Issue 50

M.A. Khiat et alii, Frattura ed Integrità Strutturale, 50 (2019) 595-601; DOI: 10.3221/IGF-ESIS.50.50

The solutions of both differential equations are given by:

c 









x

x

( ) U x C e 





3 C e

x

(8)

1

2

0

2

Ec

c 













x

x

1 (1 ) e

1 (1 ) e

 

C  



( ) U x C

x

(9)

1

2

1

2

3

A

A E

c

All applications are made on unidirectional graphite epoxy specimen with length L, width W and thickness T. Mechanical and geometrical characteristics of the studied considered material are given in Tabs. 1 and 2, these data are drawn from

E f

(GPa)

E m

(GPa)

V f

 0

 0





(MPa)

(GPa)

27.6

4.2

25.2

3.10

0.43

0.53

1.0

Table 1 : Mechanical properties of Lin/epoxy specimen.

l (mm)

w (mm)

t (mm)

r f

(mm)

n i

152.4

12.7

1.016

0.0035

43

Table 2 : Geometrical characteristics of Lin/epoxy specimen.

Figure 2 : Evolution of the ineffective length according to the number of broken fibers with progressive variation of moisture concentration for T=20° and  = 0.5  0 .

I NEFFECTIVE LENGTHS AT FIBER BREAKS

he ineffective length is defined as the length along a fiber from the break location that it takes for the fiber to regain its ability to carry full load. Therefore it must include the zone of matrix yielding a (   a), as in constitutive laws of unidirectional composites, we distinguish three regions: a plastic, transitory and elastic zone, where σ f is the T

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