Mode–I Fracture Toughness of Tetrahedral Amorphous Diamond-like Carbon (ta-C) MEMS

ABSTRACTMode-I fracture toughness studies were conducted on hydrogen-free tetrahedral amorphous diamond-like carbon (ta-C) MEMS specimens of various thicknesses. Mathematically sharp edge pre-cracks were generated through micro indentation on the Silicon dioxide sacrificial layer. An atomic force microscope (AFM) was employed to measure the precise length and orientation of each pre-crack. Upon wet etching and release the freestanding uniform width and varying thickness MEMS-scale specimens were tested in Mode-I using a custom-made micro-tensile tester. Fracture toughness values were computed from the test data using linear elastic fracture mechanics (LEFM) for a finite width specimen with an edge crack in the fixed grip loading configuration. The average Mode-I fracture toughness for 0.5 micron thick specimens was found to be while the average mode-I fracture toughness for 1 micron specimens was .

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Effect of intrinsic stress gradient on the effective mode-I fracture toughness of amorphous diamond-like carbon films for MEMS

Journal of the Mechanics and Physics of Solids ◽

10.1016/j.jmps.2007.05.013 ◽

2008 ◽

Vol 56 (2) ◽

pp. 388-401 ◽

Cited By ~ 29

Author(s):

K JONNALAGADDA ◽

S CHO ◽

I CHASIOTIS ◽

T FRIEDMANN ◽

J SULLIVAN

Keyword(s):

Fracture Toughness ◽

Stress Gradient ◽

Carbon Films ◽

Intrinsic Stress ◽

Mode I ◽

Diamond Like Carbon ◽

Mode I Fracture ◽

Mode I Fracture Toughness

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Large Displacement J-Integral Double Cantilever Beam (DCB) Test Method for Mode I Fracture Toughness

10.18122/td/1769/boisestate ◽

2020 ◽

Author(s):

Joshua Gunderson

Keyword(s):

Fracture Toughness ◽

Double Cantilever Beam ◽

Test Method ◽

Large Displacement ◽

Mode I ◽

Mode I Fracture ◽

Mode I Fracture Toughness ◽

Linear Elastic ◽

True Value ◽

Nonlinear Elastic

The J-integral is used to develop an alternative double cantilever beam (DCB) test method for the Mode I fracture toughness suitable for both small and large displacements. The current focus is the experimental determination of the Mode I interlaminar fracture toughness of composite materials, but the method is generally applicable to other similar tests and material systems, such as to the Mode I fracture toughness of adhesives. A series of five identical specimens are tested to compare the linear-elastic fracture mechanics method recommended by ASTM, which makes use of linear beam theory with root rotation, large displacement, and end block corrections, with the new nonlinear-elastic and elastic-plastic fracture mechanics method, which does not require these corrections. Experimental results show excellent agreement between the two methods over a series of five tests of primarily linear-elastic DCB specimens subjected to moderate to large displacements as defined in the ASTM standard. Furthermore, an agreement is found between the results of the derivations for the two methods being compared, whereby the large displacement equation for JIc presented in this work is identical to the equation given by J. G. Williams (1987) and which he found to be the true value of GIc. It is the true value of GIc that the large displacement and root rotation correction factors were intended to approximate, and the test method presented here allows for direct measurement of its parameters and evaluation. This method has the added benefit that specimens can be primarily linear-elastic or nonlinear-elastic at the crack tip and may extend to those that are elastic-plastic at the crack tip.

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