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.