Issue 66

K. Saada et alii, Frattura ed Integrità Strutturale, 66 (2023) 191-206; DOI: 10.3221/IGF-ESIS.66.12

k

k

k k

2      J j j jj

(2)

( ) Y x B B X B X  

B X X

ji

j

i

0





 

j

j

j

1 2 i

1

1

where Y(x) represents the bound predicted response. In addition, Xi and Xj correspond to the independent variables, while B 0 , B j , B jj and B ji denote a constant, linear first-order interaction and second-order interaction coefficients, respectively .

Levels

Symbol

Factor

Unit

Low level (1)

Intermediate level (0)

High level (+1)

-

A B

Geometry

-1

0

1

Section

mm 2

83.91

92.50

102.00

Table 1: RSM factors levels.

C HARACTERIZATION TESTS OF EPOXY SAMPLES

A

fter preparing epoxy samples (undamaged specimen, specimen with hole-notched and specimen with elliptical - notched) conforming to ASTM D638-14 and having dimensions of 165×19×7 mm³, the tensile test was carried out using a tensile machine at the laboratory of the University of Boumerdes in Algeria. For this, both ends of the samples were attached to a length of 25 mm each on a traction clamp that helped to increase grip and prevent slippage, while the rate of control of the transmission speed was 1 mm/min. The samples were stretched to failure, as shown in Fig. 3, to obtain tensile results, such as the stress-strain curve and the Young‘s Modulus .

Figure 3: Tensile test (a) Specimen with elliptical- notched (b) Specimen with hole-notched.

R ESULT AND DISCUSSION

Experimental results ig. 4 shows the standard deviation results for the three epoxy samples, namely the intact specimen, the hole notched specimen and the elliptical- notched specimen, for each of the Young modules, stresses and strains. It can be observed that the diameter and shape of the hole have an effect on the mechanical properties, as shown in Fig. 4-a which shows the average Young‘s Modulus for five tensile tests on the three epoxy samples. The average Young's Modulus was higher than that of the undamaged specimen with a value of 1812.2±61.05, while it was lower for the F

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