An apparatus for compression testing of a test specimen having a notch portion, the apparatus comprising: a base assembly and an end load element attached to the base assembly, the base assembly being rigid; a support assembly attached to the base assembly, the support assembly comprising a first support grid and a second support grid, wherein the first support grid and the second support grid each comprise a frame portion and a grid portion, which grid portion comprises a plurality of vertical members and a plurality of horizontal members that intersect the plurality of vertical members to form a plurality of window portions, the first support grid configured for attachment to the second support grid, and the first support grid and the second support grid configured to have a core assembly and the test specimen installed between them; and a core assembly installed within the support assembly between the first support grid and the second support grid, the core assembly being crushable and configured to stabilize the test specimen and protect the support assembly and the base assembly from fracture loads generated by the test specimen adjacent the core assembly during compression testing by absorbing energy that is released sideways from the test specimen upon fracture or breaking of the test specimen; the apparatus being configured for use with an optical strain measurement system, wherein the window portions are configured such that the test specimen and the notch portion are visible to said optical strain measurement system through the plurality of window portions when the test specimen is installed in the support assembly between the first support grid and the second support grid. a base assembly and an end load element attached to the base assembly, the base assembly being rigid; a support assembly attached to the base assembly, the support assembly comprising a first support grid and a second support grid, wherein the first support grid and the second support grid each comprise a frame portion and a grid portion, which grid portion comprises a plurality of vertical members and a plurality of horizontal members that intersect the plurality of vertical members to form a plurality of window portions, the first support grid configured for attachment to the second support grid, and the first support grid and the second support grid configured to have a core assembly and the test specimen installed between them; and a core assembly installed within the support assembly between the first support grid and the second support grid, the core assembly being crushable and configured to stabilize the test specimen and protect the support assembly and the base assembly from fracture loads generated by the test specimen adjacent the core assembly during compression testing by absorbing energy that is released sideways from the test specimen upon fracture or breaking of the test specimen; the apparatus being configured for use with an optical strain measurement system, wherein the window portions are configured such that the test specimen and the notch portion are visible to said optical strain measurement system through the plurality of window portions when the test specimen is installed in the support assembly between the first support grid and the second support grid.