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Failure and Thermal Examination of Hybrid Materials for a Propeller shaft in Aerospace Applications

Hybrid materials are an attractive option in case of aerospace and aviation applications since they are exceptionally strong. The current study presents the failure analysis of the hybrid material in ANSYS software. The main aim of this study is to check the suitability of the MATLAB results obtained from the previously selected composite material comprising of carbon steel + epoxy + S glass + T700 fibres using ANSYS software by creating a solid three-dimensional meshed model of the shaft. Layerwise shaft theory and finite element analysis have been employed for developing the model. The thermal analysis, delamination and buckling failure studies are conducted and found that increasing the thickness of the material will increase its load withstandability. The load failure point is found to be 8.4mm from the delamination studies. From analysis it was understood that the chosen composite material could be used for the propeller shaft of an aircraft.


I. INTRODUCTION
The leverage of using composite materials is that the design of the structures and the composite materials can be modified to withstand the applied load. To modify the designs one has to understand the stress, strains and the displacements produced by this type of loading (Hamstad, 1986).
The composite materials which are under stress will experience different damage mechanisms like delamination, buckling, matrix cracking, phase debonding, etc. (Davies, 1997). The composite can be damaged at any point; hence many studies have been conducted to understand the development in these damages since it is an important factor that has to be taken into account by the engineers while using the composite materials in different structural applications. The detection of damage is necessary for the efficient utilisation of the composite materials. Kessler, (2002) carried out a survey experimentally and analytically on the different methods through which the damages in composite materials can be detected, and inferred that the method of frequency response is reliable to detect even the smallest damage in a composite structure. Degrieck, (2001) presented a review of the fibre-reinforced polymer composites which were subjected to fatigue loadings. Alfano, (2001) conducted finite element analysis (FEA) of delamination in laminated composites by using interface elements and interface damage law. The interaction model is used in case of mixed mode delamination. Camanho, et al., (2002) proposed a decohesion element which could be used at the interface of solid finite elements which modelled the initiation of delaminations. Bolotin, (1996) reviewed the researches in the mechanics of internal and surface delaminations. The paper also presented a study on the buckling which is usually caused when delamination occurs near the surface. This usually happens in cases of composites which are under compression and tension. Many studies use finite element analysis or ANSYS software to carry out the delamination studies. Some of the authors concentrated on the design method for composite material while others concentrated on the studies related to damages in composite materials. This paper is a continuity of the previous work which carried out a comprehensive analysis of different composite materials to determine the best suitable composite material for a propeller shaft in aerospace applications. It was concluded from the previous work that low carbon steel + S glass + epoxy + T700 fibres is best suitable for the propeller shaft for aerospace application. This paper analyses the composite material in ANSYS software in order to check the suitability and load withstandability for the propeller shaft in aerospace applications. A 3D model for the shaft is generated and it is then meshed for further analysis. The buckling, delamination and thermal analysis of the structure is conducted to understand the suitability of the proposed composite material.

II. LITERATURE REVIEW
Sancho, (2006) explored different possibilities to calculate the 3D stress in composite structures. Finite element analysis and classical laminate theory are the techniques proposed for the calculations since they give accurate results with the minimal use of computer resources. The evaluation of stress distribution at singular points of the materials is done with the proposed methods. Once this is done the possible faults due to the onset of delamination is checked using fault criteria. Badie et al., (2011) examined the influences the stacking sequence and orientation angle had on the torsional stiffness, buckling, failure modes of composite tubes. The exhaustive life of the composite drive shaft was predicted using finite element analysis, and from the results, it was inferred that natural frequency and fibre orientation were inversely proportional. The experiments also showed that orientation angles of ±45 degrees experienced higher torsional stiffness and higher load carrying capacity. Impact test of low velocity was conducted on graphite epoxy laminates which have different thicknesses (Caprino et al., 1999). From the study, it was concluded that the force needed for the commencement of delamination increases with respect to the power law. Observations also suggested that shear stress is the main reason for delamination and it is calculated with the help of Hertzian law. A study on the stability of a composite drive shaft with respect to its torsion was conducted by Shokrieh et al., (2004). Torsional instability poses as a hindrance in the transfer of torque by the shafts. Buckling torque behaviour is studied using finite element method. The author also studied the effect of increased torque on the natural frequency of torsion in the composite shaft. Wettergren, H. L. (1997) studied the effect of Eigenfrequencies which were a result of the variations in the thickness of delamination in rotors of the composite shaft. The studies showed that in the case of small delaminations the effect of eigenfrequencies increased linearly with increase in delamination length. Comparative analysis of experimentally measured torsional buckling in graphite/epoxy loads and the theoretical values proves that the values are in good agreement, but the theoretical predictions slightly overestimate in case of critical loads. But the study of damage tolerance carried out in this study is in the primary stage since it deals with only the residual strength of the tubes and not on the actual ballistic impacts. Bauchau et al., (1998) conducted an experimental study of bending fatigue of composite drive shafts. The fabrication of the hybrid shafts is achieved using the technique of filament winding. The external composite layers are constructed using glass fibre and epoxy. The studies proved that increasing the number of composite layers and also a change in stacking sequence enhanced the fatigue strength. Sino, et al. (2008) assessed the dynamic instability of the rotating composite shaft which was damped internally. This research developed simplified homogenized beam theory (SHBT) and its results was compared with equivalent modulus beam theory (EMBT), modified EMBT and layerwise beam theory (LBT). The parametric study showed that the instability thresholds were sensitive to the laminate parameters. But this method does not consider the coupling effects by non-symmetrical stacking. Kaviprakash, (2014) examined the effects of stacking sequence and orientation angles on the different characteristics of the composite shaft like its frequency, buckling, torsional stiffness. The study evaluated the appropriateness of the material to use it for automotive transmission. The drive shaft was analysed with the help of ANSYS software to reduce the weight of the shaft exposed to tension and buckling. Alwan, (2010) studied the dynamic behaviour of the composite shafts emphasising on the estimation of damping in the shafts. The Eigen-frequencies of the shafts were estimated by modal testing. The results are analysed and compared with analytical and FEM results. Rotational laser vibrometer is used for the analysis of torsional vibration in the shafts.
A numerical and experimental study is conducted on Eglass-carbon/epoxy, carbon/epoxy and E-glass/epoxy shafts subjected to impact loadings to understand their surplus torsional properties (Sevkat, 2013). The studies revealed that at energy levels of 5, 10, 20, 40 J there was an impact on the shafts. It was found that resistance to the impact was highest in case of carbon reinforced shafts whereas it was the lowest in glass reinforced shafts that of hybrid shafts was between the two. Glass reinforced shafts had the best ability to absorb the energy while it was in case of carbon shaft and that of hybrid shafts was between the two. Maheta et al., (2015) developed a method for designing and evaluating a driveshaft used in automobile applications. The design process was carried out using the finite element modelling in ANSYS software. It was inferred that the Kevlar/epoxy composite had maximum strength and it was observed that at 90 degrees the fundamental frequency was the best when compared to other angles. Gayen  The results showed that the proposed theory can be efficiently utilised for dynamically analysing the III. RESEARCH METHODOLOGY This work is a continuation of the previous work in which it was determined that low carbon steel + S glass + epoxy + T700 fibres is the best suitable composite material for the propeller shaft for aerospace application. The further analysis of this composite material is carried out with the help of ANSYS software. A solid 3D model of the composite shaft is modelled, meshed then the buckling, delamination and thermal analysis is done to justify that low carbon steel + S glass + epoxy + T700 fibres is the best suitable composite material for the propeller shaft of the two seater aircraft. Figure 1 illustrates a laminated shaft with P orthotropic layers. The shaft which is laminated is modelled using the layerwise shaft theory (LST). The assumptions made are

A. Layerwise shaft theory
• The material at each layer has the property of linear elasticity • All the layer are uniformly thick • At each interface the layers perfectly bond together.

B. Finite element Modelling
The shaft element has two nodes as illustrated in figure 1. The degree of freedom of the element with P layers for each node is (3+2P). u, v, w → displacements, the slopes about the y and z axis is denoted by θ yk and θ zk for the kth layer where k ϵ [1...P ] . The linear interpolation functions of the finite element defined in the natural coordinate system is given by Where N 1 and N 2 is utilized in interpolating the variables shafts. It was also found that the shear-normal coupling, stacking sequences and fibre orientation had a powerful impact on the dynamic behaviour of shafts. The generalised displacement field is approximated using the equation (2) The global form of contribution of the E finite elements is expressed as And D ij is given by The shearing strain along xy direction is given by ∂u + ∂y (25) From equations (4) and (16)

IV. RESULTS AND ANALYSIS
The failure analysis of the composite shaft material is done in ANSYS software. First the geometrical model is generated, then it is meshed so that the shaft can be analysed. A solid 3D modelled shaft is generated using the ansys design modular as shown in figure 2. The dimensions of the shaft are shown in figure 3.      Table I The graphs in figures 5-7 show a plot of the deflections caused for the different loads applied to the three different cases considered. Figure 8 shows the point at which delamination occurs. The peak point in the figure  8 is the load failure point. V. CONCLUSION From the previously conducted study, it was determined that low carbon steel + epoxy + S glass + T700 fibre is the best suitable hybrid material for the propeller shaft of a two-seater aircraft. This study satisfies the conditions for the suitability of the results obtained from Matlab (from the previous study) in ANSYS software.