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  • 1
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    Residual strength of five boron/aluminum laminates with crack-like notches after fatigue loading (1986)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Boron/aluminum specimens were made with crack-like slits in the center and with various proportions of 0 and + or - 45 deg plies. They were fatigue loaded and then fractured to determine their residual strengths. The fatigue loads were generally in the range of 60 to 80 percent of the static tensile strength of the specimen as determined from a previous study, and the stress ratio was .05. For virtually all of the specimens the fatigue loading was continued for 100,000 cycles. The specimens were radiographed after the fatigue loading to determine the nature of the fatigue damage. A few specimens were sectioned and examined in a scanning electron microscope after being radiographed in order to verify the interpretation of the radiographs and also to get a better insight into the nature of the fatigue damage. The results indicate that the fatiguing does not significantly affect the strength of the specimens tested. The results of the radiography and of the scanning electron microscopy indicate that the 45 deg plies suffer extensive damage in the form of split and broken fibers and matrix cracking in the vicinity of the ends of the split. By contrast, the only significant damage to the 0 deg plies was a single 0 deg matric crack growing from the ends of the slit and between the 0 deg fibers.
    Keywords: COMPOSITE MATERIALS
    Format: text
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  • 2
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    Interlaminar fracture toughness of composites. II - Refinement of the edge delamination test and application to thermoplastics (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The mixed mode interlaminar fracture toughness, G(c), is obtained for the two thermoplastic matrices UDEL P1700 polysulfone and ULTEM polyetherimide by means of edge delamination tensile (EDT) tests on unnotched, eleven-ply graphite fiber reinforced composite specimens. A novel method is used to obtain the stiffness parameter employed in the closed form equation for the calculation of G(c), decreasing the number of stiffness measurements required and simplifying the calculations. The G(Ic) values from double cantilever beam (DCB) measurements on composites of the two thermoplastics were similar to each other, but slightly higher than the G(c) data obtained by EDT. Interfacial resin/fiber failures predominated in both the EDT and DCB tests.
    Keywords: COMPOSITE MATERIALS
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  • 3
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    Unknown
    Residual strength of five boron/aluminum laminates with crack-like notches after fatigue loading (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Boron/aluminum specimens were made with crack-like slits in the center and with various proportions of 0 and + or - 45 deg plies. They were fatigue loaded and then fractured to determine their residual strengths. The fatigue loads were generally in the range of 60 to 80 percent of the static tensile strength of the specimen as determined from a previous study, and the stress ratio was .05. For virtually all of the specimens the fatigue loading was continued for 100,000 cycles. The specimens were radiographed after the fatigue loading to determine the nature of the fatigue damage. A few specimens were sectioned and examined in a scanning electron microscope after being radiographed in order to verify the interpretation of the radiographs and also to get a better insight into the nature of the fatigue damage. The results indicate that the fatiguing does not significantly affect the strength of the specimens tested. The results of the radiography and of the scanning electron microscopy indicate that the 45 deg plies suffer extensive damage in the form of split and broken fibers and matrix cracking in the vicinity of the ends of the split. By contrast, the only significant damage to the 0 deg plies was a single 0 deg matric crack growing from the ends of the slit and between the 0 deg fibers.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-CR-3815 , NAS 1.26:3815
    Format: application/pdf
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  • 4
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    Unknown
    The effect of extreme temperatures on the elastic properties and fracture behavior of graphite/polyimide composites (1983)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The influence of elevated and cryogenic temperatures on the elastic moduli and fracture strengths of several C6000/PMR-15 and C6000/NR-15082 laminates was measured. Tests were conducted at -157 C, 24 C, and 316 C (-250 F, 75 F, and 600 F). Both notched and unnotched laminates were tested. The average stress failure criterion was used to predict the fracture strength of quasi-isotropic notched laminates.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-CR-172143 , NAS 1.26:172143
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  • 5
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    Comparisons of various configurations of the edge delamination test for interlaminar fracture toughness (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Various configurations of Edge Delamination Tension (EDT) test specimens, of both brittle (T300/5208) and toughened-matrix (T300/BP907) graphite reinforced composite laminates, were manufactured and tested. The mixed-mode interlaminar fracture toughness, G sub C, was measured using (30/30 sub 2/30/90 sub N)sub s, n=1 or 2, (35/-35/0/90) sub s and (35/0/-35/90) sub s layups designed to delaminate at low tensile strains. Laminates were made without inserts so that delaminations would form naturally between the central 90 deg plies and the adjacent angle plies. Laminates were also made with Teflon inserts implanted between the 90 deg plies and the adjacent angle (theta) plies at the straight edge to obtain a planar fracture surface. In addition, interlaminar tension fracture toughness, GIc, was measured from laminates with the same layup but with inserts in the midplane, between the central 90 deg plies, at the straight edge. All of the EDT configurations were useful for ranking the delamination resistance of composites with different matrix resins. Furthermore, the variety of layups and configurations available yield interlaminar fracture toughness measurements needed to generate delamination failure criteria. The influence of insert thickness and location, and coupon size on G sub c values were evaluated.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-TM-86433 , NAS 1.15:86433 , USAAVSCOM-TM-85-B-3 , AD-A160583
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  • 6
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    The effect of extreme temperatures on the elastic properties and fracture behavior of graphite/polyimide composites (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The influence of elevated and cryogenic temperatures on the elastic moduli and fracture strengths of several C6000/PMR-15 and C6000/NR-15082 laminates was measured. Tests were conducted at -157 C, 24 C, and 316 C (-250 F, 75 F, and 600 F). Both notched and unnotched laminates were tested. The average stress failure criterion was used to predict the fracture strength of quasi-isotropic notched laminates.
    Keywords: COMPOSITE MATERIALS
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  • 7
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    A simple test for the interlaminar fracture toughness of composites (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A simple test method for the measurement of delamination resistance is assessed through its application to 11-ply graphite-epoxy laminates whose matrices employ the F185 and 205 resins. The F185 resin has the same base epoxy as the 205, to which liquid and solid elastomers have been added. The critical value of the mixed mode energy release rate, calculated from a closed form equation employing nominal strain measurements from the onset of edge delamination, show that addition of the elastomers to the base epoxy increases interlaminar fracture toughness. Comparison of these results with those of width-tapered double cantilever beam (WTDCB) test data for the two materials shows a similar strain energy release rate, establishing the accuracy of the novel method. Both tests are found to be needed, however, for the quantitative characterization of interlaminar fracture toughness.
    Keywords: COMPOSITE MATERIALS
    Type: SAMPE Journal; 18; July-Aug
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  • 8
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    Crack-opening displacement transducer (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Crack-opening displacement transducer consists of 30 deg cone, coil spring, and linear-displacement transducer. Conical probe is used to measure crack opening. Cone is pressed firmly into crack by spring. As applied load causes crack to open up, cone is pushed further into it. Movement of cone, and thus crack growth, is monitored by linear-displacement transducer. Method gives more accurate measurement of crack-opening displacement of very narrow slots.
    Keywords: MECHANICS
    Type: LAR-12485 , NASA Tech Briefs (ISSN 0145-319X); 4; 3; P. 400
    Format: text
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  • 9
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    Determination of interlaminar fracture toughness and fracture mode dependence of composites using the edge delamination test (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-07-27
    Description: Edge delamination testing has been conducted in order to determine the mixed mode interlaminar fracture toughness of unnotched (+, -35/0/90)s and (0/+, -35/90)s laminates with graphite fibers and epoxy matrices, with or without elastomer additives. Although the two stacking sequences were chosen so that the total strain energy release rates were equal, the percentages of crack opening and shear mode energy release rates were found to vary widely between the layups. Plots of interlaminar fracture toughness as a function of crack opening energy release rate percentage have been drawn to generate delamination failure criteria which reflect the observed fracture mode dependence.
    Keywords: COMPOSITE MATERIALS
    Type: Testing, evaluation and quality control of composites; September 13, 14, 1983; Surrey
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  • 10
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    Matrix toughness, long-term behavior, and damage tolerance of notched graphite fiber-reinforced composite materials (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The long-term behavior of notched graphite-fiber-reinforced composite laminates with brittle or tough matrix materials and different fiber architectures was investigated using damage measurements and stiffness change, residual strength, and life data. The fiber/matrix materials included T300/5208, AS4/3501-6, AS4/1808, AS4/PEEK, and C3000/PMR-15 matrices and unidirectional tape and woven cloth fiber architectures. Results of damage evaluation and of residual strength measurements during the fatigue damage development showed that the long-term behavior and damage tolerance are controlled by a number of interacting factors such as the matrix toughness, fiber architecture, loading levels, and damage types and distributions.
    Keywords: COMPOSITE MATERIALS
    Type: Symposium on Composite Materials: Testing and Design; Apr 27, 1988 - Apr 29, 1988; Sparks, NV; United States
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