碳纖維增強塑料的銑削破壞和尺寸精度設計實驗

1、瞄芹紙賀軌昔象浼去羥帝芷擐硎Damage and dimensional precision on milling carbonfiber-reinforced爿繽恩履芩巳髦客紳訪溲脊弈瑗plastics using design experiments飽毛紐荬吲秦嘛倨概忿樹街猥碎J. Paulo Davim, Pedro Reis橇墩斡形寺蔗鬈欲盅堡鮑駑敖砟Department of Mechanical Engineering, University of Aveiro, Campus Santiago, 3810-193 Aveiro, Portugal咼匍惴緯坡佐拓循舢圃逸陸吩析Rec

2、eived 24 June 2002; received in revised form 10 May 2004; accepted 8 June 2004籀魄泛轢紊疳雁馬捧孝離甫俜蟬Abstract騙渚吉螵澠辭凄畝卵緦慫滔緦郜Milling composite materials is a rather complex task owing to its heterogeneity and the number of problems, such as surface delamination, that appear during the machining process, associ

3、ated with the characteristics of the material and the cutting parameters.踔鎧談鱔浯奄診濞洮坎呃蘸瀆抵With the purpose of understanding and reducing these problems, this paper presents a study that evaluates the cutting parameters (cutting velocity and feed rate) under the surface roughness, and damage in milling

4、laminate plates of carbon fiber-reinforced plastics (CFRPs). A plan of experiments, based on the Taguchis method, was established considering milling with prefixed cutting parameters in an autoclave CFRP composite material. An analysis of variance (ANOVA) was performed to investigate the cutting cha

5、racteristics of CFRP composite material using cemented carbide (K10) end mills. The objective was to establish a model using multiple regression analysis between cutting velocity and feed rate with the surface roughness and damage in a CFRP composite material. 獪瘧北園揎氨俺懼蟮咸飄晤噍很 2004 Elsevier B.V. All r

6、ights reserved.堪黯圩歌滏惑向屜闊徜渺鈕檳怊Keywords: Milling; Carbon fiber-reinforced plastics (CFRPs); Dimensional precision; Taguchis method; Orthogonal arrays; Analysis of variance (ANOVA)晃舢享云蜃燦絳弋鴕憫嬤九搶門1. Introduction咀犟漶餅蕢剔夢親驚筘擇來母塹1.1. Milling fiber-reinforced plastics (FRPs)頹鐨瀝舍賃疲經(jīng)攢倮稹朗逗晦柏Milling is the machin

7、ing operation most frequently used in manufacturing parts of fiber-reinforced plastics, because components made of composite materials are commonly produced by net-shape that often require the removal of excess material to control tolerances, and milling is used as a corrective operation to produce

8、a well defined and high quality surfaces 1.男迮沉聵頓草奮佟蔦弭撿割統(tǒng)推The machinability of fiber-reinforced plastics is strongly influenced by the type of fiber embedded in the composite and by its properties. 筧乍艤焐啾司以搴賃鶴忘悚痧筮Mechanical and thermal properties have an extremely importance on machining FRP. 書功斥擅裟迄冉耽

9、礎昶喔反靡羿The fiber used in the composites has a greater influence in the selection of cutting tools (cutting edge material and geometry) and machining parameters.岱纖移侮您扒滅放夾溲督呢騖常It is fundamental to ensure that the tool selected is suitable for the material. 鞫沿疽攔敕嵇堀靴慚歹蛘扣浣倒The knowledge of cutting mechani

10、sms is indispensable in view of cutting mechanics and machinability assessment in milling 1,2.縟樞很蒜爬鄉(xiāng)咣鬧浯督鹽齲冊鼬Composite materials such as carbon fiber-reinforced plastics (CFRPs) made by using carbon fibers for reinforcing plastic resin matrices, such as epoxy, are characterised by having excellent pr

11、operties as light weight, high strength and high stiffness.遜諞戢括睽入萊騾鉻俘荻虜髏倮These properties make them especially attractive for aerospace applications 2.緣諞瀾唁酊估娜鎊飄哧鏊蔡疴黍Surface roughness is a parameter that has a greater influence on dimensional precision, performance of mechanical pieces and on product

12、ion costs. 噬礫殺戳檸壕戛踟氍僥劾訝滴畸For these reasons, research developments have been carried out with the purpose of optimising the cutting conditions to reach a specific surface roughness 3,4. 閑馴埔誡繾摩芒蒼轍旖忄殆狴臺For achieving the desired quality of the machined surface, it is necessary to understand the mechanis

13、ms of material removal, the kinetics of machining processes affecting the performance of the cutting tools 5.酵吞勘刊磧若噠斬木遭娛萌砟皮The works of a number of authors 612, 嘵弊峰搗躥金嘬曦梆緙啤譏奕暈when reporting on milling of FRP, have shown that the type and orientation of the fiber, cutting parameters and tool geometry

14、 have an essential paper on the machinability. 鍍崇舴聒髻本鷚躥詔眄肚呱字諱Everstine and Rogers 6 presented the first theoretical work on the machining of FRPs in 1971, since then the research made in this area has been based on experimental investigations.輊花奔錟鰷釙冗衾耆鴯普香癮仞Koplev et al. 7, Kaneeda 8 and Puw and Hoch

15、eng 9 concluded that the principal cutting mechanisms correlate strongly to fiber arrangement and tool geometry. 腔框拇大墀笈亙翁鉛袁膺歆砑擾Santhanakrishman et al. 10 and Ramulu et al. 11 carried out a study on machining of polymeric composites and concluded that an increasing of the cutting speed leads to a bet

16、ter surface finish. 晨綃籬墑豆縹曼庇幫類乇恨曹柒Hocheng et al. 12 studied the effect of the fiber orientation on the cut quality, cutting forces and tool wear on the machinability.茫瞧慢癌锘翕萋慈陟咸躺曷規(guī)睬 In summary, it can be noticed that the works carried out on the machinability of FRP, are basically related on the wear

17、 of cutting tools and the quality on the surfaces, as a function of the cutting conditions, the distribution of staple fibers in the polymeric matrix and the angle of inclination of staple fibers. 估霧且尿澈軟斂旁旱鸞它眺闊尚The current paper investigates the influence of cutting parameters (cutting velocity and

18、feed rate) on the surface roughness (Ra), delamination factor (Fd), and international dimensional precision (IT), on CFRP composite material using cemented carbide end mills, with the purpose to establish a empirical relationship between cutting parameters (V and f) and surface roughness (Ra) and de

19、lamination factor (Fd).片抒剎襝華獨咕勰頂烊忪姣掊科1.2. Autoclave process瓦婭噶判莖埠館咎頸辭鴕簌揪極The autoclave process is widely used to produce high-performance laminates usually with fibers reinforced epoxy systems. 暖囈肥閎其奪遞劐濠戶克蕺吡慟Composite materials manufactured by autoclave are particularly important for aerospace appli

20、cations.嘟詔葡癜喟耙抿編盜襦戕筆翕堂This process uses a pressurised vessel to apply pressure and heat to both parts that have been sealed in a vacuum bag. Next it can be seen the several stages of this process. 扁好蟶飯碥僖籍揩氬鷗碗耿郗咦On the first stage, the prepreg carbon-fiberepoxy material is carefully laid out on a tab

21、le to ensure that fiber orientation meets the design requirement, where the prepreg material consists of unidirectional long carbon fibers in a partially cured epoxy matrix. On the second stage, pieces of the prepreg material are cut out and placed on top of each other on a shaped tool to form a lam

22、inate. 倍郛蘭盔諦逼菝講兄豫森奏硭汕The layers could be placed in different directions to produce the desired strength pattern since the highest strength of each layer is in direction parallel to the fibers.痘齬酉芳嘎璽锿石尾儇姜沙牯返After the required number of layers has been properly placed, the tooling and the attached lam

23、inate are vacuum-bagged, for removing the entrapped air from the laminated part.娶庀縭皚韻倌魯蕊埠祠猬侮鞘箋Finally, the vacuum bag and the tooling is put into an autoclave for the final curing of the epoxy resin.供南蛸賽焚阢多囡鴟餡佑犄嘧After removed from the autoclave, the composite material is ready for further finishing

24、operations 2,13.覽鋈鎩雍癩褊皈錢四失楹磉餒鷙2. Experimental procedure菁題榆孳趁戚邏覆襖蜊溜铘眚戎2.1. Method and materials褪靡懷膛洞醯媵趣葚獍樸屯僚士In order to reach the objective of this experimental work, mainly the establishment of the correlations between cutting parameters (V and f) and surface roughness (Ra) and delamination factor

25、(Fd), machining issues were performed under different cutting conditions on the CFRP composite material.揶港泛曝厶鏷患索恕戲劍徹遁碲 The composite material used in the tests (epoxy matrix reinforced with 55% of carbon fiber), supplied by INEGI, was produced by autoclave with a fiber orientation of 0/90, as can be

26、 observed in Fig. 1.搟鞍默吁甚煩菩誚烤仿瑁奴襻吮The experiments have been carried out in a laminate plate, made up with 16 alternating layers of fibers with 4mm of thickness, using two cemented carbide (K10) end mills, presented in Fig. 2, with 6mm of diameter. Both cemented carbide end mills, two-flute (R216.32-

27、06030-AC10P-1020) and six-flute (CCT-GSR-D0635), were manufactured according to ISO. 甾嬸蒯西步作讓瓶曰呂蹭現(xiàn)蜣徙The two-flute end mill presents the following geometry: a helix angle of 30, a rake angle of 1030_, a clearance angle of 9 and a flute length of 10 mm. 靼氣簇喔伏瀑賽醅表镢余馥髖霹The six-flute end mill presents a n

28、eutral helix and 20mm of flute length. The depth of the cut on CFRP composite material was 2 mm. 螬芥救婁衛(wèi)叭鮒豚日寡遒栽庖洳A milling machine “LC-11/2VS First” with 2.2kW spindle power and a maximum spindle speed of 2500 rpm was used to perform the experiments. 洽均僳巍癭讕樣埴敞噻祉謠揆址The fixation of the composite materia

29、l (plate) was made as observed in Fig. 3, to make sure that vibrations and displacement did not exist. 涪崆鎖糊晉車戀氐軫程醵碴挹元The surface roughness was evaluated (according to ISO 4287/1) with a Hommeltester T1000 profilometer, as can be observed in Fig. 4.鬢熬埴哧郎外埡萁逭豈劬鐘鰩吁For each test five measurements were m

30、ade over milling surfaces, according to Fig. 5. Considering the number of measurements to be carried out, a programmable technique was used, by previously selecting a roughness profile, the cut-off (0.8 mm) and the roughness evaluator parameter (Ra) according to ISO. 吮洮學羰例忝蘭沂蹲曜痦嬉殄蝶Data acquisitions

31、were made through pro-filometer, by interface RS-232 to PC using the software欷門餐悠繚數(shù)剔醚除倔俁萏番諗Hommeltester Turbo-Datawin.液呻欹躒鋇寨璁蕞取腐鲆泌伽堝The damage caused on the composite material was measured with a shop microscope, Mitutoyo TM 500, with 30 magnification and 1 _m resolution.肜皇淚樟范竅涉箍鉦印陳返莼已2.2. Plan of e

32、xperiments荏濮稷苦堤昧蟹唄鄲罨暖娜駛吶Taguchis method has been widely used in engineering analysis and consists of a plan of experiments with the objective of acquiring data in a controlled way, in order to obtain information about the behaviour of a given process. 苡焚銻拇撒井甏鈀加握鲴庸射廖The Taguchis method for two factor

33、s at three levels was used for the elaboration of the plan of experiments. Table 1 indicates the factors studied and the assignment of the corresponding levels. By levels is meant the values taken by the factors. 且健鰾鰥娼琮昆腿揭著玢醯鴻郫The orthogonal array L9 (24), was selected as shown in Table 2, which has

34、 nine rows corresponding to the number of tests (8 degrees of freedom) with two columns at three levels. The factors and the interactions are assigned to the columns. 兢崾笪糝鉚稈姹懂祺圬壞摶亭鯊The plan of experiments was made of nine tests (array rows), where the first column was assigned to the cutting velocit

35、y (V) and the second column to the feed rate (f) and the remaining were assigned to the interactions. 蒗籠鄔薈意嗣淖慵賴院鏟擘沒攻The outputs studied were surface roughness (Ra) and delamination factor (Fd), in the CFRP composite material. 驃灸靜踅兄削葶裹叮瞍遺躥觸擺The treatment of the experimental results was based on the a

36、nalysis average and the analysis of variance (ANOVA) 1417.關闡掩疊禧蠻凄寄蛄瞿舁颶侄籩An analysis of variance of the data with the surface roughness and delamination factor, on the CFRP composite material was done with the objective of analysing the influence of the cutting velocity, and the feed rate on the tota

37、l variance of the results.懵胄蘸宦蓿團臚悔轎杌連羰訂3. Results and discussion散愣臠媳醴腱腐阽愜箬棣垃咫筆The results of milling tests allowed the evaluation of the CFRP composite material manufactured by autoclave, using two cemented carbide (K10) end mills. 湍掩晾狼鈷辰苤馮夫逃慧接踺膣The machinability was evaluated by surface roughness (

38、Ra), delamination factor (Fd) and international dimensional precision (IT).笪濯煥井撙毋鎳乘驥馕彭鰩繹堋3.1. Influence of the cutting parameters on the surface燴麾踢鳋勁錘防蓬苜葆轷鈺鈁跎roughness翻贊挹淚效蟻鍪剔隴枯處十臾洎The surface roughness (Ra) was evaluated with a Hommeltester T1000 profilometer, according to ISO 4287/1. Tables 3 and

39、4 show the results of the surface roughness (Ra) as a function of the cutting parameters, for both end mills, two- and six-flute, respectively. In Fig. 6, the evolution of the surface roughness (Ra) can be seen with the feed rate, for the different cutting speed values. From Fig. 6, it can be realis

40、ed that the value of Ra increases with feed rate and decreases with the cutting velocity, i.e. with a higher cutting velocity and a lower feed rate it is possible obtain a better surface finish. It can also be observed that the two-flute end mill provides a better surface than the six-flute end mill

41、. Table 5 shows the results of the analysis of variance with the surface roughness (Ra) for both end mills. 恿矚樣涔刃夠悄驏良黢鰩頁雀氟This analysis was carried out for a level of significance of 5%, i.e. for a level of confidence of 95%. The last column of the previously shown tables indicates the percentage of

42、 contribution (P) of each factor on the total variation indicating then, the degree of influence on the result.錆鬈籠遣穎仗襟熾譯魎割棍芋箴From Table 5, it can be realised that the feed rate factor (P = 77.5%), have statistical and physical significance on the obtained surface roughness (Ra), for two-flute end mi

43、ll. The factor cutting velocity (P= 9.5%) does not present statistical and physical significance on the surface roughness, because Test F F = 5% and P (percentage of contribution) F = 5% and P (percentage of contribution) error associated. 鷺謠齡呋尖討恨挫桿笥和勺巛跬Notice that the error associated to the table

44、ANOVA for the Ra was approximately 1.7%. The value of international dimensional precision (IT) can be obtained by the following empirical equation according to UNI ISO 3963/2: IT= 30Ra (1)孑恫怪饕懇酗烙哺惜捫廖腿洄短Ra being the surface roughness in _m. Table 6 shows the results of the dimensional precision (IT),

45、 obtained by Eq. (1), as a function of the cutting parameters In Fig. 7 the evolution of the dimensional precision (IT) can be seen with the feed rate, for the different cutting speed values. According to the graph, it is evident that the IT increases with the feed rate, and decreases with the cutti

46、ng speed. 乎掘儲紋蔦檀锎貪爽杠闋吃折鈥It can also be observed that for both end mills (two- and six-flute) the surface presents ITs between 35 and 80 _m, and 40 and 80 _m, respectively, i.e. it is possible to get surfaces of quality of mechanics current construction, nominated qualities of IT 9 and 11.矯昊利架茛戍镩村馮怏豌

47、癮及渡3.2. Influence of the cutting parameters on the delamination factor顴螳著磐蝤漢嬗尸撕娃捕柃淡糜The damage caused on the laminate plate (CFRP composite material) was measured perpendicular to the feed rate with a shop microscope Mitutoyo TM 500, as can be observed in Fig. 8. 漣酣尾耨鸚萊瀘酋礎效蕉嬡均蘑The composite material

48、 (laminate plate) was positioned and fixed on the XY stage glass of the microscope, then the alignment of an initial measuring point with one of the cross-hairs was made on the machined fea ture.柁觴啄瓢弄潮肇愴癖褐弓袒粽十 Moving the XY stage glass by turning the micrometer head with a Digital Counter to the fin

49、al point with the same cross-hair has been measured the damage (maximum width). 咸鑠攪樊踢赧籪蟄嬋韶宰蛻悔瀚After the measurement of the maximum width of damage (Wmax) suffered by the material, the damage normally assigned by delamination factor (Fd) was determined. 漂穢耔螵炷獍颼殺蘸檎嘸媚苷延This factor is defined as the quo

50、tient between the maximum width of damage (Wmax), and the width of cut (W). The value of delamination factor (Fd) can be obtained by the following equation: Fd = Wmax W籌晷謀閿救掎熬握熾蘺穩(wěn)愣闖狄(2)Wmax being the maximum width of damage in _m and W the width of cut in _m珀慫申共化幣地醉鎂暹芊懶劉逅Table 7 shows the results of

51、 the delamination factor (Fd) for the two end mills, obtained as Eq. (2) as a function of the cutting parameters. In Fig. 9 the evolution of the delamination factor (Fd) can be seen with feed rate, for different cutting speed values. 碣翅鶼褡天其蹬壯蛻逑璐淌孺惺From Fig. 9, it can also be noticed that the Fd incr

52、eases with the feed rate. It can also be observed a significant variation on the delamination factor (Fd) for the six-flute end mill with the increase of the cutting speed. 嫡霪輪要游療嘈瀅蚯圣漂迦劫手Finally, it can be realised that two-flute end mill presents a lower delamination factor than the six-flute end m

53、ill, i.e. the two-flute end mill leads to a smaller damage on the CFRP composite material. Table 8 shows the results of the analysis of variance with the delamination factor (Fd) for both end mills. From Table 8, it can be realised that the feed rate factor (P = 83.9%), have statistical and physical

54、 significance on the obtained delamination factor (Fd), for two-flute end mill. 將鈣彷蟻僧狩噴鳩友赳睪鉗嘲詠The factor cutting velocity (P = 0.6%) does not present statistical and physical significance on the delamination factor (Fd), because Test F F = 5% and P (percentage of contribution)N F = 5% and P (percent

55、age of contribution) error associated. Notice that the error associated to the table ANOVA for the Fd was approximately 4.3%.衫曹唇稅呀燁經(jīng)斛朕迷荬暈田契3.3. Multiple regression analysis (MRA)胨恫挪匆躉嶼匆蟈撰盍?？酝尥he correlation between factors (cutting velocity, feed rate) and surface roughness (Ra) and delamination fa

56、ctor (Fd), for both end mills on the CFRP composite material were obtained by multiple linear regression with a sample size (n) of 9. 蛩腡搪劑差屜恨衛(wèi)傳疏肥宓尷轅The equations obtained for both end mills were as follow: Two-flute end mill: Ra = 1.76 2.40 102V + 1.71 103f, R = 0.93 (3)必頰胄含鏃倡賜推憩罹脘瑚莧則Fd = 1.00 6.58 105V + 2.34 105f, R = 0.89 (4)渴蹴形弗槔示苘策鼢釤聃到嶧琢Six-flute end mill:優(yōu)廒祭龠耿庋