Research On NOnlinear Bahavior Of PMMA's Crazing Damage

The mechanical property of polymer depends on the factors such as temperature, hold time of stress, speed to load and condition ,one of the most important is the dependence of temperature and time .At the same time , the crazing and crazing damage are characteristic phenomenon of polymer. The solicitation, development and rupture of craze in exiguous hierarchy play a connective work in the course of polymer's damage and rupture. It is a bridge in distortion mechanism of macroscopical and microcosmic. It is one of mechanisms of plastic distortion, at the same time it is also the beginning of microcosmic damage and rupture before the macroscopical destroying of materials, it representatives a mid-state between materials' macroscopical rupture and bend, it is considered a premonitory that the rupture of polymer material, which get common attention by scholar inside and outside nation .Therefore, the research for engineering polymer in mechanic action of non-linearity destroy such as distortion, destroy and depend on time and temperature is valuable in theoretic research and actual application ,which offer the important theoretic gist for changing complex material's capability and actualize polymer's perfect application with high quality of capability in engineering.In this paper, we take high molecule physics and the damage theory of rheologic material with lacuna as the basic ,make the experiment as a mostly measure, take the PMMA as a research object, to study the PMMA's nonlinear viscoelasticity of high polymer .The technique showing minute details in minute view measure is used by the author to observe the change of crazing damage density follow the change of stress, time and temperature in term of creep and flab. With the disposal of the image, we get a changing rule that the change of the sample of PMMA's surface crazing damage density follow the change of time and stress.Concretely,1 , Base on the viscoelastic mechanism of polymer depend on time , single axes stretching experiments are proceeded to research viscoelastic distortion of high polymer with the dependence on non-linearity and stress . We get each materialparameter by dealing with the data of experiments, and contrast several theories of one dimension creep.2. The PMMA's craze damage is observed on line in different temperature and invariable load, which show that the change pricks up with the increase of time and temperature. With the disposal of the image, we get a changing rule that the change of the sample of PMMA's surface crazing damage density follow the change of time and stress. Then the data from experiment is to match in non-linearity, PMMA's density of crazing damage changing with time and stress is available.3. In order to discuss polymer's crazing damage depend on temperature, also to research the essence of polymer's crazing, we put up experiments to observe PMMA's crazing damage changing with time in different temperature. The results shows that PMMA's crazing reduce with time extend .When temperature become higher, the change become fleeter. With the disposal of the data, we get PMMA's density of crazing damage in different temperature. Then data from experiment is to match in non-linearity, the rule of PMMA's density of crazing damage changing with time and stress and change depend on temperature are available.High molecule physics and the damage theory of rheologic material with lacuna are used in experiments to study the PMMA's nonlinear viscoelasticity and changing depends on time and temperature when distorting and destroying. We try to seek a common rule to polymer's crazing damage, offer a viable damage model and measure to research polymer's minute damage.