The Experiment Study Of PMMA's Crazing Damage

The crazing and craze damage are characteristic phenomenon of high polymer, it was broad noticed by scholars of domestic and overseas. The solicitation development and rupture of craze in exiguous hierarchy play an 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 premonitor that the rupture of polymer material. After the solicitation of craze, because of the growing of the craze, it occurs a rupture and come into being a micro-crack, it will form a bigger crack or cavitate, it will lead an unitary and macroscopical rupture in the end.In this paper, we will make the experiment as a mostly measure, take the PMMA as a research object, an optical technique to observe the solicitation and spread of high polymer under creep in real time on line. And collecting the image of the damage instance in the sample of PMMA in real time on line, we get the surface crazing damage density under different time and different stress passing the image dispose of a software, and giving out a changing rule that the change of the sample of PMMA's surface crazing damage density follow the change of time and stress. At the same time we study, analysis and discuss the action that non-linearity-stickiness-springiness and crazing damage of the PMMA sample under creep though making us of the knowledge about the high molecule physics the damage theory of material of rheology of bodies with defects. Through the study and theory analysis of single-axes stretching experiment in PMMA sample under creep, take the surface crazing damage density of PMMA sample as an variable, to look for a commonly rule that the crazing damage of PMMA, and to offer a feasible damage model for the sake ofstudy that of PMMA's remoteness damage.The achievements and conclusions are listed as follows:1, Basing on the single-axes stretching experiment result of PMMA sample with holes and PMMA sample without holes under creep, using non- linearity regress analysis, after non- linearity imitating the experiment data, we may get the crazing damage density evolvement curve of PMMA sample with holes and PMMA sample without holes follow the time and stress under different stress level.2 After the colligating analysis to the experiment data, using the way of suppose regression and imitation and so on, we can educe an commonly model following the stress and time that crazing damage density of PMMA sample with and without holes. Then we will validate the experiment data using the model.3 . Base on the single axes stretching experiment data of PMMA sample with holes, validating the experiment data, we can get the rule that influenced by the stress and time together of the PMMA sample's crazing damage density.4 After the regressing analysis of the experiment data, power or multinomial imitating, we can reach the relation that the crazing solicitation time and stress level respectively of PMMA sample with and without holes.5 Through forecasting the life of PMMA sample with holes, we get the commonly model and evolvement curve of the life that PMMA with holes following the stress.