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Fatigue Of Graphite Epoxy 0 90 45 45s Laminates Under Dual Stress Levels
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Book Synopsis Fatigue of Graphite/Epoxy [0/90/45/-45]s Laminates Under Dual Stress Levels by : JN. Yang
Download or read book Fatigue of Graphite/Epoxy [0/90/45/-45]s Laminates Under Dual Stress Levels written by JN. Yang and published by . This book was released on 1982 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: A model previously developed by the authors to predict the effect of loading sequence on the statistical distribution of the fatigue life and residual strength of composite materials has been generalized and applied to graphite/epoxy [0/90/45/-45]s laminates. The load sequence effects have been shown to be caused in general by the difference in residual strength when failure occurs (boundary effect) and the effect of previously applied loads (memory effect). The present model permits isolation of the memory effect from the boundary effect and estimations of the magnitude of the memory effect under dual levels of fatigue loadings. The model parameters were evaluated from baseline data, including static strength, fatigue life, and residual strength tests. Predictions of the material response were then made and verified with additional fatigue life and residual strength testing. It was shown that the material memory effect is insignificant for this material and correlations between predictions of the number of early failures agreed quite well with the verification tests. Predictions of the fatigue life and residual strength degradation under dual stress levels were also in good agreement with the test results.
Book Synopsis Advanced Fatigue Damage Development in Graphite Epoxy Laminates by : Russell Douglas Jamison
Download or read book Advanced Fatigue Damage Development in Graphite Epoxy Laminates written by Russell Douglas Jamison and published by . This book was released on 1982 with total page 238 pages. Available in PDF, EPUB and Kindle. Book excerpt: Results of an experimental investigation of damage development in T300/5208 graphite epoxy laminates subjected to tension-tension cyclic loading are reported. The concept of laminate stiffness reduction as a damage analogue is shown to be a valuable means of test control and damage interpretation. The relationship between stiffness and number of cycles is shown to be unique for each laminate type studied, each possessing three distinct stages, but markedly different among the laminate types. By using two complementary nondestructive evaluation (NDE) techniques, edge replication and penetrant-enhanced stereo X- ray radiography along with a method for deploying fatigue-damaged specimens, the stages of stiffness reduction were found to correspond variously to the predominance of matrix cracking or delamination or interactions of these matrix damage modes. A number of subordinate matrix damage modes including interior delamination, microcracking, and longitudinal splitting are identified with the matrix cracks which produce them.
Book Synopsis Fatigue Damage-Strength Relationships in Composite Laminates. Volume 2 by : Kenneth L. Reifsnider
Download or read book Fatigue Damage-Strength Relationships in Composite Laminates. Volume 2 written by Kenneth L. Reifsnider and published by . This book was released on 1984 with total page 60 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report presents information and experience generated during the subject investigation which provided support for the major thrust of the effort, but was not the eventual focus of the program. The activities are discussed in the context of the various experimental techniques used (and developed) to investigate the context of the damage development. Whil much of the information discussed is not complete, it is thought that a description of the experimental methods and experiences will be valuable to the technical community. Included are descriptions of virtually every experimental technique used in this program and a variety of findings not discussed elsewhere.
Book Synopsis Experimental and Analytical Study of Fatigue Damage in Notched Graphite/Epoxy Laminates by : JD. Whitcomb
Download or read book Experimental and Analytical Study of Fatigue Damage in Notched Graphite/Epoxy Laminates written by JD. Whitcomb and published by . This book was released on 1981 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fatigue damage development in notched (0/±45/0)s, (45/0/-45/0)s, (90/±45/0)s, and (45/90/-45/0)s graphite/epoxy laminates was investigated. Both tension and compression fatigue behaviors were studied. Most of the tests were conducted at load levels equal to two thirds of the ultimate tensile strength of the notched specimens. After fatigue loading, specimens were examined for damage type and location using light microscopy, scanning electron microscopy, ultrasonic C-scans, and X-radiography. Delamination and ply cracking were found to be the dominant types of fatigue damage. In general, ply cracks did not propagate into adjacent plies of differing fiber orientation. To help understand the varied fatigue observations, the interlaminar stress distribution was calculated with finite element analysis for the regions around the hole and along the straight free edge. Comparison of observed delamination locations with the calculated stresses indicated that both interlaminar shear and peel stresses must be considered when predicting delamination. The effects of the fatigue cycling on residual strength and stiffness were measured for some specimens of each laminate type. Fatigue loading generally caused only small stiffness losses. In all cases, residual strengths were greater than or equal to the virgin strengths.
Book Synopsis Fatigue Damage-strength Relationships in Composite Laminates. Volume 1 by : Kenneth L. Reifsnider
Download or read book Fatigue Damage-strength Relationships in Composite Laminates. Volume 1 written by Kenneth L. Reifsnider and published by . This book was released on 1983 with total page 58 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report is Vol. I of a 2-part final report on the activities which were conducted under Contract No. F33615-81-3225. The general objective of this program was to investigate the precise nature of the damage events caused by cyclic (fatigue) loading of composite laminates that are directly related to fracture of those laminates, to develop a conceptual understanding of how those damage events reduce the residual strength of the laminates, and to determine how the collective damage condition following long-term cyclic loading precipitates the final fracture event. The program was conducted in four phases: (1) the development of fatigue damage during long-term cyclic loading was investigated in such a way that the damage events which occur quite late in the fatigue life of the material, just prior to fracture, were identified and characterized; (2) the special contribution and nature of fiber fracture was investigated; (3) the nature of the collective damage condition which precipitates the fracture event under long-term fatigue loading was investigated; (4) a philosophy of fracture in composite laminates following severe damage development due to cyclic loading was developed. A wide variety of destructive and nondestructive experimental evaluation schemes were used in the program, and several analytical efforts were conducted to support the experimental activities.
Book Synopsis Experimental and Analytical Study of Fatigue Damage in Notched Graphite/epoxy Laminates by :
Download or read book Experimental and Analytical Study of Fatigue Damage in Notched Graphite/epoxy Laminates written by and published by . This book was released on 1979 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Tension Fatigue of Glass/epoxy and Graphite/epoxy Tapered Laminates by :
Download or read book Tension Fatigue of Glass/epoxy and Graphite/epoxy Tapered Laminates written by and published by . This book was released on 1990 with total page 68 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis An Evaluation of the Effects of Stacking Sequence and Thickness on the Fatigue Life of Quasi-Isotropic Graphite/Epoxy Laminates by : CE. Harris
Download or read book An Evaluation of the Effects of Stacking Sequence and Thickness on the Fatigue Life of Quasi-Isotropic Graphite/Epoxy Laminates written by CE. Harris and published by . This book was released on 1985 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt: A test program has been conducted in which the effect of specimen thickness on the fatigue lives of quasi-isotropic, graphite/epoxy lamintes was investigated. Three replicate specimens for each notched and unnotched geometry at 16, 32, and 64-ply thicknesses of a [90/45/0/-45]ns and [45/0/-45/90]ns laminate were tested in compression-compression fatigue. The fatigue lives of the notched specimens did not appear to be a strong function of laminate stacking sequence or specimen thickness. The stress concentration at the hole dominated over the interlaminar stresses at the straight free edge. The unnotched specimens of the [90/45/0/-45]ns laminate with tensile interlaminar normal stresses delaminated more readily than did the [45/0/-45/90]ns laminate with compressive interlaminar normal stress. The life of the 16-ply unnotched specimens was lower than was the life of the 32 and 64-ply specimens. Delaminations were located at the interface where the maximum ?xz shear stress occurred regardless of the sense of magnitude of the interlaminar normal stress. Finally, a specially designed antibuckling fixture was found to be effective in preventing out-of-plane motion without overconstraining the specimen.
Book Synopsis Ply-level Failure Analysis of a Graphite/epoxy Laminate Under Bearing-bypass Loading by :
Download or read book Ply-level Failure Analysis of a Graphite/epoxy Laminate Under Bearing-bypass Loading written by and published by . This book was released on 1988 with total page 40 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Effect of Moisture on the Fatigue Behavior of Graphite/epoxy Composite Laminates by :
Download or read book Effect of Moisture on the Fatigue Behavior of Graphite/epoxy Composite Laminates written by and published by . This book was released on 1979 with total page 52 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Response of Notched Graphite/epoxy and Graphite/peek Systems by : Paul A. Lagace
Download or read book Response of Notched Graphite/epoxy and Graphite/peek Systems written by Paul A. Lagace and published by . This book was released on 1991 with total page 42 pages. Available in PDF, EPUB and Kindle. Book excerpt: A test program was conducted to compare the tensile behavior of laminates made with graphite fibers and a low strain-to-failure matrix system (epoxy) versus a high strain-to-failure matrix system (PEEK), in the presence of notches. Graphite/epoxy (AS4/3501-6) and graphite/PEEK (AS4/APC-2) laminates were utilized in three different layups: [(±45)2/0/90]s, [45/02/-45/02/90]s, and [±45/0]s. These laminate represent "soft", "stiff", and "medium" configurations, respectively, in regard to their longitudinal stiffness as manifested by the percentage of 0* plies in each. Two different hole configurations, open and filled, were utilized with three different hole diameters: 6.35 mm, 9.53 mm, and 12.7 mm. All specimens were tested to failure in tension with X-ray photographs taken at various loading intervals with the aid of a dye penetrant. Semi-empirical relations were successfully used to correlate the data for both material systems. The graphite/epoxy system showed earlier and more extensive matrix damage than the graphite/PEEK system. In the case of the "soft" [(±45)2/0/90]s laminate, this led to a lower failure stress for the graphite/epoxy laminate as compared to the graphite/PEEK laminate; whereas this led to a higher failure stress for the [45/02/-45/02/90]s graphite/epoxy laminate. This is related to the number of major load-carrying plies (00) in the laminate and the load redistribution caused by the damage. These results indicate that the in-plane "toughness" of a composite laminate is a structural property and cannot be directly correlated to the "toughness" or strain-to-failure of the matrix system but must account for the damage progression which occurs in the specific laminate configuration. KEYWORDS: Graphite/epoxy, graphite/thermoplastic, fracture strength, notch sensitivity, damage accumulation
Book Synopsis The Effect of Preloading on Fatigue Damage in Composite Structures: Part 1 by :
Download or read book The Effect of Preloading on Fatigue Damage in Composite Structures: Part 1 written by and published by . This book was released on 1996 with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt: The effect of preload on damage development in unnotched graphite/epoxy laminates is studied. Two types of tension-tension fatigue tests were conducted on quasi-isotropic (0/45/-45/90)53, AS-4/3501-6 laminates, and damage was measured in the form of ply cracks. Baseline fatigue tests were run at constant amplitudes ranging from 20% to 60% of the ultimate tensile strength (UTS) while specimens with preloads of 50% to 80% UTS were tested in fatigue at the same amplitudes. The ply crack densities determined from edge replications in preloaded specimens were compared to those without preload. The effect of a preload on subsequent fatigue damage growth depended on the combination of both the preload level and the subsequent fatigue stress level. Since the tension preload was always higher than the tension-tension fatigue stress level, damage in preloaded specimens was more severe in the low-cycle region than nonpreloaded specimens. However, this preload-induced damage did not grow any more if the fatigue stress level was kept low. Preloads just above levels that cause significant damage (70% UTS and above here) appeared to retard fatigue damage development. At the highest tension-tension fatigue stress level of 40% UTS, the high-cycle damage in the form of matrix cracking rather decreased with increasing preload level. Thus, preloading could be beneficial at this stress level as far as the high-cycle ply crack damage is concerned.
Book Synopsis Damage Accumulation in Graphite/epoxy Laminates Due to Cyclic Gradient Stress Fields by : Paul A. Lagace
Download or read book Damage Accumulation in Graphite/epoxy Laminates Due to Cyclic Gradient Stress Fields written by Paul A. Lagace and published by . This book was released on 1991 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt: The progression of damage in gradient stress fields under cyclic loading was studied in simply-supported graphite/epoxy beam-columns. Three layups, [454/0-45 4/(0/90)4 4]2S, [±45/0/90]4s, and [(452/- 452/0)2/ 905]2s, were chosen to be consistent with data collected in a previous study with static loading. Specimens were loaded statically until predetermined characteristic damage levels were obtained, after which cyclic loading began. At specific intervals, cyclic loading was stopped, a static test measuring the load and the corresponding center deflection was performed, and edge replicas of the specimen's sides were taken. The damage of these specimens varied both along the length and through the thickness of the specimens with two general modes of damage present. Damage due to the static loading generally occurred on the tension side of the specimen and was controlled by matrix cracks. Delaminations initiated and grew in areas of crack saturation. Damage due to the cyclic loading also occurred on the compression side of the specimens and was controlled by delaminations which initiated and grew independently of matrix cracks, leading to sublaminate buckling. Increasing the maximum cyclic load changed the relative growth of the two modes of damage, thus changing the final failure mode. KEYWORDS: Damage accumulation, delamination, fatigue, gradient field.
Book Synopsis Advanced Residual Strength Degradation Rate Modeling for Advanced Composite Structures by : D. E. Pettit
Download or read book Advanced Residual Strength Degradation Rate Modeling for Advanced Composite Structures written by D. E. Pettit and published by . This book was released on 1979 with total page 344 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report presents the results of the first task of a three task program directed at the study of relationship between damage propagation and residual static strength of composite laminates. In Task 1: Preliminary screening, two laminates a 24-Ply 67% 0 deg. fiber and a 32-Ply quasi-isotropic laminate of T300/5208 graphite epoxy material were selected for study. Two damage types were studied, a low velocity impact condition (i.e., simulated tool drop) and a badly drilled hole. An initial study was conducted for each damage type to determine the detailed damage introduction parameters resulting in the selection of one set of impact and one set of poor drilling conditions. Baseline static tension and static compression tests were conducted on each of the four damage/laminate conditions. Stress vs life (S-N) fatigue data were then generated at range ratio R=-1 for each of the four conditions. The damage growth characteristics were monitored on each fatigue specimen using a modified Holscan ultrasonic unit. A subset of the damaged hole specimens was also evaluated in static compression and fatigue (R = -1) using TBE enhanced X-ray methods to monitor damage growth and to assess any detrimental effect of TBE on subsequent behavior of the damage. The results indicate significant reduction in initial static tension and compression strengths for the damaged hole condition in both laminates.
Book Synopsis Characterizing the Fatigue Damage in Non-traditional Laminates of Carbon Fiber Composites Using Radiography by : Joshua David Rast
Download or read book Characterizing the Fatigue Damage in Non-traditional Laminates of Carbon Fiber Composites Using Radiography written by Joshua David Rast and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The goal of this academic project was to study the effects of different variables on the damage progression around a central hole in carbon fiber composite coupon specimens. The tracked variables included the type of layup, stress ratio, stress levels, and damage mechanisms observed in each specimen. In-situ x-ray of the individual laminates recorded the extent of damage, mostly longitudinal splitting, as a function of the cycle count. The following lay-ups were included in the experiment: [45/90/-45/02/45/02/-45/0]s, ["5/65/("5)2/-65/"5]s, and ["5/65/("5)2/-65/5/65]s. More specifically, the objective of this study was to determine the stress levels at which detectable damage started to develop. The researchers chose to apply 50,000 cycles at each stress level and once damage was detected, the stress level was typically raised by 34.5 MPa (5 KSI), and then cycled another 50,000 cycles until damage exceeding 1.27 cm (0.50") in length was observed. Once the damage exceeded 1.27 cm (0.50"), cycling was continued to 1,000,000 cycles. Upon completion of the fatigue cycling, each specimen's residual strength was determined. The damage length versus stress level was plotted as a way to compare damage onset stresses and growth as a function of lay-up and stress ratio.
Book Synopsis Observations of the Load Redistribution in Polymeric Composite Laminates Under Tension-Tension Fatigue Loading by : MP. Connolly
Download or read book Observations of the Load Redistribution in Polymeric Composite Laminates Under Tension-Tension Fatigue Loading written by MP. Connolly and published by . This book was released on 1995 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt: A series of detailed measurements were obtained of the edge displacements at different stages in the fatigue life of a composite laminate subject to tension-tension fatigue loading. The objective of these measurements was to understand the nature of load redistribution in a composite laminate as it accumulates damage and fails. The measurements were performed using a computer-based stereoimaging system, which provides two-dimensional displacement maps by comparing photographs of the specimens taken at different load levels. Using this approach, a record of the edge displacements within a [0/452/-452/90]s graphite-epoxy laminate, subject to tension-tension fatigue loading, was obtained as a function of the cyclic life. These maps were used to provide a chronology of the strains and displacements along the specimen edge as the specimen failed. Very early in the fatigue life, large shear deformation occurred at the interface of the 45° and -45° layers. This deformation produced a delamination that eventually resulted in separation of the laminate into three sublaminates, consisting of the two edge [0/452] layers, together with the central [-452/902/-452] layers. No load was carried by the central off-axes layers, and final failure coincided with the failure of the outer 0° layers. The strains in each of the layers were obtained at different numbers of cycles from these displacement maps, and the results showed the redistribution of strains which occurs as the laminate accumulates damage and fails. These results are discussed in light of a recent proposed model based on a damage-dependent lamination equation to predict the stiffness degradation in composite materials subject to fatigue.
Book Synopsis An Evaluation of the Effects of Stacking Sequence and Thickness on the Fatigue Life of Quasi-isotropic Graphite/epoxy Laminates by :
Download or read book An Evaluation of the Effects of Stacking Sequence and Thickness on the Fatigue Life of Quasi-isotropic Graphite/epoxy Laminates written by and published by . This book was released on 1983 with total page 116 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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