PSI - Issue 72

P.M.M. da Silva et al. / Procedia Structural Integrity 72 (2025) 69–76

73

100 120 140

10 12 14 16

0 20 40 60 80

0 2 4 6 8

 f [MPa]

E [MPa]

0 5 101520253035404550

0 5 101520253035404550

FVF [%]

FVF [%]

a)

b)

Fig. 4. FVF influence on  f (a) and E (b).

Table 3. Average values for  f and E by the tensile tests.

Material  f [MPa] E [GPa]

SMC 15% 37.7 ±3.0 10.8 ±0.7

SMC 20% 47.6 ±5.4 11.0 ±0.8

SMC 30% 106.2 ±4.2 11.5 ±0.3

SMC 45% 124.3 ±7.2 12.8 ±0.9

3.2. Shear mechanical tests All specimens were submitted to the BS test according to the ASTM D4501-01 standard. Each test was carried out with a speed of 0.5 mm/min at room temperature in a mechanical test machine. The load-displacement ( P-  ) curves were recorded. τ f and G were plotted as a function of the fiber content (Fig. 5). There is an increase in τ f and G with FVF, although not significative. The processed condition of the SMCs can be attributed to this phenomenon. Although SMCs have random fibers, during compression molding, the fibers are mostly aligned along matrix flow plane, and just a small portion of the fibers stay in the opposite direction to the shear plane.

12

200

150

9

100

6

G [MPa]

 f [MPa]

50

3

0

0

0 5 101520253035404550

0 5 101520253035404550

FVF [%]

FVF [%]

a)

b)

Fig. 5. FVF influence on  f a) and G b).

It is shown that the shear properties ( τ f and G ) are essentially given by the polymeric matrix of SMC. Table 4 displays the average values for τ f and G along with the corresponding standard deviation. The maximum relative difference between fiber concentrations limits for τ f and G was respectively, 6.5 % and 28.5%.

Table 4. Average values for τ f and G by the BS tests.

Material τ f [MPa] G [MPa]

SMC 15%

SMC 20%

SMC 30%

SMC 45%

9.3±0.7

9.6±0.8

9.8±0.6

9.9±0.6

117.7±11.7

126.3±11.2

133.8±12.0

151.2±18.5