TY - JOUR
T1 - Anisotropic strength and fracture resistance of epoxy-ceramic composite materials produced by ultrasound freeze-casting
AU - Tanaka, Carina B.
AU - Mroz, Max
AU - Naleway, Steven E.
AU - Kruzic, Jamie J.
N1 - Funding Information:
This work was supported in part by the National Science Foundation of the United States under grant CMMI # 1660979 . The authors acknowledge the facilities and the scientific and technical assistance of Microscopy Australia at the Electron Microscope Unit (EMU) within the Mark Wainwright Analytical Centre (MWAC) at UNSW Sydney, Australia.
Funding Information:
This work was supported in part by the National Science Foundation of the United States under grant CMMI # 1660979. The authors acknowledge the facilities and the scientific and technical assistance of Microscopy Australia at the Electron Microscope Unit (EMU) within the Mark Wainwright Analytical Centre (MWAC) at UNSW Sydney, Australia.
Publisher Copyright:
© 2021 Elsevier Ltd and Techna Group S.r.l.
PY - 2022/2/15
Y1 - 2022/2/15
N2 - The anisotropic mechanical properties of ultrasound freeze cast epoxy-ceramic composite materials were studied by measuring flexural strength and fracture resistance curves (R-curves) using both unnotched and notched three-point beam bending experiments, respectively, cut in three different orientations relative to the directional freezing axis. Three ultrasound frequencies of 0.699, 1.39 and 2.097 MHz were used in order to introduce different length scales into the microstructure, with 0 MHz used as the control samples. For all cases, the composites showed higher strength and fracture resistance when the crack plane cut across the direction of ice growth (denoted as the YX orientation). The anisotropic properties were more evident for the material produced without ultrasound (0 MHz) where the flexural strength was approximately 160% higher for the YX orientation compared to two orthogonal orientations. Most of the fracture resistance increase was found to occur within a crack extension, Δa, of ∼0.5 mm. Comparing the fracture resistance at Δa = 0.5 mm for the highly anisotropic 0 MHz samples showed that the YX orientation was approximately 86% tougher than the two orthogonal orientations. When the ultrasound operation frequencies of 0.699, 1.39 and 2.097 MHz were applied, the amount of anisotropy in the strength and fracture resistance gradually decreased as the operating frequency increased. The high strength and fracture resistance for the YX orientation was attributed to the alignment of the ceramic particles along the freeze front direction creating a barrier for crack propagation. Ultrasound modifies the material microstructure, introducing relatively dense ceramic layers perpendicular to the freezing front direction that act as an additional, orthogonal barrier to crack propagation. The addition of the denser layers acts to improve the mechanical properties in the weaker orientations and reduce the overall anisotropy.
AB - The anisotropic mechanical properties of ultrasound freeze cast epoxy-ceramic composite materials were studied by measuring flexural strength and fracture resistance curves (R-curves) using both unnotched and notched three-point beam bending experiments, respectively, cut in three different orientations relative to the directional freezing axis. Three ultrasound frequencies of 0.699, 1.39 and 2.097 MHz were used in order to introduce different length scales into the microstructure, with 0 MHz used as the control samples. For all cases, the composites showed higher strength and fracture resistance when the crack plane cut across the direction of ice growth (denoted as the YX orientation). The anisotropic properties were more evident for the material produced without ultrasound (0 MHz) where the flexural strength was approximately 160% higher for the YX orientation compared to two orthogonal orientations. Most of the fracture resistance increase was found to occur within a crack extension, Δa, of ∼0.5 mm. Comparing the fracture resistance at Δa = 0.5 mm for the highly anisotropic 0 MHz samples showed that the YX orientation was approximately 86% tougher than the two orthogonal orientations. When the ultrasound operation frequencies of 0.699, 1.39 and 2.097 MHz were applied, the amount of anisotropy in the strength and fracture resistance gradually decreased as the operating frequency increased. The high strength and fracture resistance for the YX orientation was attributed to the alignment of the ceramic particles along the freeze front direction creating a barrier for crack propagation. Ultrasound modifies the material microstructure, introducing relatively dense ceramic layers perpendicular to the freezing front direction that act as an additional, orthogonal barrier to crack propagation. The addition of the denser layers acts to improve the mechanical properties in the weaker orientations and reduce the overall anisotropy.
KW - Ceramic scaffolds
KW - Composites
KW - Fracture toughness
KW - Freeze casting
KW - Strength
KW - Ultrasound
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U2 - 10.1016/j.ceramint.2021.11.027
DO - 10.1016/j.ceramint.2021.11.027
M3 - Article
AN - SCOPUS:85119040796
SN - 0272-8842
VL - 48
SP - 4904
EP - 4910
JO - Ceramics International
JF - Ceramics International
IS - 4
ER -