The objective of this study is to clarify the fracture mechanism of unidirectional CFRP (Carbon Fiber Reinforced Plastics) under static tensile loading. The advantages of CFRP are higher specific stiffness and strength than the metal material. The use of CFRP is increasing in not only the aerospace and rapid transit railway industries but also the sports, leisure and automotive industries. The tensile fracture mechanism of unidirectional CFRP has not been experimentally made clear because the fracture speed of unidirectional CFRP is quite high.
We selected the intermediate modulus and high strength unidirectional CFRP laminate which is a typical material used in the aerospace field. The fracture process under static tensile loading was captured by a conventional high-speed camera and a new type High-Speed Video Camera HPV-1. It was found that the duration of fracture is 200 microseconds or less, then images taken by a conventional camera doesn't have enough temporal-resolution. On the other hand, results obtained by HPV-1 have higher quality where the fracture process can be clearly observed.
A thin metal electrode tip instantly changes its shape into a sphere or a needlelike shape in a single electrical discharge of
high current. These changes occur within several hundred microseconds. To observe these high-speed phenomena in a
single discharge, an imaging system using a high-speed video camera and a high repetition rate pulse laser was
constructed. A nanosecond laser, the wavelength of which was 532 nm, was used as the illuminating source of a newly
developed high-speed video camera, HPV-1. The time resolution of our system was determined by the laser pulse width
and was about 80 nanoseconds. The system can take one hundred pictures at 16- or 64-microsecond intervals in a single
discharge event. A band-pass filter at 532 nm was placed in front of the camera to block the emission of the discharge
arc at other wavelengths. Therefore, clear images of the electrode were recorded even during the discharge. If the laser
was not used, only images of plasma during discharge and thermal radiation from the electrode after discharge were
observed. These results demonstrate that the combination of a high repetition rate and a short pulse laser with a high
speed video camera provides a unique and powerful method for high speed imaging.
Visualization of explosion phenomena is very important and essential to evaluate the performance of explosive
effects. The phenomena, however, generate blast waves and fragments from cases. We must protect our visualizing
equipment from any form of impact. In the tests described here, the front lens was separated from the camera head by
means of a fiber-optic cable in order to be able to use the camera, a Shimadzu Hypervision HPV-1, for tests in severe
blast environment, including the filming of explosions. It was possible to obtain clear images of the explosion that
were not inferior to the images taken by the camera with the lens directly coupled to the camera head. It could be
confirmed that this system is very useful for the visualization of dangerous events, e.g., at an explosion site, and for
visualizations at angles that would be unachievable under normal circumstances.