Recommendations for further work

The work reported in this thesis was primarily exploratory in nature. The intention was to attempt to study the behavior of materials under an intermediate kind of impact load that did not stretch the material all the way to fracture and therefore penetration. The focus was on the initiation of indentation. An experiment designed to explore such behavior has lead to certain findings which have been summarized above. However, a lot of specifically targeted work addressing individual issues highlighted in this thesis needs to be done to further this attempt to understand material behavior under a hard local punch.

Quiet a few equations defining trends for parameters such as the peak strain, peak stress, time to peak strain, strain rate, reaction force, and dent depth have been established as a function of the steel plate thickness. Each of these equations however has a coefficient which obviously incorporates the dependence of the explored variable on parameters other than the steel plate thickness. The projectile shape, velocity and weight were all kept constant throughout this experiment and further work on the effect of these parameters on the performance of plates under such impact needs to be done. Such work could eventually lead to the formulation of detailed equations incorporating more variables than the steel plate thickness which is the only parameter used as the independent variable in this study.

A clear distinction in the performance of thin plates when compared to thicker plates was identified in this thesis. A value of 25 mm was also identified as a value that seemingly marked the transformation from thin plates to thick plates. However this value could have

Chapter7: Conclusions

The exact reason for high recovery exhibited by thin plates needs to be investigated in depth.

The shear sliding effect was apparent at the edges of the impacted portion. This could clearly be seen by observing the thin plates after the impact. The effect was more pronounced in thin plates. This lead to an increase in the dent depth but it did not seem to affect the strains right below the point of impact. This effect was also not modeled by the FEM in this thesis because the FEM was restricted to the impacted portion of the specimen only. An attempt could therefore be made to incorporate the entire testing frame and the test rig within the FEM and model the entire specimen with boundary conditions between fixed and pin conditions. A detailed model of this nature could then be used to study the effect of shear sliding at the edges of the impact.

Both the amount of fibres and the length of fibres were identified as factors affecting the performance under this kind of impact. Isolation of each of these factors to better understand how each of them contributes to the apparent increase in resistance to impact as observed in this work needs to be done.

1 Holt, P. J. “A procedure for assessment of steel structures to impact or impulsive loading”, Structures under Shock and Impact 3, Proceedings of the third international conference, Madrid, Spain, 1st_-3rd _{June 1994, pp. 157-164.}

2 Struck, W. and Voggenreiter, W. “Examples of Impact and Impulsive Loading in the Field of Civil Engineering”, Materials and Structures, Vol.8, No. 44, pp. 81-87, 1975. 3 Bentur, A. and Mindess, S. Fibre Reinforced Cementitious Composites, Elsevier

Applied Science, U.K., 1990.

4 Zollo, R. F. “Fibre Reinforced Concrete: an Overview after 30 Years of Development”, Cement and Concrete Composites, Vol. 19, pp107-122, 1997.

5 “ A manual for prediction of blast and fragment loading on structures”, United States department of energy, Albuquerque operations office, 1980.

6 Siewert, T. A., Manahan, M. P., McCowan, C. N., Holt, J. L., Marsh, F. J. and Ruth, E. A. “The History and Importance of Impact Testing”, Pendulum Impact Testing – A Century of Progress, ASTM, STP 1380, pp. 3-16, 2000.

7 Tredgold, T. “Strength of Cast Iron”, pp. 245-268, 1824.

8 White, A. E. and Clark, C. L. “Bibiliography of Impact Testing”, Department of Engineering Research, University of Michigan, 1925.

9 LeChatalier, A. “On the Fragility After Immersion in a Cold Fluid”, French Testing Commission, Volume 3, 1892.

10 Russel, S. B. “Experiments with a New Machine for Testing Materials by Impact”, Transactions ASCE, Vol. 39, June 1898, pp. 237.

11 Kishimoto, K., Inoue, H., and Shibuya, T. “Dynamic Force Calibration for Measuring Impact Fracture Toughness using the Charpy Testing Machine”, Pendulum Impact Testing – A Century of Progress, ASTM, STP 1380, pp. 253-266, 2000.

12 Schindler, H. J. “Relation Between Fracture Toughness and Charpy Fracture Energy: An Analytical Approach”, Pendulum Impact Testing – A Century of Progress, ASTM, STP 1380, pp. 337-353, 2000.

13 Krenchel, H. “Fibre Reinforced Brittle Matrix Materials”, SP-44, Detroit, ACI Publication, pp. 45-77, 1974.

15 Reinhardt, H. W., Kormeling, H. A., Zielinski, A. J., “The Split Hopkinson Bar, a Versatile Tool for the Impact Testing of Concrete”, Materials and Structures, RILEM, Vol. 19, No. 6, pp. 657-671, 1964.

16 Malvern, L. E., Tang, T., Jenkins, D. A. and Gong, J. C. “Dynamic Compressive Strength of Cementitious Materials”, in “Cement Based Composites: Strain Rate Effects on Fracture”, Materials Research Society Symposia Proceedings, Vol. 64, pp. 119-138, 1986.

17 Ramakrishnan, V., Brandshaug, I., Coyle, W. V. and Schrader, E. K. “A Comparitive Evaluation of Concrete Reinforced with Straight Steel Fibres and Fibres with Deformed Ends Glued Together into Bundles”, ACI Journal, pp. 135-143, May – June 1980.

18 Toutlemonde, F., Boulay, C. and Gourraud, C. “Shock-tube Tests of Concrete Slabs”, Materials and Structures, Vol.26, pp.38-42, 1993.

19 Kalthoff, J. F. and Gregor, M. “Instrumented Impact Testing of Subsize Charpy V- Notch Specimens”, Small Specimen Test Techniques, ASTM, STP 1329, pp. 98-109, 1998.

20 Taylor, H. “Analysis of Procedures for the Determination of the Yield Force for Instrumented Sub-sized Charpy-V Specimens”, Small Specimen Test Techniques, ASTM, STP 1329, pp. 123-136, 1998.

21 Griffith, A. A., Phil Trans. Of Royal Society of London, A221, p 163, 1921.

22 Lenkey, G. B., “On the Determination of Dynamic Fracture Toughness Properties by Instrumented Impact Testing”, Pendulum Impact Testing – A Century of Progress, ASTM, STP 1380, pp. 366-381, 2000.

23 Forrestal, M. J. and Piekutowski, A. J., “ Penetration Experiments with 6061 - T6511 Aluminium Targets and Spherical Nose Projectiles at Striking Velocities between 0.5 and 3.0 Km/s”, International Journal of Impact Engineering, Vol. 24, pp. 57-67, 2000. 24 Anderson, C. E., Mullin, S. A., Piekutowski, A. J., Blaylock, N. W. and Poormon,

K.L., “Scale Model Experiments with Ceramic Laminate Targets”, International Journal of Impact Engineering, Vol. 18, pp. 1-22, 1996.

25 Dede, M., Sock, F., Schramm, S. L. and Dobbs, N., “Structures to Resist the Effects of Accidental Explosions”, Vol. 3, U.S Army Armament Research and Development Center, New Jersey, 1984.

26 Merkes, S. B. and Obat, H. J., “Broken Beams”, Exp. Mech., Vol. 13, pp. 480-486, 1973.

28 Yu, T. X. and Chen, F. L., “A Furhter Study of Plastic Shear Failure of Impulsively Loaded Damped Beams”, Hong Kong University of Science and Technology, International Journal of Impact Engineering, Vol. 24, pp 613-629, 2000.

29 Li, Q. M. and Jones, N., “Shear and Adiabatic Shear Failure in an Impulsively Loaded Fully Clamped Beam”, University of Liverpool, International Journal of Impact Engineering, Vol. 22, pp 589 - 607, 1999.

30 Li, Q. M., “Continuity Conditions at Bending and Shearing Interfaces of Rigid Perfectly Plastic Structural Elements”, Int. Solids Structures, 1999.

31 Liu, D. and Stronge, W. J., “Perforation of Rigid Plastic Plates by Blunt Missile”, International Journal of Impact Engineering, Vol. 16, pp 739 - 758, 1995.

32 Weh, H. M. and Jones, N., “Low Velocity Perforation of Punch Impact Loaded Metal Plates”, Trans. ASME, Journal Pressure Vessel Technology, 118(2), pp. 181-187, 1996.

33 Simonsen, B. C. and Lauridsen, L. P., “Energy Absorption and Ductile Failure in Metal Sheets under Lateral Indentation by a Sphere”, Technical University of Denmark, International Journal of Impact Engineering, Vol. 24, pp 1017-1039, 2000. 34 Wierzbicki, T., “Petalling of Plates Under Explosive and Impact Loading”,

Massachusetts Institute of Technology, U. S. A., International Journal of Impact Engineering, Vol. 22, pp. 935-954, 1999.

35 Yankelevsky, D. Z., “Local Response of Concrete Slabs to Low Velocity Missile Impact”, Israel Institute of Technology, International Journal of Impact Engineering, Vol. 19, No. 4, pp 331-343, 1997.

36 Khan, M. B. “Impact Behavior of Fibre Reinforced Cementitious Composite Slabs”, Ph.D Thesis, Dept. Civil Engrg., National University of Singapore, 2000.

37 Dancygier, A. N. and Yankelevsky, D. Z., “High Strength Concrete Response to Hard Projectile Impact”, Israel Institute of Technology, International Journal of Impact Engineering, Vol. 18, No. 6, pp. 583-599, 1996.

38 Nurick, G. N., Galman, M. E. and Marshall, N. S., “Tearing of Blast Loaded Plates with Clamped Boundary Conditions”, Univ. of Cape Town, International Journal of Impact Engineering, Vol. 18, No. 7-8, pp. 803-827, 1996.

40 Thomas, B. and Nurick, G. N., “The Effect of Boundary Conditions on Thin Plates Subjected to Impulsive Loads”, Plasticity 95 – Dynamic Plasticity and Structural Behaviors, Gordon Breath Publishers, 1995, pp. 85-88, 1995.

41 Shen, W. Q. and Jones, N., “Dynamic Response and Failure of Fully Clamped Circular Plates under Impulsive Loading”, University of Liverpool, International Journal of Impact Engineering, Vol. 13, No. 2, pp. 259-278, 1993.

42 Barr, B. and Bouamrata, A., “Development of a Repeated Drop-Weight Impact Testing Apparatus for Studying Fibre Reinforced Concrete Materials”, Composites, Vol. 19, No. 6, pp. 453-466, Nov.1988.

43 Banthia, N., Mindess, S., Bentur, A. and Pigeon, M., “Impact Testing of Concrete Using a Drop-Weight Impact Machine”, Experimental Mechanics, Vol. 29, No.2, pp. 63-69, 1989.

44 Mindess, S., Banthia, N. and B entur, A., “The Response of Reinforced Concrete Beams with a Fibre Concrete Matrix to Impact Loading”, The International Journal of Cement Composites and Lightweight Concrete, Vol. 8, No.3, pp. 165-170, 1986. 45 Gokuz, V. N. and Naaman, A. E., “Effect of Strain-rate on the Pull-out Behavior of

Fibres in Mortar”, The International Journal of Cement Composites, Vol. 3, No.3, pp. 187-202, 1981.

46 Vos, I. E. and Reinhardt, H. W., “ Bond Resistance of Deformed Bars, Plain Bars and Strands under Impact Loading”, Report No. 5-80-6, Department of Civil Engineering, Delft University of Technology, Delft, Netherlands, pp.84, 1980.

47 Banthia, N., Mindess, S., and Trottier, J. F., “Impact Resistance of Steel Fibre Reinforced Concrete”, ACI Materials Journal, Vol. 93, No.5, pp.472-479, 1996.

48 Yan, C., and Mindess, S., “Effect of Fibres on Bond Behavior under Impact Loading”, Proceedings, Materials Research Society, Pittsburgh, USA, Vol.22, pp.139-148, 1990. 49 Radomski, W., “Application of the Rotating Impact Machine for Testing Fibre-

reinforced Concrete”, The International Journal of Cement Composites and Lightweight Concrete, Vol.3, No.1, pp.3-12, 1981.

50 Manolis, G. D., Gareis, P. J. Tsonos, A. D. and Neal, J. A., “Dynamic Properties of Polypropylene Fibre-reinforced Concrete Slabs”, Cement and Concrete Composites, Vol. 19, pp.341-349, 1997.

51 Hughes, B. P. and Watson, A. J., “Compressive Strength and Ultimate Strain of Concrete Under Impact Loading”, Magazine of Concrete Research, Vol.30, No.105, pp. 189-199, 1978.

53 Kormeling, H. A., “Strain-rate and Temperature Behavior of Steel Fibre Concrete in Tension”, International Journal of Cement Composites and Lightweight Concrete, Vol. 9, pp. 197-204, 1987.

54 Reinhardt, H. W., Kormeling, H. A. and Zielinski, A. J., “The Split Hopkinson Bar, a Versatile Tool for Impact Testing of Concrete”, Materials and Structures, RILEM, Vol. 61, No. 6,pp. 657-671, 1964.

55 Gopalaratnam, V. S. and Shah, S. P., “Properties of Steel Fibre Reinforced Concrete Subjected to Impact Loading”, Journal of American Concrete Institute, Vol. 83, pp.117-126, 1986.

56 Kormeling, H. A. and Reinhardt, H. W., “Strain Rate Effects on Steel Fibre Concrete in Uniaxial Tension”, International Journal of Cement Composites and Lightweight Concrete, Vol.9, pp. 197-204, 1987.

57 Glinicki, M. A., “Toughness of Fibre Reinforced Mortar at High Tensile Loading Rates”, ACI Materials Journal, Vol. 91, No. 2, pp. 161-166, 1994.

58 Naaman, A. E., “Fibre reinforced concrete under dynamic loading”, In Fibre Reinforced Concrete – International Symposium, ACI SP-81, American Concrete Institute, Detroit, pp. 169-186, 1984.

59 Rostasy, F. S., and Hartwick, K., “Compressive Strength and Deformation of Steel Fibre Reinforced Concrete Under High Rate of Strain”, International Journal of Cement Composites and Lightweight Concrete, Vol. 7, pp. 21-28, 1985.

60 Suaris, W., and Shah, S. P., “Properties of Concrete Subjected to Impact”, Journal of Structural Engineering, ASCE, Vol. 109, No. 7, pp. 1727-1741, 1983.

61 Naaman, A. E. and Gopalaratnam, V. S., “Impact Properties of Steel Fibre Reinforced Concrete in Bending”, The International Journal of Cement Composites and Lightweight Concrete, Vol. 5, No. 4, pp.225-233, 1983.

62 Shah, S. P., “Concrete and Fibre Reinforced Concrete Subjected to Impact Loading”, In Cement-based Composites: Strain Rate Effects on Fracture, Materials Research Society Symposium Proceedings, Vol. 64, Materials Research Society, Pittsburgh, pp. 181-202, 1986.

65 Paul, B. K. and Pama, R. P., Ferrocement, International Ferrocement Information Center, Asian Institute of Technology, Bangkok, Thailand, 1978.

66 Shah, S. P. and Key, W. H., “Impact Resistance of Ferrocement”, Journal of Structural Division, ASCE, Vol.38, No. ST1, pp. 111-123, 1972.

67 Nimityoungskul, P., Bor-shiun, C., Karasudhi, P., “Impact Resistance of Ferrocement Boat Hulls”, Journal of Ferrocement, Vol.10, No.1, pp. 27-37, 1980.

68 Rao, P. S., Achyutha, H., Mathews, M. S. and Srinivasan, P. P., “ Impact Studies on Ferrocement Slabs”, International Symposium on Ferrocement, Bergamo, Italy, Vol.1, pp. 7-19, 1981.

69 Grabowski, J., “Ferrocement Under Impact Loads”, Journal of Ferrocement, Vol. 15, No. 4, pp. 331-341, 1985.

70 Quek, S. T., Ong, S. H., Paramasivam, P. and Lee. S. L., “Early age Reliability of Ferrocement Slabs”, ACI Materials Journal, V-88, No.6, pp. 644-649, 1991.

71 Wang, M. L. and Maji, A. K., “Shear properties of slurry infiltrated fibre concrete”, High Performance Fibre Reinforced Cement Composites, RILEM, pp. 203-211, 1992. 72 Schneider, B., “Development of SIFCON Through Applications”, High Performance

Fibre Reinforced Cement Composites, RILEM, pp. 177-194, 1992.

73 Naaman, A. E., “SIFCON: Tailored Properties for Structural Performance”, High Performance Fibre Reinforced Cement Composites, RILEM, pp. 18-37, 1992.

74 “Surefast options for Defence Structures”, Corus Construction and Industrial, http://www.corusconstructionandindustrial.com/corus/index.jsp?pageID=279

75 Backman, M. E and Goldsmith, W., “The mechanics of penetration of projectiles into targets”, International Journal of Engineering Sciences, Vol. 16, pp. 1-99, 1978.

76 Recht, R. and Ipson, T. W., Ballistic perforation dynamics, Journal of Applied Mechanics, Vol. 30, pp. 384-90, 1963.

77 Marom, I. And Bodner, S. R., “ Projectile perforation of multi-layered Beams”, International Journal of Mechanical Science, Vol. 21, pp. 489-504, 1979.

78 Corran, R. S. J., Shadbolt, P. J. and Ruiz, C., “Impact Loading of Plates – an Experimental Investigation”, International Journal of Impact Engineering, Vol. 1, pp. 3-22, 1983.

Engineering, Vol. 1, pp. 23-49, 1983.

80 Bodner, S. R., “Modelling Ballistic Perforation”, Structural Impact and Crashworthiness, Volume 1, Elsevier Applied Science Publishers, pp. 115-127, 1984. 81 Ravi-Chandar, K., Lu, J., Yang, B. and Zhu Z. “Failure mode transitions in polymers

under high strain rate loading, International Journal of Fracture, V. 101, No. 1-2, pp 33-72, 2000.

82 Rinehart, J. S. and Pearson, J., “ Behavior of metals under impulsive loads”, Dover Publications, New York, 1954.