Issue 78

R. Shivashankar et alii, Fracture and Structural Integrity, 78 (2026) 454-473; DOI: 10.3221/IGF-ESIS.78.26

Figure 4: (a) Interlaminar shear, (b)Flexural test samples, (c) Fracture toughness test samples.

HF (wt. %) BF (wt. %) Si ₃ N ₄ (wt. %) 25 15 –

Si ₃ N ₄ (Vf %) –

Ep (wt. %)

Ep (Vf %) 75.50 75.50 75.20 74.91 74.62 74.33

HF (Vf %) 20.87 20.87 20.79 20.71 20.63 20.55

BF (Vf %)

Composite designation

Untreated H/B F-Ep (S0ut) Treated H/B F-Ep (S0t)

60 60

3.63 3.63 3.61 3.60 3.58 3.57

25 25 25 25 25

15 15 15 15 15

–

–

S1 S2 S3 S4

59.5

0.5 1.0 1.5 2.0

0.40 0.78 1.17 1.55

59

58.5

58 Table 1: Weight and volume fractions of Si 3 N ₄ filled hybrid nanocomposites. Tab. 2 summarizes the specimen dimensions and test criteria used for the flexural, fracture toughness, and interlaminar shear tests.

ASTM standard

Specimen dimensions, L (mm)× W (mm) × T (mm)

Rack length ‘a’ (mm)

Test

Interlaminar shear

ASTM D2344/D2344M ASTM D790 ASTM D5045

32 × 10.5 × 4.2

—

Flexural

70 × 12.5 × 4.2 75× 8.4 × 4.2

— 4.2

Table 2: Specimen dimensions and test standards.

Mechanical properties characterization The mechanical performance of the hemp fabric/basalt fabric-reinforced epoxy (H/B F-Ep) and H/B F-Ep composite incorporating Si ₃ N ₄ nanoparticles was evaluated for ILSS, flexural, and fracture toughness tests in accordance with ASTM standards. Each experiment was conducted in a controlled laboratory environment at room temperature. To ensure statistical reliability and experimental repeatability, five specimens were analyzed for each composite formulation in compliance with established protocols for the mechanical evaluation of polymer composites. The data provided are shown as the mean value ± standard deviation for each of the five measurements. Interlaminar shear strength test The short beam shear test was used to test the interlaminar shear strength (ILSS) of the composite laminates in accord with ASTM D2344 [22]. ILSS tests were performed using a universal testing machine (Zwick/Roell 2020) equipped with a 2.5 kN load cell. The tests were conducted at a crosshead speed of 1 mm/min with a support span of 32 mm. Samples of the proper ratio of span to thickness, as mandated in the ASTM standard, were tested at a constant crosshead velocity to failure. The highest load recorded in the test was used to compute the ILSS in accordance with Eqn. (1).

3F







ILSS MPa

(1)

4 bd

459