ISSN:
0032-3888
Keywords:
Chemistry
;
Chemical Engineering
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
A test program was developed to compare the viscoelastic behavior of an untoughened epoxy (R922) with a toughened epoxy (R6376). Creep/recovery tests were performed on neat resin as well as [ ± 40° ]2s composites using T500 or IM7 graphite fibers. The composite specimens were subjected to at least five cycles of load/unload at each stress level. The goal was to study the viscoelastic response of a flexibilized and unflexibilized epoxy and to try and observe any microstructural changes that might occur. Neat resin tests did not show a significant difference in behavior between the two systems. Single cycle behavior was found to differ significantly from multiple cycle behavior. Recovery strains were observed to be much higher than predicted from linear theory. Linear parameters were also seen to vary with stress level; however, when a plasticity-based approach was used to model the creep behavior, the same parameters could then be used at all load levels. Creep and recovery behavior were seen to differ significantly. This observation leads to support for the theory of Schapery (1) that creep and recovery should be considered as different behavior in contrast to the assumptions of linear and nonlinear theory. In addition, the large difference between neat resin and composite data suggests that micromechanics models, which rely on constituent properties, will lead to large errors if neat resin properties are used to characterize composite viscoelastic behavior. Different fibers showed no influence on results. Scanning electron microscopy failed to reveal any microstructural changes.
Additional Material:
15 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pen.760332104
Permalink
