Fig 1.
Crack growth rate vs. stress intensity factor range curve [6].
Fig 2.
Fracture types in composite laminate [21].
Fig 3.
Vacuum bagging process.
Table 1.
Mechanical properties of CSM/Epoxy composite laminates.
Table 2.
Validation of CSM/Epoxy tensile test results through comparison with previous studies.
Fig 4.
Tensile Testing Setup and Specimens Fabricated via VBT (ASTM D3039).
(a) three tensile test specimens created using VBT (ASTM D3039), (b) tensile test machine, and (c) specimen fixed in jaws with extensometer.
Fig 5.
Fatigue Testing Setup and Specimen Configuration.
(a) LR-QBPL-5000N fatigue test machine and unit control, (b) fixing the specimen in jaws, and (c) dimensions of specimen in mm.
Fig 6.
Tools for detecting crack length: (a) ink needle (b) illustrated of crack growth path by ink (c) digital microscope camera (d) image by digital microscope camera.
Fig 7.
Crack growth length vs number of cycles under different repeated stress levels in MPa & initial notch (ai)= 10 mm.
Fig 8.
Beginning of crack growth at N = 2409 cycles.
Fig 9.
Crack growth behavior of CSM/Epoxy under repeated stress level (34 MPa).
Fig 10.
Fatigue fracture behavior of three CSM/epoxy composite specimens.
Fig 11.
Crack growth rate vs stress intensity factor range of CSM/Epoxy composite laminate.
Table 3.
Research of Paris law relation with stress intensity factor and strain energy release rate.
Fig 12.
Numerical and experimental fatigue test results of specimen with 44 MPa repeated stress level.
Fig 13.
Comparison between crack growth behavior for experimental and numerical results.
Fig 14.
Crack growth behavior during repeated stress level (44 MPa) in numerical simulation of CSM/Epoxy.
Fig 15.
Crack growth behavior during repeated stress level (44 MPa) in experimental test of CSM/Epoxy.
Fig 16.
Optical analysis for fatigue sample (44 MPa).
(a) Initial notch region – In this zone, both the fibers and the matrix are completely cut across approximately 10 mm of the specimen width, corresponding to the machined notch as illustrated in Fig 17 (a1). (b) Stable crack growth region – In this region, the crack advances gradually under cyclic loading. Fiber breakage occurs along the crack front and is accompanied by matrix cracking, with only limited fiber pull-out observed, as shown in Fig 17 (b1&b2). The length of this stable region increases as the applied fatigue stress level decreases, indicating that lower loads promote a longer period of controlled crack growth before final failure. (c) Catastrophic crack growth region – In this final region, the crack accelerates rapidly and propagates through most of the remaining specimen width. Extensive fiber pull-out, fiber–matrix debonding, and localized crazing are visible as illustrated in Fig 17 (c1). The extent of this catastrophic zone decreases when the applied fatigue load is reduced, which is consistent with lower crack growth rates at lower stress levels.
Fig 17.
(a1) Initial notch region, (b1&b2) Stable crack growth region, and (c1) Catastrophic crack growth region.
Region C (catastrophic crack growth region) is observed along the tensile test sample, resulting from the increased stress over time during the test, which ultimately leads to fracture, as shown in Fig 18. This region exhibits more extensive crazing compared to the fatigue test sample, as depicted in Fig 18b. This difference highlights the impact of the applied load on the sample’s failure behavior.
Fig 18.
Comparison between (a) fatigue sample and (b) tensile sample.