Investigation of the Tensile Fracture Behavior of Notched C/SiC Composite Using In Situ SEM and Micro-CT

2019 ◽  
Vol 298 ◽  
pp. 155-160
Author(s):  
Bai Hong Jiang ◽  
Yi Yu ◽  
Lei Zhang ◽  
Shi Zhang Yu ◽  
Xiao Jin Gao
Keyword(s):  
Failure Mechanism ◽  
Linear Part ◽  
Tensile Fracture ◽  
In Situ Observation ◽  
Displacement Curve ◽  
Micro Ct ◽  
Pull Out ◽  
Load Displacement ◽  
Sic Composites

In order to better understand the failure mechanism of C/SiC composites, the tensile behavior of notched C/SiC composites was investigated by the in-situ scanning electron microscopy (SEM) and the micro-CT technique. Surface morphologies of the C/SiC sample during tensile loading were in-situ observed by SEM, while the three-dimensional microscopic images of the C/SiC sample before loading and after failure were obtained by micro-CT. The results showed that no cracks formed in the initial elastic stage corresponding to the linear part of the load-displacement curve. However, corresponding to the following non-linear part of the load-displacement curve, matrix crack initiation, fiber pull-out, crack propagation and deflection appeared consecutively in the notched region of the sample. What’s more, different crack growth paths existed in different directions of the sample during tensile failure. In general, approximately flat fracture formed in the plying direction and serrated or stepped fracture were observed in the needling direction. It indicated that the in-situ observation method combining SEM and micro-CT can obtain the micro-structure images of the material in different states, which is helpful to analyze the fracture failure mechanism of composites.

PULL-OUT PROPERTIES OF GYPSUM BOARD ANCHORS

2016 ◽  
Vol 3 (2) ◽  
Author(s):  
Yoshinori Kitsutaka ◽  
Fumiya Ikedo
Keyword(s):  
Numerical Model ◽  
Fracture Energy ◽  
Tensile Tests ◽  
Displacement Curve ◽  
Gypsum Board ◽  
Hydraulic Loading ◽  
Pull Out ◽  
Loading System ◽  
Earthquake Load ◽  
Load Displacement

In this study, pull-out properties of various anchors embedded in gypsum board were investigated. Tensile tests for anchors embedded in 200mm square size gypsum board were conducted to measure the load-load displacement curves. Strength of gypsum board was changed for three conditions and twelve kinds of anchors were selected which were ordinary used for gypsum board anchoring. The loading conditions were a monotonous loading and a repeating loading controlled by a servo-controlled hydraulic loading system to achieve accurate measurement. The fracture energy for each anchors were estimated by the analysis of consumed energy calculated by the load-load displacement curve. The effect of the strength of gypsum board and the types of anchors on the pull-out properties of gypsum board anchors was cleared. A numerical model to predict the load-unload curve of pull-out deformation of gypsum board anchors caused by such as the earthquake load was proposed and the validity on the model was proved.

Study of dynamic compressive behaviors of 2D C/SiC composites at elevated temperatures based on in-situ observation

2020 ◽  
Vol 40 (15) ◽  
pp. 5103-5119
Author(s):  
Chao Zhang ◽  
Tengfei Ren ◽  
Xinyue Zhang ◽  
Wei Hu ◽  
Zhen Wang ◽  
...  
Keyword(s):  
Elevated Temperatures ◽  
In Situ Observation ◽  
Sic Composites

scholarly journals In Situ Observation of the Deformation and Fracture Behaviors of Long-Term Thermally Aged Cast Duplex Stainless Steels

Metals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 258 ◽  
Author(s):  
Shilei Li ◽  
Yanli Wang ◽  
Xitao Wang
Keyword(s):  
Thermal Aging ◽  
Critical Value ◽  
Tensile Fracture ◽  
In Situ Observation ◽  
Loading Direction ◽  
Deformation And Fracture ◽  
Fracture Behaviors ◽  
Initial Cracks

Cast duplex stainless steel (CDSS) components suffer embrittlement after long-term thermal aging. The deformation and fracture behaviors of un-aged and thermally aged (at 400 °C for 20,000 h) CDSS were investigated using in situ scanning electron microscopy (SEM). The tensile strength of CDSS had a small increase, and the tensile fracture changed from ductile to brittle after thermal aging. Observations using in situ SEM indicated that the initial cracks appeared in the ferrite perpendicular to the loading direction after the macroscopic stress exceeded a critical value. The premature fracture of ferrite grains caused stress on the phase boundaries, leading the cracks to grow into austenite. The cleavage fracture of ferrite accelerated the shearing of austenite and reduced the plasticity of the thermally aged CDSS.

scholarly journals Fabrication and mechanical properties of self-toughening ZrB2–SiC composites from in-situ reaction

2019 ◽  
Vol 8 (4) ◽  
pp. 527-536 ◽  
Author(s):  
Zhaofu Zhang ◽  
Jianjun Sha ◽  
Yufei Zu ◽  
Jixiang Dai ◽  
Yingjun Liu
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Hot Pressing ◽  
High Fracture Toughness ◽  
High Fracture ◽  
Microstructure Observation ◽  
Pull Out ◽  
Sic Composites ◽  
Reactive Hot Pressing

AbstractSelf-toughening ZrB2–SiC based composites are fabricated by in-situ reactive hot pressing. The effect of sintering additive content on the microstructure and mechanical properties of the composites is investigated. Microstructure observation found that the in-situ reactive hot pressing could promote the anisotropic growth of ZrB2 grains and the formation of interlocking microstructure. Such microstructure could improve the mechanical properties, especially, for the fracture toughness. The improved mechanical properties could be attributed to the self-toughening structure related to the ZrB2 platelets and the formed interlocking microstructure, which could trigger various toughening mechanisms such as grain pull-out, crack bridging, crack deflection, and crack branching, providing the main contribution to the high fracture toughness.

In-Situ Observation and Mechanical Criterion on Interface Cracking in Nano-Components

2012 ◽  
Vol 1415 ◽  
Author(s):  
T. Kitamura ◽  
T. Sumigawa
Keyword(s):  
Mechanical Property ◽  
Fatigue Behavior ◽  
In Situ Observation ◽  
Displacement Curve ◽  
Si Substrate ◽  
Nano Scale ◽  
Cu Film ◽  
20 Nm ◽  
Interface Edge

ABSTRACTWe have investigated the criterion of interfacial crack initiation in nanometer-scale components (nano-components) by means of a loading facility built in a transmission electron microscope (TEM). Three types of experiments are conducted in this project. (1) In order to clarify the applicability of conventional continuum mechanics to the nano-components, we prepare cantilever specimens with different size, which introduce different stress fields, containing an interface between a 20 nm-thick copper (Cu) thin film and a silicon (Si) substrate. These demonstrate the validity of the “stress” criterion even for the nano-scale fracture. (2) In order to examine the effect of microscopic structure on the mechanical property, we fabricate a bending specimen in the nano-scale with thin Cu bi-crystal (the thickness of about 100 nm) formed on Si substrate, of which understructure can be observed in situ by means of a TEM during the mechanical experiment. The initial plastic deformation takes place near the interface edge in a grain with a high critical resolved shear stress and expands preferentially in the grain. Then, the plasticity appears near the between Cu grain boundary and Cu/Si interface, and this development brings about the interfacial cracking from the junction. These indicate the governing influence of understructure on the mechanical property in the nano-components. (3) In order to investigate the fatigue behavior of metal in a nano-component, a cyclic bending experiment is carried out using nano-cantilever specimens with a 20 nm-thick Cu constrained by highly rigid materials (Si and SiN). The high strain region is in the size of 20-40 nm near the interface edge. The specimen breaks along the Cu/Si interface before the maximum load under the fatigue loading. The load-displacement curve shows nonlinear behavior and a distinct hysteresis loop, indicating plasticity in the Cu film. Reverse yielding appearing after the 2nd cycle suggests the development of a cyclic substructure in the Cu film. These indicate that the crack is caused by characteristic understructure owing to fatigue cycles.

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