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Ultra-High Performance Fiber Reinforced Concrete (UHPFRC) is a promising material for different applications such as bridge deck strengthening due to its improved strength and durability properties. Especially the tensile strength and ductility is heavily dependent on the distribution and orientation of the steel fibers within the element. This fiber behaviour can be unpredictable, causing a large scatter in material properties. This scatter is inconvenient for predicting the material properties. The novelty of the material is the main reason that UHPFRC is not included in the Eurocode. Certain countries like Switzerland and France have developed their own UHPFRC norms. In order to increase the knowledge and understanding of the fiber distribution and orientation, a non-destructive testing method has been developed. Two types of magnetic probes have been developed: the C-shaped ferrite probe and the single ferrite probe. These probes are based on other probes developed at the University of Milan and Porto. The C-shaped ferrite probe is most suitable for measuring the total fiber content and fiber orientation. The single ferrite probe is able to take fiber content measurements closer to the edge making it more efficient for fiber distribution measurements. This can result in a reliable prediction of the peak-tensile strength. The addition of UHPFRC specific design rules and this non-destructive testing method will make UHPFRC and its applications more attractive. In this research, 27 different UHPFRC plates were cast with the same dimensions of 10x200x200 mm3. These plates were cast horizontally or vertically with either 1%, 2%, 3% or 4% fiber content. Seven plates were vibrated after casting in order to analyse the influence of vibration. Each fiber content resulted in a relatively homogeneous fiber distribution and random fiber orientation. Horizontal casting of UHPFRC plates usually result in a more homogeneous fiber distribution and more rando, Civil Engineering

Hur ser framtidens hållbara förpackning ut och vad är den tillverkad av? För att besvara denna fråga blir mikromekanisk karakterisering av material en viktig parameter att utforska och förstå. I synnerhet är mikromekaniken hos tunna pappersmaterial intressant då materialet har användningspotential i flera förpackningsapplikationer. Detta examensarbete fokuserar på att studera mikromekaniska beteenden genom in situ dragprovning inuti vakuumkammaren hos ett svepelektronmikroskop. In situ testning gör det möjligt att kombinera högupplösta observationer och mätresultat under belastning, vilket ger en inblick i de mekaniska egenskaperna och deformationsmekanismerna. För att uppnå detta så utvecklades en metodiken som innefattar framställning av anpassade pappersprover med hjälp av ett programmerbart skärbord för full kontroll över orientering och dimensioner. Proverna monteras och justeras sedan i dragprovaren där de deformeras förbi brottgränsen. Under hela deformationen tas bilder, videor och kraft-förskjutningsdata. Resultaten från denna uppsats avslöjar att de mekaniska egenskaperna hos tunt papper är starkt påverkade av fiberorientering och fukthalt samt bildandet av hålrum. Den maximala dragstyrkan, brottsträckgränsen och Youngs modul varierar avsevärt beroende på fibrernas orientering inom materialet. Dessutom påverkar fukthalten i papperet det mekaniska beteendet avsevärt, varvid högre fukthalt inom intervallet 1 till 6\% visar sig minska maximal dragstyrka och öka formbarheten. Sammanfattningsvis så bidrog undersökningen av mikromekaniska beteenden hos tunt papper till utvecklingen förpackningslösningar med miljöhänsyn och påpekar behovet av fortsatt framtida forskning., What does the future sustainable package look like, and what is it made of? To answer this question, the micromechanical characterization of materials becomes an important parameter to explore and understand. In particular, the micromechanical behavior of thin paper materials is of interest due to its potential in sustainable packaging applications. This master's thesis focuses on investigating micromechanical behavior through in situ tensile testing inside the vacuum chamber of a scanning electron microscope. In situ testing makes it possible to combine high-resolution observations and measured material response under load, hence providing insights into the mechanical properties and deformation mechanisms. To achieve this, a methodology was developed that involve preparing custom paper samples using a programmable cutting table for full control over orientations and dimensions. The samples are then mounted and aligned in the tensile tester, where they are deformed beyond breakage. Throughout the deformation process, images, videos and force-displacement data are simultaneously captured. The results of this thesis reveal that the mechanical properties of thin paper are heavily influenced by fiber orientation and moisture content along with void formations. The maximum tensile strength, strain at break and Young's modulus of the paper vary significantly depending on the orientations of the fibers within the material. Furthermore, the moisture content of the paper affects the mechanical behavior considerably, with higher moisture content within the range of 1 to 6\% being found to reduce maximum tensile strength and increase ductility. In conclusion, the investigation of the micromechanical behavior of thin paper contributes to the development of packaging solutions with environmental considerations and urges the need for future research., Hur ser framtidens hållbara förpackning ut och vad är den tillverkad av? Denna studie undersöker mikromekaniska beteenden hos tunna pappersmaterial och deras användningspotential i förpackningsapplikationer.

The fiber orientation in composite materials is highly dependent on the manufacturing process and plays a crucial role in determining the mechanical, thermal, and electrical properties of the fabricated parts. Several simulation frameworks have been developed to predict the fiber orientation in the printed strands for Material EXtrusion Additive Manufacturing (MEX-AM) process, but studies have been limited to planar and 2D model reductions. Consequently, it is currently impossible to predict the full spatial variation of fiber orientations in a three-dimensional printed strand, and thus the effects of printing conditions remain not well understood. This work seeks to address this issue by introducing the first three-dimensional model capable of simulating the MEX-AM process with fiber-reinforcements. A fully coupled model is developed in this work, which is based on the finite-volume method and solved in the open-source multiphase solver OpenFOAM. Using this framework, we explored the effects of different printing conditions on fiber orientation and strand shape morphology, and we compared our results to experimental observations when possible. We found that the extrusion and nozzle velocities significantly affected the fiber orientation while altering the gap distance between the nozzle exit and substrate had a limited impact. Moreover, increasing anisotropy using longer fibers and higher volume fractions had little influence on the fiber orientation, but their impact on the rheology altered the strand shape considerably. Prediction of fiber orientation for different printing conditions within strands will open the possibility of manufacturing products that has locally engineered properties and tailored anisotropic behavior.

An engineered cementitious composite (ECC) belongs to a type of high-performance fiber-reinforced materials. Fiber alignment causes the anisotropy of such materials. Herein, the influence of the fiber orientation on water and ion penetration into an ECC was studied. Fiber alignment was achieved using an extrusion approach. Water absorption, sorptivity, chloride penetration resistance, sulfate attack resistance, and freezing–thawing resistance of specimens with fiber aligned horizontally (AH), vertically (AV), and randomly (R), corresponding to the direction of the exposure surface that was studied. The results showed that fibers oriented perpendicular to the water path delayed water migration into the ECC matrix. The sorptivity was significantly affected by the fiber direction. The sorptivity of the AH specimens was 35% and 13% lower than that of the AV and R specimens, respectively. After 180 days of exposure, the chloride penetration depth of the AH specimens was 5.7 mm, which is 13.6% and 20.8% lower than that of the AV and R specimens, respectively. The sulfate ingress profile indicates that the fiber–matrix interface oriented perpendicular to the penetration path can effectively delay sulfate migration. The fiber orientation also influences the compressive strength gain under immersion conditions (Na2SO4 solution, Na2SO4 + NaCl solution, and water). Compared with the AH and R specimens, the AV specimens are more sensitive to the immersion condition. In contrast, the fiber orientation has no significant effect on ECC specimens under freeze–thaw cycles. These findings indicate that controlling the fiber alignment and orientation in an ECC can improve its durability under certain exposure conditions., Materials and Environment

The mechanical performance of engineered cementitious composite (ECC) depends greatly on fiber orientation and distribution. In this paper, the effect of fiber orientation on ECC's mechanical properties was investigated using two different casting methods: a flow-induced casting was used to enhance the fiber orientation within ECC mixture and compared with the conventional casting. The fiber orientation was quantified using scanning electron microscope (SEM) and image processing. Mechanical tests on the specimens with various fiber orientations were performed. The failure processes of ECC specimens under compression and tensile tests were analyzed using digital image correlation (DIC) technique. The proposed flow-induced casting enhanced the fiber alignment in the flow direction. Consequently, ECC's mechanical properties were significantly improved with more finer cracks under uniaxial loading. In conclusion, the proposed flow-induced casting can be adopted as an effective approach to improve fiber bridging efficiency in ECC., Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public., Materials and Environment

Tensile performance of strain hardening cementitious composites (SHCC) is determined from uniaxial tensile specimens, in which the fiber orientation can vary with sample size and processing method. However, when interpreting the laboratory-determined tensile behaviors, synthetic fibers in SHCC are usually assumed to be randomly oriented without experimental validation. In this study, an automatic image processing workflow for obtaining accurate fiber orientation distribution over a whole section is proposed. The experimentally obtained fiber orientation distributions in PVA-SHCC tensile samples form a clear peak at around 20 degrees relative to the tensile direction, which is not revealed by any existing model on fiber distribution. A modified fiber orientation analysis considering the sample processing effect (flattening effect) is presented to derive the distribution, with parameters obtained by computational fluid dynamics simulations. The measured or derived orientation distribution can be used to replace random distributions in fiber bridging models to reduce systematic simulation errors.

Fundamental knowledge of the deposition process of electrospun fibers is of paramount importance to the fabrication of constructs with fibers oriented in specific directions, depending on the mandrel geometry. This paper presents an electrostatic finite element analysis of a parallel-plate electrospinning configuration that reveals the effects of the electric potential intensity and directionality on the deposition of aligned and randomly oriented fibers, resulting in the formation of a fibrous bilayer construct. Simulations demonstrate that polymer deposition between the collector plates yields a local effect on the electric field. This study provides a computational methodology for investigating other collector configurations and guidance for designing electrospinning setups capable of producing microfibrous constructs with tailored morphologies.

With increasing emphasis and regulations on the environmental footprint in industries, the integration of reduced carbon dioxide equivalent (CO2eq) plastic materials is desirable. Fiber-reinforced plastic materials mechanical properties differ with varying fiber orientations. Similarly, the welding line phenomenon, commonly present in more complex injection molded parts, decreases the mechanical performance. This thesis aims to experimentally investigate tensile behavior on reduced CO2eq reinforced plastics in different fiber orientations and weld line configurations. Ten materials with reduced CO2eq are investigated, the types of materials are as follows: PA6 (Polyamide6), PP (Polypropylene), and PA6/PP blend materials. Both short fiber-reinforced polymers (SFRP) and long fiber-reinforced polymers (LFRP) are investigated. The screening resulted in three selected materials for further investigation: one recycled PA6, one bio-based PA6/PP, and one alternative PP. The further investigation involves tensile testing in the five directions and three weld line configurations with non-standardized geometry specimens punched out from an injection molded plate with controlled fiber orientation. Two types of uniform fiber orientation plates are manufactured for the testing conditions, one with holes for weld line testing and one without for testing of orientation. The evaluated fiber orientations are 0° (fibers parallel to load direction), 22.5°, 45°, 67.5°, and 90° (fibers transverse to load direction). The weld line configuration consists of three consecutive holes with 96.5, 146.5, and 196.5 mm distances from the gating system. Three weld line test specimens are generated from each plate, they are denoted W1, W2, and W3 from their respective distance from the gating system, with W1 being closest to the gate. Optical microscopy of fiber orientation and failure modes for the test specimens are performed to investigate and validate the testing conditions. Varying fiber orie

With increasing emphasis and regulations on the environmental footprint in industries, the integration of reduced carbon dioxide equivalent (CO2eq) plastic materials is desirable. Fiber-reinforced plastic materials mechanical properties differ with varying fiber orientations. Similarly, the welding line phenomenon, commonly present in more complex injection molded parts, decreases the mechanical performance. This thesis aims to experimentally investigate tensile behavior on reduced CO2eq reinforced plastics in different fiber orientations and weld line configurations. Ten materials with reduced CO2eq are investigated, the types of materials are as follows: PA6 (Polyamide6), PP (Polypropylene), and PA6/PP blend materials. Both short fiber-reinforced polymers (SFRP) and long fiber-reinforced polymers (LFRP) are investigated. The screening resulted in three selected materials for further investigation: one recycled PA6, one bio-based PA6/PP, and one alternative PP. The further investigation involves tensile testing in the five directions and three weld line configurations with non-standardized geometry specimens punched out from an injection molded plate with controlled fiber orientation. Two types of uniform fiber orientation plates are manufactured for the testing conditions, one with holes for weld line testing and one without for testing of orientation. The evaluated fiber orientations are 0° (fibers parallel to load direction), 22.5°, 45°, 67.5°, and 90° (fibers transverse to load direction). The weld line configuration consists of three consecutive holes with 96.5, 146.5, and 196.5 mm distances from the gating system. Three weld line test specimens are generated from each plate, they are denoted W1, W2, and W3 from their respective distance from the gating system, with W1 being closest to the gate. Optical microscopy of fiber orientation and failure modes for the test specimens are performed to investigate and validate the testing conditions. Varying fiber orie

The anisotropy and strain rate dependence of the mechanical response of short-fiber-reinforced thermoplastics was studied using a straightforward micromechanical finite element analysis of representative volume elements (RVEs). RVEs are created based on the fiber orientation tensor, which quantifies the processing-induced fiber orientation distribution. The matrix is described by a strain rate-dependent constitutive model (the Eindhoven glassy polymer (EGP) model), which accurately captures the intrinsic response of amorphous polymers. The micromechanical results indicate that the influence of strain rate and that of the loading direction on the yield stress are multiplicatively decouplable, which confirms previous experimental observations. Moreover, it is demonstrated that the yield stress, to a good approximation, can be directly linked to the fiber orientation in the direction of loading. This leads to a new relation that uniquely links the rate dependence of the yield stress to the fiber orientation in loading direction.

Long fiber reinforced thermoplastic composites are used for creating lightweight, but mechanically sound, automotive components. Injection molding is a manufacturing technique commonly used for traditional thermoplastics due to its efficiency and ability to create complex geometries. Injection molding feedstock is often in the form of pellets. Therefore, fiber composites must be chopped for use in this manufacturing method. The fibers are cut to a length of 13 mm and then fiber attrition occurs during processing. The combination of chopping the fibers into pellets and fiber breakage creates a distribution of mostly short fiber lengths, with some longer fibers remaining. Discontinuous fiber reinforcements are classified as long for aspect ratios greater than 100. For glass fibers, that distinction occurs at a length of 1 mm, and for carbon fibers 0.5 mm. Traditional composite materials and manufacturing processes utilize continuous fibers with a controlled orientation and length. The use of chopped discontinuous fibers requires a method to predict the orientation of the fibers in the final molded piece because mechanical properties are dependent on fiber length and orientation. The properties and behavior of the flow of a fiber reinforced polymer composite during molding are directly related to the mechanical properties of the completed part. Flow affects the orientation of the fibers within the polymer matrix and at locations within the mold cavity. The ability to predict, and ultimately control, flow properties allows for the efficient design of safe parts for industrial uses, such as vehicle parts in the automotive industry. The goal of this work is to test material characterization techniques developed for measuring and predicting the orientation of fiber reinforced injection molded thermoplastics using commercial grade long carbon fiber (LCF) reinforced nylon 6,6 (PA 6,6). Forty weight percent LCF/PA 6,6 with a weight averaged fiber length of 1.242 mm was inject

Microstructural responses to the mechanical load of polymers used in tissue engineering is notably important for qualification at in vivo testing, although insufficiently studied, especially regarding promising polycaprolactone (PCL). For further investigations, electrospun PCL scaffolds with different degrees of fiber alignment were produced, using two discrete relative drum collector velocities. Development and preparation of an adjusted sample geometry enabled in situ tensile testing in scanning electron microscopy. By analyzing the microstructure and the use of selected tracking techniques, it was possible to visualize and quantify fiber/fiber area displacements as well as local fractures of single PCL fibers, considering quasi-static tensile load and fiber alignment. The possibility of displacement determination using in situ scanning electron microscopy techniques for testing fibrous PCL scaffolds was introduced and quantified. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

Long fiber reinforced thermoplastic composites are used for creating lightweight, but mechanically sound, automotive components. Injection molding is a manufacturing technique commonly used for traditional thermoplastics due to its efficiency and ability to create complex geometries. Injection molding feedstock is often in the form of pellets. Therefore, fiber composites must be chopped for use in this manufacturing method. The fibers are cut to a length of 13 mm and then fiber attrition occurs during processing. The combination of chopping the fibers into pellets and fiber breakage creates a distribution of mostly short fiber lengths, with some longer fibers remaining. Discontinuous fiber reinforcements are classified as long for aspect ratios greater than 100. For glass fibers, that distinction occurs at a length of 1 mm, and for carbon fibers 0.5 mm. Traditional composite materials and manufacturing processes utilize continuous fibers with a controlled orientation and length. The use of chopped discontinuous fibers requires a method to predict the orientation of the fibers in the final molded piece because mechanical properties are dependent on fiber length and orientation. The properties and behavior of the flow of a fiber reinforced polymer composite during molding are directly related to the mechanical properties of the completed part. Flow affects the orientation of the fibers within the polymer matrix and at locations within the mold cavity. The ability to predict, and ultimately control, flow properties allows for the efficient design of safe parts for industrial uses, such as vehicle parts in the automotive industry. The goal of this work is to test material characterization techniques developed for measuring and predicting the orientation of fiber reinforced injection molded thermoplastics using commercial grade long carbon fiber (LCF) reinforced nylon 6,6 (PA 6,6). Forty weight percent LCF/PA 6,6 with a weight averaged fiber length of 1.242 mm was inject

The anisotropy and strain rate dependence of the mechanical response of short-fiber-reinforced thermoplastics was studied using a straightforward micromechanical finite element analysis of representative volume elements (RVEs). RVEs are created based on the fiber orientation tensor, which quantifies the processing-induced fiber orientation distribution. The matrix is described by a strain rate-dependent constitutive model (the Eindhoven glassy polymer (EGP) model), which accurately captures the intrinsic response of amorphous polymers. The micromechanical results indicate that the influence of strain rate and that of the loading direction on the yield stress are multiplicatively decouplable, which confirms previous experimental observations. Moreover, it is demonstrated that the yield stress, to a good approximation, can be directly linked to the fiber orientation in the direction of loading. This leads to a new relation that uniquely links the rate dependence of the yield stress to the fiber orientation in loading direction.

The current study investigates the applicability of a dictionary-based fiber-detection algorithm for continuous textured glass fiber yarns in fiber-reinforced polymer composites. Additionally, the study discusses options for improving the fiber-detection algorithm so that it is applicable to continuous textured fiber yarns in fiber-reinforced polymers.

Packaging products find their significance in almost all classes of consumer goods and products. The use of plastic and metal based packaging for beverages is highly dominant. However, there is a constant urge for development of eco-friendly packaging alternatives. The article focuses on characterizing an inflatable core assisted paper bottle molding process with respect to the obtained fiber distribution in the bottle. Distribution of paper fibers affect product characteristics such as thickness and mechanical strength of the bottle. Assessment of fiber orientation using structure tensor analysis is therefore performed. The results confirmed non-uniform fiber compaction in the paper bottle. This gives rise to non-conformities such as non-uniform thickness distribution. The approach discussed in the work can be utilized as a Non Destructive Testing technique to evaluate the quality of paper bottles.

Native and engineered fiber-reinforced tissues are composites comprised of stiff collagen fibers embedded within an extrafibrillar matrix that is capable of swelling by absorbing water molecules. Tissue swelling is important for understanding stress distributions between collagen fibers and extrafibrillar matrix, as well as for understanding mechanisms of tissue failure. The swelling behavior of fiber-reinforced tissues in the musculoskeletal system has been largely attributed to the glycosaminoglycan content. Recent work demonstrated anisotropy in the swelling response of the annulus fibrosus in the intervertebral disc. It is well known that collagen fiber orientation affects elastic behavior, but the effect of collagen fiber network on tissue swelling behavior is not well understood. In this study, we developed three series of models to evaluate the effect of collagen fiber orientation, fiber network architecture (i.e., single or multi-fiber families within a layer), and fiber stiffness on bulk tissue swelling, which was simulated by describing the extrafibrillar matrix as a triphasic material, as proposed by Lai et al. Model results were within one standard deviation of reported mean values for changes in tissue volume, width, and thickness under free swelling conditions. The predicted swelling response of single-fiber family structures was highly dependent on fiber orientation and the number of lamellae in the bulk tissue. Moreover, matrix swelling resulted in tissue to twist, which reduced fiber deformations, demonstrating a balance between fiber deformation and matrix swelling. Large changes in fiber stiffness (20 × increase) had a relatively small effect on tissue swelling (~ 2% decrease in swelling). In conclusion, fiber angle, fiber architecture (defined as single- versus multiple fiber families in a layer), and the number of layers in a single fiber family structure directly affected tissue swelling behavior, including fiber stretch, fiber reorientation, a

Polymer-based piezoelectric biomaterials have already proven their relevance for tissue engineering applications. Furthermore, the morphology of the scaffolds plays also an important role in cell proliferation and differentiation. The present work reports on poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV), a biocompatible, biodegradable, and piezoelectric biopolymer that has been processed in different morphologies, including films, fibers, microspheres, and 3D scaffolds. The corresponding magnetically active PHBV-based composites were also produced. The effect of the morphology on physico-chemical, thermal, magnetic, and mechanical properties of pristine and composite samples was evaluated, as well as their cytotoxicity. It was observed that the morphology does not strongly affect the properties of the pristine samples but the introduction of cobalt ferrites induces changes in the degree of crystallinity that could affect the applicability of prepared biomaterials. Young's modulus is dependent of the morphology and also increases with the addition of cobalt ferrites. Both pristine and PHBV/cobalt ferrite composite samples are not cytotoxic, indicating their suitability for tissue engineering applications.

In recent years, flax fiber-reinforced polymers (FFRP) are being widely used due to their inherent properties comparable to those of glass fiber reinforced polymers (GFRP). They are partially biodegradable and light weight with good intrinsic modulus and strength. However, milling these composites introduces defects like a poor surface quality with a lot of uncut fibers. The main objective of this study is to analyze the effect of machining parameters and fiber orientation on the uncut fibers (characterized by the number and length of the uncut fibers) of unidirectional FFRP. A full Split-Split Plot Block design of experiment approach was conducted for the analysis. It is shown that the uncut fibers extent depends significantly on the feed rate, the fiber orientation and the cutting tool geometry. The cutting speed does not influence the quantity of uncut fibers. A low feed rate (0.05 mm/rev) and a cutting tool geometry which enhances the fibers shear with a zero-helix angle are shown to minimize the delamination during the up-milling process of unidirectional flax/epoxy composite.

In this article, the elastic properties of long-fiber injection-molded thermoplastics (LFTs) are investigated by micro-mechanical approaches including the Halpin-Tsai (HT) model and the Mori-Tanaka model based on Eshelby’s equivalent inclusion (EMT). In the modeling, the elastic properties are calculated by the fiber content, fiber length, and fiber orientation. Several closure approximations for the fourth-order fiber orientation tensor are evaluated by comparing the as-calculated elastic stiffness with that from the original experimental fourth-order tensor. An empirical model was developed to correct the fibers’ aspect ratio in the computation for the actual as-formed LFTs with fiber bundles under high fiber content. After the correction, the analytical predictions had good agreement with the experimental stiffness values from tensile tests on the LFTs. Our analysis shows that it is essential to incorporate the effect of the presence of fiber bundles to accurately predict the composite properties. This work involved the use of experimental values of fiber orientation and serves as the basis for computing part stiffness as a function of mold filling conditions. The work also explains why the modulus tends to level off with fiber concentration.

In this article, the elastic properties of long-fiber injection-molded thermoplastics (LFTs) are investigated by micro-mechanical approaches including the Halpin-Tsai (HT) model and the Mori-Tanaka model based on Eshelby’s equivalent inclusion (EMT). In the modeling, the elastic properties are calculated by the fiber content, fiber length, and fiber orientation. Several closure approximations for the fourth-order fiber orientation tensor are evaluated by comparing the as-calculated elastic stiffness with that from the original experimental fourth-order tensor. An empirical model was developed to correct the fibers’ aspect ratio in the computation for the actual as-formed LFTs with fiber bundles under high fiber content. After the correction, the analytical predictions had good agreement with the experimental stiffness values from tensile tests on the LFTs. Our analysis shows that it is essential to incorporate the effect of the presence of fiber bundles to accurately predict the composite properties. This work involved the use of experimental values of fiber orientation and serves as the basis for computing part stiffness as a function of mold filling conditions. The work also explains why the modulus tends to level off with fiber concentration.

Polymer-based piezoelectric biomaterials have already proven their relevance for tissue engineering applications. Furthermore, the morphology of the scaffolds plays also an important role in cell proliferation and differentiation. The present work reports on poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV), a biocompatible, biodegradable, and piezoelectric biopolymer that has been processed in different morphologies, including films, fibers, microspheres, and 3D scaffolds. The corresponding magnetically active PHBV-based composites were also produced. The effect of the morphology on physico-chemical, thermal, magnetic, and mechanical properties of pristine and composite samples was evaluated, as well as their cytotoxicity. It was observed that the morphology does not strongly affect the properties of the pristine samples but the introduction of cobalt ferrites induces changes in the degree of crystallinity that could affect the applicability of prepared biomaterials. Young's modulus is dependent of the morphology and also increases with the addition of cobalt ferrites. Both pristine and PHBV/cobalt ferrite composite samples are not cytotoxic, indicating their suitability for tissue engineering applications.

In this article, the elastic properties of long-fiber injection-molded thermoplastics (LFTs) are investigated by micro-mechanical approaches including the Halpin-Tsai (HT) model and the Mori-Tanaka model based on Eshelby’s equivalent inclusion (EMT). In the modeling, the elastic properties are calculated by the fiber content, fiber length, and fiber orientation. Several closure approximations for the fourth-order fiber orientation tensor are evaluated by comparing the as-calculated elastic stiffness with that from the original experimental fourth-order tensor. An empirical model was developed to correct the fibers’ aspect ratio in the computation for the actual as-formed LFTs with fiber bundles under high fiber content. After the correction, the analytical predictions had good agreement with the experimental stiffness values from tensile tests on the LFTs. Our analysis shows that it is essential to incorporate the effect of the presence of fiber bundles to accurately predict the composite properties. This work involved the use of experimental values of fiber orientation and serves as the basis for computing part stiffness as a function of mold filling conditions. The work also explains why the modulus tends to level off with fiber concentration.

Native and engineered fiber-reinforced tissues are composites comprised of stiff collagen fibers embedded within an extrafibrillar matrix that is capable of swelling by absorbing water molecules. Tissue swelling is important for understanding stress distributions between collagen fibers and extrafibrillar matrix, as well as for understanding mechanisms of tissue failure. The swelling behavior of fiber-reinforced tissues in the musculoskeletal system has been largely attributed to the glycosaminoglycan content. Recent work demonstrated anisotropy in the swelling response of the annulus fibrosus in the intervertebral disc. It is well known that collagen fiber orientation affects elastic behavior, but the effect of collagen fiber network on tissue swelling behavior is not well understood. In this study, we developed three series of models to evaluate the effect of collagen fiber orientation, fiber network architecture (i.e., single or multi-fiber families within a layer), and fiber stiffness on bulk tissue swelling, which was simulated by describing the extrafibrillar matrix as a triphasic material, as proposed by Lai et al. Model results were within one standard deviation of reported mean values for changes in tissue volume, width, and thickness under free swelling conditions. The predicted swelling response of single-fiber family structures was highly dependent on fiber orientation and the number of lamellae in the bulk tissue. Moreover, matrix swelling resulted in tissue to twist, which reduced fiber deformations, demonstrating a balance between fiber deformation and matrix swelling. Large changes in fiber stiffness (20 × increase) had a relatively small effect on tissue swelling (~ 2% decrease in swelling). In conclusion, fiber angle, fiber architecture (defined as single- versus multiple fiber families in a layer), and the number of layers in a single fiber family structure directly affected tissue swelling behavior, including fiber stretch, fiber reorientation, a

In recent years, flax fiber-reinforced polymers (FFRP) are being widely used due to their inherent properties comparable to those of glass fiber reinforced polymers (GFRP). They are partially biodegradable and light weight with good intrinsic modulus and strength. However, milling these composites introduces defects like a poor surface quality with a lot of uncut fibers. The main objective of this study is to analyze the effect of machining parameters and fiber orientation on the uncut fibers (characterized by the number and length of the uncut fibers) of unidirectional FFRP. A full Split-Split Plot Block design of experiment approach was conducted for the analysis. It is shown that the uncut fibers extent depends significantly on the feed rate, the fiber orientation and the cutting tool geometry. The cutting speed does not influence the quantity of uncut fibers. A low feed rate (0.05 mm/rev) and a cutting tool geometry which enhances the fibers shear with a zero-helix angle are shown to minimize the delamination during the up-milling process of unidirectional flax/epoxy composite.

An enhanced demand for lightweight materials in automotive applications has resulted in the growth of the use of injection molded discontinuous fiber-reinforced thermoplastics. During the intensive injection molding process, severe fiber breakage arises in the plasticating stage leading to a broad fiber length distribution. Fiber orientation distribution (FOD) is another highly anisotropic feature of the final injection molded parts induced by the mold filling process. The mechanical and other properties can be highly dependent on the fiber length distribution and fiber orientation distribution. The residual fiber length in the final part is of great significance determining the mechanical performances of injection molded discontinuous fiber reinforced thermoplastic composites. One goal of this research is to develop a fiber length characterization method with reproducible sampling procedure in a timely manner is described. In this work is also proposed an automatic fiber length measurement algorithm supported by Matlab®. The accuracy of this automatic algorithm is evaluated by comparing the measured results using this in-house developed tool with the manual measurement and good agreement between the two methods is observed. Accurate predictions of fiber orientation are also important for the improvement of mold design and processing parameters to optimize mechanical performances of fiber-reinforced thermoplastics. In various fiber orientation models, a strain reduction factor is usually applied to match the slower fiber orientation evolution observed experimentally. In this research, a variable strain reduction factor is determined locally by the corresponding local flow-type and used in fiber orientation simulation. The application of the variable strain reduction factor in fiber orientation simulations for both non-lubricated squeeze flow and injection molded center-gated disk, allows the simulated fiber re-orient rate to be dependent on the local flow-type. This

The design of fiber-reinforced thermoplastic (FRT) parts is hindered by the determination of the various empirical parameters associated with the fiber orientation models. A method for obtaining these parameters independent of processing doesn't exist. The work presented here continues efforts to develop a rheological test that can obtain robust orientation model parameters, either by fitting directly to orientation data or by fitting to stress-growth data. First, orientation evolution in a 10 wt% long-glass-fiber-reinforced polypropylene during two homogeneous flows (startup of shear and planar extension) was compared. This comparison had not been performed in the literature previously, and revealed that fiber orientation is significantly faster during planar extension. This contradicts a long-held assumption in the field that orientation dynamics were independent of the type of flow. In other words, shear and extension were assumed to have equal influence on the orientation dynamics. A non-lubricated squeeze flow test was subsequently implemented on 30 wt% short-glass-fiber-reinforced polypropylene. An analytical solution was developed for the Newtonian case along the lateral centerline of the sample to demonstrate that the flow is indeed a superposition of shear and extension. Furthermore, an existing fiber orientation model was fit to the gap-wise orientation profile, demonstrating that NLSF can, in principle, be used to obtain fiber orientation model parameters. Finally, model parameters obtained for the same FRT by fitting to orientation data from startup of steady shear are shown to be inadequate in predicting the gap-wise orientation profile from NLSF. This work is rounded out with a comparison of the fiber orientation dynamics during startup of shear and non-lubricated squeeze flow using a long-fiber-reinforced polypropylene. Three fiber concentrations (30, 40, and 50 wt%) were used to gauge the influence of fiber concentration on the orientation dynamics.

Polymer-based piezoelectric biomaterials have already proven their relevance for tissue engineering applications. Furthermore, the morphology of the scaffolds plays also an important role in cell proliferation and differentiation. The present work reports on poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV), a biocompatible, biodegradable, and piezoelectric biopolymer that has been processed in different morphologies, including films, fibers, microspheres, and 3D scaffolds. The corresponding magnetically active PHBV-based composites were also produced. The effect of the morphology on physico-chemical, thermal, magnetic, and mechanical properties of pristine and composite samples was evaluated, as well as their cytotoxicity. It was observed that the morphology does not strongly affect the properties of the pristine samples but the introduction of cobalt ferrites induces changes in the degree of crystallinity that could affect the applicability of prepared biomaterials. Young's modulus is dependent of the morphology and also increases with the addition of cobalt ferrites. Both pristine and PHBV/cobalt ferrite composite samples are not cytotoxic, indicating their suitability for tissue engineering applications.

In this article, the elastic properties of long-fiber injection-molded thermoplastics (LFTs) are investigated by micro-mechanical approaches including the Halpin-Tsai (HT) model and the Mori-Tanaka model based on Eshelby’s equivalent inclusion (EMT). In the modeling, the elastic properties are calculated by the fiber content, fiber length, and fiber orientation. Several closure approximations for the fourth-order fiber orientation tensor are evaluated by comparing the as-calculated elastic stiffness with that from the original experimental fourth-order tensor. An empirical model was developed to correct the fibers’ aspect ratio in the computation for the actual as-formed LFTs with fiber bundles under high fiber content. After the correction, the analytical predictions had good agreement with the experimental stiffness values from tensile tests on the LFTs. Our analysis shows that it is essential to incorporate the effect of the presence of fiber bundles to accurately predict the composite properties. This work involved the use of experimental values of fiber orientation and serves as the basis for computing part stiffness as a function of mold filling conditions. The work also explains why the modulus tends to level off with fiber concentration.

In this article, the elastic properties of long-fiber injection-molded thermoplastics (LFTs) are investigated by micro-mechanical approaches including the Halpin-Tsai (HT) model and the Mori-Tanaka model based on Eshelby’s equivalent inclusion (EMT). In the modeling, the elastic properties are calculated by the fiber content, fiber length, and fiber orientation. Several closure approximations for the fourth-order fiber orientation tensor are evaluated by comparing the as-calculated elastic stiffness with that from the original experimental fourth-order tensor. An empirical model was developed to correct the fibers’ aspect ratio in the computation for the actual as-formed LFTs with fiber bundles under high fiber content. After the correction, the analytical predictions had good agreement with the experimental stiffness values from tensile tests on the LFTs. Our analysis shows that it is essential to incorporate the effect of the presence of fiber bundles to accurately predict the composite properties. This work involved the use of experimental values of fiber orientation and serves as the basis for computing part stiffness as a function of mold filling conditions. The work also explains why the modulus tends to level off with fiber concentration.

In recent years, flax fiber-reinforced polymers (FFRP) are being widely used due to their inherent properties comparable to those of glass fiber reinforced polymers (GFRP). They are partially biodegradable and light weight with good intrinsic modulus and strength. However, milling these composites introduces defects like a poor surface quality with a lot of uncut fibers. The main objective of this study is to analyze the effect of machining parameters and fiber orientation on the uncut fibers (characterized by the number and length of the uncut fibers) of unidirectional FFRP. A full Split-Split Plot Block design of experiment approach was conducted for the analysis. It is shown that the uncut fibers extent depends significantly on the feed rate, the fiber orientation and the cutting tool geometry. The cutting speed does not influence the quantity of uncut fibers. A low feed rate (0.05 mm/rev) and a cutting tool geometry which enhances the fibers shear with a zero-helix angle are shown to minimize the delamination during the up-milling process of unidirectional flax/epoxy composite.

In this paper, an infrared thermography technique is used to assess the fiber orientation on the surface of carbon fiber reinforced polymer (CFRP) moulded with randomly-oriented strands (ROS). Due to the randomness of the material, a point by point inspection would be very time consuming. In this paper it is proposed to use a flying laser spot technique to heat a line-region on the surface of the sample instead of a spot. During our experiments, a flying laser spot inspection was performed in 30 s while a point by point inspection of the same area would require about 25 min. An artificial neural network (ANN) was then used to estimate the fiber orientation over the heated line. The classification rate obtained with the network was 91.2% for the training stage and 71.6% for the testing stage.

The use of composite materials is growing more and more every day in several applications. The arrangement or orientation of the fibers relative to one another have a significant influence on the strength and other properties of fiber reinforced composites. Thus, evaluation techniques are needed for measuring material fiber orientation. In this work infrared thermography is employed to assess the material’s fiber orientation. More specifically a pulsed infrared diode laser heating spot technique combined with a 3D model of the part is used in order to assess fiber orientation on the surface of carbon fiber-reinforced polymer complex shaped parts made of carbon/PEEK (Polyether ether ketone) randomly-oriented strands.

[EN] The aim of this work is to develop the process and tools to consider in Ansys the mechanical behavior and their temperature dependence of a short fiber reinforced polymeric material, for injection components, where fiber distribution it's known., [ES] El objetivo de éste trabajo es desarrollar un procedimiento y las herramientas necesarias, para considerar en Ansys el comportamiento mecánico y su dependencia con la temperatura de un material polimérico reforzado con fibra corta, para componentes fabricados mediante inyección, de los que se conoce la distribución de la fibra.

[EN] The aim of this work is to develop the process and tools to consider in Ansys the mechanical behavior and their temperature dependence of a short fiber reinforced polymeric material, for injection components, where fiber distribution it's known., [ES] El objetivo de éste trabajo es desarrollar un procedimiento y las herramientas necesarias, para considerar en Ansys el comportamiento mecánico y su dependencia con la temperatura de un material polimérico reforzado con fibra corta, para componentes fabricados mediante inyección, de los que se conoce la distribución de la fibra.

The mechanical performance of glass fiber-reinforced polymers depends on temperature, humidity and strain rate, and also depends on the volume fraction of fiber reinforcements and the anisotropy which is caused by fiber orientation and orientation distribution.

Two grades of 30 weight% short fiber reinforced polypropylene were processed by conventional injection moulding (skin core fiber orientation) and push pull technology (high and uniform fiber orientation in flow direction) to plates. Samples were taken out to determine fiber orientation, mean fiber length, static mechanical properties as well as creep-compliance curves parallel and perpendicular to the flow direction. The creep compliances parallel and perpendicular to the flow direction were modeled using the elementary volume concept (EVC) which assumes that a single elementary volume consisting of a matrix part and a composite part can be used to reproduce the mechanical performance of a short fiber composite. The EVC predicts that the time dependent creep of a short fiber composite depends only on the creep of the pure polymer matrix, fiber volume content, aspect ratio and stiffness of both matrix and fiber. The creep compliance parallel to the flow direction is significantly smaller than perpendicular to it. The measured creep behavior is well reproduced by calculated creep compliances derived by the EVC for the first 2 decades but for longer times experimental data are overestimated. Obviously the presence of fibers generates boundary conditions which change the creep kinetics of the matrix part. The calculated creep curves perpendicular to the flow direction are systematically smaller than the measured curves. However, this can be overcome by the introduction of an adhesion factor which reduces the reinforcement efficiency of the composite part, thus accounting for different fiber matrix adhesions. © 2016, European Conference on Composite Materials, ECCM. All rights reserved.

The inductive method has shown to be a good method for the estimation of fiber dosage in steel-fiber-reinforced concrete. The current formulations reported a strong correlation between inductance and fiber content, as well as orientation. The objective of this paper is to study how the inductive measurements are affected by fiber properties, such as its dimensions, magnetic characteristics, and sample temperature. The results obtained from numerical, simulated, and experimental data propose a shape factor to be applied in the measurements to take into account the aspect ratio of fibers. They also show that the magnetic composition of the fibers is of great importance. As for temperature, the error introduced is less than 1%, so a corrective factor is not essential., Peer Reviewed, Postprint (author's final draft)

The mechanical performance of glass fiber-reinforced polymers depends on temperature, humidity and strain rate, and also depends on the volume fraction of fiber reinforcements and the anisotropy which is caused by fiber orientation and orientation distribution.

Two grades of 30 weight% short fiber reinforced polypropylene were processed by conventional injection moulding (skin core fiber orientation) and push pull technology (high and uniform fiber orientation in flow direction) to plates. Samples were taken out to determine fiber orientation, mean fiber length, static mechanical properties as well as creep-compliance curves parallel and perpendicular to the flow direction. The creep compliances parallel and perpendicular to the flow direction were modeled using the elementary volume concept (EVC) which assumes that a single elementary volume consisting of a matrix part and a composite part can be used to reproduce the mechanical performance of a short fiber composite. The EVC predicts that the time dependent creep of a short fiber composite depends only on the creep of the pure polymer matrix, fiber volume content, aspect ratio and stiffness of both matrix and fiber. The creep compliance parallel to the flow direction is significantly smaller than perpendicular to it. The measured creep behavior is well reproduced by calculated creep compliances derived by the EVC for the first 2 decades but for longer times experimental data are overestimated. Obviously the presence of fibers generates boundary conditions which change the creep kinetics of the matrix part. The calculated creep curves perpendicular to the flow direction are systematically smaller than the measured curves. However, this can be overcome by the introduction of an adhesion factor which reduces the reinforcement efficiency of the composite part, thus accounting for different fiber matrix adhesions. © 2016, European Conference on Composite Materials, ECCM. All rights reserved.

Despite the remarkable advances in the field of macro-synthetic fibre reinforced concrete, the successful use of plastic macro-fibres as the sole reinforcement in structural elements still requires thorough research. Several questions hindering its wide-spread use have yet to be addressed. Do plastic fibres guarantee a clearly defined structural reliability? Is there any influence of the formwork and casting method on the orientation of this fibres? Does this orientation affects the structural behavior of the slabs? To answer these questions this paper focuses on the study of the structural response of hyperstatic concrete flat suspended slabs with different width/length ratio reinforced only with structural plastic macro-fibres. First, the experimental program is described and then the structural results obtained are presented. Then, a study of the influence of flowability and wall-effects of the formwork in the orientation pattern of macro-plastic fibres is carried out in order to identify the preferential orientation of fibres caused by the geometry of slabs., Postprint (published version)

Steel Fiber Reinforced Concrete (SFRC) still deserves much research because some aspects of its tension response have to be better predicted. It is accepted that the mechanical properties are intimately linked to the fiber orientation within the matrix. To determine the contribution of the fibers to the tension response is necessary to know as precisely as possible the amount of existing fibers and their orientation. Computerized Tomography (CT) is the most effective way to determine the orientation of the fibers embedded in the concrete. An experimental program consisting of analyzing 34 cylindrical cores, extracted from 9 SFRC beam specimens made with three different fiber amounts, was performed. An image recognition software was developed for determining the position and orientation of the fibers from the scans. Fiber orientation has been quantified by the two most common parameters, the orientation number and the director. The influence of factors such as the fiber content, the direction of flow or the separation to the mold walls in the fiber orientation is analyzed. Finally, a research for the best fitting probability distribution function is presented and discussed., Postprint (published version)

The use of composite materials is growing more and more every day in several applications. The arrangement or orientation of the fibers relative to one another have a significant influence on the strength and other properties of fiber reinforced composites. Thus, evaluation techniques are needed for measuring material fiber orientation. In this work infrared thermography is employed to assess the material’s fiber orientation. More specifically a pulsed infrared diode laser heating spot technique combined with a 3D model of the part is used in order to assess fiber orientation on the surface of carbon fiber-reinforced polymer complex shaped parts made of carbon/PEEK (Polyether ether ketone) randomly-oriented strands.

In this paper, an infrared thermography technique is used to assess the fiber orientation on the surface of carbon fiber reinforced polymer (CFRP) moulded with randomly-oriented strands (ROS). Due to the randomness of the material, a point by point inspection would be very time consuming. In this paper it is proposed to use a flying laser spot technique to heat a line-region on the surface of the sample instead of a spot. During our experiments, a flying laser spot inspection was performed in 30 s while a point by point inspection of the same area would require about 25 min. An artificial neural network (ANN) was then used to estimate the fiber orientation over the heated line. The classification rate obtained with the network was 91.2% for the training stage and 71.6% for the testing stage.

Within this research, factors affecting the orientation of injection molded long fiber composites in an end-gated plaque were investigated. Matrix viscosity was found to have a small effect on fiber orientation. The impact matrix viscosity had on orientation was dependent on fiber loading. At lower fiber loadings, the higher viscosity material had a more asymmetric orientation profile throughout the samples and less of a shell-core-shell orientation. At higher fiber loadings, there were few differences in orientation due to matrix viscosity. Fiber concentration was found to have a larger influence on fiber orientation than matrix viscosity. Increased fiber concentration led to a lower degree of flow alignment and a broader core region at all locations examined, following the trend previously reported for short fiber composites. The orientations of three different fiber length distributions of glass fiber (GF) were compared. The longer fibers in the fiber length distribution were shown to have a disproportionate effect on orientation, with weight average aspect ratio being better than number average aspect ratio at indicating if the GF and CF samples orientated comparably. To improve properties transverse to the main flow direction, the super critical carbon dioxide aided deagglomeration of multi-walled carbon nanotubes (CNTs) was used to create injection molded multiscale composites with CNT, CF, and polypropylene. The addition of CNTs greatly improved the tensile and electrical properties of the composites compared to those without CNTs. The degree of improvement from adding CNTs was found to be dependent on CF concentration, indicating that the CNTs were most likely interacting with the CF and not the polymer. A CNT concentration of 1 wt% with a tenfold degree of expansion at 40 wt% CF proved to be optimum. A large improvement in the tensile properties transverse to the flow direction was found implying that the CNTs were not highly flow aligned. Tensile and elect

Within this research, factors affecting the orientation of injection molded long fiber composites in an end-gated plaque were investigated. Matrix viscosity was found to have a small effect on fiber orientation. The impact matrix viscosity had on orientation was dependent on fiber loading. At lower fiber loadings, the higher viscosity material had a more asymmetric orientation profile throughout the samples and less of a shell-core-shell orientation. At higher fiber loadings, there were few differences in orientation due to matrix viscosity. Fiber concentration was found to have a larger influence on fiber orientation than matrix viscosity. Increased fiber concentration led to a lower degree of flow alignment and a broader core region at all locations examined, following the trend previously reported for short fiber composites. The orientations of three different fiber length distributions of glass fiber (GF) were compared. The longer fibers in the fiber length distribution were shown to have a disproportionate effect on orientation, with weight average aspect ratio being better than number average aspect ratio at indicating if the GF and CF samples orientated comparably. To improve properties transverse to the main flow direction, the super critical carbon dioxide aided deagglomeration of multi-walled carbon nanotubes (CNTs) was used to create injection molded multiscale composites with CNT, CF, and polypropylene. The addition of CNTs greatly improved the tensile and electrical properties of the composites compared to those without CNTs. The degree of improvement from adding CNTs was found to be dependent on CF concentration, indicating that the CNTs were most likely interacting with the CF and not the polymer. A CNT concentration of 1 wt% with a tenfold degree of expansion at 40 wt% CF proved to be optimum. A large improvement in the tensile properties transverse to the flow direction was found implying that the CNTs were not highly flow aligned. Tensile and elect

This work is concerned with determining empirical parameters in stress and fiber orientation models required to accurately simulate the fiber orientation in injection molded composites. An independent approach aims to obtain the material parameters using a sliding plate rheometer to measure the rheology of fiber suspensions at increased fiber lengths subjected to transient shear flow. Fiber orientation was measured in conjunction with shear stress to determine the relationship between stress and fiber orientation. Using a compression molding sample preparation procedure, the transient shear stress response was measured for glass and carbon fiber suspensions up to a number average fiber aspect ratio (length/diameter) of 100. Increases in concentration or fiber aspect ratio caused the magnitude of the stress response to increase by as much as an order of magnitude when compared to the suspending matrix. The degree of shear thinning at low shear rates also increased with increases in aspect ratio and concentration. The compression molding sample preparation procedure provided poor control of the initial fiber orientation which led to the investigation of samples subjected to flow reversal and samples generated through injection molding. The samples prepared through injection molding provided improved repeatability in the measured shear stress response and fiber orientation evolution during the startup of flow compared to compression molded samples and samples subjected to flow reversal. From repeatable stress and orientation evolution data, models for stress and fiber orientation were assessed independently. Current theories for stress were unable to reflect the overshoot in the measured stress response and could at best capture the steady state. The transient behavior of the fiber orientation models were found to be highly dependent on the initial fiber orientation. The repeatable orientation data obtained from the injection molding sample preparation procedure provid

Numerical models generating actual fiber architecture by including parameters such as the fiber geometry and arrangement are a powerful tool to explore the relation between the fiber architecture and mechanical properties. The generation of virtual architectures of fibrous materials is the first step toward the computation of their physical properties. In this work, a realistic 3D model is developed to describe the architecture of a complex fiber structure. The domain of application of the model could include natural fibers composites, wood fibers materials, papers, mineral and steel wools and polymer networks. The model takes into account the complex geometry of the fiber arrangement in which a fiber can be modeled with a certain degree of bending while keeping a main fiber orientation. The model is built in two steps. First, fibers are generated as a chain of overlapping spheres or as a chain of overlapping sphero-cylinders. At the end of the first step, a system of overlapping fibers is obtained. In order to obtain a hard-core configuration where fibers cannot overlap other fibers, we use an iterative method called the force-biased algorithm. It applies virtual forces on each point of the fiber: a repulsion force to suppress the overlap between two fibers and a bending and stretching force to ensure that the fiber structure is kept unchanged. The model can be used as the geometrical basis for further finite-element modelling.

[EN] First, an exhaustive revision of the state of art on 3D cardiac models has been carried out, focusing on material and methods used for their construction. As main goal of the work, a 3D cardiac model has also been developed based on in-vivo medical images, including a realistic representation of the two whole ventricles up to the cardiac valves' planes, the cardiac fiber orientation, the cardiac conduction system and an ischemic scar on the left ventricle due to a myocardial infarction. This model has been constructed to be used in 3D realistic cardiac electrophysiology simulations., [ES] En primer lugar, se ha realizado una exhaustiva revisión del estado del arte sobre los modelos cardíacos 3D, prestando especial atención al material y los métodos empleados en su construcción. Como objetivo principal del trabajo, también se ha desarrollado un modelo cardíaco 3D a partir de imagen médica in-vivo, incluyendo una representación realista de los dos ventrículos completos hasta los planos de las válvulas cardíacas, la orientación de las fibras cardíacas, el sistema de conducción cardíaco y una escara isquémica sobre el ventrículo izquierdo provocada por un infarto de miocardio. Este modelo se ha construido para su uso en simulaciones realistas de electrofisiología cardíaca en 3D.

[EN] First, an exhaustive revision of the state of art on 3D cardiac models has been carried out, focusing on material and methods used for their construction. As main goal of the work, a 3D cardiac model has also been developed based on in-vivo medical images, including a realistic representation of the two whole ventricles up to the cardiac valves' planes, the cardiac fiber orientation, the cardiac conduction system and an ischemic scar on the left ventricle due to a myocardial infarction. This model has been constructed to be used in 3D realistic cardiac electrophysiology simulations., [ES] En primer lugar, se ha realizado una exhaustiva revisión del estado del arte sobre los modelos cardíacos 3D, prestando especial atención al material y los métodos empleados en su construcción. Como objetivo principal del trabajo, también se ha desarrollado un modelo cardíaco 3D a partir de imagen médica in-vivo, incluyendo una representación realista de los dos ventrículos completos hasta los planos de las válvulas cardíacas, la orientación de las fibras cardíacas, el sistema de conducción cardíaco y una escara isquémica sobre el ventrículo izquierdo provocada por un infarto de miocardio. Este modelo se ha construido para su uso en simulaciones realistas de electrofisiología cardíaca en 3D.