Research Projects

It is proposed to optimize a procedure developed to quantify and spatio-temporally predict the magnitude of damage in composite panels under typical service life conditions. An embedded sensor based methodology for life estimation and remaining life extension, involving comparison of undamaged and damaged states of the composite panels is proposed. Specific focus will be on composites used in ballistic hard armor panels (HAP) wherein the homeland security, human lives and cost to exchequer is involved. The procedure will enable soldiers and security personnel to detect any damage to their armor at regular intervals without subjecting them to destructive testing. The method involves transmission of wave packets from one end of the composite panel which are subsequently received at the other end of the composite panel at selected frequencies using sensors. Based on the structural health condition of the medium, wave characteristics (travel time, amplitude, phase, shape) of these wave packets are measured. The composite panel acts as a band pass filter, allowing propagation of waves which are part of the continuous periodic waves falling within a varying frequency spectrum and attenuates all other waves which do not belong to that frequency spectrum. This frequency at which waves propagate without any difficulty from transmitter to the receiver is called the Pass Frequency and depends on material properties of the composite panel. Multiple sensors embedded into the composite panel, receive signals differing in frequency, amplitude and phase due to relative position of the sensor used to transmit the signal and sensor used to receive the signal in the composite panel. Once pass frequency is determined, wave packets of that particular frequency are transmitted into the composite panel. The wave characteristics of the continuous periodic wave and wave packets of pass frequency are measured in order to find any change in the structural health of the composite panels. Initial baseline tests are conducted for creating a standard result for a composite panel, and wave characteristics of the composite panel at the time of manufacture are recorded. The composite panel is then tested after a certain period of time and wave characteristics of the composite panel are compared with standard results. Any significant deviation from baseline implies that the composite panels have undergone a structural or material change (de-lamination, distortion, breakage) and that they may be unfit for use. Ability to estimate balance life and recondition reduces the time and cost factors involved for procuring immense cost of ownership and increases the battle preparedness.