Finite element analysis of the end notched flexure specimen for measuring mode II fracture toughness

Abstract In this article, mode II fracture toughness ( G IIc {G}_{\text{IIc}} ) of unidirectional E-glass/vinyl ester composites subjected to sulfuric acid aging is studied at two different temperatures (25 and 90°C). Specimens were manufactured using the hand lay-up method with the [ 0 ] 20 {{[}0]}_{20} stacking sequence. To study the effects of environmental conditions, samples were exposed to 30 wt% sulfuric acid at room temperature (25°C) for 0, 1, 2, 4, and 8 weeks. Some samples were also placed in the same solution but at 90°C and for 3, 6, 9, and 12 days to determine the interlaminar fracture toughness at different aging conditions. Fracture tests were conducted using end notched flexure (ENF) specimens according to ASTM D7905. The results obtained at 25°C showed that mode II fracture toughness increases for the first 2 weeks of aging and then it decreases for the last 8 weeks. It was also found that the flexural modulus changes with the same trend. Based on the results of the specimens aged at 90°C, a sharp drop in fracture toughness and flexural modulus with a significant decrease in maximum load have been observed due to the aging. Finite element simulations were performed using the cohesive zone model (CZM) to predict the global response of the tested beams.

Download Full-text

Displacement Rate Effects on the Mode II Shear Delamination Behavior of Carbon Fiber/Epoxy Composites

Polymers ◽

10.3390/polym13111881 ◽

2021 ◽

Vol 13 (11) ◽

pp. 1881

Author(s):

Kean Ong Low ◽

Mahzan Johar ◽

Haris Ahmad Israr ◽

Khong Wui Gan ◽

Seyed Saeid Rahimian Koloor ◽

...

Keyword(s):

Fracture Toughness ◽

Peak Load ◽

Epoxy Composites ◽

Displacement Rate ◽

Interface Debonding ◽

Mode Ii ◽

Scanning Electron Micrographs ◽

Unstable Crack ◽

Mode Ii Fracture ◽

Mode Ii Fracture Toughness

This paper studies the influence of displacement rate on mode II delamination of unidirectional carbon/epoxy composites. End-notched flexure test is performed at displacement rates of 1, 10, 100 and 500 mm/min. Experimental results reveal that the mode II fracture toughness GIIC increases with the displacement, with a maximum increment of 45% at 100 mm/min. In addition, scanning electron micrographs depict that fiber/matrix interface debonding is the major damage mechanism at 1 mm/min. At higher speeds, significant matrix-dominated shear cusps are observed contributing to higher GIIC. Besides, it is demonstrated that the proposed rate-dependent model is able to fit the experimental data from the current study and the open literature generally well. The mode II fracture toughness measured from the experiment or deduced from the proposed model can be used in the cohesive element model to predict failure. Good agreement is found between the experimental and numerical results, with a maximum difference of 10%. The numerical analyses indicate crack jump occurs suddenly after the peak load is attained, which leads to the unstable crack propagation seen in the experiment.

Download Full-text

Experimental and numerical investigation of the punch-through shear test for mode II fracture toughness determination in rock

Engineering Fracture Mechanics ◽

10.1016/j.engfracmech.2017.08.006 ◽

2017 ◽

Vol 184 ◽

pp. 59-74 ◽

Cited By ~ 14

Author(s):

Haoyan Wu ◽

John Kemeny ◽

Shunchuan Wu

Keyword(s):

Fracture Toughness ◽

Numerical Investigation ◽

Shear Test ◽

Mode Ii ◽

Mode Ii Fracture ◽

Mode Ii Fracture Toughness

Download Full-text

Double Cantilever Beam Measurement and Finite Element Analysis of Cryogenic Mode I Interlaminar Fracture Toughness of Glass-Cloth/Epoxy Laminates

Journal of Engineering Materials and Technology ◽

10.1115/1.1345527 ◽

2000 ◽

Vol 123 (2) ◽

pp. 191-197 ◽

Cited By ~ 38

Author(s):

Y. Shindo ◽

K. Horiguchi ◽

R. Wang ◽

H. Kudo

Keyword(s):

Fracture Toughness ◽

Finite Element Analysis ◽

Finite Element ◽

Cantilever Beam ◽

Double Cantilever Beam ◽

Mode I ◽

Interlaminar Fracture Toughness ◽

Element Analysis ◽

Interlaminar Fracture ◽

Delamination Crack

An experimental and analytical investigation in cryogenic Mode I interlaminar fracture behavior and toughness of SL-E woven glass-epoxy laminates was conducted. Double cantilever beam (DCB) tests were performed at room temperature (R.T.), liquid nitrogen temperature (77 K), and liquid helium temperature (4 K) to evaluate the effect of temperature and geometrical variations on the interlaminar fracture toughness. The fracture surfaces were examined by scanning electron microscopy to verify the fracture mechanisms. A finite element model was used to perform the delamination crack analysis. Critical load levels and the geometric and material properties of the test specimens were input data for the analysis which evaluated the Mode I energy release rate at the onset of delamination crack propagation. The results of the finite element analysis are utilized to supplement the experimental data.

Download Full-text