Dynamical Properties Of Epoxy Chopped Rock Wool Composites
Journal of Al-Nahrain UniversityVol.14 (3), September, 2011, pp.50-57ScienceDynamical Properties of Epoxy–Chopped Rock Wool CompositesAli Qasim Kadhum* and E. A. A. Al - AjajDepartment of Physics, College of Science, University of Baghdad.*E-mail : kasumph@yahoo.com.AbstractHand- lay up method was used to prepare epoxy (EP) – chopped rock wool composites. Thedynamical properties for EP/chopped rock wool composites with different weight percentage ofchopped rock wool (2.5, 3.5, 5, 7.5, and 10 wt %) had been studied by using ultrasonic test method(direct method).Ultrasonic test as a non destructive testing become widely used in industry and reliablemeasurements, ultrasonic is the study of sound waves of frequencies higher than the upper hearinglimit of the human ear (frequency region above 20 kHZ).A local apparatus according to ASTM C167-82 was prepared to measure the thickness for loosematerials to calculate the density of materials like rock wool.A new sonic viewer device was used to measure the average times of compressional and shearwaves(Tp,Ts) respectively which are transit through the composites to calculate their velocities(Vp,Vs) in order to calculate the dynamic elastic moduli such as Poisson ratio (μ), Shear modulus(G), Modulus of elasticity (E), Bulk modulus (B), and other parameters such as acoustic impedance(Z) for all composites.It was shown that random values of compressional velocity (Vp) were observed for EP/choppedrock wool composites due to random distribution of chopped rock wool which could be as a resultsof weak interface bond between EP and chopped rock wool. Shear velocity (Vs) values aredecreased with increasing weight percentage of chopped rock wool and less than Vp values due tothe particles of material are vibrating perpendicular to the direction of shear waves propagation.Slight variation of poisson ratio μ, and bulk modulus B for all composites with increasing weightpercentage of chopped rock wool. Larger variation of shear modulus G, and modulus of elasticityE values for EP/chopped rock wool composites due to defects such as voids and weak interfacebond, G values decrease with increasing weight percentage of rock wool as a result of decreasingshear velocity values. Almost similar values of acoustic impedance Z are observed and lie between3.57 to 3.93 106 kg/m2sec for all composites.Keywords: Dynamic elastic moduli, ultrasonic, chopped rock wool.industrial insulation such as furnaces industrial[3].Rock wool an organic and not allow togrowth funguses, parasites', and bacteria , helpto protection the environment from unclean ,in agriculture rock wool can be used as airingearth.Non destructive evaluation (NDE) is ahugeanddiversefield.Regardingexperimental methodology it includes not onlyultrasonic's but also a wide range ofcomplementary techniques such as x–rays,optical technique such as direct visualinspection using microscopic, telescopic,thermal technique such as infrared [4]. Elasticwave energy at ultrasonic frequencies has beensuccessfully heard over the past 35 years.Ultrasonic as a non destructive testing becomeIntroductionComposite materials are used into variousfields, such as aircraft and space structures,because of the excellent characteristics, e.g.,light-weight, high ratio of relative intensityand high ratio of relative rigidity [1].Most sound–absorbing materials arefibrous or porous and are easily pentrated bysound waves. The fibrous materials arecomposed of either glass fibers or mineralsfibers such as rock wool [2]. The majorapplications of rock wool, glass wool, and slagwool derive from their performance as thermaland acoustic insulators and as filtration media,as materials are noncombustible and resistmoisture and short–term wetting, out doorinsulates, they have extra merit as building and50
Ali Qasim Kadhumwater and soap solution followed by distilledwater and put it in oven at 50 oC for one hour,then coated with wax and nylon to preventadhesion of samples with aluminum mouldbefore curing and left it to dry at roomtemperature.An electronic balance of accuracy 0.01was used to measure the weight of choppedrock wool (different weight percentage) withepoxy resin. A local apparatus according toASTM C167-82 was prepared to measure thethickness for loose materials(rock wool) tocalculate the density of rock wool as shown inFig.(2)[9].widely used in industry and reliablemeasurements, used to study the dynamicproperties of materials such as compressional,shear velocitiesVp,Vs, Poisson ratio μ, shearmodulus G, modulus of elasticity E, bulkmodulus B, and other parameter such asacoustic impedance Z [5].The investigation of dynamical propertiesof polymer composites is of great interest atpresent because of the growing use of thesematerials for industrial applications likesaircraft structures were the composite shellreduce frequency noise transmission to theaircraft fuselage, rock wool fiber mat used toimproves FRP fire resistance [6],[7].The matrix material was epoxy resin(Sikadur52–A) prepared by the reaction ofbisphenol A with the hardener (Sikadur 52 –B) epichlorohydrine as shown in Fig.(1) [8] ,supplied by company sanyicad, kaynatce Turkey as matrix,(Density1.1*103 kg/ m3),loose rock wool supplied by Jordan rockwool company was added to the matrix, therock wool insulation products have a meandiameter about 4 to 6 μm and the density rangeof rock wool 23 – 200 kg /m3[3].aFig.(1) Epoxy (bisphenol A withepichlorohydrine) [8].Experimental part and measurementsEmployed MaterialsbMaterials preparationFigs. (2) a-Depth gage for thickness of loosematerial and density measurements(ASTM – standard C167-82) [9], b- Localapparatus for thickness measurement ofloose materials.Hand- lay up method was used to prepareepoxy resin; a clean disposable containerwas used for mixing an exact amount ofhardener with the EP with ratio 2: 1 part byweight. An aluminum mould with dimensions4.5 cm, 4.5 cm, 10.5cm consists of eightplate's joints was use to prepare samples.Aluminum plate mould was cleaned withThe composites were prepared by mixingepoxy resin (EP) and chopped rock wool withdifferent weight percentage (2.5, 3.5, 5, 7.5,51
Journal of Al-Nahrain UniversityVol.14 (3), September, 2011, pp.50-57and 10 wt %) by using hand- lay up method.Part of EP resin was poured into mould. Thedifferent weight percentage of rock wool wasadded then the remained matrix was added.Aluminum plate was used to compress thecomposite in order to have a uniform thicknessand getting rid of bubbles. EP/chopped rockwool composites were cured at roomtemperature for 24 hours then removed fromthe mould and release it after four hours and.To obtain smoothing surfaces of compositesusing smoothing paper. The prepared EPresin and composites are labeled as shown inTable (1), Fig.(3) shows the prepared referencesample (1), and composites.sample 4 times to calculate average times ofcompressional, shear waves of EP and EP/chopped rock wool composites. Coupland joint(greese) was used to joint transducers andsample The average times of compressional,and shear waves of reference sample (1), andEP/chopped rock wool composites are shownin Table (2).Table (2)Average times of compressional wave (Tp)and shear wave (Ts) of reference sampleEP (1), and Ep/random chopped rock woolcomposites.Table (1)Reference sample EP (1) and EP/randomchopped rock wool composites with differentrock wool weight percentage.SamplesComposites1Reference sampleEP/2.5 wt % randomchopped rock woolEP/3.5 wt % randomchopped rock woolEP/5 wt % random choppedrock woolEP/7.5 wt % randomchopped rock woolEP/10 wt % random choppedrock woolFGHIJScienceSamplesAverage times ofcompressionalwave (Tp) (μ sec)Average timesof shear wave(Ts) (μ 02.4The difference of average time's values ofwaves is due to randomly distribution of voidsinside rock wool.The average times (Tp,Ts), and length pathd (9.7cm) are used to calculate compressional,and shear velocities (Vp,Vs) in m/sec asshown in equations below[10].d. (1)Vp TΡdVs . (2)TSWhere d: Sample thickness (9.7cm).Determination of the dynamic elastic moduliFor most materials that are stressed intension and at relatively low levels, stress andstrain are proportional to other through theequationσ Eε . (3)This is known as Hooke's law,where σ:Applied stress on the material (GPa), E:Eliastic conestant(modulus of elasticity oryoung's modulus in GPa), ε : the strain ofmaterial [11]. If body is perfectly elastic, itbehaves according to Hooke's law, and strainFig.(3) Reference sample EP (1) and EP/rock wool composites.Ultrasonic testIn this study we are focusing on theultrasonic waves such as the compressionaland shear waves (with frequencies 33, and55 kHZ respectively) as they are the basicwaves propagation in materials. A new sonicviewer device model–5217A was used tomeasure the transmission time in microsecondthen recorded the times after folding the52
Ali Qasim Kadhumµ 1 VP 2 VS VP VSequal to 6 % which could be as a results of ununiform distribution voids inside rock woolstructure.C o m p re s s io n a l v e lo c i ty (m /s e c )is proportional to stress. Most of the elasticconstants are measured or defined in terms ofratio of stress to strain produced. The differentconstants are defined in terms of differentkinds of force or stress (tension, compression,shear, etc) [12].The dynamic elastic moduliwas calculated from the above Vp and Vswhich are poisson ratio(µ), shear modulus(G),modulus of elasticity(E),bulk modulus(B), andotherparameterssuchasacousticimpedance(Z) are shown in equations below.2 1 . (4)Ref chooped rock wool composite0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9 9.5 102 1 Rock wool wt%G ρ Vs2 . (5)Fig.(4) Compressional velocity (Vp) versusrock wool wt% of EP/chopped rock woolcomposites.Where:- G: shear modulus (GPa), ρ : densityof material (Kg/m3),Vs : shear velocity(m /sec).E 2G(1 µ) . (6)dpB V, where V is the volume anddvp the pressure.4Vs2) . (7)B ρ (Vp2 3Were: B: bulk modulus ( GPa)Z ρ Vp . (9)Where: Z: acoustic impedance (Rays kg/m2.sec[5, 13, 14].S h e ar ve lo city (m /s e c)Results and DiscussionDensity of rock wool was calculated byusing a local apparatus and it was equal to42.53Kg/m3. Density of reference sample 1and the average densities of EP/ chopped rockwool composites were calculated by usingArchimedes principles and they were equal to1134, 1152 Kg/m3 respectively.Compressional velocity (Vp) of reference(1) and EP/chopped rock wool composites areshown in Fig.(4). The results show the valuesof reference (1) is equal to 3316 m/sec,random values of compressional velocity forEP/chopped rock wool composites due torandom distribution of rock wool in the matrix,the variation between the maximum andminimam values of compressional velocity isShear velocity (Vs) of reference (1) andEP/chopped rock wool composites are shownin Fig.(5), where the results show that theaverage values of shear velocity for referencesample (1) is equal to 1037m/sec, the valuesof shear velocity for EP/chopped rock woolcomposites are decrease with increasingweight percentage of rock wool as a resultsof rock wool content inside the matrix.The variation between the maximum andminimam values of shear velocity is equal to22.4 %.Zimmer reported that the undirectionalof fibers array causes heterogeneous structureof the material results in dispersion of wavespropagation [15].110010501000950900850800750700650600550500Ref (1)Ep/choopd rock wool composite0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9 9.5 10Rock wool wt %Fig.(5) Shear velocity (Vs) versus rock woolwt% of chopped rock wool composites.53
Journal of Al-Nahrain UniversityVol.14 (3), September, 2011, pp.50-57P o isso n ratio ( µ )Randomly behavior of wave velocitiespropagate in the composite material areobserved and the values of compressionalvelocity are greater than the values of shearvelocity due to the particles of material arevibrating along the direction of compressionalwaves propagation while the particles ofmaterial are vibrating perpendicular to thedirection of shear waves propagation. [16].Dynamical elastic moduli are calculatedand the results of poisson ratio (μ), shearmodulus (G), modulus of elasticity (E), bulkmodulus (B),and other parameters such asacoustic impedance (Z) are shown below.Poisson ratio of reference (1) andEP/chopped rock wool composites are shownin Fig.(6), where the results show that thevalues of poisson ratio for reference (1) isequal to 0.45, slight vary of poisson ratio forEP/chopped rock wool composites withincreasing weight percentage of rock wool.The variation between the maximum andminimum values of poisson ratio is equalto 6.2 % due to randomly distribution ofvoids inside rock wool. These results agreewith the values of poisson ratio for solidmaterials (0 - 0.5) [17].Scienceminimum values of shear modulus is equal to32.2%.Ref (1)1.5EP/chooped rock wool composite1.4Shear modulus(GPa)1.31.21.110.90.80.70.60.50.40.30.20 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9 9.5 10Rock wool wt%Fig.(7) Shear modulus (G) versus rock woolwt% of EP/chopped rock wool composites.Ref oopd rock wool compositeFig.(8) Defects (voids) inside EP/choppedrock wool composites (sample H).Modulus of elasticity (E) of reference (1)and EP/chopped rock wool composites areshown in Fig.(9). Where the results show thatthe modulus of elasticity for reference (1) isequal to 3.77 GPa, while the values ofmodulus of elasticity for EP/chopped rockwool composites decrease with increasingweight percentage of rock wool due to weakinterface bond between EP and chopped rockwool due to defects such as voids inside rockwool as shown in Fig.(10). The variationbetween the maximum and minimum values ofmodulus of elasticity is equal to 35 %.In Fig.(10). The variation between themaximum and minimum values of modulus ofelasticity is equal to 35 %. maximum andminimum values of modulus of elasticity isequal to 35 %.0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9 9.5 10Rock wool wt %Fig.(6) Poisson ratio (μ) ) versus rock woolwt% of EP/chopped rock wool composites.Shear modulus (G) of reference (1) andEP/chopped rock wool composites are shownin Fig.(7), where the results show that thevalues of shear modulus for reference (1) isequal to 1.3 GPa, while the values of shearmodulus for EP/chopped rock woolcomposites almost decrease with increasingweight percentage rock wool as a result ofdecreasing the shear velocity values due todefects such as voids as shown in Figs. (8).The variation between the maximum and54
Ali Qasim KadhumRef(1)EP/chooped rock wool 80.401514131211109876543B u lk m o d u lu s ( G P a )M o d u l u s o f e la s t ic it y ( G P a )EP/choppd rock wool composite0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9 9.5 100 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9 9.5 10Rock wool wt%Rock wool wt%Fig.(11) Bulk modulus (B) versus rock woolwt% of EP/ chopped rock wool composites.Fig.(9) Modulus of elasticity (E) verse rockwool wt% of EP/chopped rock woolcomposites.Acoustic impedance (Z) of reference (1)and EP/chopped rock wool compositesare shown in Figure (12).where the resultsshow that the values of acoustic impedancefor reference (1) is equal to 3.76 kg/m2.sec,while the values of acoustic impedancefor EP/chopped rock wool compositesalmost similar with increasing weightpercentage of rock wool and lie between3.57 to 3.93 106 kg/m2sec for all composites.The variation between the maximum andminimum values of acoustic impedance isequal to 9.1 %. The values of acousticimpedance agree with the publisheddata for unsaturated polyester /carbon fibercomposites acoustic impedance with range2.5–4.5 106 kg/m2 sec, unsaturated polyester/glass fiber composites acoustic impedance3.5 106 kg/m2 sec [18]. Yet the acousticimpedance for light weight aggregateconcrete used for building is equal to0.82 106 kg/m2sec [19], and for light weightconcrete / polystyrene grains is equal to2.3 106kg/m2sec [20] which is less than ouracoustic values for EP/chopped rock woolcomposites.Fig. (10) Weak interface bond between EPand chopped rock wool due to voids (rockwool content).Bulk modulus (B) of reference (1) andEP/chopped rock wool composites are shownin Fig.(11). Where the results show that thevalues of bulk modulus for reference (1) isequal to 10.8 Gpa, the values of bulk modulusfor EP/chopped rock wool composites arealmost similar and slight variation withincreasing weight percentage of rock wool.The variation between the maximum andminimum values of bulk modulus is equal to16.9 %.55
A c o u s t ic im p e d a n c e 1 0 6 ( k g / m 2 S e c )Journal of Al-Nahrain UniversityVol.14 (3), September, 2011, pp.50-57[5] J. Szilard.," Ultrasonic Testing", JohnWiley and Sons, Ltd, New York pp.1-11,1982.[6] L.R. Koval ," SOUND TRANSMISSIONINTO A LAMINATED COMPOSITECYLINDRICAL SHELL", Journal ofsound and Vibration,Vol.71, No.4, pp.523530, 1980.[7] T.Cooke, "Composites and fire – reducingthe risk Rail and aerospace update",Reinforced, Vol.42,No.1,pp.24-25, 1998.[8] M. S. Bhatnagar.," Polymers", S. chand,India, pp. 223-224, 2004.[9] Annual Book of ASTM standard.,"Construction thermal insulation", Vol. 04,No.08, RACE, Philadelphia, pp. 12 -15,1986.[10] British Standards Institution.,"TestingConcrete", BS1881, part203, Britain,pp. 2 –5, 1986.[11] W. D. Callister., "Materials Science andEngineering", John wiley & Sons, Inc,USA, pp.117-118, 2003.[12] L.L. Nettletion.," Geophysical prospecting for oil", McGraw - Hill, New York,London, pp. 234 – 238, 1940.[13] C. Kittle," Introduction to solid statephysics", pp: 110, John Wiley andsonc.Inc, New York, London, 1971.[14] P. E. Mix., "Ultrasonic testing ", JohnWiley and sonc. Inc, New York, pp. 109 –113, 1987.[15] J. E. Zimmer, "Determination of theelastic conestant of undiractional fibercomposite using ultrasonic velocitymeasurements", J. Acou. Soc. Am, Vol.47,No. 1, pp.795-803, 1970.[16] einforcedporouscomposite materials by the measurement ofultrasonic wave velocities", Ultrasonics,Vol. 26, pp.159- 163, 1978.[17] J. Krautkrämer and H. Krautkrämer.,"Ultrasonic Testing of Materials", NewYork, pp.5-20, 1983.[18] Jassim Ali Taher," Study acousticalfactorsand mechanical Behavior ofcomposite materials" ph.D, Thesis.Baghdad Univercity, collage of education,p.66-85, 2006.Ref(1)EP/chopped rock wool .5 11.5 22.5 33.5 44.5 55.5 66.5 77.5 88.5 9Science9.5 10Rock wool wt%Fig.(12) Acoustic impedance (Z) versus rockwool wt% of EP/chopped rock woolcomposites.ConclusionsRandom values of Vp for all compositesdue to random distribution of rock wool whichcould be as a results of voids inside rock woolstructure. Vs values are decrease withincreasing weight percentage of chopped rockwool and less than Vp values due to theparticlesofmaterialarevibratingperpendicular to the direction of shear wavespropagation. Slight variation of μ, and B for allcomposites with increasing weight percentageof chopped rock wool. Larger variation of G,and E values for EP/chopped rock woolcomposites. Almost similar values of Z liebetween 3.57 to 3.93*106 kg/m2sec for allcomposites.References[1] J. Chang and C. Zheng" The Ultrasonicwave propagation in composite materialanditscharacteristicevaluation",Composite Structures, Vol.75, 2006,pp. 451-456, 2006.[2] M. Blkales and
A local apparatus according to ASTM C167-82 was prepared to measure the thickness for loose materials to calculate the density of materials like rock wool. A new sonic viewer device was used to measure the average times of compressional and shear waves(Tp,Ts) respectively which are transit through the composites to calculate their velocities (Vp,Vs) in order to calculate the dynamic elastic .
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2.2. Chopped lightning impulse voltages For tail chopped lightning impulse voltages (LIC) two different methods are investigated for the parameter evaluation. The first method is the voltage reduction ratio method and the second one the residual curve method. The analysis of front chopped lightning impulses will not be discussed.
