Low Velocity Impact Fatigue Studies on Glass Epoxy Composite Laminates with Varied Material and Test Parameters-Effect of Incident Energy and Fibre Volume Fraction

Abstract

An effort was made to study the effects of fibre volume fraction and incident energy on the impact damage tolerance of composite laminates subjected to low velocity impacts at constant strike velocities. Repeated drop tests were conducted using an in-house built drop weight impact tester. Delamination area was used as a parameter for quantifying damage while the number of drops (impacts) to failure used to assess the damage tolerance limits. The delamination area was found to increase and then saturate after a certain number of drops. Impact fatigue studies showed the existence of a critical incident energy (EC) around which design of composite structures can be based. Also the minimum incident energy required to fracture the sample in a single impact (ESDT) was evaluated from the data. One of the interesting observations made was that for any given incident energy, the delamination area was found to be minimum at a certain fibre volume fraction (0.5 in this case) of the laminate. This was explained on lines of failure mechanisms reported earlier.

Get full access to this article

View all access options for this article.

References

1. Cristescu, N. , L. E. Malvern and R. L. Sierakowski . 1975. "Failure Mechanisms in Composite Plates Impacted by Blunt Penetrators," Foreign Object Impact Damage to Composites, ASTM STP 568, American Society for Testing and Materials, pp. 159-172.

2. Agarwal, B. D. and L. J. Broutman . 1980. Analysis and Performance of Fibre Composites. John Wiley and Sons.

3. Broutman, L. J. and A. Rotem . 1975. "Impact Strength and Toughness of Fiber Composite Materials," Foreign Object Impact Damage to Composites, ASTM S7P 568, American Society for Testing and Materials, pp. 114-133.

4. Amar, C. Garg . 1988. "Delamination-A Damage Mode in Composite Structures," Engineering Fracture Mechanics, 29:557-584.

5. Liu, D. 1988. "Impact Induced Delamination-A View of Bending Stiffness Mismatching," J. of Composite Materials, 22:674-692.

6. Wyrick, D. A. and D. F. Adams . 1988. "Residual Strength of Carbon/Epoxy Composite Material Subjected to Repeated Impact:" J. of Composite Materials, 22(8):749-765.

7. Prichard, J. C. and P. J. Hogg . 1990. "The Role of Impact Damage in Post-Impact Compression Testing," Composites, 21(6):503-511.

8. Chang, L. 1988. "Impact Fatigue of PPS/Glass Composites," J. of Materials Science Letters, 4:1221-1224.

9. Jang, B. P. , C. T. Huang , C. Y. Hsieh , W. Kowbel and B. Z. Jang . 1991. "Repeated Impact Failure of Continuous Fibre Reinforced Thermoplastic and Thermoset Composites," J. of Composite Materials, 25:1171-1203.

10.

10. Kaushal, S. , K. Tankala , R. M. V. G. K. Rao and Kishore . 1991. "Some Hygrothermal Effects on the Mechanical Behavior and Fractography of Glass-Epoxy Composites with Modified Interface," J. of Materials Science, 26:6293-6299.

11.

11. Cantwell, W. J. and J. Morton . 1991. "The Impact Resistance of Composite MaterialsA Review," Composites, 22:347-362.

12.

12. Cantwell, W. J. and J. Morton . 1989. "Geometrical Effects on the Low Velocity Impact Response of CFRP," Composite Structures, 12:46-53.

13.

13. Khan, B. 1992. "Impact Fatigue Behaviour of and Damage Mechanisms in Glass-Epoxy Composite Laminates," M. tech thesis, KREC/NAL.