Did you come across this article? http://www.sciencedirect.com/science/article/pii/0013794476900187

In the same vein:

- G. P. Marshall et al. : Fracture toughness and absorbed energy measurements in impact tests on brittle materials :https://link.springer.com/article/10.1007/BF00756625 

- MIT - Introduction to Fracture Mechanics (with some interesting references) : http://web.mit.edu/course/3/3.11/www/modules/frac.pdf

Charpy tests are useful as a rapid measurement of fracture toughness in terms of energy needed to break the specimen. For measurements of fracture toughness as the critical KI value for specimens collapse, SENB specimens in typical 3-point-bending according to ASTM standards are also well suited. Even if the material is not isotropic, you can obtain the fracture toughness relatively easy.

Sivasurya Mulugundam , as I understand it. asks about the fracture toughness, not the impact strength. These are different quantities, very loosely related. To determine the fracture toughness, specimens with a notch, or crack opening techniques

Dear Sivasurya Mulugundam there are several fracture testing techniques are available to calculate the fracture toughness and strain energy release rate.

first, you have to prepare the sample by following any fracture techniques like- Compact tension (CT), 3-point bending, 4-point bending , Double Cantilever beam (DCB) specimen according to the ASTM standards available i.e. E399. while performing the test you will get the load-displacement curve. Through the maximum load from load-displacement curve (onset of cracking), you will get the fracture toughness of specimen including both (experimentally and analytically).

I think Charpy test or DIN 53 448 the strain-blow test are appropriate for the determination of toughness.

A calculated result.

Ref. Research Proposal Toughness estimation based on standard tensile data

Here is a video explanation of brittle fracture energy calculation from tensile test:

https://youtu.be/z_7QP2hzRdI