests in the tangential–longitudinal (TL) and radial–longitudinal (RL) planes. Two predominant crack propagation paths, adhesive-dominated (AD) and timber-dominated (TD), were identified by visual inspection of the fracture surfaces, and the results were compared with previously reported solid timber (ST). Equivalent R-curves were obtained from specimen compliance without direct crack-front tracking, and trilinear cohesive laws were identified through dimensional analysis. TD specimens exhibited higher mean critical strain energy release rates (G_Ic) than AD specimens, with 535.56 and 428.05 [N/m] in TL and RL, respectively, compared with 338.92 and 274.04 [N/m]. Relative to ST, the mean G_Ic was 105% and 75% higher for TD and 30% and 12% higher for AD, although the RL-AD difference was small compared with its variability. The critical opening displacement of the bonded specimens was less than half that of ST, whereas the cohesive tensile strength was only weakly identifiable and is reported as an effective parameter. The results provide a basis for simulating bonded laminated and cross-laminated timber structures.

Méthode de décomposition de domaine pour la modélisation et la simulation des structures en bois lamellé-croisé: Les avancées technologiques dans le bois lamellé croisé (CLT) ont favorisé son utilisation dans les bâtiments de moyenne et grande hauteurs grâce à son excellent rapport résistance/poids, son bon comportement sismique et sa capacité d'isolation. Cependant, prédire la réponse de structures en CLT reste un défi, car plusieurs modes de rupture sous charge, plan et hors-plan, se combinent. En particulier, pour les charges hors-plan, la rupture par cisaillement roulant est un facteur clé, affectant les couches transversales et se propageant de manière interlaminaire et intralaminaire. D'autre part, sous des charges dans le plan, l'interaction entre le flambement et la fissuration interlaminaire compromet la capacité portante des panneaux CLT. Dans les deux cas, la nature de ces endommagements et leur interaction entraînent des pertes significatives de performance structurelle, limitant l'exploitation optimale des avantages du CLT. De plus, la nature multiéchelle et anisotrope du bois, combinée au coût de calcul élevé des modèles détaillés, exige le développement de stratégies efficaces pour simuler les réponses non-linéaires des structures en CLT, et en particulier de stratégies adaptées au calcul parallèle. Ce travail développe une stratégie de calcul parallèle basée sur une méthode de décomposition de domaine mixte, la méthode LaTIn micro-macro, dont les avantages ont été précédemment démontrés pour l'étude de l'interaction entre délaminage, flambement et contact dans les composites renforcés de fibres. En combinant cette stratégie avec des modèles de zone cohésive, l'objectif est de capturer la réponse non linéaire du CLT, notamment les mécanismes de rupture mentionnés précédemment sous flexion et compression. Afin d'optimiser la stratégie, des améliorations algorithmiques sont introduites pour réduire le nombre d'itérations et représenter avec plus de précision l'initiation et la propagation des fissures dans les matériaux orthotropes. De plus, une analyse détaillée de la physique du problème est menée, accompagnée d'une revue des essais expérimentaux rapportés dans la littérature, afin de définir une sous-structuration efficace. Pour valider la stratégie, un essai de flexion en quatre points est simulé sur un panneau à trois couches, reproduisant l'apparition de ruptures par cisaillement roulant et leur interaction avec d'autres mécanismes d'endommagement, avec une bonne corrélation avec les résultats expérimentaux rapportés dans la littérature. Dans le cas des charges dans le plan, une réduction de la charge critique est observée en raison de la souplesse de l'adhésif, et des zones critiques sujettes au délaminage sont identifiées dans les panneaux CLT. L'approche proposée fournit un outil efficace pour la conception de structures CLT plus fiables, avec un potentiel d'extension aux configurations à cinq et sept couches ainsi qu'aux systèmes hybrides avec du béton.