Alderliesten rc 2007 analytical prediction model for fatigue crack propagation and delamination growth in glare. Fatigue resistance of fibermetal laminates springerlink. Table 2 fatigue crack propagation life sample fatigue lifen photo number fml 101 500000 51 fml 102 228380 23 fml 201 345495 35 fml 202 214671 22 fatigue life crack growth rates are compared and shown in figure 6. Doctor thesis, delft university of technology 2005. The stress intensity factor at the crack tip is a function of the far field opening stress and the crack closing bridging stress in the aluminium layers. This paper concerns the numerical characterization of the fatigue strength of a flat stiffened panel, designed as a fiber metal laminate fml and made of aluminum alloy and fiber glass frp. The major concept is that the stress intensity at a crack tip in the aluminium layers of glare is the factor determining the crack extension under cyclic loading. Fatigue crack growth in a fibre metal laminate like glare is accompanied by delamination growth at the interface between the aluminium and glass fibres. Summary fatigue crack growth in a f ibre m etal lam inate like glare is accom panied by delam ination growth at the interface between the aluminium and glass fibres. Glare shows excellent crack growth characteristics due to the mechanism of delamination and fibre bridging.
Fatigue crack propagation and delamination growth in glare, ph. Residual stresses in glare laminates due to the cold expansion process c. The reduction of the fatigue life at elevated temperatures is mainly due to two factors. The comparison between the predicted fatigue crack growth in the aluminum layers and the experimental observations indicated a good agreement both for shape and scale of the crack. Delamination and fatigue crack growth behavior in fiber. This paper presents a new analytical model for constantamplitude fatigue crack propagation of through cracks same crack length in all metal layers in the fibre metal laminate glare. Typical crossply layup of a fml due to the presence of bridging fibres the crack growth retardation of glare is excellent, showing very small and approximately constant crack growth rates. A400m glare fatigue crack initiation crack propagation crack growth variable. Fatigue crack propagation and delamination growth in glare. The model describes the crack propagation of the fatigue cracks in the aluminium layers and the corresponding delamination growth at the aluminiumfibre interfaces perpendicular to the crack. An analytical model has been developed based on the crack opening relations. Finite element modeling of fatigue in fibermetal laminates. The panel is full scale and was tested in a previous work under fatigue biaxial loads, applied by means of a multiaxial fatigue machine.
Residual stresses in glare laminates due to the cold. Paris law was employed to predict crack growth rates. Chang and yang 2008 examined fatigue crack growth in glare by modulating the stress intensity parameter with a bridging factor and obtained the sn curve based on the initiation and growth life of the crack. Application of the energy release rate approach for. Analytical prediction model for fatigue crack propagation. A study on ways to improve the design of the glare reinforced frame flange showed, that the performance of the glare reinforced frame flange could be improved by increasing the amount of fibre layer in the cross section relative to the amount of metal. The fatigue insensitive fibres restrain the crack opening and transfer. A crack growth equation is used for calculating the size of a fatigue crack growing from cyclic loads. Second is to obtain an accurate prediction model for fatigue crack propagation in glare accounting for fibre bridging, delamination and influence of plasticity. This thesis presents the investigation into the fatigue crack propagation behaviour and delamination growth behaviour of the fibre metal laminate glare.
Predicting fatigue crack initiation and propagation. Fatigue crack growth calculations are based on an analytical model which applies displacement compatibility at the delamination boundary, to solve for the crack tip stress intensity and subsequently calculate crack and delamination growth characteristics. Fatigue and damage tolerance of glare, applied composite. Development of a fatigue damage propagation model for. Tu delft is conducting research on the fatigue behavior of glare.
Methods have been developed to describe the fatigue initiation and propagation mechanisms in flat panels as well as mechanically fastened joints and to determine the residual strength of large flat panels. Predicting fatigue crack initiation and propagation in glare reinforced frames. The objective of this paper is to investigate the contributionrole of the crack closure and the fibre bridging effectsin stressratio influence in mode i delamination growth in carbonepoxy composite laminates. The fibres bridge the crack by leading the stresses through it. Investigation of fatigue crack growth rate in carall, arall and glare. Study on delamination propagation behavior and measurement. Delamination size dependence on fatigue crack growth in. D, was calculated from the mode ii fatigue delamination growth onset data of the material 6. This phenomenon is studied for constantamplitude loading, which is significant for fatigue loading of aircraft pressurized fuselages. On crack tunneling and planestrain delamination in laminates 403 become subject of investigation and analysis. This paper describes work done to extend this application to fmls. Notably, in the field of fatigue of fml under load cycles of constant stress ratio in ambient environment, lin et al.
The calculated results are compared with each other in fig. Several crack growth prediction models proposed in the literature and their limitations are discussed at the end of the chapter. An elevated temperature can have a negative effect on the fatigue crack growth behaviour of glare, whereas a decrease in temperatures can result in a significant increase of fatigue life. To incorporate this delamination growth in crack growth prediction methods, the energy release rate approach is applied to describe the delamination growth rate. Fatigue crack propagation in the fibre metal laminate glare consists of crack growth in the aluminium layers and delamination at the aluminiumprepreg interfaces in the wake of the aluminium crack.
The growth of fatigue cracks can result in catastrophic failure, particularly in the case of aircraft. This thesis investigation aims to address a gap in fatigue crack growth propagation prediction techniques. N g, was obtained incrementally from the material data for mode ii fatigue delamination propagation 6 by using growth. Fatigue crack growth tests with center crack tension specimen cct with loading range shifts have been performed. On the available relevant approaches for fatigue crack.
A crack growth equation can be used to ensure safety, both in the design phase and during operation, by predicting the size of cracks. The fatigue insensitive fibres restrain the crack opening and transfer load over the crack in the metal layers. Several researchers have developed theoretical concepts to describe the observed crack growth behaviour in fibre metal laminates. Threedimensional bem and fem submodelling in a cracked. Fibre metal laminate glare consists of thin aluminium layers bonded together with preimpregnated glass fibre layers and shows an excellent fatigue crack growth behaviour compared to monolithic aluminium. The intact fibre layers in the wake of the crack act as a second load path over the crack 3, reducing significantly the load transferred around the crack tip in the aluminium layers. Validation with a wide range of test data, reveals a good correlation between predicted and experimental crack growth rates, crack opening contours and delamination shapes. Chapter 2 investigates the physical phenomenon of fatigue in glare, the role of the glass fibres in crack restraining, the fibrebridging and the delamination. Fatigue crack growth in a fibre metal laminate such as glare is accompanied by delamination growth at the interface between the aluminium and glass fibreadhesive layers. Since crack propagation in glare occurs in the metal constituents only, the. Glare consists of thin aluminium layers bonded together with preimpregnated glass fibre layers and shows an excellent fatigue crack growth behaviour compared to monolithic aluminium. Fatigue crack and delamination growth in fibre metal.
Fatigue crack growth and delamination mechanisms of ti. To validate the applicability of the theory to fatigue crack propagation and delamination growth in fmls the authors seem to. Fatigue crack initiation in glare will occur in the layer with the highest stresses due to secondary bending and tensile loading. Thus the early fatigue crack growth performance of glare will also suffer from the higher stresses in the aluminum layers, further reducing its advantage. On crack tunneling and planestrain delamination in laminates. Highcycle fatigue investigations of notched glare under.
To incorporate th is delamination growth in prediction methods the energy release rate approach is a pplied. This phenomenon is studied for constantamplitude loading, which is. Predicting fatigue crack initiation and propagation in. This paper presents the results of the delamination growth investigation at different temperatures regarding the fatigue crack growth behavior of glare. In a joint, this layer will be located at the mating surface, which is the surface in contact with the other sheet of the joint. Tests were performed to determine the relationship between the 2d. During the initiation phase fibre bridging does not occur and the behaviour is dominated by the metal initiation properties. Pdf investigation of fatigue crack growth rate in carall. When the fatigue crack grows in the metal layers, the fibers do not fracture and restrain the crack tip opening. Experimental work fatigue tests were conducted on a series of glare specimens containing splice and doubler features.
In fmls, except for crack growth in the metal layers, fatigue crack propagation also causes delamination growth at the metalfiber interfaces in wake of the metal crack, that are both concerned with bridging effect of fibers. The fibres are insensitive to the occurring fatigue loads and remain intact while the fatigue. In fact, fatigue crack propagation in glare consists of crack growth in the aluminium layers and delamination of the aluminiumprepreg interfaces in the wake of the aluminium crack. To study delamination propagation property of one kind of new fiber metal laminates, by using 21 layup specimen, this article accomplished delamination propagation test under various stress levels at r0. Open hole multilayer fatigue crack growth in glare under. Fatigue and damage tolerance of glare springerlink. Fatigue and damage tolerance issues of glare in aircraft. The delamination at the interface between the aluminium and prepreg layers has greater influence on the fatigue crack growth in fiber metal laminates. The crack closure effecthas been assessed by the identification of the nonlinearity in the compliance curve of the double cantilever testspecimen after the delamination extension. Crack growth in glare is a selfbalancing mechanism with delamination growth between the aluminium and fibre layers. The major concept in this thesis is that the stress intensity at the crack tip in the metal layers of a fibre metal laminates fmls is the factor determining the extension of that.
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