Influence of stress ratio and stress concentration on the fatigue behaviour of hygrothermal aged multidirectional CFRP composite laminate

Composite laminates are used in structural applications such as aircraft wings and tail structures. Drilling holes and making cutouts in these laminates are unavoidable for practical reasons. As a result, stress concentration is introduced near the hole or cutout, and the load-bearing capacity of the structure is reduced. In addition, composite laminates used in aerospace applications are subjected to considerable fatigue loading due to service conditions. In composite laminates, fatigue causes reduction in stiffness and strength. The objective of the present work is to study the combined effect of stress concentration and fatigue on the composite laminate. Since composite laminate displays significant variation in material and strength properties, the stress distribution in the laminate is stochastic in nature. It is more appropriate to analyze the notched composite laminates using a stochastic approach and to design the laminate based on a reliability-based design approach. In the present work, such an approach is developed and the combined effect of stress concentration and fatigue on the reliability of the laminate is investigated.

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A Study on Stress Concentration Factor of Composite Laminate Mechanical Joints

Journal of the Korean Society for Aeronautical & Space Sciences ◽

10.5139/jksas.2013.41.3.194 ◽

2013 ◽

Vol 41 (3) ◽

pp. 194-200

Author(s):

Jeong-Sik Kwon ◽

Jin-Sung Kim ◽

Soo-Yong Lee

Keyword(s):

Stress Concentration ◽

Stress Concentration Factor ◽

Concentration Factor ◽

Composite Laminate ◽

Mechanical Joints

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1216 Effects of Stress Ratio on Fatigue Behaviour of Notched Specimen in Ti-6Al-4V Titanium Alloy

The Proceedings of Conference of Hokuriku-Shinetsu Branch ◽

10.1299/jsmehs.2016.53._1216-1_ ◽

2016 ◽

Vol 2016.53 (0) ◽

pp. _1216-1_-_1216-4_

Author(s):

Aye Thant Htoo ◽

Yukio Miyashita ◽

Yuichi Otsuka ◽

Yoshiharu Mutoh ◽

Shigeo Sakurai

Keyword(s):

Titanium Alloy ◽

Stress Ratio ◽

Fatigue Behaviour ◽

Notched Specimen ◽

Effects Of Stress

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Effect of prestress level on the strength of CFRP composite laminate

Journal of Mechanical Science and Technology ◽

10.1007/s12206-016-1029-1 ◽

2016 ◽

Vol 30 (11) ◽

pp. 5115-5123 ◽

Cited By ~ 3

Author(s):

Osama A. Abdullah ◽

Abdul Kareem F. Hassan

Keyword(s):

Composite Laminate ◽

Cfrp Composite

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Comparative Study on Fatigue Life of CFRP Composites with Damages

Fatigue of Aircraft Structures ◽

10.2478/fas-2019-0004 ◽

2019 ◽

Vol 2019 (11) ◽

pp. 28-38

Author(s):

Marta Baran ◽

Piotr Synaszko ◽

Janusz Lisiecki ◽

Sylwester Kłysz

Keyword(s):

Residual Strength ◽

Stress Ratio ◽

Fatigue Tests ◽

Equivalent Diameter ◽

Compression After Impact ◽

Strength Tests ◽

Cfrp Composite ◽

Sinusoidal Shape ◽

Weight Impact ◽

The Impact

AbstractIn this work, the compressive residual strength tests results, Compression After Impact (CAI), are presented. The specimens were made of carbon-epoxy prepreg E722-02 UHS 130-14. Two variants of specimens were tested: samples undamaged and samples with damage that was centrally introduced by a drop-weight impact, as per the ASTM D7136/7136M standard. An impactor with potential energy equal to 15J and the type of support required by the standard were used. The size of impacted damages, defined as an area of damage on a plane perpendicular to the impact direction, and the equivalent diameter were specified using the flash thermography method.The tests were performed using the fixtures manufactured according to the ASTM D7137/7137M standard. The specimens were compressed to determine the residual strength. This value was afterwards used to specify the force levels for the fatigue tests. The fatigue tests were carried out under force control – with a sinusoidal shape, stress ratio R equal to 0.1 and frequency f 1Hz. Maximum force in a loading cycle Pmax was being increased after each thousand of cycles N until its value was close to the residual strength determined in the previously mentioned tests. In this work, the following relationships were presented: force-displacement P-δ for both static and fatigue tests and displacement-loading cycles δ-N for fatigue tests.A method of conducting the fatigue tests of CFRP composite was proposed, in which both the CAI specimens and CAI fixture were used. This allowed researchers to accelerate making initial comparisons between the two groups of specimens with damages – grouped relative to the way of conditioning.

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Fatigue Life Properties of Circumferentially-Notched Bar of Austenitic Stainless Steel With Various Concentration Factors

Volume 6B: Materials and Fabrication ◽

10.1115/pvp2018-84420 ◽

2018 ◽

Author(s):

Naoaki Nagaishi ◽

Michio Yoshikawa ◽

Saburo Okazaki ◽

Hisao Matsunaga ◽

Junichiro Yamabe ◽

...

Keyword(s):

Stainless Steel ◽

Fatigue Life ◽

Stress Concentration ◽

Austenitic Stainless Steel ◽

Stress Concentration Factor ◽

Concentration Factor ◽

Stress Ratio ◽

Ambient Air ◽

Fatigue Tests ◽

Concentration Factors

Fatigue tests were performed using three types of round-bar specimens of Type 304, meta-stable, austenitic stainless steel. The specimens had circumferential notch with stress concentration factors, Kt, of 2, 3 or 6.6. Load controlled fatigue tests were conducted at stress ratio, R, of 0.1 and −1 in ambient air at room temperature. At R of 0.1, fatigue life was decreased with an increase in the stress concentration factor. Conversely, at R of −1, the stress concentration factor had little influence on the fatigue life. To understand the mechanism of the stress ratio effect, local deformation behavior at and beneath the notch root during the fatigue test was computed by means of finite element analysis considering that the plastic constitutive model describes the cyclic stress-strain response.

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