IJSRD - International Journal for Scientific Research & Development Vol. 3, Issue 09, 2015 ISSN (online):

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1 IJSRD - Interntionl Journl for Scientific Reserch & Development Vol. 3 Issue ISSN (online): Experimentl Studies of Lek Pressure of FRP Butt Joint between Two Aluminum Pipes R. N. Ldhwe 1 Shntnu Ldhwe 2 Nrendr Kulkrni 3 Dr. Rju Nrynro Ldhwe 4 4 Associte Professor 1234 Deprtment of Mechnicl Science 14 College of Engineering Shivjingr Pune Mhrshtr Indi 23 Modern Eduction Society s College of Engineering Pune Mhrshtr Indi Abstrct A FRP butt-joint ws formed between two dherends of luminium pipe of outside dimeter of mm nd inside dimeter of mm. The joint ws formed by winding wetted roving of glss fiber / crbon fiber with controlled quntity of epoxy t ±45 ngle. It ws cured to form the joint with glss fiber reinforced polymer (GFRP) / crbon fiber reinforced polymer (CFRP) sleeve round the joint plne. For checking lekges in this joint ded weight pressure guge tester ws used. It cn be inferred tht pressure t which lekge tkes plce through FRP joint is directly proportionl to the number of psses of glss / crbon fiber roving. It is becuse when number of psses of glss fiber increses more compct FRP joint is formed which cn undertke more pressure. Specimen with lesser number of psses of glss fiber / crbon fiber lek through center of FRP joint while specimen of higher number of psses lek through either upper or lower side of FRP joint. During lek test when the pressure inside the luminium pipe increses hoop stress lso increse leding to expnsion of luminium pipe thereby forming the strong mtrix of FRP. This formtion of strong mtrix increses the pressure t which lek occurs i.e. it enhnces the results. Key words: FRP Joint Adherends GFRP CFRP Lek Test I. INTRODUCTION The world needs pipe to survive for wter oil gs nd sewge. Pipes hve been fundmentl prt of civiliztion since 3000 BC s the world hve developed both in terms of popultion nd infrstructure. Tody we re relint on wter gs oil nd electricity nd pipes crry these mterils from their source to their users. Whenever two pipes need to be joined together butt joint is the nswer. Butt joint is typiclly used in process piping & hevier industril pplictions. The joints between pipes re likely to lek. Presence of the lekge will bring out the further problems such s sfety of the system lso problem regrding the function nd relibility of the system in prticulr. If lek is found in piping system it is possible to slow down or temporrily stop the lekge until the plumber cn repir by the ordinry methods. Thus there is need to find n economicl fst rugged nd relible solution for the sme. The butt joint by FRP hs potentil to meet these requirements. Kumr et l. [1] & [2] developed FRP-joints mde between two components by winding wetted tow mde of high strength nd high stiffness glss fibers. A T-joint between two pipes ws selected s specimen. The strength of the T-joint ws determined under four loding conditions: (i) tensile (ii) in-plne bending (iii) bending under trnsverse lod nd (iv) torsion-cum-bending. The strength of FRP-joint between mild steel pipes ws found to be comprble to the strength of welded joint. Rmkumr et l. [3] developed GFRP butt joint between two pipes by wrpping wetted glss fbric nd letting it to get cured. They found the joint to be strong ginst flexurl lods but wek under tensile lods. Imnk et l. [4] investigted the behviour of dhesively bonded GFRP pipe/steel rod joints nd found tht ftigue strength of the joint minly depended on mximum tensile stress norml to the dhesive dherend interfce t the lp end. Jio et l. [5] studied the behviour of butt-welded joint between very high strength (VHS) circulr steel tubes strengthened by GFRP nd found tht the joint filed with three kinds of modes dhesive filure fiber ter nd mixed filure. Fwzi et l. [6] lso studied the behviour of very high strength (VHS) circulr steel tubes strengthen by crbon fiber reinforced polymer (CFRP) under xil tension nd effective bond length of CFRP reinforcement ws estblished. Zho nd Zhng [7] reviewed rticles on ftigue crck propgtion in the GFRPsteel system. Rykhere et l. [8] evluted the dynmic sher strength of dhesive joints prepred using four different commercil dhesives t loding rtes in the rnge of MP/μs. Ldhwe et l. [9] formed GFRP butt joint between similr mterils luminum nd ws chrcterized under tensile nd flexurl loding. Ldhwe et l. [10] developed butt joint between the pipes of dissimilr mterils luminum nd steel using crbon fiber roving. The joint ws tested experimentlly under tensile nd flexurl loding. The experimentl results were interpreted on the bsis of numericl nlysis crried out using ANSYS. W. Hufenbch R. Böhm [11] hs nlysed tht due to their high lightweight potentil fiber reinforced plstics hve found brod ppliction in chemicl pprtus nd plnt construction. Becuse of improved stndrds for sfety relibility nd cost effectiveness of such composite components numerous technicl chllenges rise for the producers of pressure vessels tnks rectors nd pipe element systems. In this context multitude of problems pper during recurring cceptnce inspections nd equipment condition monitoring using non-destructive test methods(lek detection method). The objective of the work is to develop butt joint between two luminium pipes by winding glss fibber / crbon fibers roving wetted in epoxy resin nd letting it cured to form glss fiber reinforced polymer (GFRP) / crbon fiber reinforced polymer (CFRP) sleeve. The butt joint ws tested for lek pressure using Ded Weight Pressure Guge Testers. II. EXPERIMENTAL TECHNIQUE The specimen used for lekge test ws developed butt joint by joining two luminum pipes with glss / crbon roving reinforced epoxy mteril. For checking lekges in this joint ded weight pressure guge tester ws used. A ded weight tester is clibrtion stndrd method tht uses All rights reserved by 5

2 piston cylinder on which lod is plced to mke equilibrium with n pplied pressure underneth the piston. A. Mterils Commercilly vilble luminum pipes were used s the dherends in this study whose properties were: elstic modulus = 69 poisson s rtio = 0.33 yield stress = 152 MP nd ultimte tensile strength = 183 MP. Ech dherend member ws of mm outside dimeter mm inside dimeter nd 175 mm length. The glss fiber roving used ws of 1200 Tex nd purchsed from Owens Corning Indi Limited Rigd Indi. The crbon fiber roving used for prepring specimen ws of 210 Tex mnufctured by Hexcel Corportion 6700 West 5400 South West Vlley City UT USA. The epoxy resin employed ws Dobeckot 520 F (100 prts by weight) with hrdener Beck 758 (9 prts by weight). The mixture of epoxy resin nd hrdener enbled convenient processing time of minutes. B. FRP winding To prepre the specimen by winding wetted glss / crbon roving FRP-winding setup ws developed. The mting fces of the luminum nd the steel pipes were mchined norml to their xes nd were plced in specilly designed winding setup. It ws used to crry out the following two mjor functions (i) to wet the fiber roving with controlled mount of epoxy resin nd (ii) to wind the wetted roving. The externl surfces of both the pipes were mde rough using file in θ-direction (norml to xis of pipes). Then the surfces were clened with cetone so s to degrese them. To control the fiber volume frction the wetted roving ws pssed through specilly designed die with hole hving n enlrged conicl mouth for the smooth entry of the roving. Three kinds of winding ngles were employed ± 45º ± 70º nd 90º C loops shown in Figure 1. Windings of ±45º nd ±70º were running winding from one dherend to nother. It ws importnt to develop strong dhesion between the dherends nd the FRP sleeve. After mny lterntive trils it ws found tht good dhesion ws developed when the end points of running winding ws pressed by two locl loops of 90º winding. Psses of ± 45º winding plyed mjor role in the FRP joint but it ws found tht four psses initilly of ± 70º winding were helpful in enhncing the dhesion. Thus the four psses of 70º winding constituted the preprtic windings over which min winding of ±45º ws crried out. The configurtion of the preprtic winding ws [902/ (70/902/ 70/902)2] nd the configurtion of the min winding ws [45/ 902/ 45/902] in which n ws lrge number nd ws vried in the chrcteriztion of the FRP joint. Then the specimen ws llowed to be cured for 24 hours t the room temperture. The winding process formed FRP sleeve of bout 130 mm length. The specimen ws plced in n oven for the post curing process for 5 hours t the temperture of 80 C. Two kinds of specimen were prepred in this study: (i) Al-GFRP-Al nd (ii) Al-CFRP-Al in this investigtion. Figure 2 nd Figure 3 shows the photogrphs of the prepred specimens of both kinds. Fig. 1: Vrious winding loops: 70º 45º nd C-loop Fig. 2: Photogrph of the specimen Al-GFRP-Al Fig 3: Photogrph of the specimen Al-CFRP-Al A GFRP sleeve is n orthotropic mteril whose stress-strin reltions re expressed with nine elstic constnts. They were evluted using the rule of mixture nd Hlpin-Tsi equtions [12]. The elstic constnts thus determined with respect to principl mteril xes L T nd T' directions re listed in Tble 1. E L E T E T' ν LT ν LT ' ν TT' G LT G LT' G TT' Tble 1: Elstic constnts of GFRP sleeve mteril with respect to mteril xes L T nd T'. The elstic constnts of CFRP were determined with respect to principl mteril xes L T nd T' directions nd re listed in Tble 2. E L E T E T' ν LT ν LT' ν TT' G LT G LT' G TT' Tble 2: Elstic properties of CFRP with respect to principl mteril directions L T nd T'. The stiffness mtrix ws then evluted using the elstic constnts with respect to principl mteril xes [13 14]. The stiffness mtrix ws then trnsformed to determine it with respect to globl xes r of specimen. For the GFRP sleeve trnsformed stress-strin reltions with respect to globl xes r θ nd z were determined s follow: For ply ngle =45º All rights reserved by 6

3 The stiffness constnts in Eqution re in. For ply ngle = 45º Stiffness rtio is n importnt prmeter to chrcterize FRP joint. Stiffness rtio for the luminum dherend ws defined s For ply ngle =70º For ply ngle = 70º Similrly trnsformed stress-strin reltions with respect to globl xes r θ nd z were determined for the CFRP sleeve s: For ply ngle =45º For ply ngle = 45º where E nd A represent the elstic modulus nd the re of cross section of the luminum pipe respectively. In the bove definition of the orthotropic GFRP nd CFRP ws tken equl to C 33 nd is the re of cross section of the ±45 winding which ws the min lod bering portion of the sleeve. The stiffness rtio for the vrious specimens is lso shown in result tble. C. Ded Weight Pressure Guge Testers Piping is widely used in chemicl nd other plnts. In some pplictions the joints should not llow the lekge of the flow of liquid inside the tubes. For checking lekges t the joint in the specimen ded weight pressure guge tester ws used using lubricnt oil. A working of tester ws bsed on clibrtion method tht uses piston cylinder on which ded lod ws plced to mke equilibrium with n pplied pressure underneth the piston. The instrument used for lek detection ws mnufctured by the RAVIKA instruments Delhi. The mximum pressure tht cn be mesured by tester ws 300 br. Figure 4 shows the experimentl set-up of the ded weight pressure guge tester. For crrying out the lek test initilly the specimen ws mounted on the Ded weight pressure guge tester mchine. The oil ws pumped inside the specimen by using the inbuilt priming pump till it ws completely filled with oil nd ir inside the system ws removed. The oil used for the test ws SAE-40 Grde. The pressure ws incresed by dding the ded weights till the lekge occurred through the GFRP/CFRP butt-joint or the pressure reched which would not burst the luminum dherend. For ply ngle =70º For ply ngle = 70º Fig. 4: Experimentl Set-up of ded weight pressure guge tester All rights reserved by 7

4 D. Interfcing Between A Specimen And Testing Mchine A GFRP/CFRP butt-joined specimen required proper interfcing so tht it could be mounted on the testing mchine. A specil ttchment ws designed to conduct the lek test of the butt-joint specimen on the ded weight pressure guge tester (Figure 5). One end of the specimen ws blocked nd the other end ws required to hve mle threded portion (M 20) so tht it could be screwed on the tester. The interfce ws designed in such wy tht it did not lek during the testing. The interfce ws designed for the mximum pressure of 250 br. Beyond 250 br the luminum my fil nd test my be dngerous. Fig. 7: sectionl view of Clmp In the lower subssembly (Figure 8) the core hd drilled hole of Ø = 2.5 mm so tht the liquid of the tester could enter the specimen. The design of the cored portion nd its flnge ws sme s tht one used on the blocked end. However the other end of the core ws mchined with M20 thred so tht it could be screwed to the lek tester. Another pipe clmped ws employed to tighten the core to the specimen pipe with n oil sel in between. Fig. 5: Sectionl view of ssembly for lek testing The ssembly is divided into two subssemblies. The upper subssembly blocked the upper end of the specimen while the lower end ws suitbly designed to be ttched to the lek tester. The upper end ws blocked by inserting solid core shown in Figure 6. Fig. 8: sectionl view of Hollow Core Figures 9 nd 10 shows the photogrphs of the specimen with both subssemblies for CFRP nd GFRP butt joint specimens. Fig. 6: Sectionl view of solid core The flnged portion of the core ws screwed to pipe clmp ttched to the externl surfce of the pipe using four M6 high strength screws. The pipe clmp ws mde of two hlves (Figure 7) of mild steel. One of them ws hving tpped holes M8 nd the other one cler holes. To clmp it the two hlves were screwed to the pipe using high strength lloy steel llen screws. An oil sel mde of neoprene ws used between the flnge nd specimen end fce to ensure tht no oil leks through. It is flt ring with size 15.87x27.38x3.17 mm. It is worth mentioning here tht the core ws mde long enough in such wy tht the pipe clmp did not crush the dherend tube. Fig. 9: Photogrph of ctul ssembly GFRP sleeve specimen Fig. 10: Photogrph of ctul ssembly CFRP sleeve specimen All rights reserved by 8

5 III. RESULTS AND DISCUSSIONS Lek tests were conducted to explore how effective the joints were ginst the lekge of high pressure lubricting oil (SAE 40). The specimens of lek test were prepred between luminum dherends only but with two kinds of sleeves GFRP nd CFRP. The specimens re ddressed s Al-GFRP-Al nd Al-CFRP-Al. The glss fiber roving used ws 1200 Tex while crbon fiber roving used ws of 210 Tex. The thickness of the sleeve ws vried depending on the number of psses nd the testing ws conducted on the ded weight pressure guge tester using specilly designed ttchment s discussed erlier. A. Lek Pressure Test: Al-GFRP-AL Tble 3 shows the experimentl results on GFRP specimens (Al-GFRP-Al) with the vrious numbers of psses n. Three sets of experiments were conducted for ech psses of GFRP specimens. Tble 3: Lek test results for Al-GFRP-Al specimens Sr. No. No. of psses Stiffness Rtio S Set 1 Lekge pressure (br) Set Set Averge ± ± ± ± ± * 250* 250* 250 * No lekge Figure 11 show the reltion between the lekge pressure nd the number of psses of GFRP specimen (n). The pressure ws not llowed to exceed beyond 250 br to void the bursting of luminum dherend. It ws observed tht the specimen of lesser number of psses of glss fiber roving leked rdilly out through the GFRP joint ner the joint plne while the specimens of higher number of psses leked through the one of the ends of GFRP sleeve. Figure 12 nd Figure 13 illustrtes the mode of filure during lekge testing. No lekge of fluid ws observed for n 85 (Stiffness rtio S 0.583) of Al- GFRP-Al specimen t the fluid pressure of 250 br. Fig. 12: The oil lekge through the sleeve t the joint plne when the sleeve ws thin. Fig. 13: The oil lekge through the ends (t the leding edge) when the sleeve ws thick. B. Lek Pressure Test: Al-CFRP-Al Similr to experimenttion of Al-GFRP-AL specimen lek tests were conducted for the Al-Al-CFRP-Al specimens for vrious numbers of psses of crbon fiber roving. Tble 4 shows the experimentl results on CFRP specimens (Al- CFRP-Al) with the vrious numbers of psses n. Sr. No. No. of psses Stiffness Rtio S Set 1 Lekge pressure (br) Set Set Averge ± ± ± * 250* 250* 250 Tble 4: Lek test results for Al-CFRP-Al specimens * No lekge Figure 14 show the reltion between Lekge pressure nd the number of psses of CFRP specimen (n). Fig. 11: Lekge pressure vs. number of psses of GFRP specimen (n) Fig. 14: Lekge pressure vs. number of psses of CFRP specimen (n) Similr to GFRP specimen test the pressure ws not llowed to exceed beyond 250 br to void the bursting of luminum dherend s sme luminum mteril ws used. No lekge of fluid ws observed for n 150 (Stiffness rtio S 0.502) for Al-CFRP-Al specimen t the fluid pressure of 250 br. All rights reserved by 9

6 IV. CONCLUSION Lek tests were conducted for the specimens with vrious numbers of psses to explore how effective the joints were ginst the lekge of high pressure lubricting oil (SAE 40). Lek tests were conducted for the two types of specimens Al-GFRP-Al nd Al-CFRP-Al with vrious numbers of psses n. The tests were conducted on ded weight pressure guge tester using n ppropritely designed ttchment. The GFRP specimens were found to be lek proof t 250 br for n 85 (Stiffness rtio S 0.583) while the CFRP specimens did not show ny lekge of the oil t 250 br for n 150 (Stiffness rtio S 0.502). Thus strength of the CFRP sleeve specimen ws found to be more s compre to GFRP sleeve specimen ginst the lekge. When the FRP sleeve ws thin the fluid leked rdilly out t the joint plne. However when the sleeve ws mde thick no lekge ws found ner the joint plne. The liquid ws observed to lek through the one of the ends of the FRP sleeve. During Lek test when the pressure inside the luminium pipe increses hoop stress lso increse leding to expnsion of luminium pipe thereby forming the strong mtrix of FRP. This formtion of strong mtrix increses the pressure t which lek occurs i.e. it enhnces the results. Results re subjected to room temperture but specimen my fil t low pressure when working temperture is high. mterils. The Journl of Adhesion November doi: / [11] W. Hunfenbch R.Bohm Dmge monitoring in pressure vessels nd pipelines [12] Agrwl BD nd Broutmn LJ. Anlysis nd Performnce of Fiber Composites. John Wiley & Sons Inc. New York [13] Dnil Issc M nd Ishi Ori. Engineering Mechnics of Composite Mterils. Oxford University Press [14] Berhelot Jen-Mrie. Composite Mterils-Mechnicl Behvior nd Structurl Anlysis. Springer publiction New York REFERENCES [1] Kumr P Singh R K Kumr R Joining similr nd dissimilr mterils with GFRP. Int J Adhesion & Adhesives. 27 (2007) [2] Kumr P nd Kumr R Joining of pipes using FRP - n experimentl study J Institute of Engineers (Indi). 89 (2008) [3] Rmkumr J Singhl A K Singh R K Kumr P Butt joining of similr & dissimilr pipe mteril by cold joining process. Ad composite letters. 16 (2007) [4] Imnk M Nkym H Nkmur M Evlutions of ftigue life of dhesively bonded CFRP pipe/steel rod joints Composite SWUZMS. 31 (1995) [5] Jio H Zho XL CFRP strengthened butt-welded very high strength (VHS) circulr steel tubes Thin-Wlled Structures. 42 (2004) [6] Fwzi S Al-Mhidi R Zho X L Rizkll S Strengthening of circulr hollow steel tubulr sections using high modulus CFRP sheets Construction nd Building Mterils. 21 (2007) [7] Zho X L Zhng L Stte-of-the-rt review on FRP strengthened steel structures Engineering Structures. 29 (2007) [8] Rykhere S L Kumr P Singh R K Prmeswrn V Dynmic sher strength of dhesive joints mde of metllic nd composite dherends Mterils nd Design. 31 (2010) [9] Ldhwe R.N. Kumr P. Singh K.K. nd Srkr P.K. Chrcteriztion of GFRP butt-joint under tensile nd flexurl loding. Journl of Composite Mteril September doi: / [10] Ldhwe R.N. Kumr P. Singh K.K. Srkr P.K. nd Ugle V. Experimentl study nd numericl nlysis of CFRP butt-joint between the pipes of dissimilr All rights reserved by 10