Aging of polymeric composites : a literature review

Abstract

Due to their increased use in today's society, an extensive survey was undertaken in this report to condense what's been, thus far, discovered as to the effects of aging on polymeric composites. Special emphasis was placed on composites with vinyl ester as the matrix reinforced with glass or carbon fibers. Moisture exposure, thermal conditioning, and cyclic loading were the aging mechanisms used to mimic environmental effects. Fatigue, flexural, tensile tests, and scanning electron microscopy were among the many methods used in studies to determine the effects of aging on composites. The deleterious effect of moisture on composite performance was undeniable, with the drop in flexural strength being as high as 48%. Studies found no difference between salt and distilled water aging, although salt water was reported as being more slowly absorbed. Composite materials were observed to experience no further loss of strength beyond the point of saturation. Findings showed that, after aging, composites retained some of their strength, with flexural strength retention reported as high as 66%. Frequently, the glass transition temperatures of the materials changed depending on the aging process. In most cases, Fick's law of diffusion was confirmed as an accurate model for moisture absorption. Temperature fluctuations were always deemed as damaging to composite structures. Due to the haziness still present in current research coupled with the importance of composite applications, the need for additional investigation in this topic is urgently obvious. All in all, future studies are encouraged to tabulate test procedures and results in an effort to minimize the current ambiguities in the aging information accumulated thus far.