impact behavior of cement based materials 4.07

Question 1

why investigate impact?

Answer 1

prevention of accidents and natural catastrophically events. protection of the built environment

Question 2

solutions for brittle failure in concrete members (exceptional loading conditions)

Answer 2

-rebuild
-strengthen, with thin mineral-bonded composite layers:
* mineral matrix: compatible with concrete substrates
*short fibers: ductile behavior and dissipation capacity
*textiles: membrane-like and confinement attitude

Question 3

what is strain rate?

Answer 3

change in strain of material with respect to time

Question 4

how fast is impact ?

Answer 4

1-1000 strains units per second

Question 5

dynamic response vs quasi-static one

Answer 5

dynamic is higher

Question 6

main reasons for rate dependency performance of concrete:

Answer 6

1. time dependent micro crack growth
2. viscoelastic character of the hardened cement paste

Question 7

what does DIF means?

Answer 7

dynamic increase factor

Question 8

what happen to mechanicals properties of materials when subject to dynamic loadings?

Answer 8

they change significantly

Question 9

split-hopkinson pressure bar is used and modify to test materials under what?

Answer 9

-compression
-tension
-torsion
-shear

Question 10

what happens to the PVA fibers in quasi -static loadings vs dynamic loadings ?

Answer 10

-in quasi static : dominant fiber tensile failure, no plastic deformation of fibers
-in dynamic: dominant fiber pull-out, obvious plastic deformation of fibers.

Question 11

what happens to the PE fibers in quasi -static loadings vs dynamic loadings ?

Answer 11

opposite behavior of the PVA fibers.

-in quasi static: dominant fiber pull-out
-in dynamic: dominant fiber failure.