7/27/2019 1-s2.0-0010436195989169-main

1/5

UTTERWORTH~ ] E I N E M A N NComposites 26 (1995) 669-673

1995 Elsevier Science LimitedPrinted in G reat Britain. All rights reserved0010-4361/95/$10.00

Appl icat ion of Taguchi method for processenh anc em ent of on-line consol idat iontechniqueS . K . M a z u m d a r a n d S . V . H o a *Concordia Center for Composites, D epa rtmen t of Mech anical Engineer ing, ConcordiaUniversity, M ontreal, Quebec, Canada HG3 1M B(Received Janua ry 1994; revised 1 Decem ber 1994)

Du ring laser assisted processing of therm oplastic composites, the individual effects of laser power, tapespeed and consol idat ion pressure on the interply bond s trength cannot be eas ily separated unless a largenum ber of experiments is carried ou t. Because the properties of an end prod uct depe nd upo n the selec-tion of processing conditions, it is essential that the conditions under which a well consolidated part isobtained should be defined. To investigate the effects of individual process parameters from a minimumnumber of tes ts , the Taguchi method is appl ied. For this inves t igat ion, PEEK/carbon fibre (APC-2)thermoplas t ic composi te r ings were manufactured by a thermoplas t ic tape winding process a t se lectedcondit ions , and the influence of dom inan t process p arameters on interply bond s trength was evaluated.The influence of three do min ant factors , namely laser power, con sol idat ion pressure and tape speed, onbon d stren gth were investigated. T he experimental design involved using L9 orth ogo nal arrays, and thepercentage contribut ion of each factor to the qual i ty of bonding was es t imated by the AN OV A technique.(Keyword s: comp os i tes manufacturing; Taguchi method; PEEK /carbon com pos i tes ; on- line consol idat ion)

I N T R O D U C T I O NI n t h e m a n u f a c t u r e o f a c o m p o s i t e c o m p o n e n t , s e v er a lp r o c e s s i n g v a r i a b l e s i n f l u e n c e t h e p e r f o r m a n c e o f t h ep r o d u c t . T h e t e c h n i q u e o f d e f in i n g a n d i n v e s ti g a t in g a l lp o s s ib l e c o n d i t i o n s i n a n e x p e r i m e n t i n v o l v i n g m u l t i p l ef a c t o r s is k n o w n a s t h e d e s i g n o f e x p e ri m e n t s . I n t h e o l dd a y s i t w a s b e l i e v e d t h a t t h e s c i e n t i f ic a l l y c o r r e c t w a y t oc o n d u c t a n e x p e r i m e n t w a s t o v a r y j u s t o n e f a c t o r a t at i m e , h o l d i n g e v e r y t h i n g e ls e f i x ed . T h u s f o r a f u l l f a c t o -r i a l d e s i g n , t h e n u m b e r o f p o s s i b l e d e s i g n s N i s:

N = L m (1 )w h e r e L = n u m b e r o f le v el s f o r e a c h f a c t o r a n d m =n u m b e r o f f a c t o r s .T h u s , i f t h e q u a l i t y o f a g iv e n p r o d u c t d e p e n d s o nt h r e e f a c t o r s , A , B , a n d C , a n d e a c h f a c t o r i s t o b e t e s t e da t th ree l eve l s , the equa t ion (1 ) ind ica te s 33 (27) pos s ib led e s ig n c o n f i g u r a t i o n s . I t m e a n s t h e e x p e r i m e n t e r h a s t oc o n d u c t 2 7 t e s t s t o g e t e n o u g h i n f o r m a t i o n a b o u t t h ep r o ce s s. A s t h e n u m b e r o f f a c t o r s o r n u m b e r o f le v el si n c r e a se s , t h e t o t a l n u m b e r o f t e st s a l so i n c r e a s es . F o re x a m p l e , i f a n e n g i n e e r w a n t s t o d e t e r m i n e t h e e f f e c to f s e v e n f a c t o r s a t t w o l e v e l s t h e n t h e t o t a l n u m b e r o f* To whom correspondence should be addressed

exper im ents becom es 27 (128) , which wi l l inc rease thec o s t o f t h e e x p e r i m e n t s .T e c h n i q u e s s u c h a s f r a c t i o n a l f a c t o r i a l d e s ig n a r e u s e dt o s i m p l i f y t h e d e s i g n o f e x p e r i m e n t s . F r a c t i o n a l f a c t o -r i a l d e s i g n i n v e s t i g a te s o n l y a f r a c t i o n o f a l l t h e p o s s i b l ec o m b i n a t i o n s . T h i s a p p r o a c h s a v e s c o n s i d e r a b l e t i m ea n d m o n e y b u t r e q u i r e s r i g o r o u s m a t h e m a t i c a l t r e a t -m e n t , b o t h i n t h e d e s i g n o f th e e x p e r i m e n t a n d i n t h ea n a l y s i s o f t h e r e s u l t s , t o c o r r e c t l y u n d e r s t a n d t h ep r o c e s s. E a c h e x p e r i m e n t e r m a y d e s i g n a d i f f e r e n t se t o ff r a c t i o n a l f a c t o r i a l e x p e r i m e n t s . T h e r e f o r e , a s y s t e m a t i ca p p r o a c h t o d e t e r m i n e t h e e f f e c t o f p r o c es s p a r a m e t e r so n t h e q u a l i t y o f e n d p r o d u c t i s h e l p f u l . H e r e i n l ie sT a g u c h i ' s c o n t r i b u t i o n t o t h e s c ie n c e o f t h e d e s ig n o fe x p e r i m e n t s . H e s i m p l if i e d a n d s t a n d a r d i z e d t h e f r a c -t i o n a l f a c t o r i a l d e s i g n s u s i n g a s p e c ia l s e t o f o r t h o g o n a la r r a y s . A c c o r d i n g t o T a g u c h i ' s e x p e r i m e n t a l d e s ig n , o n l ya m i n i m u m o f 8 e x p e r im e n t s i n s t e ad o f 1 2 8 e x p e r im e n t sf o r s e v e n f a c t o r s a t t w o l e ve l s a r e r e q u i r e d t o g e t e n o u g hi n f o r m a t i o n a b o u t t h e p r oc e ss . D e t a i l e d e x p l a n a t i o n s o fT a g u c h i m e t h o d o l o g y c a n b e f o u n d i n r ef s 1 - 4.F o r m a n u f a c t u r i n g p r o c e s s e s w h e r e a l a r g e n u m b e ro f f a c t o r s i n f l u e n c e t h e f i n a l o u t c o m e , t h e T a g u c h ia p p r o a c h c a n b e u t i l i z ed to a r r i v e a t t h e b e s t p a r a m e t e r sf o r t h e o p t i m u m d e s i g n c o n f i g u r a t i o n w i t h t h e l e a s tn u m b e r o f a n a l y t i c a l i n v e s t i g a t i o n s . T h e r e f o r e t h eT a g u c h i m e t h o d h a s g r e a t p o t e n t i al i n t h e a r e a o f lo w

COMPOSITES Volume 26 Number 9 1995 669

7/27/2019 1-s2.0-0010436195989169-main

2/5

Taguchi method for process enhancement: S.K. Mazumdar and S. V Hoac o s t c o m p o s i t e s m a n u f a c t u r i n g a n d m a t e r i a l s p ro c e s s in g .In sp i t e o f th i s , u se o f s t a t is t i ca l t echn i ques i n t he a r e ao f c o m p o s i t e s m a n u f a c t u r i n g i s l a c k in g . W i l k in s e t a l . 5u s e d t h e T a g u c h i m e t h o d f o r p r o p e r t y a n d p r o c e s se n h a n c e m e n t o f a r e si n tr a n s f e r m o u l d i n g ( R T M )process .R e c e n t l y s e v e r a l r e s e a r c h e r s h a v e a d d r e s s e d v a r i o u sa s p e c t s o f th e r m o p l a s t i c t a p e l a y i n g a n d t a p e w i n d i n gp r o c e s se s . B e y e l e r a n d G u c e r i 6, G r o v e 7. N e j h a d s a n dA n d e r s o n a n d C o l t o n 9 h a v e d e v e l o p e d m o d e l s f o r t h ep r e d i c t i o n o f t e m p e r a t u r e h i s t o r y f o r a k n o w n a m o u n to f h e a t s u p p l y a n d k n o w n t a p e s p e e d f o r a t a p e l a y in gopera t i on . Ot h er r esearcher s 1-~4 have s t ud i ed t he exper i -m e n t a l a s p e c t s o f th e r m o p l a s t i c t a p e w i n d in g . B e y e l e r e tal. 1 d i scussed t he f eas i b i l i t y o f l aser p rocess i ng byp r o d u c i n g s e v e r a l r i n g s u s i n g R y t o n A C 4 0 - 6 0 p r e p r e gt apes . H au be r an d h i s co -w orke r 11,12 used rob o t s and ho tn i t ro g e n g a s f o r t h e m a n u f a c t u r e o f c i r c u la r c y l i nd e r s .W e r d e r m a n n e t a l . 13 des i gned and f ab r i ca t ed a n on - l i nec o n s o l i d a t i o n f a c i li ty f o r t h e m a n u f a c t u r e o f c i r c u la rr in g s a n d s h o r t t u b e s f o r th e r m o p l a s t i c c o m p o s i t e s . T h e yu s e d i n fr a - re d a n d h o t n i t r o g e n g a s f o r h e a t i n g t h e p r e -i m p r e g n a t e d t o w . C a r p e n t e r a n d C o l t o n 14 u s e d h o t a i ras a hea t sou rce fo r t he f ab r i ca t i on o f c i r cu l a r r ings . Them a j o r e m p h a s i s i n t h e s e w o r k s ~q 4 w a s o n t h e d e s i g n a n dd e v e l o p m e n t o f a n e x p e r i m e n t a l s e t - u p a n d t h e d e t e rm i -n a t i o n o f q u a l it y o f c o n s o l id a t i o n b y o p t i c a l m i c r o s c o p i cs t udy . N on e o f t he abo ve r esearcher s 1-14 exper i m en t a l l yd e t e r m i n e d t h e t e m p e r a t u r e h i s t o r y , p r o c e s s i n d u c e dd e f o r m a t i o n s , c r y s ta l l in i ty o r q u a l i t y o f t h e b o n d .M a z u m d a r a n d H o a 15-18 p e r f o r m e d q u a l i ta t i v e a n a l y -s e s o f t h e e f f ec t s o f d o m i n a n t p r o c e s s p a r a m e t e r s , s u c ha s t h e a m o u n t o f h e a t s u p p l y , t a p e s p e e d a n d c o n s o l i -d a t i o n p r e s s u r e , o n t h e t e m p e r a t u r e h i s t o r y , p r o c e s si n d u c e d d e f o r m a t i o n , c r y s ta l li n it y a n d q u a l i t y o f c o n s o l -i da t i on fo r l aser and ho t n i t rogen gas a i ded p rocess i ng .Agarwa119 s t ud i ed t he e f f ec t o f l aser power on c rys -t a l l i n i t y , vo i d con t en t , t empera t u re d i s t r i bu t i on andi n t e r l a m i n a r b o n d q u a l i t y f o r a c o n s t a n t t a p e s p e e d o f1 5. 4 m m s l . T h e a b o v e w o r k s l a c k a n y q u a n t i ta t i v ea n a l y s is o n t h e e f f e c t o f p r o c e s s p a r a m e t e r s o n b o n dqual i t y . Th i s paper emphas i zes t he quan t i t a t i ve ana l ys i so f th e i n fl u e n c e o f d o m i n a n t p r o c e s s p a r a m e t e r s o n b o n ds t re n g t h. T h e s t u d y p r o v i d e s i m p o r t a n t i n f o r m a t i o n a n dgu i de l i nes fo r t he t hermop l as t i c t ape wi nd i ng p rocess ,a n d d e t e r m i n e s t h e p e r c e n t a g e c o n t r i b u t i o n o f i nd i v id -u a l p a r a m e t e r s t o t h e b o n d q u a l i t y .

Beam elvery ~ Air cylindersystem Consolidated~ _ ~ laminate M a n d r e lLaser eam1

~ RollerI ContactIncoming p o i n tt a p eLaserHead\Cooler

~ PowerControllerFigure 1 Schem aticdiagram o f the laser assisted thermoplastic tapewinding processa r e s h o w n i n F i g u r e 2 . A 65 W CO2 l aser hav i ng a wave-l e n g th o f 1 0 . 6 / a n ( M P B T e c h n o l o g i e s) w a s u s e d f o rp r o c e s s i n g t h e c o m p o s i t e s . T h e e x p e r i m e n t a l s e t - u p u s e dfo r manufac t u r i ng t he r i ngs i s descr i bed i n de t a i l i n r e f .2 0 . I n t h e t a p e w i n d i n g p r o c e s s t h e t h r e e d o m i n a n tp r o c e s s i n g p a r a m e t e r s a r e l a s e r p o w e r , t a p e s p e e d a n dc o n s o l i d a t i o n p r e s s u re . B y c h a n g i n g t h e l a s e r p o w e r a n dt a p e s p e e d , t h e t e m p e r a t u r e h i s t o r y a n d t h u s q u a l i t y o ft h e p a r t c a n b e c h a n g e d .Fo r t he p resen t i nves t i ga t i on , 10 -p ly r i ngs were ma nu-f a c t u r e d a t s e l ec t e d p r o c e s s i n g p a r a m e t e r s . M a z u m d a r 2charac t e r i ze d t he i n t e r f ac i a l p l y bond i n g o f r i ng spec i-

O B J E C T I V E ST h e p r e s e n t s t u d y i s p e r f o r m e d t o f u lf il th e f o l l o w i n g t w oob j ec t i ves :1 . t o u se a s t a t i s t i ca l met hod fo r de t e rmi n i ng t heo p t i m u m c o n d i t i o n ; a n d2 . t o es t i mat e t he con t r i bu t i on o f i nd i v i dua l p roces sp a r a m e t e r s , s u c h a s l a s e r p o w e r , c o n s o l i d a t io n p r e s -s u r e a n d t a p e s p e e d , t o t h e q u a l i t y o f th e b o n d .E X P E R I M E N T A L P R O C E D U R EA P C - 2 t a p e ( I C I F i b e r i t e ) w i t h a 6 . 3 5 m m w i d t h a n d0 . 1 2 5 m m t h i c k n e s s w a s u s e d t o m a n u f a c t u r e 1 4 6 m md i a m e t e r r in g s u s i n g a t h e r m o p l a s t i c t a p e w i n d i n g t e c h -n i q u e . A s c h e m a t i c d i a g r a m f o r m a n u f a c t u r i n g a n A P C -2 r i ng i s shown i n F i g u r e 1 . P h o t o g r a p h s o f th e s e t -u p l~gmre 2 Photographs from ba ck and front o f the experimental set-up

6 7 0 COMPOSITES Volume 26 Number 9 1995

7/27/2019 1-s2.0-0010436195989169-main

3/5

Taguch i me tho d fo r p rocess enhan cemen t : S .K . Ma zum dar and S .V . Hoam e n s u s i n g a s h o r t b e a m s h e a r ( S B S ) t e s t , a d o u b l ec a n t i l e v e r c u r v e d b e a m ( D C C B ) t e s t a n d a f r a c t u r es u r f a c e s t u d y b y s c a n n i n g e l e c t r o n m i c r o s c o p y ( S E M ) .T h e y f o u n d t h a t t h e S B S t e s t i s s e n s i t i v e t o i n t e r p l yb o n d i n g a n d c a n e a s i l y d e t e c t d i f f e re n c e s in t h e i n t e r p l yb o n d q u a l i t y . T h e r e f o r e , i n t h e p r e s e n t c a s e S B S te s t sw e r e c o n d u c t e d f o r q u a l i ty c o n t r o l p u r p o s e s .I M P L E M E N T A T I O N O F T A G U C H I M E T H O DDesigning the experiment

E x p e r i m e n t a l d e s i g n i n v o l v e s d e f i n i n g a l l t h e p o s s i b l ec o n d i t i o n s i n a n e x p e r i m e n t i n v o l v i n g m u l t ip l e f a c t o r s .A n e x p e r i m e n t a l d e s i g n m u s t s a t is f y t w o ' o b j e c t i v e s . I nt h e f i rs t , t h e n u m b e r o f t r i a l s i s c a l c u l a t e d a n d i n t h es e c o n d , t h e c o n d i t i o n s f o r e a c h t r i a l a r e s p e c i f i e d .T a g u c h i d e v e l o p e d s e v e r al se ts o f o r t h o g o n a l a r r a y s( O A s ) f o r d e s i g n i n g e x p e r i m e n t s w i t h v a r i o u s f a c t o r s a n dl e v el s . I n t h e p r e s e n t c a s e t h r e e f a c t o r s a t t h r e e l e v e l s a r es t u d i e d , a s l i s t e d i n Table 1. T h r e e l e v e l s a r e s e l e c t e dw h e n i t i s s u s p e c t e d t h a t t h e i n f lu e n c e o f a f a c t o r o n t h er e s u l t c a n b e n o n - l i n e a r . F o r t h e p r e s e n t c a s e , a n L9 o m ,a s s h o w n i n Figure 3, w i l l b e s u i t a b l e f o r e x p e r i m e n t a ld e s i g n I . T h e r e a r e n i n e i n d e p e n d e n t c o n d i t i o n s i n a n L 9.T h e s e c o n d i t i o n s a r e d e s c r i b e d b y t h e n u m b e r s i n t h er o w s . E x p e r i m e n t s w e r e p e r f o r m e d a t l a s er p o w e r s o f 40 ,5 0 a n d 6 0 W , c o n s o l i d a t i o n p r e s s u r e s o f 5 0 .4 , 1 0 0 .8 a n d1 5 1 . 3 k N m - l, a n d t a p e s p e e d s o f 6 .4 2 , 1 3 . 0 a n d 2 7 . 0 m ms -~. H e r e c o n s o l i d a t i o n p r e s s u r e i s m e a s u r e d i n t e r m s o fl o a d p e r u n i t w i d t h o f t h e l a m i n a t e , w i t h t h e a s s u m p t i o nt h a t t h e r e i s l i n e a r c o n t a c t b e t w e e n t h e c o n s o l i d a t i o nr o l l e r a n d l a m i n a t e 2. F o r c l a r it y , t h e e x p e r i m e n t a lc o n d i t io n s o f Figure 3 c a n b e e x p l a i n e d a s f o ll o w s :E x p e r i m e n t N o . 1:

4 0 W ( A I ) , 5 0 . 4 k N m -1 ( B 0 , 6 . 4 2 m m s ( C t )E x p e r i m e n t N o . 2 :

40 W ( A 0, 100 .8 k N m -1 ( B2) , 13 .0 m m s ( C2)E x p e r i m e n t N o . 3 :

40 W ( A 0, 151 .3 kN m -1 ( B3) , 27 .0 mm s 1 ( C3)E x p e r i m e n t N o . 4 :

50 W ( A2), 50 .4 kN m - t ( B 0 , 13 .0 mm s -1 ( ( :2 )E x p e r t m e n t N o . 5 :

50 W ( A2) , 100 .8 kN m - t (B2), 27 .0 m m s-t (C3)E x p e r i m e n t N o . 6 :50 W ( A2) , 151 .4 kN m -1 ( B3) , 6 .42 m m s ( CO

E x p e r i m e n t N o . 7 :6 0 W ( A3 ), 5 0 . 4 k N m -1 (B l ) , 2 7 . 0 m m s"l ((73)

E x p e r i m e n t N o . 8 :60 W ( A3), 100 .8 k N m - l (B2), 6 .42 m m s a ( C i )

E x p e r i m e n t N o . 9 :T~ le 1 Control factors and their levels for thermoplastic tapewinding processFac tor Level 1 Level 2 Level 3Laser p o w e r (W) 40 50 ~ 60Consolidationpres sure (kN m 1) 50.4 100.8 151.3Tape speed(mm"l) 6.42 13.0 27.0

6 0 W (A3) , 151 .4 kN m - l (B3), 13 .0 mm s-1 (C2)F o r t h e p r e s e n t c a s e o n l y o n e e x p e r i m e n t a t e a c h o ft h e a b o v e c o n d i t i o n s w a s p e r f o r m e d t o d e t e r m i n e t h em a i n e f f e ct s o f i n d i v i d u a l p r o c e s s in g p a r a m e t e r s . T h eo p t i m u m c o n d i t i o n i s i d e n t i f i e d b y s t u d y i n g t h e m a i n

e f f e ct s o f e a c h o f t h e f a c t o rs .Analysis o f results

A s d e s c r i b e d a b o v e , t in g s w e r e m a n u f a c t u r e d a t s p e c -i f ie d c o n d i t i o n s a n d t h e r e s u l t s o f t h e S B S t e st s , i n te r m so f a q u a l i t y c h a r a c t e ri s t ic Y , w e r e m e a s u r e d a s s h o w nb e l o w :Yl - - 25 .66 M P a ,Y4 TM 3 5 . 0 9 M P a ,Y7 - - 35 .66 M P a ,

Y2 = 28 .06 M P aY5 = 29 .79 M P aY8 = 35 .73 M P a

Y3 = 20 .65 M P aY6 = 29 .15 M P aY9 = 39 .57 M P a

T h e s e r e s u l ts w e r e r e c o r d e d i n t h e f a r ti g h t c o l u m n o ft h e O A (Figure 3). S i n c e th e r e w a s o n l y o n e t e s t f o r e a c hc o n d i t i o n , t h e r e s u lt s w e r e r e c o r d e d i n o n e c o l u m n . F o rs o m e t r i a l c o n d i t i o n s s u c h a s e x p e r i m e n t n u m b e r s 4 a n d7 , m u l t i p l e t e s t s w e r e p e r f o r m e d . E x p e r i m e n t s 4 a n d 7w e r e s e l e c te d f o r m u l t ip l e r u n s b e c a u s e t h e y w e r e c l o s et o t h e o p t i m u m c o n d i ti o n s . T h e s t a n d a r d d e v i a ti o n f o re x p e r i m e n t n u m b e r 4 w i t h t w o t e s t r u n s w a s f o u n d t ob e 0 . 5 6 4 a n d t h a t f o r e x p e r i m e n t n u m b e r 7 w i t h t h r e et e s t r u n s w a s f o u n d t o b e 1 . 7 7 3 . O n c e t h e m a i n e f f e c t sa r e k n o w n , t h e n n e w l e v el s f o r c o n t r o l f a c t o r s a r es e l e c t e d t o l o c a t e t h e b e s t c o n d i t i o n f o r h i g h e r p e r f o r -m a n c e : T h e r e s u l ts f o r t h e n e w l ev e ls a r e p r e s e n t e d i nr e f . 20 .

T o s p e e d u p a n a l y si s , T a g u c h i h a s p r o v i d e d s o m e k e yp r o c e d u r e s w h i c h a r e u s e d h e r e . W h e n t h e s e s t e p s a r es t ri c tl y f o l l o w e d b y d i f f e r e n t in d i v i d u a l s p e r f o r m i n g t h ea n a l y s i s , t h e y a r e l i k e ly t o a r r i v e a t t h e s a m e c o n c l u s i o n s .Com putation o f average performance

T o c o m p u t e t h e a v e r ag e p e r f o r m a n c e o f f a c t o r A a tl e v e l 1 , i . e . A t a t 4 0 W l a s e r p o w e r , w e a d d t h e r e s u l t sf o r t r i a ls i n c l u d i n g f a c t o r A~ , a n d t h e n d i v i d e b y t h en u m b e r o f s u c h t ri a ls . F o r A ~, w e l o o k i n t h e c o l u m n f o rA a n d f i nd t h a t l e ve l 1 o c c u r s i n e x p e r i m e n t s n u m b e r s1 , 2 a n d 3 . T h e a v e r a g e e f f e c t o f A t i s t h e r e f o r e c a l c u -l a t e d b y a d d i n g t h e r e s u l t s Y o f t h e s e t ri a l s a s fo l l o w s :

or s A B C YLaser Pres sure Tape SBS tes tTrials ~1 Power Speed resu lts (MPa)123231312

25.6628.0020.6535.0929.7929.1535.6635.7339.57

Fig ~e 3 An experimental lay-out using L9 a r r a y

COMPOSIJ'ESMolume 26N um be r 9 1 9 9 5 6 7 1

7/27/2019 1-s2.0-0010436195989169-main

4/5

T aguch i m e t ho d f o r p r oc es s enhanc em en t : S . K . M az um dar and S .V . H oaAlav = ( ] I 1 + ] I 2 + } ' 3 ) / 3 = (2 5 . 6 6 + 2 8 . 0 0 + 20.65)/3= 24.77T h e a v e r a g e e f f e c ts o f o t h e r f a c t o r s a r e c o m p u t e d i n as i mi l a r manner :

A2av : (Y4 + Y5 + Y6)/3 : 31 .3 4A3av = (Y7 + Y8 + Y9)/3 = 36.9 9B~av = (Y~ + Y4 + Y7)/3 = 32.1 4B2av = (Y2 + }'5 + Y8)/3 = 31.1 7B3av = (Y3 + Y6 + Y9)/3 = 2 9.7 9Clay = (Y l + Y6 + Y8)/3 = 30.18C2av = (Y2 + Y4 + Y9)/3 = 34122C3av = (Y3 + Ys + Y7)/3 = 28.7 0

T h e a b o v e v a l u e s a r e p l o t t e d i n Figure 4 t o s h o w t h em a i n e f f e c ts o f e a c h f a c t o r o n t h e q u a l i t y o f t h e b o n d .I t i s c l ear f rom t he f i gu re t ha t t he i ncrease i n l aser powe ri ncreases t he bond s t r eng t h , wh ereas e f f ec t o f conso l i -da t i on p ressu re i n t he r ange 50 .4 -151 .3 k N m - ! i s neg l i-g ib l e. T h e i n fl u e n ce o f t a p e s p e e d o n b o n d s t r e n g th i sf o u n d t o b e n o n - l in e a r , a n d t h e q u a l i t y o f in t e r la m i n a rp r o p e r t i e s is f o u n d t o b e p o o r a t l o w e r a n d h i g h e r t a p espeeds .The r eason fo r t he i ncrease i n i n t e rp l y bond s t r eng t hwi t h t he i ncrease i n l aser power i s t ha t t he h i gher l aserp o w e r c a u s e s a h i g h e r t e m p e r a t u r e a t t h e c o n s o l i d a t i o np o i n t . H i g h e r p r o c e s s i n g t e m p e r a t u r e s w o u l d r e s u l t i nl o w e r p o l y m e r v i s c o s it y a n d h i g h e r i n t e r m o l e c u l a r d i f fu -s i on , wh i ch wi l l cause a g rea t e r deg ree o f res i n f l ow andmol ecu l ar i n t e rd i f fu s i on , and wi l l r esu l t i n be t t e r i n t e r -p l y b ond p rope r t i es 18'2. The e f f ec t o f var i a t i on i n con so l -i da t i on p ressu re i n t he r ange 50 .4 -151 .3 k N m -1 on b on ds t r eng t h i s neg l i g i b l e . The r eason fo r t h i s cou l d be t ha tt he deg ree o f i n t i mat e con t ac t i s no t a f f ec t e d in t h i s p res -su re r ange 2. Dec reas i ng t he c onso l i da t i on p ressu re t o 25k N m ~ d e c r e a s e s th e d e g r e e o f i n ti m a t e c o n t a c t a n d t h u saf f ec t s t he b ond s t r eng t h 2. Beca use t here ma y be su f f i -c i en t wet t i ng be t ween p l i es i n t he conso l i da t i on p ressu rerange 50 .4 -151 .3 k N m ~ , var i a t i on i n i n t e rp ly b on ds t r e n g th i s f o u n d t o b e m i n i m a l . T h e e f f e c t o f t a p e s p e e don t he SBS t es t r esu l t s i s found t o be non- l i near .M a z u m d a r 2 d i v i d e d t h e t a p e s p e e d i n t o t h r e e c a t e g o r ie s ;l o w s p e e d ra n g e ( t h e r m o p l a s t ic d e g r a d e s) , m e d i u m s p e e dr a n g e ( g o o d c o n s o l i d a t i o n ) a n d h i g h s p e e d r a n g e ( p o o rw e t ti n g ). B e c a u s e o f p o l y m e r d e g r a d a t i o n a t l o w e r s p e e dand i n su f f i c i en t wet t i ng a t h i gher speed , i n t e rp l y bonds t r eng t h i s r ed uced 2.

4 0

35

0rn20

F i g e r e 4

//4

--o-- __~ o / %

I I I I t I I I IA1 A2 A3 B 1 B 2 B 3 C 1 C 2 C 3

Main effects of factors on SBS test results

Quality characteristicsF o r a p r o d u c t o b t a i n e d b y t h e r m o p l a s t i c t a p ewi nd i ng , t he b i gger t he va l ue o f bond s t r eng t h i s , t heb e t t e r t h e q u a l it y o f t h e p r o d u c t . T h u s f r o m Figure 4 th eA3 (60 W) , B l (50 .4 kN m -1 ) and C2 (13 .0 m m s l ) com bi -

na t i on i s l i ke l y t o p roduce t he bes t r esu l t and t herefo rer e p r e s e n t s t h e o p t i m u m c o n d i t i o n f o r t h e p r e s e n t c a s e .F r o m Figure 4 i t can be observed t ha t t he i n f l uence o ft ape speed on bond s t r eng t h i s non - l i near . The exac tt r e n d o f th e c u r v e i s n o t k n o w n . M o r e t e s t s a t 6 0 W l a se rp o w e r a n d a t t a p e s p e e d s in t h e r a n g e 1 3 . 0- 2 7 .0 m m s la r e n e e d e d t o l o c a t e t h e o p t i m u m c o n d i t i o n s . I t i so b v i o u s f r o m t h e r e s u l t s o f Figure 4 t ha t t o fu r t heri m p r o v e t h e q u a l i t y o f la s e r p ~ o c e ss e d p a rt s , o n e s h o u l ds t u d y t h e e f f e c ts o f l a s er p o w e r a b o v e 6 0 W a n d t a p espeeds h i gher t han 13 .0 m m s l . I n t he p resen t case , t es t sa r e n o t c o n d u c t e d a t a l a s e r p o w e r h i g h e r t h a n 6 0 Wb e c a u s e o f t h e l i m i ta t io n s o f t h e e q u i p m e n t . T h i s i n f o r -mat i on i s very usefu l i n dec i d i ng abou t fu r t her se t s o fe x p e r i m e n t s f o r o b t a i n i n g h i g h e r p e r f o r m a n c e .Relative c ontributions o f variables

T h e r e la t iv e c o n t r i b u t i o n o f p r o c e s s in g p a r a m e t e r s i ses t ab l i shed by compar i ng t he i r var i ances . The ana l ys i so f v a r ia n c e ( A N O V A ) t e c h n i q u e i s u s e d f o r t h is p u r p o s e .C a l c u l a t io n s o f d i f fe r e n t t e r m s o f A N O V A a r e o m i t t e dh e r e . F o r a d e t a i l e d s t u d y o n A N O V A r e f e r t o r e f . 1 .R e s u l ts o f A N O V A i n te r m s o f p e r c e n t c o n tr i bu t io n so f e a c h p r o c e s s p a r a m e t e r a r e e x p r e s s e d a s :PA = 79.08%, PB = 2 .72% P c = 17.05%

w h e r e P A , P B a n d P c a r e t h e p e r c e n t c o n t r i b u t i o n b yl a s e r p o w e r , c o n s o l i d a t i o n p r e s s u r e a n d t a p e s p e e drespec t i ve l y .T h e r e s u lt s s h o w t h a t t h e l a se r p o w e r c o n t r ib u t e s7 9 .0 8 % t o t h e d e v e l o p m e n t o f b o n d s t re n g t h , a n d t h e re -f o r e l a s e r p o w e r s h o u l d b e c o n t r o l l e d p r o p e r l y . T h ec o n t r i b u t i o n o f c o n s o l i d a t io n p r e s s u r e t o t h e d e v e l o p -m e n t o f b o n d s t r e n g th i s o n l y 2 . 72 % , a n d t h e r e f o r e v a ri -a t i o n s i n c o n s o l i d a t i o n p r e s s u r e d u r i n g p r o c e s s i n g w o u l dno t s i gn if i can tl y a f f ec t t he qua l i t y o f bond . The i n f luenceo f t a p e s p e e d d u r i n g o n - li n e c o n s o l i d a t io n i s f o u n d t o b e17.05%.I n . m o s t c a s e s v a r ia t i o n i n t h e q u a l i t y o f a p r o d u c t i su n a v o i d a b l e b e c a u s e o f v a r i a t io n i n p r o c e s s p a r a m e t e r sd u r i n g m a n u f a c t u r i n g . T h i s v a r i a ti o n c a n b e b r o u g h t t oa m i n i m u m b y u n d e r s t a n d i n g t h e e f fe c t s o f p r o c e s s p a r a -met er s . In t he p resen t case , l aser power has t he h i ghes ti n f luence on t he var i a t i on o f t he p roper t i es i n a t ape-w o u n d p r o d u c t . T h e r e f o r e d u r i n g t h e r m o p l a s t i c t a p ewi nd i ng , t he var i a t i on i n l aser power shou l d be mi n i -m i z e d t o a c h i e v e c o n s is t e n t q u a l it y o f t h e e n d p r o d u c t .The p resen t r esu l t s a r e found t o be very he l p fu l i nd e s i g n i n g p r o c e s s i n g e q u i p m e n t f o r m a n u f a c t u r i n gc o m p l e x c o m p o s i t e c o m p o n e n t s b y th e r m o p l a s t i c t a p ewi nd i ng21. In t he f a b r i ca t i on o f non-ax i sym met r i cs h a p e s , t a p e s p e e d v a ri e s fo r a c o n s t a n t m a n d r e l s p e e d .F o r e x a m p l e , d u r i n g m a n u f a c t u r i n g o f r in g s o f e l li p ti c alc ross - sec t i ons wi t h a semi -m aj o r ax i s o f 7 .8 cm a nd asem i -mi nor ax i s o f 3 .9 cm, i t i s foun d t ha t t he t ap e speedvar i es f rom 2 t o 16 .2 cm s1 d u r i n g o n e r e v o l u t i o n o f t h em a n d r e l a t a c o n s t a n t m a n d r e l r o t a t i o n o f 1 0 re v m i n l( r e f . 21 ) . Wi t h t he change i n t ape speed , l aser powerc a n n o t b e k e p t c o n s t a n t f o r u n i f o r m b o n d i n g b e t w e e n

6 7 2 C O M P O S I T E S V o l u m e 2 6 N u m b e r 9 1 9 95

7/27/2019 1-s2.0-0010436195989169-main

5/5

Taguch i methodlayers. To solve this problem, either the laser powershould be varied to compensate for changes in tape speedor the tape speed should be held constant to prevent thevariation in laser power. Present results show that thelaser power should be kept at a maximum level (60 Win this case) for higher bond quality. Reduct ion in laserpower will decrease the bond strength. Therefore in theproduc tion of complex shapes such as elliptical rings bythe tape winding technique, variation in laser powershould be prevented and tape speed should remainconstan t at an optimum value. Mazum dar and Hoa 21have designed and developed a thermoplastic tapewinding machine for the fabrication of non-axisymmet-tic composite parts using a laser as the heating source.During the manufacture of non-axisymmetric parts,mandrel speed was varied using a computer controlledmotor to achieve a constant tape feed rate. Calculationof mandrel speed for achieving constant tape speed wasperformed using analytical models21.Projection of optimum performance

From the above analysis, A3 Bt C2 is found to be theoptimum condition for interply bond strength. Theactual result for the above calculation is not knownbecause it was not among the trial runs performed forthe present case. Prediction of the result at the optimumcondition is determined by the following relation1:Yopt = T/N + (A3av - T/N) + ( B l a v - T/N)

+ ( C 2 a v - T/N) ( 2 )= average performance + contributions of A3, BL and C2above average performance, where T -- grand total ofall results; N = to tal number o f results; and Yopt -- perfor-mance at optimum condition.In this case:T= 279.3, N = 9, A3av = 36.99, Blav = 32.14, C2av = 34.22and thereforero p t z 31.03 + (36.99-

+ (34.22 - 31.03)= 41.28

31.03) + (32.14 - 31.03)

which is slightly above the value o f 39.57 MPa obtainedduring trial run 9.CONCLUSIONSThe Taguchi method was applied for the experimentaldesign of a thermoplastic tape winding process. Usingthe Taguchi me thod, only nine experiments were needed

f o r p rocess enhancem ent : S .K . Ma zum dar and S .V . Hoato determine the per cent contribution of each processparameter on the quality of bond. The optimum condi-tion for the tape winding process was thus estimated.It was found that bond strength increases with anincrease in laser power. The effect of consolidation pres-sure on bond strength was found to be negligible. Theinfluence of tape speed on the quality of bond was foundto be non-linear, with the highest strength at a mediumtape speed. It was estimated that laser power has a majo rcontribution to the improvement of bond quality. Theper cent contributions to the enhancement of bondquality of laser power, consolidation pressure and tapespeed were found to be 79.08, 2.72 and 17.05%, respec-tively.REFERENCES

1 Roy , R .K . 'A P r i m er on t he Taguch i Me t hod ' , V NR P ub l ishers ,New York , 19902 Taguch i , G . ' In t roduc t i on t o Qua l it y Eng inee r i ng ', UN IP U B,Kraus In t e rna t i ona l P ub l i ca t i ons , New York , 19863 Barker, T.B. 'Engineerin g Qua l i ty by Design: In terpret ing theTaguch i Approach ' , Marce l Dekke r , Inc . , New York , 19904 Box, G.E .P . and Bisgaard , S . Quality ProgressJune 1987, 545 Wi l k i n s , D .J . , Ka rbha r i , V .M. and S t eenkam er , D .A . P roc .Am erican Soc iety for Com posi tes, 1991, p . 8436 Beyeler, E.P . , and Guceri , S .I .J . Heat Transfer 1988, 110, 4247 Grove , S .M. Composites 1988, 19, 3678 Ghasem i Ne j had , M.N . 'Th ree d im ens i ona l t he rm a l and re s idua lst ress analysis of in-si tu thermoplast ic com posi te f i lament winding 'PhD Thesis, Depar t m en t o f Mechan i ca l Eng i nee r ing , Un i ve rs i t yo f De l aware , Newark , US A, 19929 Anderson , B .J. , and Co l t on , J .S . J . Compos. Mater. 1990, 24, 150l0 Beyeler, E., Philips, W. and Guceri, S.I .J. Thermoplastic Compos.Mater. 1988, 1, 10711 Hauber , D .E . and H i l l , L .A . 'Au t om at ed f i be r p l acem en t o f the r -m op l as t i c com pos i t e s on com pl ex shapes ' , Report EM90-658,S oc i e ty o f Manufac t u r i ng Eng i nee rs , Dea rbo rn , MI , 199012 Hauber , D . 'Robo t i c f il am en t w i nd i ng w i t h advanced the rm o-plast ics ' , Report EM87-552, S oc i e ty o f M anufac t u r i ng Eng i nee rs ,Dea rbo rn , MI , 198713 We rderm ann, C., Friedrich , K., Cirino, M. and Pipes, R.B.J. Thermoplastic Compos. Mater. 1989, 2, 29314 Carpenter, C.E. and Col ton, J .S . 'Proc. 38th In t . SAMPES ym pos i um ' , S AMP E, Anahe i m , CA, May 1993 , p . 20515 Mazum dar , S .K . and Hoa , S .V . ' P roc . 38 t h In t . S AMP ES ym pos i um ' , S AM P E, Anahe i m , CA , May 1993 , p . 18916 Mazum dar , S .K . and Hoa , S .V . ' P roc . ICCM -9 ' , Un i ve rs it y o fZa ragoza , S pa i n and Woodhead P ub l i sh i ng , Cam br i dge , 199317 Mazum dar , S .K . and Hoa , S .V . Heat Mass Transfer Mater.Process. Manufacturing 1993, 26, 11518 Maz umd ar, S .K. and Hoa, S .V. ,L Thermoplastic Compos. Mater.in press19 Agarw al , V. 'The role of molec ular mobi l i ty in the consol idat ionand bond i ng o f t he rm op l as t i c com pos i t e m a t e r i a l s ' PhDDissertation, Mat e r i a l s S c i ence P rog ram , Un i ve rs i t y o f De l aware ,Newark , US A, 199120 Mazum dar , S .K . 'Au t om at ed m anufac t u r i ng o f com pos it ecom ponen t s by t he rm op l as t i c t ape w i nd i ng and f i l am en t w i nd i ng 'PhD Thesis, Depar t m en t o f Mechan i ca l Eng i nee r i ng , Conco rd i aUn i ve rs i ty , Mon t rea l , Canada , 199421 Mazum dar , S .K . and Hoa , S .V . Mater. Manufacturing Process.1995, Ill(D, 47

C O M P O S I T E S V o lu m e 2 6 N u m b e r 9 1 9 9 5 6 7 3