Microstructural Effects on Fracture Toughness of Polycrystalline Ceramics in Combined Mode I and Mode II Loading

1989 ◽  
Vol 111 (1) ◽  
pp. 174-180 ◽  
Author(s):  
D. Singh ◽  
D. K. Shetty
Keyword(s):  
Fracture Toughness ◽  
Mode I ◽  
Mode Ii ◽  
Mixed Mode Fracture ◽  
Transgranular Fracture ◽  
Pure Mode ◽  
Polycrystalline Alumina ◽  
Polycrystalline Ceramics ◽  
Mode Ii Loading ◽  
Combined Mode

Fracture toughness of polycrystalline alumina and ceria partially stabilized tetragonal zirconia (CeO2-TZP) ceramics were assessed in combined mode I and mode II loading using precracked disk specimens in diametral compression. Stress states ranging from pure mode I, combined mode I and mode II, and pure mode II were obtained by aligning the center crack at specific angles relative to the loading diameter. The resulting mixed-mode fracture toughness envelope showed significant deviation to higher fracture toughness in mode II relative to the predictions of the linear elastic fracture mechanics theory. Critical comparison with corresponding results on soda-lime glass and fracture surface observations showed that crack surface resistance arising from grain interlocking and abrasion were the main sources of the increased fracture toughness in mode II loading of the polycrystalline ceramics. The normalized fracture toughness for pure mode II loading, (KII/KIc), increased with increasing grain size for the CeO2-TZP ceramics. Quantitative fractography confirmed an increased percentage of transgranular fracture of the grains in mode II loading.

Fracture toughness of aged dental composites in combined mode I and mode II loading

2000 ◽  
Vol 53 (4) ◽  
pp. 362-370 ◽  
Author(s):  
Susanne S. Scherrer ◽  
John Botsis ◽  
Michel Studer ◽  
Monica Pini ◽  
H. W. Anselm Wiskott ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Dental Composites ◽  
Mode I ◽  
Mode Ii ◽  
Mode Ii Loading ◽  
Combined Mode

Fracture characterization and modeling of Gyroid filled 3D printed PLA structures

2021 ◽  
Vol 63 (5) ◽  
pp. 397-401
Author(s):  
Ahmet Refah Torun ◽  
Ali Sinan Dike ◽  
Ege Can Yıldız ◽  
İsmail Sağlam ◽  
Naghdali Choupani
Keyword(s):  
Fracture Toughness ◽  
Shear Fracture ◽  
Industrial Applications ◽  
Shear Mode ◽  
Mode I ◽  
Mode Ii ◽  
Mixed Mode Fracture ◽  
Pure Mode ◽  
Two Dimensional ◽  
3D Printed

Abstract Polylactic acid (PLA) is a commonly used biodegradable material in medical and increasingly in industrial applications. These materials are often exposed to various flaws and faults due to working and production conditions, and increasing the demand for PLA for various applications requires a full understanding of its fracture behavior. In addition to ABS, PLA is a widely used polymeric material in 3D printing. The gyroid type of filling is advantageous for overcoming the relatively higher brittleness of PLA in comparison with conventional thermoplastic polymers. In this study, the effects of various filling ratios on the fracture toughness of 3D printed PLA samples with gyroid pattern were investigated numerically and experimentally for pure mode I, combined mode I/II, and pure mode II. Two-dimensional finite element modeling was created, and the two-dimensional functions of stress intensity coefficients were extracted in loading mode I, mode I/II, and mode II at varied filling ratios of the gyroid PLA samples. Mixed-mode fracture tests for 3D printed PLA samples with a gyroid pattern at various filling ratios were performed by using a specially developed fracture testing fixture. The results showed that the amount of fracture toughness of the samples under study in tensile mode was much higher than those values in shear mode. Also, as the percentages of the filling ratios in the samples increased, both tensile and shear fracture toughness improved.

Experimental and Numerical Investigation of the Mixed-Mode Delamination of PAN Based Carbon/Epoxy Composite Using Modified Arcan Fixture

2011 ◽  
Vol 471-472 ◽  
pp. 880-885 ◽  
Author(s):  
M. Ziaee ◽  
Naghdali Choupani
Keyword(s):  
Fracture Toughness ◽  
Stress Intensity ◽  
Mixed Mode ◽  
Sliding Mode ◽  
Epoxy Composite ◽  
Mode I ◽  
Mode Ii ◽  
Mixed Mode Fracture ◽  
Pure Mode ◽  
Element Analysis

The present research examines analytically and experimentally the mode-I and mode-II and mixed mode-Interlaminar fracture toughness of PAN based carbon/epoxy composite. A modified Arcan fixture, well-suited for the study of the behavior of used composite assemblies, was developed in order to focus on the analysis of the fracture behavior of the material. The edge effects are minimized by using an appropriate design of the substrates so that experimental results give reliable data. Also the mode-I and mode-II stress intensity factors were computed for different crack lengths and load orientation angles using finite element analysis. The numerical results show that the modified Arcan specimen is able to provide pure mode-I, pure mode-II and any mixed mode loading conditions. It is shown that the results obtained from the fracture tests are consistent very well with mixed mode fracture theories. Obtained results indicated that fracture toughness and stress intensity factor for sliding mode enhanced up when the loading angle increased. Mechanism of fracture and toughening were examined by using scanning electron microscopy.

scholarly journals Mixed-Mode Interlaminar Fracture Toughness of Glass and Carbon Fibre Powder Epoxy Composites—For Design of Wind and Tidal Turbine Blades

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2103
Author(s):  
Christophe Floreani ◽  
Colin Robert ◽  
Parvez Alam ◽  
Peter Davies ◽  
Conchúr M. Ó. Brádaigh
Keyword(s):  
Fracture Toughness ◽  
Carbon Fibre ◽  
Composite Structures ◽  
Mixed Mode ◽  
Epoxy Composites ◽  
Mode I ◽  
Mode Ii ◽  
Pure Mode ◽  
Interlaminar Fracture Toughness ◽  
Interlaminar Fracture

Powder epoxy composites have several advantages for the processing of large composite structures, including low exotherm, viscosity and material cost, as well as the ability to carry out separate melting and curing operations. This work studies the mode I and mixed-mode toughness, as well as the in-plane mechanical properties of unidirectional stitched glass and carbon fibre reinforced powder epoxy composites. The interlaminar fracture toughness is studied in pure mode I by performing Double Cantilever Beam tests and at 25% mode II, 50% mode II and 75% mode II by performing Mixed Mode Bending testing according to the ASTM D5528-13 test standard. The tensile and compressive properties are comparable to that of standard epoxy composites but both the mode I and mixed-mode toughness are shown to be significantly higher than that of other epoxy composites, even when comparing to toughened epoxies. The mixed-mode critical strain energy release rate as a function of the delamination mode ratio is also provided. This paper highlights the potential for powder epoxy composites in the manufacturing of structures where there is a risk of delamination.

Combined Mode Fracture Toughness Measurement by the Disk Test

1978 ◽  
Vol 100 (2) ◽  
pp. 175-182 ◽  
Author(s):  
Hideo Awaji ◽  
Sennosuke Sato
Keyword(s):  
Fracture Toughness ◽  
Internal Crack ◽  
Mode I ◽  
Mode Ii ◽  
Mode Fracture ◽  
Fracture Toughness Measurement ◽  
Circular Specimen ◽  
Combined Mode ◽  
Toughness Measurement ◽  
Disk Test

The disk test in which a circular specimen with an internal crack is subjected to diametral compression is used to investigate combined mode I and mode II fracture. The stress intensity factors in the disk test are calculated numerically by means of the boundary collocation procedure and the dislocation method. Special care was taken to analyze the effect of the compression anvils. This method has the advantage, of allowing successive measurement of mode I, mode II and the combined mode fracture toughness under the same conditions. Some kinds of graphite, plaster and marble are examined to obtain the fracture toughness values, KIC, KIIC and the combined mode fracture criterion.

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