Extra wide specimen geometry was used for the conducted angle-ply tension tests to prevent delamination failure.
By means of detailed finite element analyses a new quadrilaterally waisted specimen geometry was developed and validated by mechanical testing.
The specimen geometry was designed to allow for biaxial stress state and incipient crack in the center of the active part under biaxial tensile loading.
In subsequent testing the specimen geometry was altered to reduce the compressive footprint and the notches (slits) made deeper to reduce the specimen's ligament length.
This innovative specimen geometry was chosen because a simple, monotonically increasing uniaxial compressive force produces a hoop tensile stress at the C-sphere's outer surface that ultimately initiates fracture.
The first specimen geometry was the standard coupon geometry of the ASTM D5961 bearing response test with a pitch distance ratio 'w/D' of 6 and an end distance ratio 'e/D' of 3. The second and third geometries used a 'w/D=6, e/D=6' and 'w/D=2, e/D=3'.
