Bernhard Plank

Fachhochschule Oberösterreich | fh-ooe · Computed Tomography Research Group

In this work active thermography was successfully applied as a quantitative method for the non-destructive evaluation of porosity in carbon fiber reinforced polymers. Results showed that not only the level of porosity, but also the shape of the pores strongly influences the active thermography results, in particular the measured thermal diffusivity...

For the material properties of carbon fibre reinforced polymers (CFRP), not only the porosity values (void content) are important, but also the shape and the distribution of voids. The state-of-the-art non-destructive testing (NDT) method for porosity detection in CFRP is ultrasonic testing (UT). Several publications proposed that the shapes of the...

In this work carbon fibre-reinforced polymer (CFRP) laminates and short glass fibre-reinforced polymers (sGFRP) were investigated by means of X-ray scatter dark field imaging (SDFI) using Talbot-Lau grating interferometer computed tomography. For the characterisation of the laminate structures of CFRP the anisotropic properties of the small angle s...

The fast and correct determination of porosity in carbon fibre–reinforced polymers and other polymeric material is an important application area of X-ray computed tomography (CT). In this CT simulation study, microstructures such as individual carbon fibres, micro-voids, as well as the polymer matrix including mesoscale voids, were taken into accou...

This study demonstrates the utilization of deep learning techniques for binary semantic segmentation of pores in carbon fiber reinforced polymers (CFRP) using X-ray computed tomography (XCT) datasets. The proposed workflow is designed to generate efficient segmentation models with reasonable execution time, applicable even for users using consumer-...

High strength and low density make epoxy-based CFRP a highly interesting construction material for the aerospace manufacturing industry. Porosity represents an unavoidable defect and significantly weakens strength values dominated by the matrix. To evaluate the quality of safety-relevant components, non-destructive evaluation and thus the character...

This work illustrates the use of deep learning methods applied on X-ray computed tomography (XCT) datasets to segment pores and fibres in reinforced composite components from the aeronautic industry by binary semantic segmentation. We first apply data pre-processing, and then employ a modified 3D U-Net, representing a convolutional neural network....

Purpose 3D printing techniques such as material extrusion based additive manufacturing provide a promising and cost effective manufacturing technique. However, the main challenges in industrial applications remain with the quality assurance of mass produced parts. The purpose of this study is to investigate the effect of compression moulding as a r...

Discontinuous carbon fiber composites have been reported to be damage tolerant materials with insensitivity to notches and defects. Meso-scale damage mechanisms and crack arresting are responsible for high apparent fracture toughness and pseudo-ductility. This work studies the effect of manufacturing and structure formation on the mechanical behavi...

Composite filament co-extrusion (CFC) additive manufacturing (AM) is a bi-matrix rapid fabrication technique that is used to produce highly customisable composite parts. By this method, pre-cured, thermoset-based composite carbon fibre (CCF) is simultaneously extruded along with thermoplastic (TP) binding melt as the matrix. Like additive manufactu...

The formation of an inhomogeneous structure with central segregation occurs in commercial twin-roll cast AA 3003 aluminum alloy. The segregations form as manganese, iron, and silicon-rich channels spread in the rolling direction. Diffusion of silicon occurs during annealing at 450 °C, and the formation and growth of voids due to the Kirkendall effe...

Various methods are used to characterize the deterioration of mechanical properties in polymers. The focus is set on distinguishing between time‐dependent and irreversible damage in two different grades of polypropylene. First, digital image correlation is utilized to capture the stress–strain behavior during monotonic tensile tests. Changes in spe...

Carbon fiber reinforced tapes are a feasible option to tailor material properties of composite structures and to reduce waste due to cut‐offs. But composite properties are not only influenced by the selected material, but also via the applied curing process. The aim of this experimental investigation is a comparison of the mechanical properties of...

In this study new insights regarding quantitative porosity determination using X-ray computed tomography (CT) could gained by using CT simulation tools to generated synthetical 3D data with a well known nominal porosity content. Therefore 1,988 typical microstructure elements such as individual carbon fibres, needle like micro voids as well some ma...

Due to their potential of decreasing weight and emission, the importance of lightweight designs with carbon fibre reinforced polymers (CFRP) in the aeronautic and automotive industry is increasing constantly. However, the formation of cracks and delaminations is one of the most prominent failure mechanisms during mechanical loading of CFRP, signifi...

Modeling how thermoplastic composites are processed using thermoforming is a challenging task, and not only due to the heterogenic nature of the material. During the thermoforming processes, the polymeric matrix has to be heated above the softening temperature, enabling the composite to be formed into three‐dimensional parts. As the system mobility...

This study investigates the impact of two different processing methods, Injection molding (IM) and 3D printing (3Dp), on neat/unfilled polylactic acid (NPLA) and the short carbon fibers (SCFs) filled polylactic acid (SPLA). Furthermore, the resulting processing conditions and the influence on mechanical properties, such as tensile, flexural, notche...

Selective laser sintering (SLS) is an additive manufacturing process which nowadays receives abundant attention from industry sectors. However, the number of materials which can be processed by SLS is still very limited and requires further research. The present work aims to contribute to this topic by investigating the mechanical properties of nea...

Additive Manufacturing represents a quite new material processing technology. Parts are formed by adding material layer by layer until it is finished without requiring any additional tools. Therefore, using Additive Manufacturing can save time and costs in comparison to commercial production methods particularly when manufacturing complex prototype...

This work evaluates and compares the accuracy of different fiber orientation prediction models for a short fiber reinforced injection molded Venturi-shaped part which displays variable thickness. The experimental characterization of the specimen fiber orientation distribution (FOD) was carried out by the micro computed tomography technique (micro-C...

Discontinuous prepreg platelet based carbon fibre sheet moulding compound (CF-SMC) materials offer huge potential for lightweight applications in the automotive industry. The composition of these materials and the flow behaviour during compression moulding result in a complex stochastic mesostructure, which presents a challenge in the modelling of...

As bonded composite repairs are gaining importance for modern civil aircraft, it is necessary to investigate such repairs in detail under relevant environmental conditions. In this work, X-ray computed tomography (XCT) was performed on bonded repairs for carbon fiber (CF) reinforced epoxy matrix composites before and after cyclic conditioning betwe...

Structural simulations close the gap between CT imaging and material behavior, giving a prediction on the mechanical characteristics of an investigated material specimen. When dealing with data originating from CT measurements, depending on the final use of the simulated results, two distinct approaches can be identified: the first approach focuses...

As bonded composite repairs are gaining importance for modern civil aircraft, it is necessary to investigate such repairs in detail under relevant environmental conditions. In this work, X-ray computed tomography (XCT) was performed on bonded repairs for carbon fiber (CF) reinforced epoxy matrix composites before and after cyclic conditioning betwe...

Composite structures are increasingly present in various types of structures, especially in the aircraft industry. As a result, suitable repair strategies have to be developed and tested. Hereby, an important part is testing under relevant environmental conditions. As a consequence, the current research work is focused on the influence of (1) testi...

Limitations in the packaging industry require improvements in lead-based microelectronics, because regulations restricting hazardous substances have ended the use of conventional lead-based solders. Sintered silver paste presents an alternative method for bonding chips to a substrate because it has low sensitivity to the oxidation, high melting poi...

Using Talbot-Lau grating interferometer X-ray computed tomography (TLGI-XCT) we determine the fiber lay-up and quantify defects in loaded carbon fibre-reinforced polymer samples in three dimensions. In contrast to conventional XCT, TLGI-XCT provides three complementary image characteristics during image acquisition: a) attenuation contrast (AC), b)...

X-ray imaging methods, such as conventional X-ray computed tomography (XCT) based on absorption, are essential techniques in various domains, for example medicine and materials science. In the last 15 years, an important innovation in X-ray imaging technology has emerged through the introduction of Talbot-Lau grating interferometry (TLGI) [1-4] . U...

Sintered silver materials possess an advantage that allows excellent bonding between chips and their substrate. Stress manifests as the materials resistance against external and internal forces, however during stress analysis the complex physical behavior caused by the forces and the nature of the material is often disregarded by researchers. This...

Using Talbot-Lau grating interferometer X-ray computed tomography (TLGI-XCT) we determine the fiber lay-up and quantify defects in loaded carbon fibre-reinforced polymer samples in three dimensions. In contrast to conventional XCT, TLGI-XCT provides three complementary image characteristics during image acquisition: a) attenuation contrast (AC), b)...

Ti6Al4V is a suitable titanium alloy for all kinds of medical implants and prostheses because of its high durability and biocompatibility. Furthermore, components of high complexity can be produced via additive manufacturing which allows for more flexibility and easy prototyping of patient specific implants. However, this flexibility implies the ri...

Ti6Al4V is a suitable titanium alloy for all kinds of medical implants and prostheses because of its high durability and biocompatibility. Furthermore, components of high complexity can be produced via additive manufacturing which allows for more flexibility and easy prototyping of patient specific implants. However, this flexibility implies the ri...

This paper presents multi-modal image data of different fibre reinforced polymer samples acquired with a desktop Talbot-Lau grating interferometer (TLGI) X-ray computed tomography (XCT) system and compare the results with images acquired using conventional absorption-based XCT. Two different fibre reinforced polymer samples are investigated: (i) a...

Fiber-reinforced polymers (FRPs) are of great importance in various industries because of their superior properties as compared to conventional materials, their versatile processing, and their wide application possibilities. To fulfil the high-quality standards in its respective applications, industrial 3D X-ray computed tomography (XCT) is increas...

In this work we present a method to characterize microcracks in carbon fiber reinforced polymer (CFRP) samples with a diameter up to 120 mm using quantitative grating-based X-ray dark-field imaging. In contrast to conventional microcomputed tomography (XCT), grating-based X-ray radiography and XCT provide three complementary images: (a) attenuation...

This work investigates the preparation of silicon carbide ceramics (C/Si/SiC ceramics) from extruded thermoset-based wood polymer composites (WPC). The extruded WPC green bodies are carbonised forming open porous carbon templates (C-templates). These C-templates are converted by liquid silicon infiltration into bio-based C/Si/SiC ceramics. The mate...

Silicon carbide (SiC) is one of the most important technical ceramics due to its high hardness, chemical resistance and thermal properties even at very high temperatures. The excellent properties are attended by high costs. For broader use, cost reduction in materials and processing is inevitable. Therefore, Wood K plus has developed an extrusion p...

Twin-roll casting allows production of sheets and strips with required thickness without subsequent homogenization or hot rolling and therefore has a high potential for industrial applications. One of the drawbacks of this method is a formation of inhomogeneous structure with central segregation. Sheet prepared from 3003 aluminum alloy with 1 wt.%...

The thermomechanical behavior of cast Al-Si piston alloys is highly dependent on the condition of the highly interconnected hybrid 3D network which is composed of primary and eutectic silicon and intermetallic phases which are found embedded in the α-Al matrix. The very similar X-ray absorption of silicon and the α-Al matrix is problematic for the...

3D computed tomography (CT) is used as a quality control tool in composite manufacturing. The analyzed materials include natural fiber reinforced polymers (thermoplastics and thermosets), porous carbons, and silicon carbide (SiC) ceramics. Multistep manufacturing processes were used for the production of the composite materials. One manufacturing r...

During the liquid composite molding process, e.g. resin transfer molding (RTM), a liquid state matrix material is forced into a dry, preformed reinforcing material (e.g. carbon fiber fabric). Resin-rich zones are a common phenomenon in RTM processes and cause unwanted residual stress and deformation. However, since the absorption coefficients of ma...

Due to the low cost, the ease of processing, and excellent material properties, polymer foams are used in various applications, e.g. packaging, building and construction, furnitures and bedding, and the automotive and aerospace sector. The mechanical response of polymer foams is primarily influenced by density and morphology. While foam density can...

In this paper we present multi-modal image data acquired by Talbot-Lau grating interferometer µXCT (Talbot-Lau µXCT) and conventional µXCT devices. Samples are made of carbon fibre reinforced polymers (CFRP) with a copper mesh near the surface for lightning conduction. The inspection task includes the detection and characterization of internal defe...

This work presents the possibility of using infrared (IR) thermography as a fast, contactless and therefore nondestructive inspection method to detect failures in commercial thermoelectric (TE) modules. For this the TE modules were thermally excited by internal Joule heating. The temperature at the hot side of the TE module was recorded with an IR...

In this work we present a method to detect failures in commercial thermoelectric (TE) modules using Infrared (IR) thermography. The TE modules consist of 252 pn thermoelectric junctions based on Bi2Te3 alloys. The dimension of a TE module is 40 mm x 40 mm x 4,7 mm. In general, failures which are located inside the TE module (typically cracks, physi...

Bark is a highly efficient natural tree protective layer with outstanding properties. It is a classic by-product of the wood industries and most of the time directly burned where it accrues. The present study focuses on using bark as a material in form of thermal insulation panels. Therefore, insulation boards out of softwood (Larix decidua) bark w...

In recent years, advanced composite materials such as carbon fiber reinforced polymers (CFRP) are used in many fields of application (e.g., automotive, aeronautic and leisure industry). These materials are characterized by their high stiffness and strength, while having low weight. Especially, woven carbon fiber reinforced materials have outstandin...

In recent years, advanced composite materials such as carbon fiber reinforced polymers (CFRP) are used in many fields of application (e.g., automotive, aeronautic and leisure industry). These materials are characterized by their high stiffness and strength, while having low weight. Especially, woven carbon fiber reinforced materials have outstandin...

Insulation boards made out of larch bark were pressed and scanned with an industrial X-ray computed tomograph (CT) in order to study the structure of the boards and to allow structure-based thermal modeling. The CT images were segmented using a categorization algorithm based on ANOVA. Apart from gaining knowledge about panel porosity, understanding...

Porosity in carbon fibre reinforced polymers (CFRP) degrades the engineering performance, especially the interlaminar shear strength. In this work the porosity of CFRP was successfully determined by means of pulsed thermography. Additionally cone beam X-ray computed tomography (XCT) measurements were carried out. The observation time and the result...

The paper demonstrates the possibility of a correct (within the experimental scatter) calculation of a textile reinforcement permeability based on X-ray micro-computed tomography registration of the textile internal architecture, introduces the image segmentation procedures to achieve the necessary precision of reconstruction of the geometry and st...

The ability of bone graft substitutes to promote new bone formation has been increasingly used in the medical field to repair skeletal defects or to replace missing bone in a broad range of applications in dentistry and orthopedics. A common way to assess such materials is via micro computed tomography (µ-CT), through the density information conten...

X-ray scatter dark field imaging (SDFI) tomography was used to investigate the glass fibre orientation of short fibre-reinforced polymers (SFRPs). The fibre orientation of fibre-reinforced polymers is decisive for the mechanical strength of injection-moulded parts. For this paper four different positions, with volumes along the melt flow and with w...

The continuous trend to energy saving and sustainable constructions in buildings leads to an increasing demand of efficient and sustainable thermal insulation materials. One promising development is the usage of the natural “tree insulation material,” namely bark, for building insulations. Insulation boards out of larch bark were scanned with an in...

The general trend towards energy efficient building constructions has led to an increased need of insulation materials. Basically, organic (hydrocarbons) and inorganic insulation materials can be distinguished whereby the first group is dominated by petrol based products (polystyrene) and the second one is mainly mineral wool, which both have a rat...

In the pathogenesis of diabetic neuropathic osteoarthropathy (Charcot's foot) fractures cause chronic destruction of soft tissue and bone structure. To improve an early diagnosis of Charcot foot, modern diagnostic imaging is mainly based on magnetic resonance imaging (MRI), for example in relation to the detection of cortical bone fractures. In thi...

In diesem Artikel wird die Dauerhaftigkeit von Terrassendielen aus verschiedenen Materialien bezüglich der Standfestigkeit während eines Zyklustests untersucht. Als Vergleichsmaterialien wurden Terrassendielen aus diversen Hölzern, thermisch modifiziertem Holz (TMT) und Wood-Polymer-Composites (WPC) verwendet. Als Grundlage für die Festlegung der T...

Dieser Beitrag beschäftigt sich mit der Herstellung und Charakterisierung von C/Si/SiC-Keramiken aus einem Holz-PolymerVerbundwerkstoff (WPC). Dabei werden die Proben zwischen den einzelnen Produktionsschritten mittels Röntgen-Computertomografie (XCT) analysiert, um die Vorgänge im Material besser zu verstehen. XCT wurde für diese erste Machbarkeit...

Industrial X-ray Computed Tomography (XCT) techniques are used in a wide variety of different applications. In recent years the inspection of Carbon Fiber Reinforced Polymers (CFRP) has also been added to these applications. Besides defect detection, an increasing interest is observed in characterizing the inner structure and in providing in-depth...

The quality of a ceramic is defined by its homogenous and non-porous volume. These parameters determine the durability and failure probability of a component. By means of XCT, the structural changes within the samples over the whole manufacturing route were evaluated. In the qualitative evaluation at lower XCT resolutions (> (70 µm)³ voxel size) po...

Wood based composites in general are built up from a matrix of more or less defined shaped wood particles and a certain amount of resin. CT‐measurements by means of cold neutrons and X‐ray were carried out using one and the same set of specially prepared specimens. The used radiographic methods and achieved results are compared regarding the specia...

The paper describes for the first time the analysis of the structure of compressed wood using computed tomography. The anatomical structures of Douglas-fir and hybrid poplar before and after densification with the viscoelastic thermal compression (VTC) process were described by pore size distributions and mean pore sizes and compared. The compressi...

We report on the characterization of glass-fiber-filled polypropylene compounds identified by means of rotational rheometry in parallel plate mode. The small gap between the plates and the length of the glass fibers cause considerable wall and initial orientation effects, which we minimized by applying various degrees of pre-shearing, optimizing bo...

Wet-white and wet-blue leather shavings were investigated as promising new raw materials as they seem to offer a high availability and cost competitiveness compared to wood, and they also show some interesting new properties. In order to determine a new field of application for the leather shavings and to understand the fiber particle interaction,...

In recent years, bone graft substitutes have been increasingly used in the medical field, for example, in order to promote new bone formation. Microcomputed tomography ( μ -CT) is an image-guided technique used in medicine as well as in materials science, enabling the characterization of biomaterials with high spatial resolution. X-ray-based method...

The shrinkage behavior of European beech wood was successfully observed on a time series of images obtained by high resolution X-ray computed tomography (μXCT). The calculated measures for shrinkage and shrinkage anisotropy are consistent with published data. Evidence was provided for the ‘ray restraint’ theory of shrinkage anisotropy. This techniq...

Full-field optical coherence microscopy performed with a supercontinuum light source based on a Q-switched micro-chip laser pumped photonic crystal fiber is shown to provide ultra-high resolution images from the interior of scattering samples. We exemplify our imaging approach by a detailed analysis of fiber reinforced polymer samples: comparative...

In this work a novel method for the characterization of porosity in carbon fiber reinforced polymers (CFRP) is presented. A visualization pipeline for the interactive exploration and visual analysis of CFRP specimens is developed to enhance the evaluation workflow for non-destructive testing (NDT) practitioners based on specified tasks. Besides qua...

X-ray computed tomography (XCT) has become a very important tool for the non-destructive characterisation of materials. Continuous improvements in the quality and performance of X-ray tubes and detectors have led to cone-beam XCT systems that can now achieve spatial resolutions down to 1 μm and even below. Since not only the amplitude but also the...

In this paper the sub-micrometre computer tomography (sub-μm-CT) was used in order to investigate the structure of OSB and particle board. The data obtained were analysed using mathematical morphology and image analysis in order to obtain information on the pore size distribution. The observed distributions were found to follow Γ-law. Between the p...

Acoustic emission (AE) and radial shrinkage were compared between fully saturated fresh and pre-dried Norway spruce sapwood during dehydration at ambient temperature. Hydraulic conductivity measurements, anatomical investigations on bordered pits and X-ray computed tomography (CT) scans were done to search for possible AE sources other than the bre...

Thermal diffusivity imaging has the potential to reflect the existence of inhomogeneous material properties which are correlated to increased porosity. For calibration of the thermal diffusivity values the porosity were measured using Computed‐Tomography, which yields data on the porosity as well as on the pore morphology. The experimental results...

Der Artikel befasst sich mit der Anwendung der Sub-Mikrometer-Computertomographie (Sub-μm-CT) zur Charakterisierung von Holzwerkstoffen, im speziellen von Oriented Strand Board (OSB), Spanplatte (PB) und mitteldichter Faserplatte (MDF). Eine der größten Herausforderungen stellte die Probengröße und die damit erreichbare maximale Auflösung dar. Die...

The porosity of carbon fibre-reinforced polymers is a very important topic for the practical applications of this material since there is a direct correlation between porosity and mechanical properties, such as shear strength. Therefore the porosity values of carbon fibre-reinforced composites for practical use in aircraft and cars must be lower th...

X-ray computed tomography (XCT) with cone beam geometry has become a very important method for non-destructive 3D-characterisation and evaluation of materials. Compact XCT systems can reach resolutions down to 1 µm and even below. However, the polychromatic nature of the source, limited photon flux and the consequent long measurement times as well...