scholarly journals PIP Preparation of Silica Fibre Fabric Reinforced Silicon Nitride-Based Composites using Polyhydridomethylsilazane

2005 ◽  
Vol 14 (4) ◽  
pp. 096369350501400
Author(s):  
Gong-jin Qi ◽  
Chang-rui Zhang ◽  
Hai-feng Hu ◽  
Chang-cheng Zhou
Keyword(s):  
Mechanical Property ◽  
Silicon Nitride ◽  
Three Dimensional ◽  
Matrix Interface ◽  
Interface Bonding ◽  
Pull Out ◽  
New Type ◽  
Ammonia Atmosphere ◽  
Fibre Matrix ◽  
Silica Fibre

A new type of composites, three-dimensional silica fibre fabric reinforced silicon nitride-based composites, were prepared by PIP method through repeated infiltration of polyhydridomethylsilazane and pyrolysis at 773-873K in ammonia atmosphere. The density of the composites reached 1.66g/cm3 after four PIP cycles, and the flexural strength was 56.3 MPa. The composites showed a near-brittle fracture mode without long fibre pull-out in the fracture surface. It was the relatively strong fibre/matrix interface bonding that led to the moderate mechanical property.

Microstructure and Mechanical Property of Three-Dimensional Needled C/SiC Composites Prepared by Precursor Pyrolysis

2010 ◽  
Vol 434-435 ◽  
pp. 45-47 ◽  
Author(s):  
Cui Lin Han ◽  
Dong Lin Zhao ◽  
Lei Zhang ◽  
Zeng Min Shen
Keyword(s):  
Mechanical Property ◽  
Silicon Carbide ◽  
Interfacial Layer ◽  
Three Dimensional ◽  
Pyrolytic Carbon ◽  
Failure Behavior ◽  
Pull Out ◽  
Sic Composites ◽  
Silicon Carbide Ceramics ◽  
Microstructure And Mechanical Property

Three-dimensional needled carbon/silicon carbide (C/SiC) composites with pyrolytic carbon interfacial layer were fabricated by precursor pyrolysis. The microstructure and mechanical property of the three-dimensional needled C/SiC composites were investigated. A thin pyrolysis carbon layer (0.2m) was firstly deposited on the surface of carbon fiber as the interfacial layer with C3H6 at 850 °C and 0.1 MPa by chemical vapor infiltration. Polycarbosilane and divinylbenzene were selected as a precursor to silicon carbide ceramics and a cross-linking reagent for PCS, respectively. The density of the composites was 1.94 g cm-3. The flexural strength of the three-dimensional needled C/SiC composites was 135 MPa. The three-dimensional needled C/SiC composites with pyrolytic carbon interfacial layer exhibit good mechanical properties and a typical failure behavior involving fibers pull-out and brittle fracture of sub-bundle.

Modelling of Fibre-Matrix Interface of Brittle Matrix Long Fibre Composite by Application of Cohesive Zone Method

2011 ◽  
Vol 465 ◽  
pp. 231-234 ◽  
Author(s):  
Vladislav Kozák ◽  
Zdeněk Chlup
Keyword(s):  
Cohesive Zone ◽  
Room Temperature ◽  
Fibre Composite ◽  
Ceramic Matrix Composites ◽  
Matrix Composites ◽  
Matrix Interface ◽  
Toughening Mechanism ◽  
Zone Method ◽  
Pull Out ◽  
Fibre Matrix

Ceramic matrix composites reinforced by unidirectional long ceramic fibre are very perspective materials. The only disadvantage of such materials is relatively high brittleness at room temperature. The main micromechanism acting as toughening mechanism is the pull out. There are other mechanisms as crack bridging, crack deflection etc. but the primer mechanism is mentioned pull out which is governed by interface between fibre and matrix. The contribution shows a way how to predict and/or optimise behaviour of composite by application of cohesive zone method using the FEM numerical package Abaqus. The presented results from numerical calculations are compared with experimental data.

scholarly journals Effect of the Reynolds Number and Clearance Flow on the Aerodynamic Characteristics of a New Variable Inlet Guide Vane

Aerospace ◽  
2021 ◽  
Vol 8 (7) ◽  
pp. 172
Author(s):  
Hengtao Shi
Keyword(s):  
Reynolds Number ◽  
Guide Vane ◽  
Three Dimensional ◽  
High Growth ◽  
Aerodynamic Characteristics ◽  
Inlet Guide Vane ◽  
Separation Region ◽  
Clearance Flow ◽  
New Type ◽  
Variable Inlet Guide Vane

Recently, a new type of low-loss variable inlet guide vane (VIGV) was proposed for improving a compressor’s performance under off-design conditions. To provide more information for applications, this work investigated the effect of the Reynolds number and clearance flow on the aerodynamic characteristics of this new type of VIGV. The performance and flow field of two representative airfoils with different chord Reynolds numbers were studied with the widely used commercial software ANSYS CFX after validation was completed. Calculations indicate that, with the decrease in the Reynolds number Rec, the airfoil loss coefficient ω and deviation δ first increase slightly and then entered a high growth rate in a low range of Rec. Afterwards, a detailed boundary-layer analysis was conducted to reveal the flow mechanism for the airfoil performance degradation with a low Reynolds number. For the design point, it is the appearance and extension of the separation region on the rear portion; for the maximum incidence point, it is the increase in the length and height of the separation region on the former portion. The three-dimensional VIGV research confirms the Reynolds number effect on airfoils. Furthermore, the clearance leakage flow forms a strong stream-wise vortex by injection into the mainflow, resulting in a high total-pressure loss and under-turning in the endwall region, which shows the potential benefits of seal treatment.

scholarly journals Experimental & FEM Analysis of Orthodontic Mini-Implant Design on Primary Stability

2021 ◽  
Vol 11 (12) ◽  
pp. 5461
Author(s):  
Elmedin Mešić ◽  
Enis Muratović ◽  
Lejla Redžepagić-Vražalica ◽  
Nedim Pervan ◽  
Adis J. Muminović ◽  
...  
Keyword(s):  
Finite Element ◽  
Three Dimensional ◽  
Primary Stability ◽  
Fem Analysis ◽  
Implant Design ◽  
Special Focus ◽  
Engineering System ◽  
Mini Implants ◽  
Pull Out ◽  
Computer Aided

The main objective of this research is to establish a connection between orthodontic mini-implant design, pull-out force and primary stability by comparing two commercial mini-implants or temporary anchorage devices, Tomas®-pin and Perfect Anchor. Mini-implant geometric analysis and quantification of bone characteristics are performed, whereupon experimental in vitro pull-out test is conducted. With the use of the CATIA (Computer Aided Three-dimensional Interactive Application) CAD (Computer Aided Design)/CAM (Computer Aided Manufacturing)/CAE (Computer Aided Engineering) system, 3D (Three-dimensional) geometric models of mini-implants and bone segments are created. Afterwards, those same models are imported into Abaqus software, where finite element models are generated with a special focus on material properties, boundary conditions and interactions. FEM (Finite Element Method) analysis is used to simulate the pull-out test. Then, the results of the structural analysis are compared with the experimental results. The FEM analysis results contain information about maximum stresses on implant–bone system caused due to the pull-out force. It is determined that the core diameter of a screw thread and conicity are the main factors of the mini-implant design that have a direct impact on primary stability. Additionally, stresses generated on the Tomas®-pin model are lower than stresses on Perfect Anchor, even though Tomas®-pin endures greater pull-out forces, the implant system with implemented Tomas®-pin still represents a more stressed system due to the uniform distribution of stresses with bigger values.

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