The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform

Christoph Broeckmann - One of the best experts on this subject based on the ideXlab platform.

  • influence of the interface strength on the mechanical properties of discontinuous tungsten fiber reinforced tungsten composites produced by field assisted sintering technology
    Composites Part A-applied Science and Manufacturing, 2018
    Co-Authors: J W Coenen, J Riesch, S Sistla, J Almanstotter, B Jasper, A Terra, T Hoschen, H Gietl, Ch Linsmeier, Christoph Broeckmann
    Abstract:

    Abstract In future fusion reactors, tungsten is a main candidate material for plasma-facing components. However, the intrinsic brittleness of tungsten is an issue under the extreme fusion environment. To overcome this drawback, tungsten fiber-reinforced tungsten (W f /W) composites are being developed relying on an extrinsic toughening principle. In this study W f /W composites are produced by a Field-Assisted Sintering Technology (FAST) process with different fiber–matrix Interfaces. The fracture behavior was studied by 3-point bending tests on notched samples. 4-point bending tests and tensile tests are performed to measure the flexural strength and tensile strength, respectively. W f /W with a weak interface shows a typical pseudo-ductile fracture behavior, similar to ceramic matrix composites. A strong interface is beneficial to achieve higher flexural strength and tensile strength, but in turn, weakens the pseudo-ductile behavior.

T Hoschen - One of the best experts on this subject based on the ideXlab platform.

  • influence of the interface strength on the mechanical properties of discontinuous tungsten fiber reinforced tungsten composites produced by field assisted sintering technology
    Composites Part A-applied Science and Manufacturing, 2018
    Co-Authors: J W Coenen, J Riesch, S Sistla, J Almanstotter, B Jasper, A Terra, T Hoschen, H Gietl, Ch Linsmeier, Christoph Broeckmann
    Abstract:

    Abstract In future fusion reactors, tungsten is a main candidate material for plasma-facing components. However, the intrinsic brittleness of tungsten is an issue under the extreme fusion environment. To overcome this drawback, tungsten fiber-reinforced tungsten (W f /W) composites are being developed relying on an extrinsic toughening principle. In this study W f /W composites are produced by a Field-Assisted Sintering Technology (FAST) process with different fiber–matrix Interfaces. The fracture behavior was studied by 3-point bending tests on notched samples. 4-point bending tests and tensile tests are performed to measure the flexural strength and tensile strength, respectively. W f /W with a weak interface shows a typical pseudo-ductile fracture behavior, similar to ceramic matrix composites. A strong interface is beneficial to achieve higher flexural strength and tensile strength, but in turn, weakens the pseudo-ductile behavior.

  • shear debonding behavior of a carbon coated interface in a tungsten fiber reinforced tungsten matrix composite
    Journal of Nuclear Materials, 2011
    Co-Authors: T Hoschen, M. Rasinski, J H You
    Abstract:

    Abstract One of the crucial issues related to structural application of tungsten for fusion reactor components is its brittleness. To improve tungsten toughness we explored a novel toughening method based on W fiber reinforcement. The idea is to utilize the effective energy dissipation caused by controlled cracking and friction at fiber/matrix Interfaces. To realize this, the Interfaces need to be engineered by means of adequate coating. In this work we investigated fracture behavior of a carbon-coated (0.6 μm) interface in a single-filament mini-composite using fiber push-out test. The composite was fabricated by CVD process. Mechanical parameters were determined by fitting the related theoretical models with the experimental data. Calibrated fracture energy and debonding strength was 7.4 J/m 2 and 285 MPa, respectively. This fracture energy value satisfied the theoretical criterion of controlled crack deflection. The result of the carbon coating was compared to the case of uncoated interface which exhibited stronger friction.

  • Feasibility Study of a Tungsten Wire Reinforced Tungsten Matrix Composite with ZrO Interfacial Coatings
    Composites Science and Technology, 2007
    Co-Authors: J. Du, T Hoschen, M. Rasinski, S. Wurster, W. Grosinger
    Abstract:

    Brittleness problem imposes a severe restriction on the potential application of tungsten as high-temperature structural material. In this paper, a novel toughening method for tungsten is proposed based on reinforcement by tungsten wires. The underlying toughening mechanism is analogous to that of fiber-reinforced ceramic matrix composites. Strain energy is dissipated by debonding and frictional sliding at engineered fiber/matrix Interfaces. To achieve maximum composite toughness fracture mechanical properties have to be optimized by interface coating. In this work, we evaluated six kinds of ZrOx-based interface coatings. Interfacial parameters such as shear strength and fracture energy were determined by means of fiber push-out tests. The parameter values of the six coatings were comparable to each other and satisfied the criterion for crack deflection. Microscopic analysis showed that debonding occurred mostly between the W filament and the ZrO coating. Feasibility of interfacial crack deflection was also demonstrated by a three-point bending test.

Yoshikazu Sano - One of the best experts on this subject based on the ideXlab platform.

  • Single-fiber pull-out analysis comparing the intensities of singular stress fields (ISSFs) at fiber end/entry points
    International Journal of Mechanical Sciences, 2020
    Co-Authors: Nao-aki Noda, Dong Chen, Guowei Zhang, Yoshikazu Sano
    Abstract:

    Abstract This paper deals with a partially-embedded single-fiber under pull-out force in comparison with a single fiber embedded in matrix focusing on two distinct singular stress fields. Then, the intensities of the singular stress fields (ISSFs) are compared at the fiber end named Point A and the fiber/surface intersection named Point E. The results show that if the embedded length lin is shorter, interface debonding may occur at Point A. Instead, if lin is longer, the interface debonding may occur at Point E. To analyze the ISSFs accurately, a mesh-independent technique coupled with the finite element method (FEM) is indicated by applying the same FEM mesh pattern to the pull-out model and the reference model. As the reference solution, a single fiber embedded in matrix is also calculated under arbitrary material combinations by using the body force method (BFM). Stress distributions along the fiber/matrix Interfaces are also calculated for carbon and glass fibers.

  • single fiber pull out analysis comparing the intensities of singular stress fields issfs at fiber end entry points
    International Journal of Mechanical Sciences, 2020
    Co-Authors: Nao-aki Noda, Dong Chen, Guowei Zhang, Yoshikazu Sano
    Abstract:

    Abstract This paper deals with a partially-embedded single-fiber under pull-out force in comparison with a single fiber embedded in matrix focusing on two distinct singular stress fields. Then, the intensities of the singular stress fields (ISSFs) are compared at the fiber end named Point A and the fiber/surface intersection named Point E. The results show that if the embedded length lin is shorter, interface debonding may occur at Point A. Instead, if lin is longer, the interface debonding may occur at Point E. To analyze the ISSFs accurately, a mesh-independent technique coupled with the finite element method (FEM) is indicated by applying the same FEM mesh pattern to the pull-out model and the reference model. As the reference solution, a single fiber embedded in matrix is also calculated under arbitrary material combinations by using the body force method (BFM). Stress distributions along the fiber/matrix Interfaces are also calculated for carbon and glass fibers.

J W Coenen - One of the best experts on this subject based on the ideXlab platform.

  • influence of the interface strength on the mechanical properties of discontinuous tungsten fiber reinforced tungsten composites produced by field assisted sintering technology
    Composites Part A-applied Science and Manufacturing, 2018
    Co-Authors: J W Coenen, J Riesch, S Sistla, J Almanstotter, B Jasper, A Terra, T Hoschen, H Gietl, Ch Linsmeier, Christoph Broeckmann
    Abstract:

    Abstract In future fusion reactors, tungsten is a main candidate material for plasma-facing components. However, the intrinsic brittleness of tungsten is an issue under the extreme fusion environment. To overcome this drawback, tungsten fiber-reinforced tungsten (W f /W) composites are being developed relying on an extrinsic toughening principle. In this study W f /W composites are produced by a Field-Assisted Sintering Technology (FAST) process with different fiber–matrix Interfaces. The fracture behavior was studied by 3-point bending tests on notched samples. 4-point bending tests and tensile tests are performed to measure the flexural strength and tensile strength, respectively. W f /W with a weak interface shows a typical pseudo-ductile fracture behavior, similar to ceramic matrix composites. A strong interface is beneficial to achieve higher flexural strength and tensile strength, but in turn, weakens the pseudo-ductile behavior.

T E Matikas - One of the best experts on this subject based on the ideXlab platform.

  • fracture strength and damage progression of the fiber matrix Interfaces in titanium based mmcs with different interfacial layers
    Composites Part B-engineering, 1998
    Co-Authors: Leon L Shaw, Prasanna Karpur, T E Matikas
    Abstract:

    Abstract In this paper, a concerted utilization of finite element analysis and an ultrasonic characterization technique is described to assess the interfacial fracture strength and to monitor the progression of damage at the interfacial region in titanium-based metal-matrix composites. The finite element model developed here encompasses an interfacial element with a finite thickness to simulate the interfacial region of the coating or reaction products. The finite element model has been used in conjunction with the ultrasonic evaluation technique to assess the in situ interfacial fracture strength. The different responses of the ultrasonic amplitudes for Ti-6A1-4V/SCS-0 SiC and Ti-6A1-4V/ SCS-6 SiC Interfaces have been explained in terms of the reflection of ultrasonic waves from the fiber/matrix interface. It is established that the non-monotonic stress dependence of the ultrasonic reflection amplitude for both the SCS-0 and SCS-6 Interfaces is related to the debonding between the fiber and matrix. The results indicate that the SCS-0 interface has a much higher fracture strength than the SCS-6 interface although both these Interfaces exhibit similar apparent debonding stresses.

  • Fracture strength and damage progression of the fiber/matrix Interfaces in titanium-based MMCs with different interfacial layers
    Composites Part B: Engineering, 1998
    Co-Authors: Leon L Shaw, Prasanna Karpur, T E Matikas
    Abstract:

    Abstract In this paper, a concerted utilization of finite element analysis and an ultrasonic characterization technique is described to assess the interfacial fracture strength and to monitor the progression of damage at the interfacial region in titanium-based metal-matrix composites. The finite element model developed here encompasses an interfacial element with a finite thickness to simulate the interfacial region of the coating or reaction products. The finite element model has been used in conjunction with the ultrasonic evaluation technique to assess the in situ interfacial fracture strength. The different responses of the ultrasonic amplitudes for Ti-6A1-4V/SCS-0 SiC and Ti-6A1-4V/ SCS-6 SiC Interfaces have been explained in terms of the reflection of ultrasonic waves from the fiber/matrix interface. It is established that the non-monotonic stress dependence of the ultrasonic reflection amplitude for both the SCS-0 and SCS-6 Interfaces is related to the debonding between the fiber and matrix. The results indicate that the SCS-0 interface has a much higher fracture strength than the SCS-6 interface although both these Interfaces exhibit similar apparent debonding stresses.