Specimen gripping effects in composites fatigue testing -– Concerns from initial investigation

Bailey, P.B.S.; Lafferty, Austin D.

doi:10.3144/expresspolymlett.2015.45

Cited by 17 publications

(3 citation statements)

References 15 publications

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“…Furthermore, a correlation between clamping pressure and constraint of the specimen exists. [11] A higher constrained specimen end will enlarge the required gauge length for layups with larger Poisson's ratio or more angle plies. Using self-clamping wedge grips, this effect leads to differently constrained specimen ends for different loading levels in fatigue testing, which could potentially influence the measured slope of the S-N curve for a fixed gauge length.…”

Section: Shear Loadingmentioning

confidence: 99%

Compression Fatigue Testing Setups for Composites—A Review

Baumann

Hausmann

2020

Adv Eng Mater

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Continuous fiber reinforced plastics show major advantages in tensile loading conditions. This is especially true for cyclic loading due to the good fatigue performance provided by glass and carbon fibers. However, it is widely accepted that compressive loading is a critical load case for most composites. For fiber reinforced plastics, this is mostly due to instabilities on different length scales-beginning at the smallest scale with microbuckling of single fibers to instabilities of fiber bundles, namely, fiber kinking, up to global buckling of the hole laminate. The sequence of events is hard to discern for quasi-static testing, and often, it remains unclear as to the cause of failure. This is even more the case for compressive fatigue testing. Different approaches can be found in the literature on how fatigue tests should be performed. A mandatory requirement for reliable design data is tested under conditions found in subsequently manufactured components. Therefore, it is generally sought to prevent the global buckling while allowing for all other damage mechanisms to take place. Two main testing strategies for axially loaded plates or strip-like specimens can be identified to achieve this goal. One common strategy is shortening the gauge length to a value where global buckling occurs after compressive failure. The second approach uses anti-buckling guides to prevent global buckling. These testing strategies are established methods for static compression testing and are sometimes also used for fatigue testing. However, the number of fixtures in both approaches is numerous, and only some of the fixtures are viable for fatigue testing. These generally accepted methods for compression testing are supplemented by different specimen geometries or loading conditions. A generalized overview is given in Figure 1. The aim of this review is to evaluate the applicability of these testing methods in terms of compressive fatigue testing, namely, loading ratios (load ratio R < 0 and R > 1) containing compressive loads. The evaluation is based on the reported use of a test setup or by discussion of pros and cons of setups for quasi-static testing. This approach is necessary, as the number of reported works on compressive fatigue testing is sparse. This review is structured by testing type rather than chronological order. Before evaluating compression testing methods, a quick summary of failure modes observed in static compression testing is given along with the damage progression under compressive fatigue loading. The review of testing methods then starts with axially loaded flat specimens. In the second and third parts, work on bending tests and tubular specimens is reviewed, respectively. 2. Failure Modes 2.1. Compressive Failure Modes in Fiber Reinforced Composites The properties of fiber reinforced plastics depend mainly on the type of reinforcement chosen as well as the stacking sequence of layers within a laminate. For compressive loads, the matrix

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Section: Shear Loadingmentioning

confidence: 99%

Compression Fatigue Testing Setups for Composites—A Review

Baumann

Hausmann

2020

Adv Eng Mater

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“…It suggests that the length of the tabs should be 50 mm and it should hang 10 mm out of the grips. When loaded statically or dynamically, the material must fail within the gauge length or in the zone where perceptively stress concentration is greater so as to assess the failure mechanism . Failure is unacceptable in or near the tabs or even in the grips where there are no tabs.…”

Section: Notch/stress Concentrationmentioning

confidence: 99%

Fatigue behavior of FRP composites and CNT‐Embedded FRP composites: A review

Gaurav

Singh

2016

Polymer Composites

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Composite materials have emerged as an effective substitute for conventional materials in various fields of engineering and structural science. For replacement of regular metals, composites, especially fiber‐reinforced polymer composites, have proved to be a suitable alternative. One of the important tests that conventional and composite materials have to undergo is fatigue test. It refers to the testing of materials for their cyclic behavior. In fatigue testing, depending on the choice of the researchers, materials are loaded till reaching their failure or till reaching a fraction of the total stiffness loss. Composite materials are different from metals and they show a distinct behavior under fatigue loading. In metals, failure occurs from the commencement of a single crack and then its propagation. In composite materials, conversely, it is a complex process as these materials possess crack‐arresting properties. This review paper highlights various aspects of the cyclic or fatigue behavior in composite materials. Factors triggering such behavior in composite materials include reinforcing substance, matrix material, fiber orientation or stacking sequence, fiber content, testing environment and so on, together with the damage development process at the microscopic level. Loading condition parameters pertain to stress ratio, mean stress, loading condition, multiaxial stress, and testing frequency. This article also includes the effect of carbon nanotubes on the fatigue life of the polymer composites. POLYM. COMPOS., 39:1785–1808, 2018. © 2016 Society of Plastics Engineers

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“…When no sudden fracture occurs the related fracture mechanical concepts consider the energy dissipation during crack growth. 42 However, in order to derive fracture mechanical parameters, crack growth needs to be tracked. Moreover, it would be desirable to follow crack growth in real-time.…”

Section: Crack Growthmentioning

confidence: 99%

Failure Assessment and Evaluation of Damage Development and Crack Growth in Polymer Composites Via Localization of Acoustic Emission Events: A Review

2017

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This review aims at showing how the location of acoustic emission (AE) in loaded polymer composites can be used to get a deeper insight into the onset and growth of damage, and associated failure events and sequences. Different location methods (experimental and theoretical) are briefly introduced along with AE characteristics in time and frequency domains. Linear (1D), planar (2D), and spatial (3D) locations of AE are examined through selected examples. The cited works demonstrate the versatile use of AE. Apart from damage and failure assessment, AE can be used to reconstruct crack growth, and thereby help determine the accurate fracture mechanical parameters. Unlike the detection of the development of damage, the identification of failure mechanisms by analyzing selected AE signal parameters, including their clustering, requires further research. Unraveling the failure mode is, however, a key topic with respect to structural integrity, residual strength, and lifespan expectation of composite parts. A recent major challenge is to establish a reliable, real-time structural health monitoring system making use of located AE events monitored by built-in sensors.

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Specimen gripping effects in composites fatigue testing -– Concerns from initial investigation

Cited by 17 publications

References 15 publications

Compression Fatigue Testing Setups for Composites—A Review

Compression Fatigue Testing Setups for Composites—A Review

Fatigue behavior of FRP composites and CNT‐Embedded FRP composites: A review

Failure Assessment and Evaluation of Damage Development and Crack Growth in Polymer Composites Via Localization of Acoustic Emission Events: A Review

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