Interlocking thin-ply reinforcement concept for improved fracture toughness and damage tolerance

2019 ◽  
Vol 181 ◽  
pp. 107681 ◽  
Author(s):  
John-Alan Pascoe ◽  
Soraia Pimenta ◽  
Silvestre T. Pinho
Keyword(s):  
Fracture Toughness ◽  
Damage Tolerance

High Toughness Ceramic Laminates by Design of Residual Stresses

2001 ◽  
Vol 702 ◽  
Author(s):  
Nina A. Orlovskaya ◽  
Jakob Kuebler ◽  
Vladimir I. Subotin ◽  
Mykola Lugovy
Keyword(s):  
Fracture Toughness ◽  
Residual Stresses ◽  
Damage Tolerance ◽  
High Strength ◽  
Ceramic Composites ◽  
Tensile Stresses ◽  
High Toughness ◽  
Apparent Fracture Toughness ◽  
Layered Ceramics ◽  
Compressive Residual Stresses

ABSTRACTMultilayered ceramic composites are very promising materials for different engineering applications. Laminates with strong interfaces can provide high apparent fracture toughness and damage tolerance along with the high strength and reliability. The control over the mechanical behavior of laminates can be obtained through design of residual stresses in separate layers. Here we report a development of tough silicon nitride based layered ceramics with controlled compressive and tensile stresses in separate layers. We design laminates in a way to achieve high compressive residual stresses in thin (100-150 micron) Si3N4 layers and low tensile residual stresses in thick (600-700 micron) Si3N4-TiN layers. The residual stresses are controlled by the amount of TiN in layers with residual tensile stresses and the layers thickness. The fracture toughness of pure Si3N4(5wt%Y2O3+2wt%Al2O3) ceramics was measured to be of 5 MPa m1/2, while the apparent fracture toughness of Si3N4/Si3N4-TiN laminates was in the range of 7-8 MPa m1/2 depending on the composition and thickness of the layers.

Effect of Heat Treatment on the Damage Tolerance Properties of Ti-6Al-2Zr-2V-1.5Mo ELI Alloy Plate

2011 ◽  
Vol 690 ◽  
pp. 282-285
Author(s):  
Xiao Xiang Wang ◽  
Song Xiao Hui
Keyword(s):  
Heat Treatment ◽  
Fracture Toughness ◽  
Fatigue Crack ◽  
Annealing Temperature ◽  
Damage Tolerance ◽  
Phase Zone ◽  
Alloy Plate ◽  
Β Phase ◽  
Α Phase ◽  
Treatment Conditions

Effect of heat treatment on the damage tolerance properties of a newly developed middle strength high damage tolerance Ti-6Al-2Zr-2V-1.5Mo ELI alloy plate has been investigated in this paper by testing fracture toughness and fatigue crack-extending rate of the plate under three heat treatment conditions and fractograph inspection of the samples. It has been found that with the increasing of the primary annealing temperature from 900°C to 950°C, the fracture toughness increased and the fatigue crack extending rate decreased significantly. Microstructural observation has found that the crack expanded through the α beaming and mainly are perpendicular to the α orientation in the lamellar structure which annealed in α+β phase zone. For the Widmanstaten structure, which can be obtained from annealing in single β phase zone, the continuous grain boundary α phase and α beaming boundary hinder the crack expanding significantly.

scholarly journals Further Studies into Crack Growth in Additively Manufactured Materials

Materials ◽  
2020 ◽  
Vol 13 (10) ◽  
pp. 2223 ◽  
Author(s):  
Athanasios P. Iliopoulos ◽  
Rhys Jones ◽  
John G. Michopoulos ◽  
Nam Phan ◽  
Calvin Rans
Keyword(s):  
Fracture Toughness ◽  
Crack Growth ◽  
Damage Tolerance ◽  
Inconel 625 ◽  
Growth Equation ◽  
Selective Layer ◽  
Aging Aircraft ◽  
Crack Growth Rates ◽  
Am Processes ◽  
Layer Melting

Understanding and characterizing crack growth is central to meeting the damage tolerance and durability requirements delineated in USAF Structures Bulletin EZ-SB-19-01 for the utilization of additive manufacturing (AM) in the sustainment of aging aircraft. In this context, the present paper discusses the effect of different AM processes, different build directions, and the variability in the crack growth rates related to AM Ti-6Al-4V, AM Inconel 625, and AM 17-4 PH stainless steel. This study reveals that crack growth in these three AM materials can be captured using the Hartman–Schijve crack growth equation and that the variability in the various da/dN versus ΔK curves can be modeled by allowing the terms ΔKthr and A to vary. It is also shown that for the AM Ti-6AL-4V processes considered, the variability in the cyclic fracture toughness appears to be greatest for specimens manufactured using selective layer melting (SLM).

The Quantitative Relationships between Microstructure and Damage Tolerance of TC21 Titanium Alloy

2013 ◽  
Vol 770 ◽  
pp. 335-340
Author(s):  
Jun Cheng ◽  
Ming He Chen ◽  
Zhi Shou Zhu
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Titanium Alloy ◽  
Fatigue Crack ◽  
Damage Tolerance ◽  
Lamellar Microstructure ◽  
Quantitative Metallography ◽  
Characteristic Parameters ◽  
Microstructure Parameters ◽  
The Relationship

Mechanical properties, including fracture toughness and the fatigue crack propagation, have been investigated for two different microstructures in TC21 titanium alloy. The characteristic parameters of lamellar microstructure were measured through quantitative metallography. On the basis of analyzing the influence of microstructure on the fracture toughness of TC21 titanium alloy, the mathematical models between the fracture toughness and microstructure parameters were constructed. Furthermore, the relationship between fatigue crack growth rate and mean length values of α lamellar have been also investigated and a novel predicting model was established.

Damage Tolerance Evaluation of Adhesively Laminated Titanium

1983 ◽  
Vol 105 (3) ◽  
pp. 182-187 ◽  
Author(s):  
W. S. Johnson
Keyword(s):  
Fracture Toughness ◽  
Growth Rate ◽  
Crack Growth Rate ◽  
Thick Plate ◽  
Damage Tolerance ◽  
Thin Sheet ◽  
Compact Tension ◽  
Thin Sheets ◽  
Laminated Plate ◽  
Titanium Plate

Basic damage tolerance properties of Ti-6Al-4V titanium plate can be improved by laminating thin sheets of titanium with adhesives. Compact tension and center-cracked tension specimens made from thick plate, thin sheet, and laminated plate (six plies of thin sheet) were tested. The fracture toughness of the laminated plate was 39 percent higher than the monolithic plate. The laminated plate’s through-the-thickness crack growth rate was about 20 percent less than that of the monolithic plate. The damage tolerance life of the surface-cracked laminate was 6 to over 15 times the life of a monolithic specimen.

Precipitation in Al-Li-Zr alloys

1992 ◽  
Vol 50 (1) ◽  
pp. 186-187
Author(s):  
D.M. Vanderwalker
Keyword(s):  
Fracture Toughness ◽  
Precipitation Hardening ◽  
Weight Ratio ◽  
High Strength ◽  
Transmission Electron ◽  
Water Quench ◽  
Aluminum Lithium ◽  
Aluminum Lithium Alloys ◽  
Lithium Alloys ◽  
Zr Alloys

Aluminum-lithium alloys have a low density and high strength to weight ratio. They are being developed for the aerospace industry.The high strength of Al-Li can be attributed to precipitation hardening. Unfortunately when aged, Al-Li aquires a low ductility and fracture toughness. The precipitate in Al-Li is part of a sequence SSSS → Al3Li → AlLi A description of the phases may be found in reference 1 . This paper is primarily concerned with the Al3Li phase. The addition of Zr to Al-Li is being explored to find the optimum in properties. Zirconium improves fracture toughness and inhibits recrystallization. This study is a comparision between two Al-Li-Zr alloys differing in Zr concentration.Al-2.99Li-0.17Zr(alloy A) and Al-2.99Li-0.67Zr (alloy B) were solutionized for one hour at 500oc followed by a water quench. The specimens were then aged at 150°C for 16 or 40 hours. The foils were punched into 3mm discs. The specimens were electropolished with a 1/3 nitric acid 2/3 methanol solution. The transmission electron microscopy was conducted on the JEM 200CX microscope.

Microstructural and fractographic characterization of B4C-Al cermets tested under dynamic and static loading

1989 ◽  
Vol 47 ◽  
pp. 562-563
Author(s):  
Gyeung Ho Kim ◽  
Mehmet Sarikaya ◽  
D. L. Milius ◽  
I. A. Aksay
Keyword(s):  
Thin Film ◽  
Mechanical Properties ◽  
Fracture Toughness ◽  
Static Loading ◽  
Carbon Deposition ◽  
Full Density ◽  
Unique Combination ◽  
Strong Component ◽  
Reaction Products

Cermets are designed to optimize the mechanical properties of ceramics (hard and strong component) and metals (ductile and tough component) into one system. However, the processing of such systems is a problem in obtaining fully dense composite without deleterious reaction products. In the lightweight (2.65 g/cc) B4C-Al cermet, many of the processing problems have been circumvented. It is now possible to process fully dense B4C-Al cermet with tailored microstructures and achieve unique combination of mechanical properties (fracture strength of over 600 MPa and fracture toughness of 12 MPa-m1/2). In this paper, microstructure and fractography of B4C-Al cermets, tested under dynamic and static loading conditions, are described.The cermet is prepared by infiltration of Al at 1150°C into partially sintered B4C compact under vacuum to full density. Fracture surface replicas were prepared by using cellulose acetate and thin-film carbon deposition. Samples were observed with a Philips 3000 at 100 kV.

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