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. Analytical prediction model for fatigue crack propagation. 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. Similarly, fatigue threshold was studied initially for fmls, 41 see, for example, figure 6, until it was understood that the interplay between a threshold in crack growth and the apparent absence of threshold in delamination growth yield different slow crack growth characteristics compared with monolithic metals. Second, the number of cycles during stable delamination growth. 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. Doctor thesis, delft university of technology 2005. Fatigue resistance of fibermetal laminates springerlink. Investigation of fatigue crack growth rate in carall, arall and glare. Thus the early fatigue crack growth performance of glare will also suffer from the higher stresses in the aluminum layers, further reducing its advantage.
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. 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. During the initiation phase fibre bridging does not occur and the behaviour is dominated by the metal initiation properties. Data on the crack initiation periods in each of the layers are also presented. The delamination at the interface between the aluminium and prepreg layers has greater influence on the fatigue crack growth in fiber metal laminates. Fatigue and damage tolerance of glare, applied composite. To incorporate this delamination growth in crack growth prediction methods, the energy release rate approach is applied to describe the delamination growth rate. Residual stresses in glare laminates due to the cold expansion process c. Since crack propagation in glare occurs in the metal constituents only, the. The reduction of the fatigue life at elevated temperatures is mainly due to two factors. Study on delamination propagation behavior and measurement. This phenomenon is studied for constantamplitude loading, which is significant for fatigue loading of aircraft pressurized fuselages.
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. This thesis investigation aims to address a gap in fatigue crack growth propagation prediction techniques. To incorporate th is delamination growth in prediction methods the energy release rate approach is a pplied. The growth of fatigue cracks can result in catastrophic failure, particularly in the case of aircraft. Fatigue and damage tolerance issues of glare in aircraft. This phenomenon is studied for constantamplitude loading, which is. An analytical model has been developed based on the crack opening relations. 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. Tu delft is conducting research on the fatigue behavior of glare. To validate the applicability of the theory to fatigue crack propagation and delamination growth in fmls the authors seem to. The fatigue insensitive fibres restrain the crack opening and transfer. 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 calculated results are compared with each other in fig.
Delamination size dependence on fatigue crack growth in. 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. Tests were performed to determine the relationship between the 2d. D, was calculated from the mode ii fatigue delamination growth onset data of the material 6. On the available relevant approaches for fatigue crack propagation prediction in glare article pdf available in international journal of fatigue 292. 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. Development of a fatigue damage propagation model for. The fatigue insensitive fibres restrain the crack opening and transfer load over the crack in the metal layers.
Fatigue crack growth in a fibre metal laminate like glare is accompanied by delamination growth at the interface between the aluminium and glass fibres. Several crack growth prediction models proposed in the literature and their limitations are discussed at the end of the chapter. Chapter 2 investigates the physical phenomenon of fatigue in glare, the role of the glass fibres in crack restraining, the fibrebridging and the delamination. 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. Fatigue and damage tolerance of glare springerlink. 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. Threedimensional bem and fem submodelling in a cracked. Application of the energy release rate approach for. Fatigue crack propagation and delamination growth in glare. 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. 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. On the available relevant approaches for fatigue crack. A400m glare fatigue crack initiation crack propagation crack growth variable. Fatigue crack initiation in glare will occur in the layer with the highest stresses due to secondary bending and tensile loading.
Open hole multilayer fatigue crack growth in glare under. Predicting fatigue crack initiation and propagation in glare reinforced frames. Highcycle fatigue investigations of notched glare under. A crack growth equation is used for calculating the size of a fatigue crack growing from cyclic loads.
Alderliesten rc 2007 analytical prediction model for fatigue crack propagation and delamination growth in glare. This thesis presents the investigation into the fatigue crack propagation behaviour and delamination growth behaviour of the fibre metal laminate glare. A crack growth equation can be used to ensure safety, both in the design phase and during operation, by predicting the size of cracks. Predicting fatigue crack initiation and propagation in. Pdf investigation of fatigue crack growth rate in carall. The panel is full scale and was tested in a previous work under fatigue biaxial loads, applied by means of a multiaxial fatigue machine. This paper presents the results of the delamination growth investigation at different temperatures regarding the fatigue crack growth behavior of glare. Notably, in the field of fatigue of fml under load cycles of constant stress ratio in ambient environment, lin et al. Fatigue crack growth tests with center crack tension specimen cct with loading range shifts have been performed. 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. Second is to obtain an accurate prediction model for fatigue crack propagation in glare accounting for fibre bridging, delamination and influence of plasticity. Fatigue crack propagation and delamination growth in glare, ph.
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 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. This paper describes work done to extend this application to fmls. 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. 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. Crack growth in glare is a selfbalancing mechanism with delamination growth between the aluminium and fibre layers.
Finite element modeling of fatigue in fibermetal laminates. 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. Glare shows excellent crack growth characteristics due to the mechanism of delamination and fibre bridging. 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. On crack tunneling and planestrain delamination in laminates 403 become subject of investigation and analysis. Several researchers have developed theoretical concepts to describe the observed crack growth behaviour in fibre metal laminates. N g, was obtained incrementally from the material data for mode ii fatigue delamination propagation 6 by using growth. The fibres are insensitive to the occurring fatigue loads and remain intact while the fatigue. On crack tunneling and planestrain delamination in laminates. 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. 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. 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.
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