MAterial Response Studies (MARS I). Volume V. Dynamic Behavior of Polymers and Composites.
GENERAL MOTORS TECHNICAL CENTER WARREN MI MATERIALS AND STRUCTURES LAB
Pagination or Media Count:
The mechanical behavior of polymers at high strain rates can be rationalized in terms of molecular mechanisms of deformation. The sigmoidal shape of the stress vs strain rate curve of polymethyl methacrylate was attributed to the beta transition. The strain rate sensitivity increased with strain but decreased with increasing temperature. These trends are applicable to phenolic resin as well. Crystalline polymers were generally found to be more strain rate sensitive than amorphous polymers. The effect of strain rate on the strain required to produce failure is intimately related to the mode of fracture. In quartz phenolic the ratio of the bond strength to fiber strength is small leading to a splintery fracture, and increasing strain rate increases strain to fracture. However, in carbon phenolic the ratio of bond strength to fiber strength is nearer unity, the fracture is localized and increasing strain rate reduces the strain to fracture. In quartz phenolic, interlaminate failure determines the plane of fracture in compression. While in the case of carbon phenolic, the fracture is along the plane of maximum shear. Author