Break strength is generally the tensile or compressive load required to fracture or to cause the sample to fail.
To determine the failure point or break strength, you will need to define what a break is (break detector). Generally, there are two common types of breaks: the sharp break is referred to the measurement when load or force drops by 5% from its peak load measurement. A percentage break is another form of break and is generally determined by the sample material and its relationship to load degradation from a peak load measurement. A plastic material is likely to have a load drop of 5%, but will not represent a break. In this case, a percentage break would need to be applied. In a tensile test, the breaking load is the break strength.
Virtually any test standard for a product or material will have a break strength characteristic. Pass/fail criteria can be defined for each test for quality control purposes. There are many ASTM standards for break strength for specific materials.
Other common results available for break strength are: