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The inclined double notch shear test for determination of interlaminar shear properties of composite laminates
KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.).
2005 (English)Doctoral thesis, comprehensive summary (Other scientific)
Place, publisher, year, edition, pages
Stockholm: KTH , 2005. , 23 p.
Series
Trita-HFL. Report / Royal Institute of Technology, Solid mechanics, ISSN 1654-1472 ; 0369
Keyword [en]
compisite, laminate, interlaminar, shear, test method, experimental comparison, strength
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-557OAI: oai:DiVA.org:kth-557DiVA: diva2:14428
Public defence
2005-12-19, Sal D2, Lindstedtsvägen 3, Stockholm, 10:00
Opponent
Supervisors
Note

QC 20101012

Available from: 2005-12-14 Created: 2005-12-14 Last updated: 2013-01-14Bibliographically approved
List of papers
1. Analysis of the IDNS test for composite interlaminar shear properties
Open this publication in new window or tab >>Analysis of the IDNS test for composite interlaminar shear properties
(English)Article in journal (Other academic) In press
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-25192 (URN)
Note
QC 20101012Available from: 2010-10-12 Created: 2010-10-12 Last updated: 2010-10-12Bibliographically approved
2. Experimental determination of composite interlaminar shear properties and evaluation of the IDNS Setup.
Open this publication in new window or tab >>Experimental determination of composite interlaminar shear properties and evaluation of the IDNS Setup.
(English)In: Composites Science And Technology, ISSN 0266-3538Article in journal (Other academic) In press
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-25197 (URN)
Note
QC 20101012Available from: 2010-10-12 Created: 2010-10-12 Last updated: 2010-10-12Bibliographically approved
3. Evaluation of four composite shear test methods by digital speckle strain mapping and fractographic analysis
Open this publication in new window or tab >>Evaluation of four composite shear test methods by digital speckle strain mapping and fractographic analysis
Show others...
2000 (English)In: Journal of composites technology & research, ISSN 0884-6804, Vol. 22, no 3, 161-172 p.Article in journal (Refereed) Published
Abstract [en]

Four methods to determine composite interlaminar shear strength (ILSS) are evaluated. In particular, the recently devised inclined double-notch shear test (IDNS) is compared with three existing and more established methods: the Iosipescu test, the short three-point bending test (S3PB) and the double-notch compression test (DNC). The uniformity of strain field in the test region in a real test situation-which is the crucial test method quality parameter-is investigated by strain mapping using digital speckle photography. The measured strain fields are compared with FE-calculated strains representing ideal conditions and both known advantages and drawbacks of the different methods are confirmed. The IDNS test produces the most uniform strain fields and also consistently high ILSS values. A fractographic analysis indicates shear separation over a major part of the fracture surfaces of all specimen types; typical shear cusps were found over about 80% of the IDNS fracture surface and in about 50% to 70% in the other specimens. For the Iosipescu tests, failure initiation could be ascribed to initiation in tension at defects. Experimentally determined stress-strain responses in shear exhibit a distinct variation among the different methods. For the best methods, a notable material softening was observed Drier to failure. Observed formation of shear cusps is believed to be the primary cause for this softening of the composite material studied here.

Keyword
composite, shear test, Iosipescu, short beam, double notch, inclined, experiment, comparison, evaluation, fractography, strain mapping
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-25199 (URN)000088320100005 ()
Note
QC 20101012Available from: 2010-10-12 Created: 2010-10-12 Last updated: 2010-10-12Bibliographically approved
4. V-notched shear specimens for the idns test method
Open this publication in new window or tab >>V-notched shear specimens for the idns test method
2001 (English)Report (Other academic)
Publisher
25 p.
Series
KTH Department of Solid Mechanics Report, 290
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-25200 (URN)
Note
QC 20101012Available from: 2010-10-12 Created: 2010-10-12 Last updated: 2010-10-12Bibliographically approved
5. A tensile setup for the IDNS composite shear test
Open this publication in new window or tab >>A tensile setup for the IDNS composite shear test
2006 (English)In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, Vol. 37, no 2, 229-242 p.Article in journal (Refereed) Published
Abstract [en]

An existing test method, the inclined double notch shear (IDNS-) test, for determination of interlaminar shear properties in thin panels of layered composite materials was developed further. Experimentally observed and unresolved issues with the original IDNS-test setup were addressed. Undesired specimen deformation (and potential instability) is observed at high loads with the original compressive setup, particularly for more compliant materials. Then, testing conditions continuously change throughout a test. Here, a tensile setup which applied a statically determined combination of loads to the doubly notched specimen was used instead. The proper combination of loads minimized the arising stress concentrations at the notch roots while it produced a homogeneous state of true inter-laminar shear stress over the test region. Numerical (FE-) analyses and experimental studies to investigate testing conditions such as: specimen geometry parameters, appropriate loading combinations, and recommendations for optimal test performance in terms of achieved shear strengths and shear strain fields, were performed. In addition to the tensile setup, the possibility to use tilted notches was studied. The tensile IDNS-setup produced more homogeneous fields over the test region, even for short notch distances, further it achieved interlaminar shear strength values in the same range as or even higher than the original setup. Finally, distinctly less specimen deformation was observed with the tensile setup, and thus proper adjustment was much simpler while instability was completely avoided.

Keyword
iosipescu specimen, elasticity analysis, concentrated loads, orthotropic beams, 3-point
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-25195 (URN)10.1016/j.compositesa.2005.08.018 (DOI)000235931100010 ()2-s2.0-32344432285 (Scopus ID)
Conference
2nd International Conference on Composites Testing and Model Identification (CompTest 200) Univ Bristol, Bristol, ENGLAND, SEP 21-23, 2004
Note
QC 20101012Available from: 2010-10-12 Created: 2010-10-12 Last updated: 2011-10-03Bibliographically approved
6. Stiffness reduction, creep, and irreversible strains in fiber composites tested in repeated interlaminar shear
Open this publication in new window or tab >>Stiffness reduction, creep, and irreversible strains in fiber composites tested in repeated interlaminar shear
2006 (English)In: Composite structures, ISSN 0263-8223, Vol. 76, no 1-2, 151-161 p.Article in journal (Refereed) Published
Abstract [en]

Interlaminar shear of a unidirectional carbon fiber/epoxy composite was studied experimentally by use of a tensile inclined double notch shear (IDNS-) test-setup. The non-linear constitutive behavior, the degradation and stiffness reduction, under monotonic and repeated loading with successively increasing peak strains were investigated. Shear strains (average values) up to 7-8% prior to failure were observed in the test region together with irreversible strains approaching 2.5% when unloaded. Hysteresis loops of notable width, increasing with higher peak strains, were observed. Several shear moduli measures were investigated. A notable decay in unloading secant moduli (similar to 30-40%) was present. Tangent (re-)loading and unloading moduli could be reliably measured only with a 2 h hold time prior to each load reversal. A quite early drop of > 10% was observed in the elastic reloading tangent modulus, but not for the unloading tangent modulus. To the knowledge of the authors, no previous experiments have achieved global interlaminar shear strain levels of such magnitudes, and moreover, stress levels were higher than obtained with previously established methods. Several mechanisms were deemed to contribute to the overall strains; such were higher elastic-but also higher irreversible shear strains in the epoxy matrix and the fibers; damage within the epoxy; conceivably also in the fibers; appearance of microcracks in epoxy-rich regions; possibly separation of the interfaces, and also notable creep deformation at higher loads. None of these phenomena alone could account for the dominating part of the obtained strains. Matrix cracks (shear hackles) were found post mortem, but could not be confirmed during the test: a different damage mechanism is responsible for the early loss of elastic stiffness. Friction-like processes (sliding, viscosity) contributed substantially to the total strains.

Keyword
interlaminar shear, constitutive behavior, creep, loading-unloading, carbon fiber/epoxy, optical whole field strains, stiffness loss, degradation
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-25203 (URN)10.1016/j.compstruct.2006.06.021 (DOI)000241777000021 ()2-s2.0-33747371456 (Scopus ID)
Note
QC 20101012. Conference: 15th International Conference on Composite Materials (ICCM-15). Durban, SOUTH AFRICA. JUN 27-JUL 01, 2005Available from: 2010-10-12 Created: 2010-10-12 Last updated: 2011-09-28Bibliographically approved

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