José Xavier

• Ph.D.
• Associate Professor at Universidade NOVA de Lisboa

The strain rate dependent mechanical behaviour was studied for the common out-of-autoclave aerospace textile composite 5-harness-satin carbon-epoxy. End-loaded and off-axis and compression tests were carried out at three different strain rate levels ( and ) to determine the effect of strain rate for transverse compression and combined transverse co...

This paper presents an experimental investigation of the mechanical response of a new class of advanced composite materials manufactured using thin non-crimp fabrics. Tensile and compressive tests in both unnotched and notched specimens were performed using two different lay-ups. The notched tests were based on specimens with central cracks and wit...

In this work, the evaluation of the longitudinal modulus of elasticity (EL) of maritime pine (Pinus pinaster Ait.) was investigated by means of compression tests parallel to the grain. Strain data was collected by digital image correlation (DIC) and compared with results from glued strain gauges. The DIC method provided similar results compared to...

This paper deals with the characterisation of bending stiffness components of medium density fibreboard (MDF) by carrying out a single plate bending test. The approach couples full-field slope measurements with an inverse identification method. MDF panels manufactured with different fractions of Eucalyptus fibres and sugarcane bagasse particles wer...

This paper presents an experimental investigation of strain rate effects on polymer-based composite materials. Quasi-static and dynamic experiments at strain rates up to 350 s−1 were performed with end-loaded, rectangular off-axis compression and transverse compression specimens. The dynamic tests were performed on a split-Hopkinson pressure bar, w...

This study focused on standard Compact Tension (CT) specimens and two loading modes during the numerical analyses carried out, namely: pure mode I and mixed-mode loading (Modes I+II). Numerical stress intensity factors, KI, were calculated using Abaqus® 2022 and compared with those given analytically under pure mode I loading, showing very good agr...

Functionally Graded Materials (FGMs) can outperform their homogeneous counterparts. Advances in digitalization technologies, mainly additive manufacturing, have enabled the synthesis of materials with tailored properties and functionalities. Joining dissimilar metals to attain compositional grading is a relatively unexplored research area and holds...

Citation: Valente, R.; Mourato, A.; Xavier, J.; Sousa, P.; Domingues, T.; Tavares, P.; Avril, S.; Tomás, A.; Fragata, J. Experimental Protocols to Test Aortic Soft Tissues: A Systematic Review. Bioengineering 2024, 11, 745. Abstract: Experimental protocols are fundamental for quantifying the mechanical behaviour of soft tissue. These data are cruci...

Computational Fluid Dynamics (CFD) models dedicated to the Ascending Thoracic Aortic Aneurysm (ATAA) hemodynamics have been improved over the years with Fluid–Structure Interaction (FSI) methods with prescribed patient-specific boundary conditions However, the utilization of FSI entails significantly higher computational costs. Moreover, these meth...

The extensive reporting time is one of the main bottlenecks towards introducing numerical models to clinical practice. There is an open question regarding the importance of modelling blood-vessel interaction using Fluid–Structure Interaction (FSI) models, known to yield more accurate results but at the expense of increased computational requirement...

Citation: Quinaz, T.; Freire, T.F.; Olmos, A.; Martins, M.; Ferreira, F.B.N.; de Moura, M.F.S.M.; Zille, A.; Nguyễn, Q.; Xavier, J.; Dourado, N. The Influence of Hydroxyapatite Crystals on the Viscoelastic Behavior of Poly(vinyl alcohol) Braid Systems. Biomimetics 2024, 9, 93. Abstract: Composites of poly(vinyl alcohol) (PVA) in the shape of braids...

The protective and preservative role of apple skin in maintaining the integrity of the fruit is well-known, with its mechanical behaviour playing a pivotal role in determining fruit storage capacity. This study employs a combination of experimental and numerical methodologies, specifically utilising the digital image correlation (DIC) technique. A...

In the present work, single-and double-dowel joints following different geometric configurations are experimentally and numerically investigated to derive the splitting behaviour of beech wood (Fagus sylvatica L.), one of the most widespread hardwood species in Europe for structural purposes. The influence of the spacing between dowels, their dista...

III Congreso Ibero-Latinoamericano MAD de la Madera en la Construcción (CIMAD 24) : Libro de Actas de Resúmenes Extendidos

Digital Image Correlation (DIC) is an optical-numerical method used to compute displacement and strain fields of target surfaces. This method has been widely implemented in the study of structures and to perform inspections, at several observation scales. Several software have been already proposed to carry out DIC measurements. In this study, a ne...

Modelling and simulation are critical stages of product development in modern industry. Simulation tools in solid mechanics use constitutive models and their parameters to describe the behaviour of materials. Nowadays, with the use of heterogeneous test configurations and full-field measurements, it is possible to measure a combination of multiple...

This work presents a design framework for the selection of the topology and cross-section size of elastic timber gridshells, taking as constraints the shape of the structure and the maximum value of bending stress that can be reached in a given area of the gridshell. For this purpose, a par-ametric design environment and a genetic optimisation algo...

An experimental and numerical study on mode II fracture behaviour of European beech ( Fagus sylvatica L.) in the RL and TL crack propagation systems is performed. It is a hardwood species that has attracted increasing interest for structural use in Europe in recent years. Three-point end notched flexure tests are performed. The R -curves of both cr...

Miniaturized mechanical testing based on small sample testing technology is a powerful technique to characterize the mechanical properties of different materials, and it is being used in different application fields. However, the small size of the specimens poses several challenges because the results are highly sensitive to measurement accuracy an...

Purpose This work aims to identify the linear elastic orthotropic material paramters of Pinus pinaster Ait. wood, using full-field measurements and an inverse identification strategy based on the finite element (FE) method updating technique. Design/methodology/approach Compression tests are carried out under uniaxial and quasi-static loading cond...

Aortic aneurysm is a cardiovascular disease related to the alteration of the aortic tissue. It is an important cause of death in developed countries, especially for older patients. The diagnosis and treatment of such pathology is performed according to guidelines, which suggest surgical or interventional (stenting) procedures for aneurysms with a m...

Computer-aided engineering systems rely on constitutive models and their parameters to describe the material behaviour. The calibration of more elaborated material models with a larger number of parameters becomes very time and cost consuming. The development of image-based technology has enhanced the interest in inverse identification methods, whi...

This work presents an out-of-the-box python-based open-source 3D Digital Image Correlation (3D-DIC) software for both in-plane and out-of-plane full-field measurements, denoted by iCorrVision-3D. The software includes an integrated stereo grabber for image acquisition, stereo calibration, numerical stereo correlation and post-processing modules. Th...

The main purpose of this work is to present a new fully-customizable out-of-the-box open-source 2D Digital Image Correlation (2D-DIC) software, so-called iCorrVision-2D. It is implemented in Python, including image acquisition (grabber), numerical correlation and post-processing modules. The proposed software has an intuitive graphical user interfa...

In timber structures, knowledge of the splitting capacity of beams loaded perpendicular to the grain by dowel-type connections is of primordial importance since brittle failure can occur. In the present work, single-and double-dowel-type connections following different loaded edged distance arrangements are experimentally investigated to derive the...

Ascending Thoracic Aortic Aneurysm (ATAA) is a permanent dilatation of the aorta which is usually related to tissue degeneration, hemodynamic conditions, lifestyle, environmental and genetic factors. As the mechanical conditions can become critical in a dilated aorta, a patient-specific computational model can be very useful to assist clinical deci...

Mixed-mode I+II fracture characterization of cortical bone tissue is addressed in this work. The mixed-mode bending test was used to impose different mode ratios. An equivalent crack length data reduction method was considered to obtain the strain energy release rate components. Crack opening and shear displacements were measured by means of digita...

One of the main challenges in experimental fracture mechanics is to correctly estimate fracture parameters of a nonhomogeneous and nonlinear material under large deformation. The crack tip detection is strongly affected by fibers at crack tip, leading to inaccurate measures. To overcome this limitation, a novel methodology based on the Digital Imag...

Eucalyptus globulus L. is a hardwood species with high mechanical properties and great potential for engineered timber products. In the development of glued laminated products using high density wood species such as eucalyptus, bonded joints (e.g. finger-joints) could be a weak point and therefore require special analysis. Numerical cohesive zone m...

This paper presents a case study of in situ monitoring during wire and arc additive manufacturing (WAAM) process by using digital image correlation (DIC). A feasibility study is carried out aiming at proposing a suitable experimental setup for in situ measurements during a WAAM process. In this work a stainless steel AISI316L was used to manufactur...

Computer-aided engineering systems rely on constitutive models and their parameters to describe the material behaviour. The identification process, however, grows in complexity for more elaborated material models, increasing the number of experimental tests needed, therefore time and cost consuming. Recently, with the development of digital image t...

This work addresses the determination of the cohesive laws in Mode I and tangential-longitudinal (TL) propagation system of Fagus Sylvatica L. This species is one of the ever-growing and most widely used hardwood species in Europe for engineered timber products. Double Cantilever Beam (DCB) tests are performed. The strain energy release rate (GI) i...

This work aims to determine the orthotropic linear elastic constitutive parameters of Pinus pinaster Ait. wood from a single uniaxial compressive experimental test, under quasi-static loading conditions, based on two different specimen configurations: (a) on-axis rectangular specimens oriented on the radial-tangential plane, (b) off-axis specimens...

In this study, we investigate the cracking behaviour of softwood species using the MMCG fracture test. Our primary objective is to directly measure crack length propagation in mode I loading and the associated fracture parameters. To achieve this, we employ the Arcan system to apply load to the specimen. We used Digital Image Correlation (DIC) to m...

This work presents the results of an experimental study performed in carbon/epoxy composite materials manufactured using a ply-level hybridization technique. The aim of the study is to investigate the potential of such hybridization technique to promote pseudo-ductile failure, and to enhance fracture toughness. Two thin-ply carbon-epoxy systems and...

Additive manufacturing (AM) has become a viable option for producing structural parts with a high degree of geometrical complexity. Despite such trend, accurate material properties, under diversified testing conditions, are scarce or practically non-existent for the most recent additively manufactured (AMed) materials. Such data gap may compromise...

This paper is a critical review of in situ full-field measurements provided by digital image correlation (DIC) for inspecting and enhancing additive manufacturing (AM) processes. The principle of DIC is firstly recalled and its applicability during different AM processes systematically addressed. Relevant customisations of DIC in AM processes are h...

Despite the growing use of cross-laminated timber (CLT) panels in the construction industry, their behaviours under weather conditions, especially cyclic moisture which generated additional strains, requires further investigation. To address this gap, an extensive experimental campaign was carried out to evaluate CLT elements, in which strains are...

Background Understanding the kinematics of the spine in the interaction with an implanted device is of utmost importance from a clinical point of view. The characterization of the biomechanical movement of the spine occurring at each functional unit is a difficult task as it involves the measurement of complex patterns of motion while identifying m...

This work presents an experimental study on the effect of: ply thickness; ply-level hybridization; and type of ply architecture on the damage mechanisms that dominate failure and strength of multidirectional laminates. Nine effectively equivalent 0°dominated multidirectional laminates made from unidirectional carbon fibre tapes (UD), non-crimp fabr...

Governing cohesive laws in mixed mode I+II loading of Pinus pinaster Ait. are directly identified by coupling the mixed mode bending test with full-field displacements measured at the crack tip by Digital Image Correlation (DIC). A sequence of mixed mode ratios is studied. The proposed data reduction relies on: (i) the compliance-based beam method...

Metallic additive manufacturing has been developed as a manufacturing process for complex functional parts that may be potentially applied in various engineering fields, with very distinct mechanical performance requisites. Therefore, it is of primary importance to characterize additive manufacturing materials under various loading conditions in ot...

Four different methods to experimentally determine the J-curve of quasi-brittle materials are analysed and discussed in this work. The first two methods measure the integral of the cohesive law, J (ω), from an initial notch. However, the correct definition of the notch geometry is of critical importance for an accurate identification of the cohesiv...

The mode I fracture parameters for an orthotropic body are directly calculated from full-field deformation measurements provided by Digital Image Correlation (DIC). Three complementary and direct approaches are evaluated and compared: i) the determination of the Stress Intensity Factor (SIF) by fitting the displacement field using the analytical ex...

The mechanical performance of fused filament fabrication printed parts is considered the weak point of the technology due to its high anisotropic structure and irregular behaviour. This research focuses on the application of the Arcan-based method to fused filament fabrication printed parts, to better understand their mechanical behaviour. In order...

Eucalyptus globulus Labill is a hardwood species of broad growth in temperate climates, which is receiving increasing interest for structural applications due to its high mechanical properties. Knowing the fracture behaviour is crucial to predict, through finite element models, the load carrying capacity of engineering designs with possibility of b...

The elastic parameters, strengths, and intralaminar fracture toughness are determined for an E-Glass polymer composite material system, statically and at high strain rate, adapting methodologies previously developed by the authors for different carbon composites. Dynamic experiments are conducted using tension and compression Split-Hopkinson Bars (...

An optical experimental procedure for evaluating the J-Integral from full-field displacement fields under dynamic loading is proposed in this work. The methodology is applied to measure the J-integral in the dynamic compressive loading of fiber-reinforced composites and to calculate the dynamic fracture toughness associated with the propagation of...

The high strain rate compressive behaviour of Pinus pinaster Ait. wood along the radial and tangential material axes was addressed in this work. Both quasi-static and dynamic tests were considered for comparation purposes. The quasi-static compression tests were performed on rectangular prismatic specimens along the radial and tangential directions...

Assessing wood fracture behavior is essential in the design of structural timber elements and connections. This is particularly the case for connections with the possibility of brittle splitting failure. The numerical cohesive zone models that are used to simulate the fracture behavior of wood make it necessary to assume a cohesive law of the mater...

Despite extensive research regarding metal cutting simulation, the current industrial practice very often relies on empirical data when it comes to tool design. In order accurately simulate the cutting process it is not only important to have robust numerical models that closely portray the phenomenon, but also to properly characterize the material...

Pipelines can be submitted to extreme loading scenarios, which can engender structural instability in the form of large deformations and fracture by both monotonic plastic deformations of cyclic loads. Both monotonic ductile and low-cycle fatigue (LCF) damage mechanisms can occur for X52, X60 and X65 piping steel grades. The evaluation and predicti...

Orthotropic stiffness components of Pinus pinaster Ait. wood are simultaneously determined by means of a heterogeneous plate bending test. The proposed inverse identification approach couples full-field slope measurements provided by deflectometry with the virtual fields methods. Wooden plates oriented in the longitudinal-radial and longitudinal-ta...

This study presents two alternative methods to determine the cohesive law of bovine cortical bone under mode II loading, employing the End Notched Flexure (ENF) test. The direct method results from the combination of the progress of the mode II strain energy release rate with the crack tip shear displacement, obtained by digital image correlation....

The non-linear shear behaviour of bovine cortical bone is measured by coupling the Arcan test with digital image correlation. The experimental study is carried out on specimens taken from bovine femur and oriented along the longitudinal-tangential material plane. An a d hoc Arcan fixture is built to transfer the cross-head displacement of the testi...

This work addresses the reconstruction of strain gradient fields at the wood growth ring scale from full-field deformation measurements provided by digital image correlation. Moreover, the spatial distribution of the earlywood and latewood radial modulus of elasticity is assessed. Meso-scale tensile tests are carried out on Pinus pinaster Ait. wood...

This paper presents the determination of the crack resistance curve of the unidirectional carbon-epoxy composite material IM7-8552 for intralaminar fiber tensile failure under dynamic loading. The methodology, proposed by Catalanotti et al. (2014) for quasi-static loading conditions, was enhanced to high rate loading in the order of about 60 s⁻¹. D...

The prediction of the fracture behaviour through reliable and practical criteria in the design of structural timber elements and connections has become of great importance and demands a proper fracture characterization of the material. Eucalyptus globulus Labill is envisioned as a hardwood species with great potential for high performance structura...

Purpose The antique structures are part of the inheritance that our elders left, being important to preserve their memories. It is important to preserve, rehabilitate and restore the historic buildings protecting the cultural patrimony, attending to the actual comfort and habitability requirements. It is necessary to study the behaviour of the var...

The enhanced mechanical performance of thin-ply laminates results from their ability to delay the onset of damage typically observed in composite materials. However, in notched structures, subcritical damage growth causes beneficial stress redistributions in the vicinity of the notch, blunting the stress concentration. Precluding these damage mecha...

Automotive and aeronautical composite structures can be subjected to dynamic loading scenarios (e.g. crash, bird strike). In both industrial areas, energy-based damage models for composite materials, able to predict initiation and evolution of damage of a composite ply under various loading conditions, are increasingly used. These models require th...

The behaviour of standard bolted steel connections submitted to monotonic loads, through the use of numerical models, is presented in the current paper. The bolted connections allow speed up constructive processes in an increasingly competitive and globalized world in which the costs are a decisive factor in the development of a project. The use of...

Ancient structures are part of the inheritance our elders left us. These historical inheritance needs to be preserved, so the historic structures need to be rehabilitated and restored, protecting the cultural patrimony and attending to the comfort and habitability required nowadays. In order to accomplish a good and economic rehabilitation is essen...

This work presents an experimental method to measure the compressive crack resistance curve of fiber-reinforced polymer composites when subjected to dynamic loading. The data reduction couples the concepts of energy release rate, size effect law and R-curve. Double-edge notched specimens of four different sizes are used. Both split-Hopkinson pressu...

This work addresses the determination of the cohesive law under mode I loading of bovine cortical bone tissue using the Double Cantilever Beam (DCB) test. Direct and inverse methods were proposed to assess the cohesive laws representative of bone fracture under mode I loading. The direct method combines the evolution of the strain energy release ra...

The effect of ply thickness on the onset of intralaminar and interlaminar damage is extremely important for the structural response of laminated composite structures. This subject has gained particular interest in recent years due to the introduction in the market of spread-tow, ultra-thin carbon-fibre reinforcements with different configurations....

This paper proposes an experimental study aiming to evaluate stress intensity factors (SIFs) for fatigue cracks propagating under pure mode I and mixed-mode I+II for a S235 structural steel. Compact tension (CT) specimens with a side hole were manufactured in order to generate a stress field, ahead of the crack tip, resulting in mixed-mode fatigue...

Fracture characterization of human cortical bone under mode II loading was analyzed using a miniaturized version of the end-notched flexure test. A data reduction scheme based on crack equivalent concept was employed to overcome uncertainties on crack length monitoring during the test. The crack tip shear displacement was experimentally measured us...

This work presents an experimental study on the effect of ply-level hybridisation on the tensile unnotched and notched response of composite laminates. In a first assessment, notched tests were performed on laminates with nominal ply thicknesses between 0.03 mm and 0.30 mm. From the understanding of the effect of ply thickness on the damage mechani...

Biodegradable polymers such as PLA have been studied for medical applications, human ligament repair is one of such cases. However, these materials can be applied in other sectors as aerospace, aeronautics, automotive, food packaging. PLA presents a relatively brittle on the mode I fracture behavior, being often blend with other biodegradable or no...

The robustness of the test method based on a single 3D off-axis prismatic specimen for the simultaneous identification of the orthotropic stiffness components of clear wood is addressed. In this method, the specimen is consecutively submitted to uniaxial compression tests along its three orthogonal axes. A data reduction based on anisotropic elasti...

This paper reports the first attempt of developing macro-scale auxetic structures based on re-entrant hexagon design from braided composite materials for civil engineering applications. Braided composite rods (BCRs) were produced and arranged as longitudinal and horizontal elements to produce three types of auxetic structures: (1) basic re-entrant...

Probabilistic fatigue models are required to account conveniently for several sources of uncertainty arising in the prediction procedures for structural details, such as the scatter in material behaviour. In this paper, a procedure to derive probabilistic S-N fields for structural details [1] is applied to a notched geometry with elliptic central h...

With the aim of characterising a commercially available epoxy adhesive used for fibre-reinforced polymers strengthening applications, when submitted to different environmental conditions, mainly thermal (TC), freeze-thaw (FT), and wet-dry (WD) cycles and immersion in pure (PW) and water with chlorides (CW) for periods of exposure that lasted up to...

A miniaturized version of the double cantilever beam (DCB) test is used to determine the fracture energy in human cortical bone under pure mode I loading. An equivalent crack length based data reduction scheme is used with remarkable advantages relative to classical methods. Digital image correlation technique is employed to determine crack opening...

Mixed-mode I+II fracture characterization of human cortical bone was analyzed in this work. A miniaturized version of the Single Leg Bending test (SLB) was used owing to its simplicity. A power law criterion was verified to accurately describe the material fracture envelop under mixed-mode I+II loading. The crack tip opening displacements measured...

Fracture characterization under mode I loading of a cement-based material using the single-edge-notched beam loaded in tree-point-bending was performed. A new method based on beam theory and crack equivalent concept is proposed to evaluate the Resistance-curve, which is essential to determine fracture toughness with accuracy. The method considers t...

All violinists and violists face the difficulties of playing a nonsymmetrical instrument, which makes it quite easy to create wrong postures and technics. Many authors discuss different ways how to work on intonation as exercises or empiric opinions about possible problems. However, these approaches aren't scientifically and anatomically based and...

Biodegradable polymers such as poly(lactic) acid (PLA) have been studied for biomaterials applications such as natural human ligament replacement, however these materials could be applied to other sectors as aerospace, aeronautics, automotive, food packaging. PLA presents a relatively brittle with a mode I fracture behavior, being often blend with...

This paper describes theoretical and experimental work undertaken to obtain a structural model for assessment of historical Latin-American vertically laminated planked timber arches, as built by the Spanish, mainly in the seventeenth and eighteenth centuries. Many such arches still stand, and represent an important historical heritage. Following in...

This paper describes theoretical and experimental work undertaken to obtain a structural model for assessment of historical Latin-American vertically laminated planked timber arches, as built by the Spanish, mainly in the seventeenth and eighteenth centuries. Many such arches still stand, and represent an important historical heritage. Following in...

Direct identification of cohesive laws in modes I and II of wood bonded joints is addressed by the double cantilever beam (DCB) and end-notched flexure (ENF) tests, respectively. Moreover, the development and extension of fracture process zone (FPZ) ahead of the initial crack tip, is analysed by means of digital image correlation (DIC) and embedded...