Thin film specimen for tensile test and physical property evaluation method for thin film specimen

1 . A method for evaluating physical properties of a thin film specimen, comprising:

measuring a tensile strength of a thin film specimen by applying tensile force in directions opposite to each other in a state that a grip portion of the thin film specimen having a speckle pattern is fixed; and

analyzing a strain rate of the speckle pattern while applying tensile force to the thin film specimen,

wherein, in the thin film specimen on which the speckle pattern is formed, a width (a) of a parallel portion is 10 mm, a width (b) of the grip portion is 40 mm, a gauge length (c) of the thin film specimen is 60 mm, and a total length (d) of the thin film specimen is 300 mm,

wherein the thin film specimen includes a first shoulder portion and a second shoulder portion where a curvature is formed on an outer surface and an inner surface between a parallel portion and a grip portion, respectively, and

wherein a radius of curvature of both the first shoulder portion and a radius of curvature of the second shoulder portion is 25 mm.

2 . The method of claim 1 , wherein the analyzing the strain rate of the speckle pattern comprises:

continuously and sequentially photographing a surface of the thin film specimen with a camera;

wherein the analyzing the strain rate of the speckle pattern is conducted by using a digital image correlation (DIC) analysis scheme by comparing an image before the photographing the surface with an image after the photographing the surface.

3 . The method of claim 2 , wherein the analyzing the strain rate comprises:

measuring a length strain rate (L/D) for a diameter of the speckle pattern.

4 . The method of claim 2 , wherein the analyzing the strain rate comprises:

predicting a broken portion of the thin film specimen by distinguishing regions and comparing a length strain rate (L/D) for an area of the speckle pattern for each region.

5 . The method of claim 1 , wherein a grip portion of the thin film specimen includes a non-slip protrusion.

6 . The method of claim 1 , wherein a number of dots per cm 2 of the speckle pattern formed on the thin film specimen is in a range of 50 to 300.

7 . The method of claim 1 , further comprising: forming a speckle pattern on a surface of the thin film specimen,

wherein the forming the speckle pattern comprises spraying a paint having a color, which is in contrast to a color of the thin film specimen, on the surface of the thin film specimen.

8 . The method of claim 7 , wherein the speckle pattern formed on the thin film specimen has fluidity.

9 . The method of claim 8 , further comprising: measuring tensile strength of the thin film specimen within 3 to 10 minutes after forming a pattern by spraying paint on the surface of the thin film specimen.

10 . The method of claim 1 , wherein the thin film specimen is an electrode, a current collector or a separator of a secondary battery.

11 . The method of claim 1 , wherein a thickness of the thin film specimen is 10 to 30 μm.

12 . A thin film specimen for a tensile test, wherein a width (a) of a parallel portion is 10 mm, a width (b) of a grip portion is 40 mm, a gauge length (c) of the thin film specimen is 60 mm, and a total length (d) of the thin film specimen is 300 mm, and

wherein the thin film specimen includes a first shoulder portion and a second shoulder portion where a curvature is formed on an outer surface and an inner surface between a parallel portion and a grip portion, respectively,

wherein a radius of curvature of both the first shoulder portion and a radius of curvature of the second shoulder portion is 25 mm, and

wherein a surface of the thin film specimen comprises a speckle pattern.

13 . The thin film specimen of claim 12 , wherein a speckle pattern formed on the surface of the thin film specimen in case of applying physical property evaluation has fluidity.