PSI - Issue 28

Jamal A. Abdalla et al. / Procedia Structural Integrity 28 (2020) 2312–2319 Author name / Structural Integrity Procedia 00 (2019) 000–000

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load for the hybrid CFRP+AA increased by up to 4.55 times that of CFRP alone (ultimate strain = 1.7%) while the strain ratio for SMH+AA increased by up to 6.52 times that of GSM (ultimate strain 1.6%). Failure of all specimens occurred within the gauge length and the failure modes varied as shown in Figure 4 and Table 2.

Table 2. Ultimate load, maximum extension and failure modes for coupons

Failure Mode

Label*

Average ultimate load (kN)

Average strain at ultimate load (%)

Increase in strain ratio at ultimate load over CFRP or GSM

Average maximum extension (mm)

AA

18.03 36.82 16.40 34.05 26.70 16.85

26.15

-

26.15 12.51 14.69 18.77 15.20 23.37

Yielding of AA

CP+AA CS+AA SH+AA

CFRP rapture + de-bonding

7.73 4.32

4.55 2.54 6.24 6.52 6.08

CFRP rapture then AA

CFRP rapture + de-bonding then AA Failure FRP rapture + de-bonding

9.99

SM+AA

10.43

SL+AA FRP rapture + de-bonding * Where CP for CFRP Plate; CS for CFRP Sheet; SH, SM and SL for High, Medium and Low density, respectively. 9.73

(a)

(b)

0 10 20 30 40 50 0 10 20 30 40

10 15 20

CP1 CP2 CP3

CS1 CS2 CS3

0 5

Loads (kN)

Loads (kN)

0

10

20

30

0

10

20

30

Extension (mm)

Extension (mm)

(c)

(d)

10 15 20

SH1 SH2 SH3

SL1 SL2 SL3

0 5

Loads (kN)

Loads (kN)

0

10

20

30

0

10

20

30

Extension (mm)

Extension (mm)

Fig. 4. FRP coupon test results.

3.2 Beam specimens Table 3 shows the the experimental results of the ultimate load, maximum extension, the ratio of ultimate load of the strengthened beam (hybrid beam) to the ultimate load of the control beam, and the related failure mode. It can be observed from Table 3 that the increase in flexural capacity of strengthened beams ranged from 27% to 37% over the control beam. It is also observed that the beam strengthened with hybrid SMH+AA laminates yielded the highest increase in ductility by up to 98.5% compared to that of the control beam. Figure 5 below shows the load