Issue 15

I. S

. Raju et alii, Fr

attura ed Integri

tà Strutturale, 1

5 (2011) 35-49

; DOI: 10.3221/I

GF-ESIS.15.05

r when G T is efect is stab [11] is used

G Ic ; per, ture

def i.e. Alt the crit

ect growth (i , G T /G Ic ≥ 1. ernately, a m two-dimens erion. This B

.e., defect is ixed-mode fr ional plane-s -K criterion

likely to grow acture criteri train criterio is expressed

in a catast on is used to n given by B as

rophic mann

er) may occu hether the d and Kenane

greater than le or unstabl as the mixe

or equal to e. In this pa d-mode frac

determine w enzeggagh

G

T 

1

(3)

R

ere G T repre ing force. T resistance R

2, and R rep l fracture tou

sents the tot he resistanc is given by

al defect dri e R is also re

ving force, g ferred to as

iven in Eq. G c , the critica

resents the ghness base

the total de a. The value

fect for

wh driv the

resistance to d on test dat

m

  

T II G G   







 I c

m

GR 

G  

G G  

G  

(4)

c

c

c G

I c

c

I

I

II

II

y,  = G II /G s shown syst rowth is unl is likely.

ere G Ic and G de-mixity rat When the r o equals or e

wh mo 14. rati

IIc represent io, and m rep atio of G T to xceeds unity,

the Mode I resents the e R is less tha the defect is

and Mode II xponent of  n unity, the said to be un

material tou used to fit th defect is said stable, and c

ghness value e mixed-mo to be stable atastrophic d

s, respectivel de test data a , and defect g efect growth

T represents ematically in ikely. When

the Fig. the

G IIc

Line

ar m=1 curve fit

G

c

Deter to mix

mined as a curve f ed-mode data, m> it 1

Mode

I dominated

Mixed mode dominated

G Ic

0



1

~

0.2

G I

/G T

I

Figure

14 : Typical cu

rve fit of mixe

d-mode fractu

re data.

stance R give ermined usin nse like the olymeric mat . A typical m se is domina xure test con a value of tw evaluating E

nt m as indic ed from mat on-conserva =2 or 3 app in Fig. 14. etermine G Ic addition, th conservative

For in F test crit to

ated erial tive ears For and e B- .

a mixed-mo ig. 14. This ing. For a v erion. Mixed fit mixed-mo de-mixity rat gle cantilever c . In the abs is fracture to

de response, exponent is alue of m =1, -mode fract de fracture d ios less than beam and e ence of furth ughness valu

the B-K resi typically det a linear respo ure tests of p ata accurately  , the respon nd-notch fle er test data, es are used in

n in Eq. 4 is g a curve fit green dashed rix composit ixed-mode ted by Mode figurations w o was select q. 4 as they

dependent o for mixed-m line in Fig. 1 es show that fracture crite I behavior. ere used in ed as the valu provide a sm

n the value o ode fracture 4 is obtained the B-K crit rion curve is RCC fracture e of the exp aller value fo

f the expone data obtain , which is a n erion using m shown as red testing to d onent m . In r R , which is

mo Sin G II bas

R E I

D ISCUSSIO

SULTS AND

N

the G T value e defects are

and iled

n this secti the on-orb analyses an

on, only repr it cold cond d results can

esentative re ition are pre be found in

sults in term sented. Bo Ref. 1-6.

s of defect d th interface

riving forces, and substrat

s, for entry p considered

eak heating . More deta

44