Carlos Gonzalez

• Industrial University of Santander

Bioabsorbable Mg wire‐reinforced poly‐lactic acid (PLA) matrix composites are potential candidate for load‐bearing orthopedic implants offering tailorable mechanical and degradation properties by stacking sequence, volume fraction and surface modification of Mg wires. In this study, we investigated the cytocompatibility, cell‐material interaction,...

Unidirectional and multidirectional laminates of Mg‐wire‐reinforced poly‐lactic‐acid–matrix composites are manufactured by an improved compression molding strategy that allows excellent control on the position and orientation of the wires. Two different types of Mg wires, with and without surface modification by continuous plasma electrolytic oxida...

Medical grade PLDL, PLDL/Mg and PLDL/Zn filaments were manufactured by a dual extrusion method and used to prepare coupons and scaffolds with controlled porosity by fused filament fabrication. The mechanical properties, degradation mechanisms and biological performance were carefully analyzed. It was found that the presence of 4 vol.% of Mg and Zn...

The mechanical behavior, corrosion mechanisms, and cytocompatibility at the interface of magnesium wires reinforced poly-lactic acid polymer composites were studied by in vitro degradation study of 180 days. Surface modification of Mg wires by plasma-electrolytic oxidation improved the interface shear strength from 10.9 MPa to 26.3 MPa which decrea...

In our work, a novel processing strategy for the continuous fabrication and surface modification of wires from Magnesium alloy WE43 by means of plasma-electrolytic oxidation (PEO) is presented. In the first step, wires with a strong basal texture and small grain size (≈ 1 μm) were manufactured by combined cold drawing and in-line stress-relief heat...

The corrosion, mechanical degradation and biological performance of cold-drawn WE43 Mg wires were analyzed as a function of thermo-mechanical processing and the presence of a protective oxide layer created by continuous plasma electrolytic oxidation (PEO). It was found that the corrosion properties of the non-surface-treated wire could be optimized...

The corrosion, mechanical degradation and biological performance of cold-drawn WE43 Mg wires were analyzed as a function of thermo-mechanical processing and the presence of a protective oxide layer created by continuous plasma electrolytic oxidation (PEO). It was found that the corrosion properties of the non-surface-treated wire could be optimized...

In our work, a novel processing strategy for the continuous fabrication and surface modification of wires from Magnesium alloy WE43 by means of plasma-electrolytic oxidation (PEO) is presented. In the first step, wires with a strong basal texture and small grain size ($\approx$ 1 $\mu$m) were manufactured by combined cold drawing and in-line stress...

A simulation strategy based in the finite element model was developed to model the corrosion and mechanical properties of biodegradable Mg scaffolds manufactured by laser power bed fusion after immersion in simulated body fluid. Corrosion was simulated through a phenomenological, diffusion-based model which can take into account pitting. The elemen...

A simulation strategy based in the finite element model was developed to model the corrosion and mechanical properties of biodegradable Mg scaffolds manufactured by laser power bed fusion after immersion in simulated body fluid. Corrosion was simulated through a phenomenological, diffusion-based model which can take into account pitting. The elemen...

The tensile testing of a needle-punched nonwoven fabric is presented. A high-sensitivity Split-Hopkinson Tensile Bar device was specifically designed for this purpose. The strain gauge measurements were combined with high-speed photography and Digital Image Correlation to analyse the deformation micromechanisms at high strain rates. The experimenta...

A new mesoscale material model is proposed to analyze structures that fail by the fiber kinking damage mode. The model is formulated following the fiber kinking theory such that the interaction of shear nonlinearity and fiber rotation are tracked throughout the loading history. The model is implemented as a user-defined material in a commercial fin...

The translaminar fracture behaviors of partially different unidirectional composite systems, constituted by the same carbon fibers but different (thermoset vs. thermoplastic) matrices, were characterized by means of compact tension fracture tests. The resulting crack resistance curves (R-curves) and fracture surfaces, were studied in detail and fou...

A mesoscale finite element material model is proposed to analyze structures that fail by the fiber kinking damage mode. To evaluate the assumptions of the mesoscale model, the results were compared with those of a high-fidelity micromechanical model. A direct comparison between the two models shows remarkable correlation, indicating that the key fe...

Virtual testing is emerging as a powerful tool for the analysis and design of composite materials laminates subjected to a variety of loading conditions, static, dynamic, and impact events. The representative physical deformation and damage mechanisms, as intraply failure and interply delamination, were taken into account explicitly in the finite e...

A workflow supported by high-fidelity virtual testing for the selection of candidate materials to be incorporated into shielding protection systems is presented. Modeling techniques for the accurate simulation of impact events on carbon-based composite shields hybridized with several materials of standout ballistic performance are described. A Cont...

This work shows evidence of conventional liquid and polymer molecules doping macroscopic yarns made up of carbon nanotubes (CNT), an effect that is exploited to monitor polymer flow and thermoset curing during fabrication of a structural composite by vacuum infusion. The sensing mechanism is based on adsorption of liquid/polymer molecules after inf...

This study is concerned with the failure characteristics of notched and unnotched specimens of a highly porous, multilayered non-woven fiber network material subjected to uniaxial tension. The network consists of glass fibers locally bonded by a polymer resin. The multilayer character of the material emerges from the manufacturing process in which...

Vacuum infusion experiments with and without distribution medium were carried out in woven E-glass fabric preforms. The experimental set-up was carefully designed to obtain a unidimensional in-plane flow between the inlet and outlet gate, which was combined with through-the-thickness infiltration in the tests carried out with a distribution medium....

El objetivo del presente estudio es la caracterización de la tenacidad de fractura de fibras de carbono, vidrio y aramida individualmente mediante la introducción de una entalla haciendo uso de un cañón de iones (Focused Ion Beam, FIB). Con esta técnica, se genera una entalla de dimensiones nanométricas que representa una grieta. El diámetro de la...

In situ vacuum-assisted infiltration experiments were carried out using synchrotron X-ray computed tomography (SXCT) to study the mechanisms of microfluid flow within a fiber tow. A single tow of E glass fibers was infused with a water and syrup blend using an apparatus designed and built for this purpose. The high resolution of the SXCT images all...

The influence of the carbon nanotubes (CNTs) content on the fiber/matrix interfacial shear strength (IFSS) in glass/fiber epoxy composites was measured by means of push-in and push-out tests. Both experimental methodologies provided equivalent values of the IFSS for each material. It was found that the dispersion of CNTs increased in IFSS by 19% in...

Computational micromechanics of composites is an emerging tool required for virtual materials design (VMD) in order to address the effect of the involved variables before materials are manufactured. This strategy will avoid unnecessary costs reducing trial-and-error campaigns leading to fast material developments for tailored properties. In this wo...

Transverse cracking in cross-ply carbon/epoxy and glass/epoxy laminates in tension is analyzed by means of computational micromechanics. Longitudinal plies were modeled as homogenized, anisotropic elastic solids while the actual fiber distribution was included in the transverse plies. The mechanical response was obtained by the finite element analy...

The strength of materials is always reduced in the presence of notches and cracks and this phenomenon –known as notch sensitivity– is critical in structural design. Good structural materials (ductile metals, elastomers) tend to be notch insensitive, which was considered to be the optimum behavior. Here, we report that inverse notch insensitivity (w...

Fluid flow and fabric compaction during vacuum assisted resin infusion (VARI) of composite materials was simulated using a level set-based approach. Fluid infusion through the fiber preform was modeled using Darcy’s equations for the fluid flow through a porous media. The stress partition between the fluid and the fiber bed was included by means of...

Ignoring crack tip effects, the stability of the X-FEM discretizations is trivial for open cracks but remains a challenge if we constrain the crack to be closed (i.e., the bi-material problem). Here, we develop a formulation for general cohesive interactions between crack faces within the X-FEM framework. The stability of the new formulation is dem...

Low-velocity impact events occur with some frequency on composite applications such as airplane components. From ground operations to unavoidable birds, there is a range of situations where an aircraft outer component may be subjected to unexpected impact loads. In most cases, such as tool dropping, the impactor has a relatively high mass but low v...

The effect of porosity on the transverse mechanical properties of unidirectional fiber-reinforced composites is studied by means of computational micromechanics. The composite behavior is simulated by the finite element analysis of a representative volume element of the composite microstructure in which the random distribution of fibers and the voi...

Carbon fiber-reinforced polymers, used in primary structures for aircraft due to an excellent strength-to-weight ratio when compared with conventional aluminium alloy counterparts, may nowadays be considered as mature structural materials. Their use has been extended in recent decades, with several aircraft manufacturers delivering fuselages entire...

By using resin transfer molding (RTM) technology, carbon fiber (CF) reinforced epoxy composites (CF/Epoxy, CF/PES/Epoxy, and CF/PES-MWCNT/Epoxy) are prepared. CF is the reinforced fiber, Epoxy is the epoxy matrix, and PES-MWCNT is the multiwall carbon nanotubes doped polyethersulfone film. Their fire behavior is systematically studied according to...

A constitutive model is presented for the in-plane mechanical behavior of nonwoven fabrics. The model is developed within the context of the finite element method and provides the constitutive response for a mesodomain of the fabric corresponding to the area associated to a finite element. The model is built upon the ensemble of three blocks, namel...

The fracture behavior parallel to the fibers of an E-glass/epoxy unidirectional laminate was studied by means of three-point tests on notched beams. Selected tests were carried out within a scanning electron microscope to ascertain the damage and fracture micromechanisms upon loading. The mechanical behavior of the notched beam was simulated within...

The failure locus, the characteristics of the stress–strain curve and the damage localization patterns were analyzed in a polypropylene nonwoven fabric under in-plane biaxial deformation. The analysis was carried out by means of a homogenization model developed within the context of the finite element method. It provides the constitutive response f...

The effect of nitrogen and oxygen plasma surface treatments on the compressive strength of PBO fibers has been studied. To this end, the nucleation and propagation of compression-induced kink bands was carefully monitored by means of in situ bending tests inside a scanning electron microscope. The micromechanisms of deformation were identical irres...

The pattern of damage localization and fracture under uniaxial and biaxial tension was studied in glass-fiber nonwoven felts. The analyses were carried out within the framework of the finite-element simulation of plain and notched specimens in which the microstructure of the felt, made up of fiber bundles connected at the cross point through an org...

A bottom-up, multiscale modeling strategy has been developed to carry out high fidelity virtual mechanical tests of composite materials and structures. The whole strategy is based on finite element simulations performed at different length scales (lamina, laminate and component) and the main features each simulation strategy as well as the informat...

The micromechanisms of deformation and fracture in tension were analyzed in a commercial polypropylene nonwoven geotextile material in a wide range of strain rates. Two different loading scenarios (smooth and notched specimens) were considered to study how these mechanisms are modified in presence of a stress concentration. The nonwoven fabric pres...

The deformation and damage micromechanisms of a glass-fiber non-woven felt were analyzed with a combination of experiments and simulations. Tensile tests were carried out on unnotched and notched rectangular panels to ascertain the physical phenomena which control the development of damage. It was found that fracture began by interbundle bond fract...

material specimens, along with tests of components and structures up to entire tails, wing boxes, and fuselages, to achieve safety certification. This cost has to date been unavoidable: while computational stress analyses provide good predictions in the elastic regime, they have not achieved predictive accuracy in the presence of damage and fractur...

The effect of fiber, matrix and interface properties on the in-plane shear response of carbon-fiber reinforced epoxy laminates was studied by means of a combination of experiments and numerical simulations. Two cross-ply laminates with the same epoxy matrix and different carbon fibers (high-strength and high-modulus) were tested in shear until fail...

The mechanisms of in-plane shear deformation in a cross-ply glass fiber-epoxy laminate were studied through a combination of experiments and simulations. Shear deformation parallel and perpendicular to the fibers led to very different deformation and fracture patterns. Deformation was localized in a matrix shear band parallel to the fibers in the f...

The potential of computational micromechanics to predict the failure locus of a unidirectional C/PEEK composite subjected to transverse compression and longitudinal shear was established. Numerical simulations were compared with the experimental results of Vogler and Kyriakides [Vogler TJ, Kyriakides S. Inelastic behavior of an AS4/PEEK composite u...

The mechanical behavior of polymer–matrix composites unidirectionally reinforced with carbon or glass fibers subjected to compression perpendicular to the fibers was studied using computational micromechanics. The stress–strain curve was determined by the finite element analysis of a representative volume element of the microstructure idealized as...

The use of multiscale finite element simulations to perform virtual fracture tests of composite materials is demonstrated. The fracture behavior of a fiber-reinforced composite beam in presence of a notch perpendicular to the fibers was modeled using an embedded cell approach in three dimensions. The representation of the material in front of the n...

The fracture behavior of a Ti-6Al-4V matrix uniaxially reinforced with SiC fibers was analyzed between 20 °C and 400 °C using a multiscale approach that involved the finite element simulation of a three-point bend test on a notched beam of the composite. The material in front of the notch tip was discretized taking into account the actual fiber-mat...

The fracture behavior of a fiber-reinforced composite beam in the presence of a notch perpendicular to the fibers is simulated by means of a multiscale model based on an embedded cell approach in three dimensions. The representation of the material in front of the notch tip – where damage is concentrated – included the actual fiber/matrix topology...

The deformation of an inextensible, curved elastic beam subjected to axial load is studied using the Bernouilli–Euler hypothesis and including the effect of large displacements. The axial displacement of the beam was expressed as a function of the axial load in terms of two incomplete elliptic integrals and contained a singularity as the beam was f...

The residual thermoelastic stresses were studied in Al2O3–ZrO2 (monoclinic zirconia, m-ZrO2) and Al2O3–ZrO2(Y2O3) (tetragonal zirconia, t-ZrO2) fibrous eutectics that were produced via the laser floating zone method, using different piezospectrosocopic probes. The luminescence of the R-lines of ruby (Cr3+ in Al2O3 phase) was used to determine the s...

The fracture behavior of Ti–6Al–4V uniaxially reinforced with 35 vol% SiC Sigma 1140+ fibers was studied between 20 and 550 °C by three-point bend tests of notched beams. It was found that the fracture energy remained essentially constant in the whole temperature range while the initial toughness decreased linearly with temperature from 78 MPa at 2...

Al2O3-ZrO2 eutectics containing 0 to 12.2 mol% Y2O3 (with respect to zirconia) were produced by directional solidification using the laser floating zone (LFZ) method. Processing variables were chosen to obtain homogeneous, colony-free, interpenetrating microstructure for all of the compositional range, optimum from the viewpoint of mechanical prope...

The spatial distribution of particles and the development of damage underlie some important mechanical properties of composites. New algorithms were developed to generate composite microstructures with homogeneous and randomly clustered particle distributions, and the statistical parameters which characterize the reinforcement spatial distribution...

The failure locus a fiber-reinforced composite lamina, made up of 50 vol. % of carbon fibers embedded in an epoxy matrix, is computed under multiaxial stress states involving transverse compression, in-plane and out-of-plane shear. The mechanical response was obtained by the finite element method of a representative volume element of the lamina. Th...