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Splitting Initiation And Propagation In Flawed Unidirectional Graphite Epoxy Composites Under Tension Tension Cyclic Loading
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Book Synopsis Splitting Initiation and Propagation in Flawed Unidirectional Graphite/epoxy Composites Under Tension-tension Cyclic Loading by : Mahmoud Hatem M. Helmi Daken
Download or read book Splitting Initiation and Propagation in Flawed Unidirectional Graphite/epoxy Composites Under Tension-tension Cyclic Loading written by Mahmoud Hatem M. Helmi Daken and published by . This book was released on 1983 with total page 334 pages. Available in PDF, EPUB and Kindle. Book excerpt: Damage by two distinct mechanisms is observed when flawed unidirectional graphite/epoxy composite specimens are monotonically loaded in tension along the fiber direction. The first mechanism is splitting damage i.e. the initiation of cracks at.the flaw tips that subsequently propagate in the matrix, parallel to the fibers, and towards the ends of specimen. This process divides the specimen into two outer load-carrying regions and a central load-free one whose width is equal to the flaw size. The second mechanism is the ultimate specimen failure by fiber breakage along planes normal to load direction and adjacent to the gripped ends. The initiation and propagation of splits under tension-tension cyclic loading were experimentally investigated. Ninety uni-directional [0]8 specimens with slits or holes of sizes 1/8", 1/4", and 3/8" were cyclically loaded to 80%, 70%, and 60% of their static splitting stress. The stress ratio of the load cycle was maintained at a nominal value of R[alpha] = 0.1 while cycling frequency was changed according to stress amplitude so as to keep a constant loading rate in all the tests. It was found that crack length varies with the natural logarithm of cycles endured in a linear fashion. The intercept of this line depends on flaw type, flaw size, and stress level while its slope depends only on flaw size and stress level. The functional forms of these dependencies were derived using multiple linear regression analysis of test data.
Book Synopsis Splitting Initiation and Propagation in Flawed Unidirectional G/E Composites Under Tension-tension Cyclic Loading by : Mahmoud Hatem M. Helmi Daken
Download or read book Splitting Initiation and Propagation in Flawed Unidirectional G/E Composites Under Tension-tension Cyclic Loading written by Mahmoud Hatem M. Helmi Daken and published by . This book was released on 1983 with total page 668 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Masters Theses in the Pure and Applied Sciences by : Wade H. Shafer
Download or read book Masters Theses in the Pure and Applied Sciences written by Wade H. Shafer and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 314 pages. Available in PDF, EPUB and Kindle. Book excerpt: Masters Theses in the Pure and Applied Sciences was first conceived, published, and disseminated by the Center for Information and Numerical Data Analysis and Synthesis (CINDAS) * at Purdue University in 1 957, starting its coverage of theses with the academic year 1955. Beginning with Volume 13, the printing and dissemination phases of the activity were transferred to University Microfilms/Xerox of Ann Arbor, Michigan, with the thought that such an arrangement would be more beneficial to the academic and general scientific and technical community. After five years of this joint undertaking we had concluded that it was in the interest of all con cerned if the printing and distribution of the volumes were handled by an interna tional publishing house to assure improved service and broader dissemination. Hence, starting with Volume 18, Masters Theses in the Pure and Applied Sciences has been disseminated on a worldwide basis by Plenum Publishing Cor poration of New York, and in the same year the coverage was broadened to include Canadian universities. All back issues can also be ordered from Plenum. We have reported in Volume 28 (thesis year 1 983) a total of 10,661 theses titles from 26 Canadian and 197 United States universities. We are sure that this broader base for these titles reported will greatly enhance the value of this important annual reference work. While Volume 28 reports theses submitted in-1983, on occasion, certain univer sities do report theses submitted in previous years but not reported at the time.
Book Synopsis Composites Engineering Handbook by : P.K. Mallick
Download or read book Composites Engineering Handbook written by P.K. Mallick and published by CRC Press. This book was released on 1997-03-19 with total page 1262 pages. Available in PDF, EPUB and Kindle. Book excerpt: Offers information on the fundamental principles, processes, methods and procedures related to fibre-reinforced composites. The book presents a comparative view, and provides design properties of polymeric, metal, ceramic and cement matrix composites. It also gives current test methods, joining techniques and design methodologies.
Book Synopsis Longitudinal Splitting in Unidirectional Composites, Analysis and Experiments by : J. G. Goree
Download or read book Longitudinal Splitting in Unidirectional Composites, Analysis and Experiments written by J. G. Goree and published by . This book was released on 1985 with total page 120 pages. Available in PDF, EPUB and Kindle. Book excerpt: An experimental study is conducted to determine the fracture behavior of center notched, unidirectional graphite/epoxy laminates when subjected to tensile loading. The actual behavior is compared to the behavior predicted by a mathematical model based on classical shear-lag assumptions. The model allows for damage to occur in the form of longitudinal matrix yielding and splitting with the matrix assumed to fail in pure shear. Results indicate that the model is capable of predicting split initiation stress levels accurately, but does not describe the subsequent split growth adequately. The model predicts rapid split growth following split initiation due to shear failure, while the actual behavior involves a slow split growth region prior to the rapid growth region. It is suggested that transverse matrix normal stresses are responsible for split initiation and the early, slow split growth. The model predicts the actual initiation stress levels reliably, and also appears to be able to predict the point at which the shear failure mode begins to dominate. The shear failure mode does eventually dominate, but at a slower rate than predicted. The nonuniform structure of the graphite/epoxy laminates is thought to be responsible for decreasing the split growth rate due to shear failure.
Book Synopsis Effect of Ply Thickness on Longitudinal Splitting and Delamination in Graphite/Epoxy Under Compressive Cyclic Load by : PA. Lagace
Download or read book Effect of Ply Thickness on Longitudinal Splitting and Delamination in Graphite/Epoxy Under Compressive Cyclic Load written by PA. Lagace and published by . This book was released on 1986 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt: The initiation and growth of damage due to compressive cyclic loading was investigated in [±45n/0n]s graphite/epoxy laminates where the "effective ply thickness" was varied by allowing n to take on the values 1, 2, and 3. A total of 35 axially loaded sandwich specimens with 6.35-mm-diameter holes were cycled at 7 Hz at peak stress levels of 52% to 72% of the static ultimate compressive stress of 425 MPa (which was experimentally determined to be independent of the value of n). Out-of-plane moiré interferometry and pulse-echo ultrasound techniques were used to nondestructively inspect the specimens and showed that three distinct modes of damage growth occur in these laminates. Delamination which initiates at the hole and grows in a radial or transverse fashion occurred only in 60% of the [±45/0]s specimens. For these two types of damage, the growth was rapid and led to catastrophic failure of the specimen. The remainder of the [±45/0]s specimens and all the laminates where the effective ply thickness was doubled and tripled, [±452/02]s and [±453/03]s, exhibited delaminations which initiated at the hole edges and grew parallel to the load direction with the width of the delamination equal to the width of the hole. Catastrophic failure did not occur in these cases. There is a linear relationship between the delamination length and the logarithm of the number of applied load cycles in all these cases. However, the delamination initiated earlier and at lower stress levels for laminates with larger effective ply thicknesses. Specimen sectioning and microscopic examination show that this damage depends on the development of splitting in the 0-deg plies and subsequent delamination as a result of shear failure at the -45°/0° ply interface in the region between the splits. Several [0/±45]s and [02/±452]s coupon specimens were cycled in tension and this splitting and subsequent delamination also developed. Residual tensile strength tests conducted on graphite/epoxy coupons debonded from the honeycomb after cycling showed a 50% increase in tensile strength over undamaged specimens with 6.35-mm-diameter holes. This is attributed to the redistribution of stress around the hole due to the relieving of stress concentration in the 0-deg plies by the splitting and delamination.
Download or read book Engineered Materials Abstracts written by and published by . This book was released on 1993-10 with total page 826 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Scientific and Technical Aerospace Reports by :
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1973 with total page 1064 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis The Effect of Ply Thickness on Longitudinal Splitting and Delamination in Graphite/epoxy Under Compressive Cyclic Load by : Paul A. Lagace
Download or read book The Effect of Ply Thickness on Longitudinal Splitting and Delamination in Graphite/epoxy Under Compressive Cyclic Load written by Paul A. Lagace and published by . This book was released on 1984 with total page 56 pages. Available in PDF, EPUB and Kindle. Book excerpt: The initiation and growth of damage due to compressive cyclic loading was investigated in [±45n/0/n]s graphite/epoxy laminates where the "effective ply thickness" was varied by allowing n to take on the values 1, 2, and 3. A total of thirty-five axially-loaded sandwich specimens with 6.35 mm diameter holes were cycled at 7 Hz at peak stress levels of 52% to 72% of the static ultimate compressive stress of 425 MPa (which was experimentally determined to be independent of the value of n). Out-of-plane moire interferometry and pulse-echo ultrasound techniques were used to nondestructively inspect the specimens and showed that three distinct modes of damage growth occur in these laminates. Delamination which initiates at the hole and grows in a radial or transverse fashion occurred only in 60% of the [±45/0]s specimens. For these two types of damage, the growth was rapid and led to catastrophic failure of the specimen. The remainder of the [±45/0]s specimens and all the laminates where the effective ply thickness was doubled and tripled, [±45 2/02]s and [± 45 3/03]s, exhibited delaminations which initiated at the hole edges and grew parallel to the load direction with the width of the delamination equal to the width of the hole. Catastrophic failure did not occur in these cases. There is a linear relationship between the delamination length and the logarithm of the number of applied load cycles in all these cases. However, the delamination initiated earlier and at lower stress levels for laminates with larger effective ply thicknesses. Specimen sectioning and microscopic examination shows that this damage depends on the development of splitting in the 0° plies and subsequent delamination as a result of shear failure at the -45°/0° ply interface in the region between the splits. Several [0/±45]s and [02/±45 2]s coupon specimens were cycled in tension and this splitting and subsequent delamination also developed. Residual tensile strength tests conducted on graphite/epoxy coupons debonded from the honeycomb after cycling showed a 50% increase in tensile strength over undamaged specimens with 6.35 mm diameter holes. This is attributed to the redistribution of stress around the hole due to the relieving of stress concentration in the 0° plies by the splitting and delamination
Book Synopsis Fibre Reinforced Polymers, International Dissertation by : John Summerscales
Download or read book Fibre Reinforced Polymers, International Dissertation written by John Summerscales and published by CRC Press. This book was released on 1988 with total page 174 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Damage Initiation and Propagation During Compressive Fatigue of Flawed Graphite/epoxy Composites by : Jerome Paul Fanucci
Download or read book Damage Initiation and Propagation During Compressive Fatigue of Flawed Graphite/epoxy Composites written by Jerome Paul Fanucci and published by . This book was released on 1981 with total page 616 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Mode II Delamination Fracture Toughness of Unidirectional Graphite/Epoxy Composites by : WL. Bradley
Download or read book Mode II Delamination Fracture Toughness of Unidirectional Graphite/Epoxy Composites written by WL. Bradley and published by . This book was released on 1989 with total page 21 pages. Available in PDF, EPUB and Kindle. Book excerpt: The mode II delamination fracture toughness of a ductile and a brittle unidirectional graphite/epoxy composite has been studied using the end-notched flexure (ENF) test and the end-loaded split laminate (ELS) test. The stress field in the vicinity of the crack tip of a split laminate beam under mode I and mode II (ELS test) conditions has been determined by means of a finite-element analysis. Also, the micromechanics of mode II fracture have been studied during in situ and postmortem observations of the fracture process. Both the ENF and ELS tests give similar values for GIIc. However, because elastic material behavior is assumed in the analysis, the GIIc results for a ductile composite are somewhat uncertain because permanent deformation is observed. The ELS test provides a pure shear stress state in the vicinity of the crack tip. The formation of hackles in composites made with brittle resins provides a more tortuous path for the crack leading to an increased resistance to delamination under mode II conditions compared to mode I. However, extensive resin deformation and yielding play a more significant role in the fracture resistance for mode II loading of composites made using a rubber-toughened epoxy.
Book Synopsis Scientific and Technical Aerospace Reports by :
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1989 with total page 1148 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Applied Mechanics Reviews written by and published by . This book was released on 1987 with total page 338 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Assessment of Damage in a Unidirectional Off-axis Carbon-Epoxy Composite Under Cyclic Loading by : LK. Sorenser
Download or read book Assessment of Damage in a Unidirectional Off-axis Carbon-Epoxy Composite Under Cyclic Loading written by LK. Sorenser and published by . This book was released on 2003 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt: Cyclic tests were conducted on unidirectional HTA/6376 specimens in order to isolate and describe the degradation of an off-axis composite, resulting in matrix dominated failure. Specimens were loaded at 45° to the fibre axis and tested first under quasi-static conditions and then under tension-tension fatigue. Resulting stress-life curves for the 45° off-axis carbon fibre-reinforced epoxy were shallow, resulting in a large amount of scatter.
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 The Failure of Integrally Stiffened Graphite/epoxy Panels by : Adam John Sawicki
Download or read book The Failure of Integrally Stiffened Graphite/epoxy Panels written by Adam John Sawicki and published by . This book was released on 1991 with total page 54 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nine graphite/epoxy panels were tested in uniaxial tension to examine the ability of stiffening strips to redirect propagating damage. The materials used were Hercules A370-5H/3501-6 prepreg fabric and AS4/3501-6 prepreg unidirectional tape. The layup of the unstiffened regions of the panels was four plies of fabric with the quasi-isotropic layup [0f/45f]s. Three different four ply unidirectional tape stiffener layups parallel to the applied load were tested. Specimen width was 203 mm with stiffener widths either 48 mm or 64 mm. Slits of three lengths, 51 mm, 71 mm and 102 mm (1.0 mm wide), were pre-cut into the panels perpendicular to the direction of loading. The panels were tested under load control. Stress-strain and photoelastic data was taken. The finite element code ADINA was used to examine the two-dimensional response of the panels. The three slit lengths were modeled to gain an understanding of the local stress and strain response ahead of the slit in the stiffened region. Contour plots of maximum strain and the orientation of these maximum values with respect to the load direction near slits and stiffened regions were generated. These analytical models showed higher strains in the stiffened regions ahead of the slit compared to the strains in the unstiffened regions. The local orientation of the maximum tensile strains in the stiffened regions ahead of the slit remained perpendicular to the slit and parallel to the applied load. At failure, propagating damage progressed directly across the stiffener either perpendicular to the applied load or at 45° with respect to the applied load. It is concluded that the maximum tensile strain and its orientation ahead of the slit as derived from the analysis plays a key role in the prediction of subsequent damage propagation in these laminates. It is also concluded that the structural and material couplings due to the unsymmetric layups in the stiffener regions have little if any affect on the ability of the stiffener to redirect damage propagation, since in all cases damage progressed through the stiffeners. KEY WORDS: graphite/epoxy fabric composites, stiffened panels, stiffening strips, stress concentrations, damage propagation, two dimensional finite-element analysis.
