Numerical Investigation of Composite Structures under Blast Loading

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1 Journal of Materials and Environmental Sienes ISSN : CODEN : JMESCN Copyright 07, University of Mohammed Premier Oujda Moroo JMES, 07 Volume 8, Issue 6, Page Numerial Investigation of Composite Strutures under Blast Loading Reza Haghi, Bashir Behjat *, Mojtaba Yazdani Mehanial Engineering Department, Sahand University of ehnology, abriz, Iran, P.O.Box Reeived 7 Aug 06, Revised 0 Ot 06, Aepted 04 Ot 06 Keywords Blast Loading, Composite Shell, Numerial Analysis, Layer Upping Behjat@sut.a.ir, el: , Fax: Abstrat In this paper, the behavior of omposite strutures against the explosive phenomenon has been investigated using finite element method. Some omposite shells suh as omposite plates and hemispheres with different layer-uppinghave been investigated using LS-DYNA software. he blast loading is simulated by explosion's pressure versus time urves and is diretly defined in LS-DYNA software. he sai-wu failure riterion is used to predit the behavior of the omposite struture.in this paper, the effet of layer-upping on the blast resistane of the struture is investigated. he results show that, hemisphere omposite has better performane against the blast loading than plate and failure our under greater load. Also it is shown that angle ply omposite strutures has good resistane in omparison with ross plies one.. Introdution Composite strutures are important in different areas of industry suh as aero, marine airrafts, ships, automotive and so on. Many of the strutures experiene blast loading during war or terrorist attak or aidental explosions. Response of omposite strutures subjeted to explosion has been a field of intense ativity of researhers in reent deades. So omposite plates and shells form one of the basi elements of the strutures, therefore, studying the blast response of suh strutures helps understanding and improving their blast resistane. here are too many papers dealing with the blast loading on the strutures. Rajendran [] investigated the plate behavior under the blast loading. In this review paper, he fouses on the phenomenologial evolution of blast damage of plates. Arora et al. [] studied the resistane of glass-fiber reinfored polymer(gfrp) sandwih panels and laminate due blast in air and underwater environments. hey used an experimental method to obtain the behavior of the plates. he dynami response and blast behavior of metalli sandwih-walled hollow shells with graded aluminum foam ores are investigated by Liu [3]. hey used finite element simulations to model the blast and ompared results with those of onventional ungraded ones. Fallah et al [4] studied the dynami response of a blast-resistant lightweight fiber omposites struture alternative to steel for military appliations. he results of loalized air-blast loading on struture are reported and analyzed by using experimental and numerial methods. A theoretial method is used to predit the large defletion response of fy lamped retangular sandwih plates subjeted to blast loading by Qin et al. [5]. hey used energy dissipation balane theory and obtained the solutions for the dynami response of retangular sandwih plate. A multi-layered omposite struture that made of layers of aluminum alloy AA 7075 bonded with toughened epoxy resin is investigated for blast resistant appliations By Johnson et al. [6]. he performane of the proposed thik omposite plate made of thik AA 7075 layers, was numerially studied under loalized impulsive loading. In the other artile represented by Logdon et al [7] the influene of material properties on the response of plates subjeted to airblast loading is investigated using an experimental method. hey obtained the failure of mild steel, armor steel, aluminum alloy and fiber reinfored polymer omposite plates experimentally by detonating disks of plasti Bahjat et al., JMES, 07, 8 (6), pp

2 explosive at small stand-off distanes. Imbalzano et al [8] investigated sandwih panels omposed of axeni ellular ores and metal faets are for blast resistane appliations. he performane of this hybrid omposite struture under impulsive loading is numerially studied, taking into aount the rate-dependent effets and Johnson Cook law is used to model the behavior of omposite materials at high strain rates. Zhu and Khanna [9] represented a numerial model that is developed to simulate the dynami response of the laminated glassomposite panel under blast loading. hey validated the simulated model, in terms of the midpoint defletion, orrelates well with the experiments onduted in a blast load simulator. Auora et al [0] presented experimental investigation on the influene of stand-off distane on the dynami response of thin dutile plates subjeted to air blast loading. he square plates were manufatured from two different materials, i.e., mediumstrength steel and low-strength aluminum. Low energy impat and post impat behavior of epoxy matrix-woven flax fabri omposites are investigated by Papaniolaou et al. []. he progressive damage due to inreased impat energy levels was studied as a funtion of impat energy. Johnson et al. [] studied a multi-layered omposite by hierarhial struture made of layers of aluminum alloy AA 7075 bonded with toughened epoxy resin for blast resistant appliations. Hazratiet et al. [3] investigated a numerial approah to predit failure in the reinfored V-shape plates subjeted to blast loading. In the present study, the behavior of omposite strutures suh as plates and spherial shells has been investigated using LS-DYNA software. he stress field and time response of the struture is presented. he sai-wu failure riterion is used to predit the strength of the struture due to impulse loading. he results are shown in good graphial and tabular forms to understand the behavior of the omposite struture in blast loading.. Blast loading he explosion is a sudden phenomenon that release high values of the energy in a short time. he pressure-time diagram for an explosion is shown in Figure. It is seen in this figure that, the pressure is high in first but derease during time. It is obvious that the modelling of the explosion is very ompliate so there are some experimental relations that desribe this ourrene. One of the most famous relations of the blast pressure is suggested by the Graham and Kenni as bellows [4]: In whih: p so p o = + z z = R 3 () W z z.35 + z 0.3 Where W is the mass of the explosive material and R is the distane. AlsoP so is the maximum pressure and P o is atmospheri pressure. he destrution of an explosion is measured by the impulse funtion whih is the area underneath the pressure urve. here is an empirial funtion based on above mentioned pressure funtion for impulse as bellows [5]: I = pdt (3) In whih I is the impulse of the explosion. An empirial relation is used to alulate this parameter as below [5] () I 3 = W z z z z 9.00 (4) In this artile the blast loading on the struture is simulated as an approximate funtion as [6]: P t = p m t t p e αt t p (5) In whih α, t, t p are wave parameters, time and positive pressure time, respetively. he eq. 5 is plotted in figure. Bahjat et al., JMES, 07, 8 (6), pp

3 Figure :Pressure versus time based on Eq. 5 and parameter definitions 3. Numerial modeling and failure riteria 3. Finite element modelling In this paper the struture is modeled using finite element method and blast loading as eq. 5.In this paper expliit LS-DYNA software is used to solve the nonlinear equation of the motion. At first the model is reated by using ANSYS software and the final model is imported in LS-DYNA to solve by the expliit solver. he etrahedral solid elements are used in LS-DYNA software to model the struture. his element has 8 nodes and formulated by the linear interpolation funtions. his element has 6 faes. Eah of the nodes had 3 degree of freedom for displaements in diretions x, y and z. this element has other degree of freedoms suh as thermal, magneti and so on but in our analysis only the displaement degrees of freedom are exploited. his element is seleted beause of its auray and meshing the entire domain without any error. he omposite layer is onsists of 4 layer and eah layer is modeled by 3 elements in thikness diretion. Also between the layers the automati surfae to surfae ontat is modeled to avoid any breaking down of the elements. he 900 and 960 elements are used for modeling of omposite plate and half sphere respetively. hese numbers of elements are seleted to obtain good auray of the results. he thikness of the struture is to be 7 m. Figure shows the mesh of sphere. Figure : he mesh of the half sphere Bahjat et al., JMES, 07, 8 (6), pp

4 3.. Failure riteria for omposite material LS-DYNA software used various failure riteria for omposites. In this paper sai-wu failure riterion is used to simulate the damage of the elements. his failure model based on Beltrami strains rupture energy. In this method it is assumed that the lamina is safe when [7]: H + H + H 6 τ + H + H + H 66 τ + H < (6) In whih: H = (7) H = (8) H = (9) H = (0) H 6 = 0 () H 66 = τ () H = (3) he materials properties of the omposite layer that is used in this artile are listed in able. able :Material properties of omposite laminate [7] (MPa) (MPa) (MPa) (MPa) τ (MPa) Results and disussions 4. Composite plates under blast loading In the first ase a omposite plate with the laminate sequening [0-0-0] is investigated exposed to blast loading. he loading is equal to 34. gram N explosion and explosive material distane from the plate is 0 m. his is the basi loading and in future ases it is mentioned by this onept. he Figure 3 shows the defletion of the omposite plate due to basi blast loading. By inreasing the explosive material to.9 times of basi value, the plate starts to fail beause of the loads. he ourrene of this phenomenon is seen in Figure 4 by the deviation of elements from eah other. In the seond ase, the omposite plate by [0-90-0] layer sequening is investigated. It is seen that in this type of layer sequening, the final failure load is inreased to.95 times of basi loading. he Figure 5 shows the rupture of the omposite plate. Bahjat et al., JMES, 07, 8 (6), pp

5 Figure 3: Displaement of plate enter due to basi blast loading. Figure 4: Failure of the [0-0-0] omposite plate due to.9 times of the basi blast load Figure 5: Failure of the [0-90-0] omposite plate due to.95 times of the basi blast load From Figures 4-5 it is inferred that the ross ply laminate has more resistane than single ply omposite. In the third ase, the blast loading is applied to the angle ply laminate [ ] s. he analysis shows that in this layer upping, the load to rupture of the plate is.05 times greater than the basi loading. So ross ply omposites an resist more than angle ply in blast loading. Bahjat et al., JMES, 07, 8 (6), pp

6 Figure 6: Failure of the [ ] s omposite plate due to.05times of the basi blast load 4. omposite spherial shells under blast loading In this setion, the response of the omposite spherial and ylindrial shells under blast loading is investigated. he meshof the shells are presented in Figures. Figure 7 shows the top point defletion of the sphere with layer upping [0-90-0] versus time. he loading is equal to time of referene loading. Figure 8 shows the Von- Mises stress in the sphere in the times of referene loading. It is obvious that the stress is high in the top of the shell. By inreasing the load, it is seen that the failure of the shell is ourred when the loading is times of referene loading. Figure 9 shows the failed struture in the blast loading. It is obvious that the top point of the sphere begin to fail during loading. Figure 7: Defletion of the top point of the sphere versus time in referene loading. Figure 8: distribution of the Von-Mises stress in the shell Bahjat et al., JMES, 07, 8 (6), pp

7 Figure 9:Failure of the shell during blast loading Conlusions In the present study, the behavior of omposite strutures under blast loading is investigated using finite element method. heblast pressure urve has been defined to LS-DYNA software diretly and all analysis has been done with this simplifiation and struture's resistane against blast loading is investigated. he sai-wu failure riterion is employed to predit thestrength of the omposite struture. he stress field and time response of the struture is presented and sai-wu failure riterion is exploited to investigate the strength of the struture due to this type of loading. he results show that hemisphere omposite shell under the same load has better resistane against blast in omparison with the plates in the same thiknesses. Also it is inferred that the angle ply layer upping has good resistane from ross ply layer upping in the blast loading and fails at bigger values of explosive material. Referenes. Rajendran R., Lee J.M., Mar.Stru., (009)99.. Arora H., Hooper P.A., Dear J.P., Exper. Meh., 5 (0) LiuX., ianx., Lu. J., Zhou D., Liang B., Comp. Stru., 94 (0) Fallah A.S., Miallef K., Langdon G.S., Lee W.C., Curtis P.., Loua L.A., Int. J. Imp. Eng., 73 (04) Qin Q., Yuan C., Zhang J., Wang.J., Europ. J. Meh. A/Sol., 47(04) Flores-Johnson E.A., Shen L., Guiamatsia I., Nguyen G. D., Comp.Stru., 6(05) Langdon G.S., Lee W.C., Loua L.A., International Journal of Impat Engineering, 78 (05) Imbalzano G., ran P., Ngo. D., Lee P. V.S., Comp. Stru., 35 (06) Zhu H., Khanna S. K., Int. J. Imp. Eng., 89 (06) Aune V., Fagerholt E., Hauge K.O., Langseth M., Borvik., Int. J. Imp. Eng., 90 (06) 06.. Papaniolaou G., Chalkias D., Koutsomitopoulou A., U.P.B. Si. B., Series D, 78(06) 5.. Johnson E.A., Sehn L., Guiamatsia I., Nguyen G., Comp. Stru., 6 (05) Hazrati B., Saeimi M.A., J. Fail. Anal. Prev., 6 (06) Kinney G. F., Graham K. J., Explosive shoks in air, Springer-Verlag, (985). 5. Goodman H., Compiled free-air blast data on bare spherial pentolite, DIC Doument, Kazanı Z., Z. Meitoğlu, J. Sound and Vib., 37 (008) Kaw A. K., Mehanis of Composite Materials, CRC Press, th edition, (005) (07) ; Bahjat et al., JMES, 07, 8 (6), pp