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  • 1
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    On the enhancement of impact damage tolerance of composite laminates (1993)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: This paper examines the use of a thin layer of Ultra High Molecular Weight Polyethylene (UHMWPE) on the outer surface of carbon/epoxy composite materials as a method of improving impact resistance and damage tolerance through hybridization. Flat 16-ply laminates as well as honeycomb sandwich structures with eight-ply facesheets were tested in this study. Instrumented drop-weight impact testing was used to inflict damage upon the specimens. Evaluation of damage resistance included instrumented impact data, visual examination, C-scanning and compression after impact (CAI) testing. The results show that only one lamina of UHMWPE did not improve the damage tolerance (strength retention) of the 16-ply flat laminate specimens or the honeycomb sandwich beams, however, a modest gain in impact resistance (detectable damage) was found for the honeycomb sandwich specimens that contained an outer layer of UHMWPE.
    Keywords: COMPOSITE MATERIALS
    Type: Composites Engineering (ISSN 0961-9526); 3; 5; p. 383-391, 393, 394
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    Materials and processes laboratory composite materials characterization task, part 1. Damage tolerance (1991)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A test run was performed on IM6/3501-6 carbon-epoxy in which the material was processed, machined into specimens, and tested for damage tolerance capabilities. Nondestructive test data played a major role in this element of composite characterization. A time chart was produced showing the time the composite material spent within each Branch or Division in order to identify those areas which produce a long turnaround time. Instrumented drop weight testing was performed on the specimens with nondestructive evaluation being performed before and after the impacts. Destructive testing in the form of cross-sectional photomicrography and compression-after-impact testing were used. Results show that the processing and machining steps needed to be performed more rapidly if data on composite material is to be collected within a reasonable timeframe. The results of the damage tolerance testing showed that IM6/3501-6 is a brittle material that is very susceptible to impact damage.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-TM-103553 , NAS 1.15:103553
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    A damage tolerance comparison of IM7/8551 and IM8G/8553 carbon/epoxy composites (1991)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A damage tolerance study of two new toughened carbon fiber/epoxy resin systems was undertaken as a continuation of ongoing work into screening new opposites for resistance to foreign object impact. This report is intended to be a supplement to NASA TP 3029 in which four new fiber/resin systems were tested for damage tolerance. Instrumented drop weight impact testing was used to inflict damage to 16-ply quasi-isotropic specimens. Instrumented output data and cross-sectional examinations of the damage zone were utilized to quantify the damage. It was found that the two fiber/resin systems tested in this study were much more impact resistant than an untoughened composite such as T300/934, but were not as impact resistant as other materials previously studied.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-TM-103526 , NAS 1.15:103526
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 4
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    The effects of compressive preloads on the compression-after-impact strength of carbon/epoxy (1992)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A preloading device was used to examine the effects of compressive prestress on the compression-after-impact (CAI) strength of 16-ply, quasi-isotropic carbon epoxy test coupons. T300/934 material was evaluated at preloads from 200 to 4000 lb at impact energies from 1 to 9 joules. IM7/8551-7 material was evaluated at preloads from 4000 to 10,000 lb at impact energies from 4 to 16 joules. Advanced design of experiments methodology was used to design and evaluate the test matrices. The results showed that no statistically significant change in CAI strength could be contributed to the amount of compressive preload applied to the specimen.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-TP-3303 , M-701 , NAS 1.60:3303
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 5
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    Low velocity instrumented impact testing of four new damage tolerant carbon/epoxy composite systems (1990)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Low velocity drop weight instrumented impact testing was utilized to examine the damage resistance of four recently developed carbon fiber/epoxy resin systems. A fifth material, T300/934, for which a large data base exists, was also tested for comparison purposes. A 16-ply quasi-isotropic lay-up configuration was used for all the specimens. Force/absorbed energy-time plots were generated for each impact test. The specimens were cross-sectionally analyzed to record the damage corresponding to each impact energy level. Maximum force of impact versus impact energy plots were constructed to compare the various systems for impact damage resistance. Results show that the four new damage tolerant fiber/resin systems far outclassed the T300/934 material. The most damage tolerant material tested was the IM7/1962 fiber/resin system.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-TP-3029 , NAS 1.60:3029
    Format: application/pdf
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  • 6
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    An examination of the damage tolerance enhancement of carbon/epoxy using an outer lamina of spectra (R) (1991)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Low velocity instrumented impact testing was utilized to examine the effects of an outer lamina of ultra-high molecular weight polyethylene (Spectra) on the damage tolerance of carbon epoxy composites. Four types of 16-ply quasi-isotropic panels (0, +45, 90, -45) were tested. Some panels contained no Spectra, while others had a lamina of Spectra bonded to the top (impacted side), bottom, or both sides of the composite plates. The specimens were impacted with energies up to 8.5 J. Force time plots and maximum force versus impact energy graphs were generated for comparison purposes. Specimens were also subjected to cross-sectional analysis and compression after impact tests. The results show that while the Spectra improved the maximum load that the panels could withstand before fiber breakage, the Spectra seemingly reduced the residual strength of the composites.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-TP-3160 , M-671 , NAS 1.60:3160
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 7
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    An examination of impact damage in glass-phenolic and aluminum honeycomb core composite panels (1990)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An examination of low velocity impact damage to glass-phenolic and aluminum core honeycomb sandwich panels with carbon-epoxy facesheets is presented. An instrumented drop weight impact test apparatus was utilized to inflict damage at energy ranges between 0.7 and 4.2 joules. Specimens were checked for extent of damage by cross sectional examination. The effect of core damage was assessed by subjecting impact-damaged beams to four-point bend tests. Skin-only specimens (facings not bonded to honeycomb) were also tested for comparison purposes. Results show that core buckling is the first damage mode, followed by delaminations in the facings, matrix cracking, and finally fiber breakage. The aluminum honeycomb panels exhibited a larger core damage zone and more facing delaminations than the glass-phenolic core, but could withstand more shear stress when damaged than the glass-phenolic core specimens.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-TP-3042 , NAS 1.60:3042
    Format: application/pdf
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  • 8
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    Effect Of Preloads On Postimpact Strengths Of Composites (1994)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Report presents results of experimental study of effect of compressive preload on compression-after-impact strengths of epoxy-matrix/carbon-fiber composite materials.
    Keywords: MATERIALS
    Type: MFS-27312 , NASA Tech Briefs (ISSN 0145-319X); 18; 9; P. 129
    Format: text
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