TESTING PROCEDURE
Impact test apparatus ( CEAST Fractovis) with 0.5 inch-ball bearing (ASTM D3029)
Three impact energies: 10 J, 18 J, 22 J
After impact, image analysis (false colours: pixels 0-255)
Compression test: loading velocity 0.04 kN/s
NON-DESTRUCTIVE MONITORING
Acoustic emission monitoring (LOCAN-AT): 2 acquisition sensors at two sides of impact zone & 2 guard sensors on compression frame + Image analysis of impacted area (pixel counting and colour discrimination).
RESULTS
Image analysis discerns the different levels of damage and allows us to evaluate if the post-impact situation can be allowed. If not, the material should be redesigned.
The growth of damage area with impact energy was easily discernible.
The introduction of more reinforcement wires throughout the structure produces preferential ways for delamination, due to the non constant volume distribution of the wires themselves.
· Acoustic emission monitoring during compression tests shows a decreased ultimate load due to increased stitching density and to presence of relevant mechanical problems even in the basic material. Post-impact damage is exalted, as the dimensions and inaccuracies in grid size of the stitching proved not able to stop progressing of delamination.
