Fatigue life methodology for tapered hybrid composite flexbeams

Murri, Gretchen B.; Schaff, Jeffery R.

doi:10.1016/j.compscitech.2005.06.010

Cited by 28 publications

(13 citation statements)

References 11 publications

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“…Much of this work took place in the 1990's and a comprehensive review of the ply drop studies conducted during this period is provided by He et al (2000). More recently, increasing attention has been placed on the analysis of fatigue delamination (Murri, 2006;Murri and Schaff, 2006) but the majority of studies to date have focused on the number of cycles for a crack to initiate at a stress concentration rather than subsequent damage propagation. For structures where fatigue is a critical design driver, such as the tidal turbine blades considered in the current article, considering only crack initiation can lead to over-conservative design, particularly in cases where there are sharp stress concentrations at very localized regions such as ply drops.…”

Section: Figure 2: the Structural Design Process For Tidal Turbine Blmentioning

confidence: 99%

Advanced numerical modelling techniques for the structural design of composite tidal turbine blades

Harper

Hallett

2015

Ocean Engineering

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Abstract:Tidal Stream turbine blades must withstand both extreme one-off loads and severe fatigue loads during their 20-25 year required lifetimes in harsh marine environments. This necessitates the use of high-strength fibre reinforced composite materials to provide the required stiffness, strength and fatigue life, as well as resistance to corrosion, whilst minimising the mass of material required for blade construction and allowing its geometric form to provide the required hydrodynamic performance. Although composites provide superior performance to metals, potential failure mechanisms are more complicated and difficult to predict. A dominant failure mechanism is interfacial failure (delamination) between the composite layers (plies). This paper demonstrates how the development of numerical techniques for modelling the growth of interfacial cracks can aid the design process, allowing the effects on crack growth from potential manufacturing defects and the effect of stacking sequence of composite plies to be analysed. This can ultimately lead to reduced design safety margins and a reduction in the mass of material required for blade manufacture, essential for reducing lifecycle costs. Although the examples provided in this article are specific to tidal turbine blades, the analysis techniques are applicable to all composite structures where fatigue delamination is a primary failure concern.

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Section: Figure 2: the Structural Design Process For Tidal Turbine Blmentioning

confidence: 99%

Advanced numerical modelling techniques for the structural design of composite tidal turbine blades

Harper

Hallett

2015

Ocean Engineering

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“…The applicability of mode I fatigue test procedures to glass fiber-reinforced polymer-matrix (GFRP) laminates was investigated [22,27] and it was shown that different types of FRP laminates could be discriminated [37]. The 2009 round robin exercise carried out by ESIS TC4 investigated the influences of control mode (load vs. displacement control), test frequency and test duration on the overall test results [36] performed at three laboratories.…”

Section: /39mentioning

confidence: 99%

“…Several research groups have further published results of cyclic mode I delamination measurements on FRP [12,[14][15][16][17][18][19][20][21][22][23][24][25]. There are approaches for incorporating delamination properties into structural design [26] and quasi-static as well as cyclic fatigue fracture mechanics data from composite laminates have been used to predict the delamination behavior of composite structures [27][28][29][30][31].…”

Section: Introductionmentioning

confidence: 99%

Mode I delamination fatigue crack growth in unidirectional fiber reinforced composites: Results from ESIS TC4 round-robins

Stelzer¹,

Brunner²,

Argüelles³

et al. 2014

Engineering Fracture Mechanics

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Two round robins on mode I fatigue delamination propagation organized by Technical Committee 4 of the European Structural Integrity Society compared three unidirectional carbon fiber reinforced composites, one with thermoplastic (poly-ether-ether-ketone) and two with thermoset (epoxy) matrix tested at five laboratories. Different approaches for data evaluation and their effect on the in-and inter-laboratory scatter are discussed and compared. Results are very sensitive to small scatter in the load signal, and, therefore, a new route to evaluate the crack growth rate from pairs of load and displacement data is presented.

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“…In the following studies [18][19][20], a combination of experiments and FEA of nonlinear tapered laminates under combined loading was used to predict delamination onset in these laminates. A fracture mechanics methodology, using strain energy release rate values calculated from the FEA, and material characterization data, was used to calculate a curve relating maximum surface strain in the flexbeam to the number of loading cycles at delamination onset.…”

Section: Non-linear Tapered Flexbeams With Combined Tension-bending Lmentioning

confidence: 99%

“…Test specimens from [19,20] were cut from the outboard tapered region of full-size flexbeams on a commercial…”

Section: Non-linear Tapered Flexbeams With Combined Tension-bending Lmentioning

confidence: 99%

Testing and life prediction for composite rotor hub flexbeams☆

Murri

2006

International Journal of Fatigue

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A summary of several studies of delamination in tapered composite laminates with internal ply-drops is presented.Initial studies used 2D FE models to calculate interlaminar stresses at the ply-ending locations in linear tapered laminates under tension loading. Strain energy release rates for delamination in these laminates indicated that delamination would likely start at the juncture of the tapered and thin regions and grow unstably in both directions.Tests of glass/epoxy and graphite/epoxy linear tapered laminates under axial tension delaminated as predicted.Nonlinear tapered specimens were cut from a full-size helicopter rotor hub and were tested under combined constant axial tension and cyclic transverse bending loading to simulate the loading experienced by a rotorhub flexbeam in flight. For all the tested specimens, delamination began at the tip of the outermost dropped ply group and grew first toward the tapered region. A 2D FE model was created that duplicated the test flexbeam layup, geometry, and loading. Surface strains calculated by the model agreed very closely with the measured surface strains in the specimens. The delamination patterns observed in the tests were simulated in the model by releasing pairs of MPCs along those interfaces. Strain energy release rates associated with the delamination growth were calculated for several configurations and using two different FE analysis codes. Calculations from the codes agreed very closely. The strain energy release rate results were used with material characterization data to predict fatigue delamination onset lives for nonlinear tapered flexbeams with two different ply-dropping schemes. The predicted curves agreed well with the test data for each case studied.

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Fatigue life methodology for tapered hybrid composite flexbeams

Cited by 28 publications

References 11 publications

Advanced numerical modelling techniques for the structural design of composite tidal turbine blades

Advanced numerical modelling techniques for the structural design of composite tidal turbine blades

Mode I delamination fatigue crack growth in unidirectional fiber reinforced composites: Results from ESIS TC4 round-robins

Testing and life prediction for composite rotor hub flexbeams☆

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