Aerospace and Materials最新文献_第2页

Creep Behaviour of Hot Isostatically Pressed Metal-Matrix Composite 热等静压金属基复合材料的蠕变行为

Aerospace and Materials Pub Date : 1996-11-17 DOI: 10.1115/imece1996-0496

C. S. Lim, N. P. Hung, Y. C. Tan, N. Loh

引用次数: 0

Effects of High Heat on the Strength and Fatigue Life of Unidirectional Polymer-Matrix Composites 高热对单向聚合物基复合材料强度和疲劳寿命的影响

Aerospace and Materials Pub Date : 1996-11-17 DOI: 10.1115/imece1996-0495

P. Mclaughlin, Henry A. McShane, R. Cochran, E. Armstrong-Carroll

{"title":"Effects of High Heat on the Strength and Fatigue Life of Unidirectional Polymer-Matrix Composites","authors":"P. Mclaughlin, Henry A. McShane, R. Cochran, E. Armstrong-Carroll","doi":"10.1115/imece1996-0495","DOIUrl":"https://doi.org/10.1115/imece1996-0495","url":null,"abstract":"\u0000 An analysis of local fiber/matrix interface damage growth in unidirectional composites under tension-tension loading is modified to include thermal residual stresses and subsequent temperature histories with the goal of estimating the loss of strength and fatigue life occurring when a graphite/epoxy composite structure is subjected to flame or hot exhaust gasses. Tests show that epoxy thermomechanical and strength properties degrade rapidly from 200 to 300°C, and that time-at-temperature is important. Using properties estimated from these tests, two mechanisms of static strength and fatigue life reduction are studied: thermal-stress-induced interface cracking parallel to fibers, and degradation of room-temperature interface properties. The effects of heat on static strength and constant-amplitude fatigue life of a particular graphite/epoxy material system are then analytically determined for two heat exposure scenarios: one, a relatively short-time exposure of five minutes; and two, a long-time exposure of more than an hour. Strength and life loss are found to be dependent on temperature, time-at-temperature, and length of damage zone, with severe reductions in static and fatigue strengths at temperatures above 200°C.","PeriodicalId":326220,"journal":{"name":"Aerospace and Materials","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1996-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123806765","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Microscopic Examination of Titanium Matrix Composites Subjected to Testing Designed to Cause Varying Dominant Damage Mechanisms 钛基复合材料在不同主要损伤机制下的显微检查

Aerospace and Materials Pub Date : 1996-11-17 DOI: 10.1115/imece1996-0476

J. Calcaterra, W. S. Johnson

{"title":"Microscopic Examination of Titanium Matrix Composites Subjected to Testing Designed to Cause Varying Dominant Damage Mechanisms","authors":"J. Calcaterra, W. S. Johnson","doi":"10.1115/imece1996-0476","DOIUrl":"https://doi.org/10.1115/imece1996-0476","url":null,"abstract":"\u0000 Titanium Matrix Composites (TMC’s) like SCS-6/Timetal 21S are envisioned for use as a structural material for advanced aircraft and in the next generation of turbine engine. In general, damage in representative temperature and load regimes can be dominated by either mechanical, environmental or time dependent deformation and damage mechanisms. Mechanical deformation, present under all load conditions, includes mechanisms such as matrix yielding and fiber/matrix debonding. Time dependent deformation refers to either the creep or relaxation of the matrix and will typically occur at moderately high elevated temperatures. Environmental damage is also time dependent but is distinguished by the fact that it describes the chemical interaction of the composite and the environment. Environmental damage in SCS-6/Timetal 21S composites is commonly thought to be caused by the oxygen embrittlement of the matrix. This damage type becomes prevalent at high elevated temperatures which are near the operational limit of the material. Testing has been completed at Georgia Tech to separate the three damage types listed above. This test matrix involved isothermal constant amplitude fatigue tests at temperatures of 400, 500 and 650°C with hold times at the maximum stress varying from 1 to 100 seconds. Testing was conducted on laminates with stacking sequences of both [0/±45/90]s and [90/±45/0]s. The changes in stacking sequence yielded significant differences in cyclic lives for identical test conditions. Fractographic examination of the specimens indicate that the true cause for environmental attack is not the formation of brittle oxides, but the coarsening of the alpha grains in the microstructure. This form of damage is shown to affect the fracture morphology of specimens at all temperatures, but proper selection of the stacking sequence can reduce the importance of this effect and increase cyclic lives.","PeriodicalId":326220,"journal":{"name":"Aerospace and Materials","volume":"83 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1996-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127106992","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Damage Accumulation Mechanisms in Thermal Barrier Coatings 热障涂层的损伤积累机制

Aerospace and Materials Pub Date : 1996-11-17 DOI: 10.1115/1.2807004

G. Newaz, S. Nusier, Z. Chaudhury

{"title":"Damage Accumulation Mechanisms in Thermal Barrier Coatings","authors":"G. Newaz, S. Nusier, Z. Chaudhury","doi":"10.1115/1.2807004","DOIUrl":"https://doi.org/10.1115/1.2807004","url":null,"abstract":"\u0000 Spallation is a major failure condition experienced by thermal barrier coatings (TBCs) subjected to thermal and mechanical loads. Although evidence of spallation is substantiated and mechanistic models to describe the failure condition is prevalent in literature, the progressive nature of damage evolution leading to spallation has not been addressed adequately. In this paper, we investigated the damage evolution in partially stabilized zirconia TBC on Nickel-based single crystal superalloy, Rene N5. Thermal cycles were imposed on button specimens with Electron Beam - Plasma Vapor Deposition (EB-PVD) TBC coating. The bond coat was PtAl. The temperature range used was 200–1177C. Progressive damage evolution was tracked using microscopy on samples subjected to a series of thermal cycles. Fick’s law can describe the thermally grown oxide (TGO) buildup for early cycles. However, at higher number of thermal cycles, damage in the form of microcracks and their coalescence results in the loss of integrity of the TGO. Thus, both oxidation kinetics and damage appears to have significant roles to play as it relates to spallation. As these microcracks coalesce to form major delamination cracks or interlayer separation, the susceptibility for coating buckling is increased. The delamination cracks finally consume the TGO layer. The loss of TBC integrity from the bond coat and the substrate facilitates its buckling during cool down from elevated temperature. Our estimations show that a delamination crack length of about sixteen times the TBC thickness is needed for the current material system to initiate buckling. Progressive microcrack linking is a possible mechanism to develop such critical delamination crack lengths. Physical evidence of buckling was found in specimens prior to complete spallation.","PeriodicalId":326220,"journal":{"name":"Aerospace and Materials","volume":"278 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1996-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124473277","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 22

Fatigue Damage Modeling and Life Prediction of Titanium Matrix Composites 钛基复合材料疲劳损伤建模与寿命预测

Aerospace and Materials Pub Date : 1996-11-17 DOI: 10.1115/imece1996-0472

P. C. Wang, J. Yang, A. Mal

引用次数: 0

Dislocation Punching in Functionally-Graded Materials 功能梯度材料中的位错冲孔

Aerospace and Materials Pub Date : 1996-11-17 DOI: 10.1115/imece1996-0473

M. Taya, J. Lee, T. Mori

引用次数: 0

Crack Deflection and Penetration Criteria for Brittle Matrix Composites 脆性基复合材料裂纹挠度和侵彻准则

Aerospace and Materials Pub Date : 1996-11-17 DOI: 10.1115/imece1996-0479

N. Pagano