Crack Paths 2006

Affiarlnn (a), e)+ AlA2l“‘+“2_l (H12 (0, e)+ 11,, (a), 9)) + A22l“2_1H2, (a), e) 2 G,

U

(7)

a G. A12 lH11(w>6)+m(H12(60> lgl‘l' H21 (w>6))+m2H22(wfili

l

where

A, - =—l”‘20"

8 ( )

m A

The upper limit can be obtained from:

(790 (1» 6) : Alla?1 also) (9)‘l' A2la2—1O-g§)(9) 2 at

U

(9)

2

, S [when marrow-2a‘

O'

C

If both the toughness and strength criteria have to hold at the instance of failure then the

upper and lower bounds have to coincide, yielding:

“F1

Zoq-l

G, 0', AIC — {H11(w’9)+m(H12(a), 9)+H21 ((0, 9))‘l‘ m2H22((09 6)] {O-éh)(6)+ m o - g w g

(10)

and

(1)

(2)

2

o

l :

G a

066'

"lo-66'

H11(w’6)+m(H12(w’9)+H21(w’9))+m2H22(w’9) 6c

The crack initiation direction 190 is the direction which for a given A2 /A1 ratio gives the

smallest Alc. Failure will initiate once for a given load A1 2 All?“ and will take the form

of the creation of a finite crack with the length of l0 .

V A L I D A T I OFN T H E F A I L U R EC R I T E R I OBNY E X P E R I M E N T A L

O B S E R V A T I O N

Experimentson three pointbendingspecimensm a d eofP M M A

Three point bending (3PB) experiments were preformedon P M MnoAtched specimens at