Recoil compression test

Obtaining the compressive strength of a slender fiber is even more difficult than measuring its tensile strength. An indirect technique has been devised to obtain compressive strength of fibers. It is well known that the recoil of a tensile stress wave generates a compressive wave. This principle is used in the recoil compression test, which allows one to estimate the compressive strength of fibers. 

Crasto AS, Kumar S, Recoil compression testing of advanced carbon fibers, 35th International SAMPE Symposium, 318-331, Apr 2-5, 1990. 

In all cases the anisotropic polymerization mixtures (10% by weight) could be used directly in the formation of dry-jet wet-spun fibers. Monofilament fibers were obtained by coagulation in water, tension dried at 150 °C and heat treated at 500-600 °C with a 30s residence time. The best fibers were obtained from the high molecular weight PBZT polymer (VII) which exhibited modulus values that ranged between 172 GPa and 207 GPa and tenacity values up to 2.4 GPa. Unfortunately, the compressive property as measured by the tensile recoil test was only 380 MPa, showing only a slight improvement over PBZT. 

Several methods have been used to determine the compression strength of carbon fiber and its composites—The Loop Test [90] Single Filament in a Beam [91] Critical Length under Compression [92] Micro-compression [93,94] Fiber Recoil [95-97] Piezo Method [98,99] Raman Spectroscopy [100-102] Composite [103,104] and Mini-composite [105]. 

---