micro-CT Characterization Research Articles

Unraveling the reinforcing mechanisms for cementitious composites with 3D printed multidirectional auxetic lattices using X-ray computed tomography

This study investigates the mechanical properties of cementitious composites with 3D-printed auxetic lattices, featuring negative Poisson’s ratios (auxetic behavior) in multiple directions. These lattices were fabricated using vat photopolymerization 3D printing, and three base materials with varying stiffness and deformation capacities were analyzed to determine their impact on the composites’ mechanical behavior. To unravel the reinforcing mechanisms of multidirectional auxetic lattices, which exhibit auxetic behavior in both planar and out-of-plane directions, X-ray computed tomography (X-ray CT) was utilized to analyze composite damage evolutions under different strain levels. The micro-CT characterization reveals that auxetic lattices more effectively constrain crack growth and dissipate energy by distributing stress evenly within the cement matrix. In contrast, due to lack of lateral confinement, the non-auxetic lattice reinforced composites primarily dissipate energy through extensive crack propagation and interfacial damage, leading to lower peak strength. When strain exceeding 5%, although the confinement from the auxetic behavior diminished with crack propagation, the lattice can still maintain the composite’s structural integrity, resulting in 1.7 times higher densification energy than conventional cement-based materials. These findings provide valuable insights for designing auxetic lattice-reinforced cementitious composites with enhanced load-bearing capacity and improved dissipation capabilities.

Damage Recognition of Acoustic Emission and Micro-CT Characterization of Bi-adhesive Repaired Composites Based on the Machine Learning Method

Damage Recognition of Acoustic Emission and Micro-CT Characterization of Bi-adhesive Repaired Composites Based on the Machine Learning Method

Micro-CT characterization on pore structure evolution of low-permeability sandstone under acid treatment

Permeability enhancement via acid has drawn broad attention in mining and oil industries to treat low-permeability formations to increase the resource recovery rate. In this study, experiments including static acid permeability enhancement tests, flooding acid permeability enhancement tests, and micro-CT scanning were conducted to investigate the mechanism of permeability enhancement and changes in pore structure during acid treatment. First, the extent of reaction between low-permeability sandstone samples and four different acids was evaluated by static tests. The hydrochloric and formic acids exhibited good performance to dissolve filling minerals during static tests. Second, acid flooding in sandstone cores was carried out under reservoir conditions. After acid flooding, the porosities of sandstone cores were significantly increased and a decrease in pressure difference was observed, demonstrating a permeability increase. The pressure difference of hydrochloric acids was lower than that of formic acids at the end of flooding, and the permeability results indicated that the percentage of permeability increase by hydrochloric acid treatment and formic acid treatment were 283% and 120%, respectively. Third, all samples were scanned by micro-CT before and after acid permeability enhancement tests, and CT images were analyzed to study changes in pores, pore throats, and coordination numbers using Avizo software. The mineral compositions and 2D micromorphology were characterized by SEM-EDS, XRD and ICP. After acid treatment, the number of interconnected pores, pore throats, and their equivalent radii all increased, leading to a higher permeability. The improved permeability was mainly due to the dissolution of dolomite, which was identified by SEM-EDS and ICP.

Pre-wetting of sand for high speed oil-water separation

The search for a simple, affordable, and rapid separation method for oil-water mixtures is one of the most serious challenges that the world is facing today. Superhydrophobic, or superoleophilic, materials and surfaces are promising choices for these types of separations. In the present study, a high speed gravity-driven oil–water separation method has been realized by using pre-wetting of river sand, sea sand, and desert sand. The superoleophobicity properties of these pre-wetted sand materials have been found to be good, with a maximum oil contact angle of about 141.1° for desert sand and a minimum oil contact angel of 113.8° for sea sand. Also, the relationship between the porosity of the respective sand type and the water phase separation rate was, for the first time, obtained by using the LBM Shan-Chen model and micro-CT characterization. As a result of a simple particle size screening, the highest kerosene-water separation rate for sea sand was 24.3 ± 2.4 mm/s. In fact, this is the highest oil-water separation rate that has ever been achieved for a sand material. In addition to the effect of sand particle size, other factors affecting the rate of oil-water separation (such as number of separation cycles, thickness of sand layer, temperature, pH value, salt concentration, and different oil-water mixtures) have also been investigated.

Experimental investigation on the mechanical behavior and damage of 3D printed composites under three-point bending

Three-dimensional (3D) printing has been triumphantly applied for the manufacture of various composite components. In this work, acoustic emission (AE), X-ray micro-computed tomography (Micro-CT) are used in conjunction with digital image correlation (DIC) measurement to investigate the mechanical behaviors of 3D printed continuous fiber reinforced composites under three-point bending test. Meanwhile, several mechanical experiments are carried out to study the flexural properties of three kinds of composite specimens, among which the specimens with larger glass fiber content exhibit more superior mechanical properties. Furthermore, AE response characterizations and microscopic damage morphology are also examined. In consequence, the complementary nondestructive testing (NDT) technology combining AE, DIC, and Micro CT is successfully applied to evaluate the mechanical behaviors of 3D printed composites, and the flexural deformation and damage are comparatively investigated for different composite specimens. The cross-validation results of cluster analysis (k-means), K-Nearest Neighbor (KNN) and principal component analysis (PCA) show that AE parameters including frequency, amplitude, and RA value (rise time divided by peak amplitude) are closely associated with the damage process of different specimens. The results show that the PCA can confirm the selected K-means cluster analysis parameters (peak frequency and peak amplitude) and the dimensionality reduction effects of 20% glass fiber specimens have the best results, indicating that the proportion of the principal components extracted can represent the original parameters is 81%. It was also confirmed that the supervised learning KNN algorithm corresponding to different damage patterns can verify the unsupervised learning k-means cluster. Correspondingly, the strain fields characterized by DIC are reasonably matched with the AE signal responses. In addition, the critical damage and delamination mechanisms of the 3D printed continuous fiber reinforced composites are clearly revealed by Micro-CT characterization.

Biomimetic cuttlebone polyvinyl alcohol/carbon nanotubes/hydroxyapatite aerogel scaffolds enhanced bone regeneration

Inspired by the ordered porous nanostructure of bone, biomimetic functionalization porous biomaterial could be considered as promising substitutes for bone regeneration. To realize the relevant biomimetic porous structure, polyvinyl alcohol (PVA)-based biomimetic cuttlebone aerogel scaffold which simultaneously contained modified carbon nanotubes (MCNTs) and hydroxyapatite (HAP) was first prepared using a one-step rapid freeze-drying method. By adjusting the MCNTs contents, both the surface hydrophilicity and the mechanical properties of the scaffold could be improved concurrently. Besides, the PVA/MCNTs/HAP enhanced the adhesion, differentiation and gene expression of osteogenic markers performances of MC3T3-E1 cells. Furthermore, the aerogel scaffolds were implanted into the calvarial defect model of SD IGS Rat to evaluate osteogenic performance in vivo. The Micro-CT characterization and bone content theoretical analysis after 8 weeks together indicated that the PVA/MCNTs/HAP aerogel scaffolds could accelerate bone regeneration without the contribution of endogenous cytokines. The unique biomimetic porous structure, superior mechanical properties and excellent bone regeneration capacity of PVA/MCNTs/HAP aerogel scaffolds made them potential materials for bone regeneration.

A novel damage mechanism analysis of integrally braided CFRP and CFRP/Aluminum hybrid composite tube subjected to transverse impact

High-speed infrared thermography, micro-CT characterization and full-scale mesostructural simulation were jointly applied to reveal the impact deformation and damage mechanism of composite tubes. Two different failure modes, namely the Impact Side Dominated (ISD) and Impact-/Non-impact Side (INIS), were found to have relation with the braiding angle and localized temperature rise. The hybrid effect can not only prevent resin fragmentation in the triangle region at the lateral side and the diamond region at the non-impact side, but also inhibit the CFRP damage development at the lateral and non-impact side. In small-angle braided tube, the impact-side rebound trend of CFRP layer leads to mismatch at the CFRP-Al interface, which results in opening delamination. In large-angle braided tube, the non-impact-side damage plays an important role in further load-bearing capacity. Apart from the structure effect, temperature rise has an effect on composite damage mode by degrading the localized matrix stiffness.

Three-Dimensional Characterization of Spalled Al5083 by Micro CT and In-Situ Femtosecond Laser - FIB

Spall cracks were formed in an equal channel angular extruded aluminum 5083 sample shock loaded to 1.45 GPa. A combined 3D characterization method using micro x-ray computed tomography (micro-CT) and in-situ femtosecond laser serial sectioning in the focused ion beam was used to characterize these spall cracks. The benefit of using both techniques lies in the ability to characterize the microstructure and spall cracks at multiple length-scales. The micro-CT characterization method is applied to non-destructively analyze the spall cracks at a higher targeted length-scale, and destructively explore the microstructure at a lower length-scale using the in-situ method. The femtosecond laser milling in the focused ion beam (FIB) in-situ method also allows for electron backscattered diffraction for crystallographic orientation determination. This paper describes the development of using both methods for 3D characterization of a single region of interest.

In-situ micro-CT characterization of mechanical properties and failure mechanism of cementitious syntactic foams

The advancements in structural materials are guided by the desire of lowering the density and increasing the strength. Composite materials show promise in tuning the density and strength to meet specific design requirements. Lightweight cementitious materials, such as foamed concretes, are generally known to show poor mechanical properties (e.g., compressive strength and elastic modulus). The lack of control over the size, shape, and distribution of air voids severely limits the improvement of mechanical properties in lightweight cementitious materials. This work is focused on manufacturing and examining the mechanical properties of cementitious syntactic foams with hollow glass microspheres. Use of hollow particles to incorporate porosity allows for the control over the size, shape, and volume fraction of voids present in the composite. Hollow glass microspheres with several different densities (0.15–0.60 g/cm3) are used in different volume fractions (20%–50%) to manufacture the cementitious syntactic foams. The results show that cementitious syntactic foams (CSF) have compressive strengths (32–88 MPa) and elastic moduli (10–20 GPa) for a given range of low density (1.15–1.80 g/cm3), which are better than other cellular cementitious materials in the same density range. In-situ micro-CT scan results reveal that the micro-fracture mechanisms in CSFs under compressive loading depend on the microsphere density and aging of the material.

In situ X-ray micro-CT characterization of chemo-mechanical relaxations during Sn lithiation

Sn has been proposed for use as a high capacity anode material. Because of its ductile metallic nature, Sn may exhibit unique stress evolution during lithiation. Here, 2D radiography and 3D tomography are employed to visualize the evolution of geometry, internal structure, alloying, and damage during lithiation, delithiation, and rest of Sn wires with micron scale diameters. Lithiation proceeds isotropically, resulting in geometric and dimensional changes after 25% of total lithiation when the tensile stresses are sufficiently high to exceed the flow stress of the unlithiated Sn core and cause elongation and diameter increase. Damage occurs at later stages in the form of cracks terminating at the wire surface and voids forming in the unlithiated core. Notably, significant fragmentation occurs during delithiation which, due to void formation that accommodates the resulting stresses, does not measurably alter the wire cross-section and length. The distinguishing feature of the chemo-mechanics of Sn compared to Si or Ge is the pronounced creep rate at applied strain rates as high as 10−6 s−1, which promotes large strains in the core, eventually leading to void nucleation in the unlithiated core during lithiation, and more importantly, continues driving the deformation of the anode while at rest.

Exploiting LBL-assembled Au nanoparticles to enhance Raman signals for point-of-care testing of osteoporosis with excreta sample

Due to the intrinsic lack of specific biomarkers, there is an increasing demand for degenerative diseases to develop a testing method independent upon the targeting biomolecules. In this paper, we proposed a novel idea for this issue which was to analyze the characteristic information of metabolites with Raman spectrum. First, we achieved the fabrication of stable, uniform and reproducible substrate to enhance the Raman signals, which is crucial to the following analysis of information. This idea was confirmed with the osteoporosis-modeled mice. Furthermore, the testing results with clinical samples also preliminarily exhibited the feasibility of this strategy. The substrate to enhance Raman signal was fabricated by the layer-by-layer assembly of Au nanoparticles. The osteoporosis modeling was made by bilateral ovariectomy. Ten female mice were randomly divided into two groups. The urine and dejecta samples of mice were collected every week. Clinic urine samples were collected from patients with osteoporosis while the controlled samples were from the young students in our university. The LBL-assembled substrate of Au nanoparticles was uniform, stable and reproducible to significantly enhance the Raman signals from tiny amount of samples. With a simple data processing technique, the Raman signal-based method can effectively reflect the development of osteoporosis by comparison with micro-CT characterization. Moreover, the Raman signal from samples of clinic patients also showed the obvious difference with that of the control. Raman spectrum may be a good tool to convey the pathological information of metabolites in molecular level. Our results manifested that the information-based testing is possibly feasible and promising. Our strategy utilizes the characteristic information rather than the biological recognition to test the diseases which are difficult to find specific biomarkers. This will be greatly beneficial to the prevention and diagnosis of degenerative diseases. Also, we believe the combination of big bio-data and characteristic recognition will change the current paradigm of medical diagnosis essentially.

Reactive transport in porous media for CO2 sequestration: Pore scale modeling using the lattice Boltzmann method

Injection of CO2 subsurface may lead to chemical reactivity of rock where CO2 is dissolved in groundwater. This process can modify pore networks to increase or decrease porosity through mineral dissolution and precipitation. A lattice Boltzmann (LB) based computational model study on the pore scale reactive transport in three dimensional heterogeneous porous media (sandstone consisting of both reactive and non-reactive minerals) is described. This study examines how fluid transport in porous materials subject to reactive conditions is affected by unsteady state local reactions and unstable dissolution fronts. The reaction of a calcite cemented core sub-plug from the Hutton Sandstone of the Surat Basin, Australia, is used as a study case. In particular, the work studies the interaction of acidic fluid (an aqueous solution with an elevated concentration of carbonic acid) with reactive (e.g. calcite) and assumed non-reactive (e.g. quartz) mineral surfaces, mineral dissolution and mass transfer, and resultant porosity change. The proposed model is implemented in our custom LBM code and suitable for studies of multiple mineral reactions with disparate reaction rates. A model for carbonic acid reaction with calcite cemented sandstone in the CO2-water-rock system is verified through laboratory experimental data including micro-CT characterization before and after core reaction at reservoir conditions. The experimentally validated model shows: (1) the dissolution of calcite cement forms conductive channels at the pore scale, and enables the generation of pore throats and connectivity; (2) the model is able to simulate the reaction process until the reaction equilibrium status is achieved (around 1440 days); (3) calcite constituting a volume of around 9.6% of the whole core volume is dissolved and porosity is consequently increased from 1.1% to 10.7% on reaching equilibrium; (4) more than a third of the calcite (constituting 7.4% of the total core volume) is unaffected, which suggests that this calcite is not connected with open pores (at the resolution of the model) that the acidic fluid can access. The model enables exploration of the porosity change in systems as they react, which has applications for analysis of the induced permeability change at the macroscale.

Micro-CT Characterization on the Meso-Structure of Three-Dimensional Full Five-Directional Braided Composite

The meso-structure is important in predicting mechanical properties of the three-dimensional (3D) braided composite. In this paper, the internal structure and porosity of three-dimensional full five-directional (3DF5D) braided composite is characterized at mesoscopic scale (the scale of the yarns) using micro-computed tomography (micro-CT) non-destructively. Glass fiber yarns as tracer are added into the sample made of carbon fiber to enhance the contrast in the sectional images. The model of tracer yarns is established with 3D reconstruction method to analyze the cross-section and path of yarns. The porosities are reconstructed and characterized in the end. The results demonstrate that the cross sections of braiding yarns and axial yarns change with the regions and the heights in one pitch of 3DF5D braided composites. The path of braiding yarns are various in the different regions while the axial yarns are always straight. Helical indentations appear on the surfaces of the axial yarns because of the squeeze from braiding yarns. Moreover, the porosities in different shapes and sizes are almost located in the matrix and between the yarns.

Combining microCT-based characterization with empirical modelling as a robust screening approach for the design of optimized CaP-containing scaffolds for progenitor cell-mediated bone formation

Biomaterials are a key ingredient to the success of bone tissue engineering (TE), which focuses on the healing of bone defects by combining scaffolds with cells and/or growth factors. Due to the widely variable material characteristics and patient-specificities, however, current bone TE strategies still suffer from low repeatability and lack of robustness, which hamper clinical translation. Hence, optimal TE construct (i.e. cells and scaffold) characteristics are still under debate. This study aimed to reduce the material-specific variability for cell-based construct design, avoiding trial-and-error, by combining microCT characterization and empirical modelling as an innovative and robust screening approach. Via microCT characterization we have built a quantitative construct library of morphological and compositional properties of six CE approved CaP-based scaffolds (CopiOs®, BioOss™, Integra Mozaik™, chronOS Vivify, MBCP™ and ReproBone™), and of their bone forming capacity and in vivo scaffold degradation when combined with human periosteal derived cells (hPDCs). The empirical model, based on the construct library, allowed identification of the construct characteristics driving optimized bone formation, i.e. (a) the percentage of β-TCP and dibasic calcium phosphate, (b) the concavity of the CaP structure, (c) the average CaP structure thickness and (d) the seeded cell amount (taking into account the seeding efficiency). Additionally, the model allowed to quantitatively predict the bone forming response of different hPDC-CaP scaffold combinations, thus providing input for a more robust design of optimized constructs and avoiding trial-and error. This could improve and facilitate clinical translation. Statement of SignificanceBiomaterials that support regenerative processes are a key ingredient for successful bone tissue engineering (TE). However, the optimal scaffold structure is still under debate. In this study, we have provided a useful innovative approach for robust screening of potential biomaterials or constructs (i.e. scaffolds seeded with cells and/or growth factors) by combining microCT characterization with empirical modelling. This novel approach leads to a better insight in the scaffold parameters influencing progenitor cell-mediated bone formation. Additionally, it serves as input for more controlled and robust design of optimized CaP-containing bone TE scaffolds. Hence, this novel approach could improve and facilitate clinical translation.

Micro-CT characterization on porosity structure of 3D C f/SiC m composite

The fabric architecture and porosity of three-dimensional (3D) C f/SiC m composites are characterized using commercial X-ray microcomputed tomography (microCT). The non-destructive observation exhibits an inhomogeneous structure of the carbon fiber performs with gradiently distributed porosity. The shape of fiber bundles and porosity are investigated with respect to the gas transport during chemical vapor infiltration (CVI). Difference in growth rate of deposition between outer surface and inner porosity are identified through reconstructing the porosity morphology, which coincides well with the “node-bond” theoretical model. Moreover, in the light of the porosity features, gas retention and viscous flow is revealed to play key roles in the formation of the inner structure of C f/SiC m.

Micro-CT characterization of structural features and deformation behavior of fly ash/aluminum syntactic foam

The structure of a fly ash/aluminum syntactic foam was characterized using X-ray microcomputed tomography. Microstructural features, such as size, morphology and distribution of fly ash microballoons, were quantitatively related to the deformation behavior using interrupted compression tests. The syntactic foam was found to exhibit four distinct stages of deformation: (i) elastic; (ii) dispersed collapse of the fly ash microballoons; (iii) unification of the dispersed collapse region forming a band of densification, usually normal to the loading axis, via localized plasticity; and (iv) final densification. The tomographic observations show that deformation is initially controlled by the fragmentation and collapse of dispersed individual fly ash particles. After significant strain, sufficient microballoons have collapsed, localizing the stress and hence damage, and forming densification bands through severe plastic deformation of the aluminum matrix. A peak stress of 73 MPa and an energy absorption capacity of 27 MJ m −3 at 47% strain were obtained.

Micro-CT characterization of variability in 3D textile architecture

In the present work, we explore the potential of X-ray micro-computed tomography (X-ray micro CT) to characterize the micro-structural variation of four different 3D warp-interlaced fabrics. The accuracy of the technique was determined quantitatively by comparing measured values of yarn thickness, width and spacing between the yarns from X-ray micro CT images with measurements obtained from optical micrographs of the same textile. This comparison indicates that the difference between the two techniques is not statistically significant, lending credence to X-ray micro CT as a means to acquire input for models of textiles and textile composites. Micro-structural variation in a given fabric was found to be quite large (standard deviation of the geometrical parameters up to 16%). A comparison of similar yarns in different directions and fabrics also resulted in large variations. Variability of the fabric parameters is implemented in a “virtual textile” model of 3D fabrics. The influence of the variability of the fabric internal geometry on the mechanical properties of the composite is estimated using a micro-mechanical model.

Free-form fabrication and micro-CT characterization of poly-/spl epsiv/-caprolactone tissue scaffolds

One of the dominant approaches to tissue engineering is the seeding of biodegradable, biocompatible polymer scaffolds with progenitor cells prior to three-dimensional (3-D) culture or implantation. While the macroarchitecture of these scaffolds is important for anatomic fit, the microarchitecture has direct effects upon the ability of cells to attach, migrate, and thrive. Free-form fabrication - specifically, fused deposition - allows for simultaneous control of scaffold shape and microarchitectural characteristics. Microtomographic (micro-CT) scanners enable high-speed 3-D characterization of the salient features of these polymer scaffolds. A micro-CT scan followed by a 3-D reconstruction of serial image sections can determine porosity, pore size, pore interconnectivity, strut size, and 3-D microarchitecture. In this study, a number of polymer samples with different microarchitectures were manufactured through fused deposition free-form fabrication and subsequently characterized through micro-CT analysis. A desktop micro-CT scanner was used to examine each sample at approximately 19.1 μm resolution. Three-dimensional reconstruction and an analysis of core regions of each sample were performed. The results indicate that scaffolds of a specific shape may be constructed with interconnected pores of desired size.