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<p>To reveal the fracture evolution characteristics of composite rock strata under high strain rates, dynamic three-point bending (notched semi-circular bend, NSCB) tests were conducted using a split Hopkinson pressure bar (SHPB) system on both homogeneous rocks and composite specimens. A coupled PFC3D–FLAC3D model integrating the particle flow and finite difference methods was developed to analyze the effects of incident wave parameters on crack evolution. The results indicate that the peak strength increases by approximately 35% as the impact pressure rises from 0.3&#xa0;MPa to 0.5&#xa0;MPa, while increasing the notch length from 5&#xa0;mm to 10&#xa0;mm reduces the strength by about 20%. The dynamic fracture toughness increases with the loading rate. With increasing impact pressure, specimens with a layer inclination of 135° exhibit a transition from mode I to mixed mode I–II fracture, whereas cracks in specimens with inclinations of 45° and 90° mainly propagate near the loading supports. The numerical results show that when the incident wave wavelengths are 100, 300, and 500 µs, the composite specimen with a 45° layer inclination exhibits the lowest peak strength at a wavelength of 300 µs, while the peak strength of specimens with other inclinations decreases as the incident wave wavelength increases. Higher wave amplitudes lead to increased crack density and fragmentation. The inclination and propagation direction of cracks are governed by layer inclination and notch geometry.</p>

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Study on the dynamic fracture mechanical properties of composite specimens under mode I loading conditions

  • 期刊论文

  • 发表日期：

    2026年3月24日

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  • Sen Wen,
  • Ruotong Song,
  • Shaofeng Wang,
  • Ruizhi Huang,
  • Wen Wang,
  • Xinlei Shi

摘要

To reveal the fracture evolution characteristics of composite rock strata under high strain rates, dynamic three-point bending (notched semi-circular bend, NSCB) tests were conducted using a split Hopkinson pressure bar (SHPB) system on both homogeneous rocks and composite specimens. A coupled PFC3D–FLAC3D model integrating the particle flow and finite difference methods was developed to analyze the effects of incident wave parameters on crack evolution. The results indicate that the peak strength increases by approximately 35% as the impact pressure rises from 0.3 MPa to 0.5 MPa, while increasing the notch length from 5 mm to 10 mm reduces the strength by about 20%. The dynamic fracture toughness increases with the loading rate. With increasing impact pressure, specimens with a layer inclination of 135° exhibit a transition from mode I to mixed mode I–II fracture, whereas cracks in specimens with inclinations of 45° and 90° mainly propagate near the loading supports. The numerical results show that when the incident wave wavelengths are 100, 300, and 500 µs, the composite specimen with a 45° layer inclination exhibits the lowest peak strength at a wavelength of 300 µs, while the peak strength of specimens with other inclinations decreases as the incident wave wavelength increases. Higher wave amplitudes lead to increased crack density and fragmentation. The inclination and propagation direction of cracks are governed by layer inclination and notch geometry.