Ultrasonic Techniques to Quantify Material Degradation in FRP Composites

This is a progress report of research into use of ultrasonic waves to quantify the amount of damage in fiber reinforced polymeric (FRP) composites. The planned scope of the research involves three distinct stages of experimental work. First is the pre-damage stage when a baseline set of measurements on the composite material is taken. In this stage an effort is made to answer questions on issues like material variability, what range of frequencies can be propagated through it, or whether the material exhibits viscoelastic properties. Stage two, the damage stage, involves the introduction of damage into the material in an accelerated manner in order to simulate the effects of long periods of exposure to damaging environments. Damage mechanisms used are long term temperature aging, temperature aging in a water bath and bending fatigue. Optical imaging techniques will be used to verify that the damaging procedures have indeed produced a noticeable amount of damage in the matrix and fiber before we proceed to the next stage of experimentation. Stage three is the post-damage stage at which final measurements are taken. These final measurements must show a sufficient change from the stage one measurements above the known variability of the material for the imparted degradation change to be quantifiable. The report that follows here represents tests and measurements that are part of the stage one of the planned scope of work