PSI - Issue 72

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

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2. Experimental details 2.1. Material selection

Material selection was based on the FVF (Table 1). The LP 2502 R15 SMC from Polynt was chosen for the lowest fiber concentration, with FVF of 15%. The LS3123 R20 from Inapal and with 20% FVF was also selected. The PG45-H330.LE and HUP 12/30 LE, also from Inapal, have FVF of 30% and 45% fiber, respectively.

Table 1. SMC characteristics with different fiber additions.

Property

LP 2502 R15

LS 3123 R20

HUP 12/30 LE

PG45-H330.LE

Linear contraction Specific weight Flexural strength Flexural modulus

0.15 %

0.1 %

-0.07 %

0.05 %

1.75 g/cm 3 100 MPa 9 500 MPa 45 kJ/m 2

1.75 g/cm 3 120 MPa 9 000 MPa 80 kJ/m 2

1.89 g/cm 3 155 MPa 9 800 MPa 80 kJ/m 2

1.7 g/cm 3 210 MPa

12 500 MPa 100 kJ/m 2

Impact resistance (Charpy)

2.2. Specimen fabrication and testing A specific mold for the manufacture of canteen trays was chosen for SMC molding, to obtain constant thickness plates. Thus, the specimens were cut to the required dimensions. For the tensile and BS tests, trays of each material were molded with thicknesses of 4 and 8 mm, respectively. For the DCB and ENF tests, 6 mm thick trays were molded. Initially, the SMC required for each of the desired thicknesses was calculated by multiplying the density of the material indicated by the supplier by the known volume of the part, the results of which are shown in Table 2.

Table 2. Weight of the molding loads of the canteen trays. SMC 15% SMC 20%

SMC 30%

SMC 45%

Density [g/mm 2 ]

1.70 1208 1812 2415

1.89 1343 2014 2685

1.75 1243 1865 2486

1.75 1243 1865 2486

Plate load w/ 4 mm [g] Plate load w/ 6 mm [g] Plate load w/ 8 mm [g]

2.2.1. Tensile test specimens The CNC cut tensile test specimens are illustrated in Fig. 1. The planned dimensions of the specimens, according to the ISO 527-04 standard, are 200×25 mm 2 , which add to a 4 mm constant thickness.

Fig. 1. Specimens after cutting, respectively catalogued by material and thickness.

2.2.2. Block shear test specimens Specimens with the dimensions defined in the ASTM D4501 standard were machined, except for the thickness, and 8 mm trays were used. Initially, 37.5×25 mm 2 rectangles were cut. The stepped effect was machined by milling. The process involved reducing the thickness from 8 to 4 mm alternatively on both sides, over a length of 6.25 mm.