Some Aspects of the Mechanical Response of PMR-15 Neat Resin at 288oC

<p>The mechanical response of PMR-15 neat resin was investigated at 288 -C. The effect of loading rate on monotonic stress-strain behavior was explored in monotonic tests at several constant stress rates. Considerable rate dependence was observed especially on the unloading path. Effect of prior stress rate on creep behavior was evaluated in creep tests preceded by uninterrupted loading to a target stress where loading rate was changed from test to test. Creep response was dependent on the prior stress rate. Effect of loading history was studied in stepwise creep tests where specimens were subjected to a constant stress rate loading followed by unloading to zero stress with intermittent creep periods during both loading and unloading. Comparison of creep strains accumulated during a stepwise creep test to those accumulated during creep preceded by uninterrupted loading indicate that the prior stress history affects the creep behavior. Negative creep as well as creep rate reversal was observed on the unloading path. A nonlinear viscoelastic model (Schapery's formulation) was characterized using creep and recovery tests at 288 -C. The model was verified by comparing the predictions with experimental results obtained in monotonic loading/unloading tests and single-step as well as multi-step creep tests. The model qualitatively predicted creep response to single- and multi-step creep tests including negative creep and creep rate reversal during unloading. However predictions were not quantitatively accurate. The model was unable to accurately predict the recovery behavior and could not account for rate effects.</p><p>This work has been selected by scholars as being culturally important and is part of the knowledge base of civilization as we know it. This work was reproduced from the original artifact and remains as true to the original work as possible. Therefore you will see the original copyright references library stamps (as most of these works have been housed in our most important libraries around the world) and other notations in the work.</p><p>This work is in the public domain in the United States of America and possibly other nations. Within the United States you may freely copy and distribute this work as no entity (individual or corporate) has a copyright on the body of the work.</p><p>As a reproduction of a historical artifact this work may contain missing or blurred pages poor pictures errant marks etc. Scholars believe and we concur that this work is important enough to be preserved reproduced and made generally available to the public. We appreciate your support of the preservation process and thank you for being an important part of keeping this knowledge alive and relevant.</p>