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  • 1
    Electronic Resource
    Electronic Resource
    Fibre concrete materials (1977)
    Springer
    Materials and structures 10 (1977), S. 103-120 
    Details
    ISSN: 1359-5997
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02474859
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Delayed yielding of epoxy resin. II. Behavior under constant stressProd. No. 1578 (1967)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 11 (1967), S. 1863-1880 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Creep tests were carried out on epoxy resin specimens at room temperature and at different high stress levels under tension, compression, and flexure. Compared with the behavior at constant strain rate (CSR) reported in Part I of this work, creep strain-time curves revealed a distinct delayed yielding region of constant minimum rate (secondary creep) followed by a post-yielding region of increasing slope (tertiary creep). In all cases, results indicate linearity between creep stress and log secondary creep rate, which is almost coincident with the corresponding relationship between yield stress and strain rate obtained in subsequent CSR loading cycles with the same specimens. The similarity in behavior under both the creep and CSR modes conforms to Eyring's theory of non-Newtonian viscous flow at high stress levels and low temperature. Theoretical analysis yields reasonable values of the activation volume, which is unaffected by the loading and test modes or by loading history, and could thus be regarded as an intrinsic parameter of the microstructure, inherently related to the viscoplastic process involved. The above considerations indicate a deviatoric stress-biased diffusional mechanism as the predominant factor in the yielding of an amorphous glassy epoxy system.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1967.070111005
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  • 3
    Electronic Resource
    Electronic Resource
    Environmental effects on deformation, strength, and degradation of unidirectional glass-fiber reinforced plastics. I. Survey (1975)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 15 (1975), S. 486-490 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: This survey covers the topic of environmental effects on the mechanical behavior of fiber-reinforced plastics. It deals also with the separate and combined effects of temperature, hygrometry and loading on mechanical characteristics. The response of the phases of the composite-fiber, the matrix and the interfacial region to the environmental loading history, is discussed. Conflicting hypotheses regarding the causes and mechanism of the degradation process and of the long-range durability of the composites are examined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760150703
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  • 4
    Electronic Resource
    Electronic Resource
    Environmental effects on deformation, strength, and degradation of unidirectional glass-fiber reinforced plastics. II. Experimental study (1975)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 15 (1975), S. 491-499 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Glass-fiber reinforced epoxy (GRP) and unfilled epoxy specimens were exposed to different environmental conditions consisting of hot- and cold-water absorption and subsequent drying. Effects of the environmental history on deformational and strength characteristics of the composite material were investigated.GRP specimens exposed to hot water undergo pronounced degradation, which sets in shortly after exposure and is associated with a significant irrecoverable weight loss. Degraded specimens are characterized by higher void content and lower strength compared with their cold-water and reference counterparts. The degradation process is attributed to penetration of water into the matrix-fiber interfaces and is followed by an attack, at high temperatures, on the glass-fibers surface and coupling agent. As a result, glass constituents are leached out and then removed from the system by diffusion.The degradation effect was also confirmed by micro-observation of the fractured surfaces and by infra-red spectroscopy. A simple and effective testing method is recommended, permitting detection of degradation onset and its progress by simultaneous measurement of weight and dimensional changes with time.
    Additional Material: 21 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760150704
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  • 5
    Electronic Resource
    Electronic Resource
    Delayed yielding of epoxy resin under tension, compression, and flexure. I. Behavior under constant strain rate (1967)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 11 (1967), S. 963-981 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Series of loading tests were carried out on epoxy resin specimens, at varying constant strain rates, under tension, compression, and flexure. The stress-strain relationship revealed a distinct yielding stage followed shortly by a post-yielding region of decreasing load. In all cases, results indicate linearity between yield stress and log strain rate, in accordance with Eyring's theory of viscous flow. For specimens unloaded close to the yield point, photoelastic observations revealed a residual pattern parallel to the theoretical principal shear stresses. These results, supported by additional data from other works, indicate a viscoplastic deviatoric stress-biased diffusional mechanism as the dominant factor in the yielding of an amorphous crosslinked epoxy system.
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1967.070110616
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  • 6
    facet.materialart.
    Unknown
    Design of highly damage-tolerant sandwich panels (1992)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: The effects of different fabrication procedures to increase the damage tolerance of sandwich panels were studied. Baseline panels consisted of a 25.4 mm premolded core, surfaced with 177 C cure film adhesive and carbon-bismaleimide prepreg which were subsequently cocured onto the core. It was found that panels with a prefabricated skin, which was subsequently bonded onto the core with room temperature cure adhesive, showed greatly increased damage tolerance.
    Keywords: STRUCTURAL MECHANICS
    Type: In: International SAMPE Symposium and Exhibition, 37th, Anaheim, CA, Mar. 9-12, 1992, Proceedings (A93-15726 04-23); p. 1228-1242.
    Format: text
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  • 7
    facet.materialart.
    Unknown
    Long-term hygrothermal effects on damage tolerance of hybrid composite sandwich panels (1995)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: A sandwich construction, composed of hybrid carbon-glass fiber-reinforced plastic skins and a syntactic foam core, was selected as the design concept for a wind tunnel compressor blade application, where high damage tolerance and durability are of major importance. Beam specimens were prepared from open-edge and encapsulated sandwich panels which had previously been immersed in water at different temperatures for periods of up to about two years in the extreme case. Moisture absorption and strength characteristics, as related to time of exposure to hygrothermal conditions, were evaluated for the sandwich specimens and their constituents (skins and foam). After different exposure periods, low-velocity impact damage was inflicted on most sandwich specimens and damage characteristics were related to impact energy. Eventually, the residual compressive strengths of the damaged (and undamaged) beams were determined flexurally. Test results show that exposure to hygrothermal conditions leads to significant strength reductions for foam specimens and open-edge sandwich panels, compared with reference specimens stored at room temperature. In the case of skin specimens and for beams prepared from encapsulated sanwich panels that had previously been exposed to hygrothermal conditions, moisture absorption was found to improve strength as related to the reference case. The beneficial effect of moisture on skin performance was, however, limited to moisture contents below 1% (at 50 C and lower temperatures). Above this moisture level and at higher temperatures, strength degradation of the skin seems to prevail.
    Keywords: COMPOSITE MATERIALS
    Type: Composites (ISSN 0010-4361); 26; 1; p. 47-61
    Format: text
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  • 8
    facet.materialart.
    Unknown
    Damage tolerance of a composite sandwich with interleaved foam core (1992)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: A composite sandwich panel consisting of carbon fiber-reinforced plastic (CFRP) skins and a syntactic foam core was selected as an appropriate structural concept for the design of wind tunnel compressor blades. Interleaving of the core with tough interlayers was done to prevent core cracking and to improve damage tolerance of the sandwich. Simply supported sandwich beam specimens were subjected to low-velocity drop-weight impacts as well as high velocity ballistic impacts. The performance of the interleaved core sandwich panels was characterized by localized skin damage and minor cracking of the core. Residual compressive strength (RCS) of the skin, which was derived from flexural test, shows the expected trend of decreasing with increasing size of the damage, impact energy, and velocity. In the case of skin damage, RCS values of around 50 percent of the virgin interleaved reference were obtained at the upper impact energy range. Based on the similarity between low-velocity and ballistic-impact effects, it was concluded that impact energy is the main variable controlling damage and residual strength, where as velocity plays a minor role.
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Composites Technology & Research (ISSN 0885-6804); 14; 3; p. 155-168.
    Format: text
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  • 9
    facet.materialart.
    Unknown
    Low and high velocity impact response of thick hybrid composites (1993)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The effects of low and high velocity impact on thick hybrid composites (THC's) were experimentally compared. Test Beams consisted of CFRP skins which were bonded onto an interleaved syntactic foam core and cured at 177 C (350 F). The impactor tip for both cases was a 16 mm (0.625 inch) steel hemisphere. In spite of the order of magnitude difference in velocity ranges and impactor weights, similar relationships between impact energy, damage size, and residual strength were found. The dependence of the skin compressive strength on damage size agree well with analytical open hole models for composite laminates and may enable the prediction of ultimate performance for the damaged composite, based on visual inspection.
    Keywords: COMPOSITE MATERIALS
    Type: Texas Univ., Effect of Impact Damage and Open Hole on Compressive Strength of Hybrid Composite Laminates; p 1149-1159
    Format: application/pdf
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