Determining wave velocities in polymer fibers using electromagnetic radiation

A new technique for determining wave velocities in polymer fibers using electromagnetic radiation (EMR) is developed by measuring an electric response signal. EMR in fibers is detected by using sensors based on three-turn coils made of isolated copper wire, and the fibers are passed through sensors fixed in the crossbeam grips. The instantaneous removal of loading generates longitudinal and weaker secondary elastic unloading waves, which appear as steps propagating at various velocities. The results indicate that the wave front propagates with an instantaneous velocity and then tends to a long-term velocity corresponding to the Young modulus for a slow stretching. The initial velocity of motion of fiber end is determined with a video camera, showing the EMR method measures exactly the velocities of longitudinal waves rather than some uncertain electric effects.