Research On The Aging Of Glass Fiber/Phenolic Ablative Material In Storage

In this paper, we study four kinds of glass fiber/phenolic composite: the originalsample, samples respectively under hot-oxygen and hot-humid conditions of artificialand specimens under natural stored conditions. Using molecular dynamics simulationtechnology to predict and analyse the aging factors of glass fiber/phenolic composite.We find the differences between samples under different conditions: before and afterthe accelerated aging tests through DSC, the glass transition temperature (Tg) andthermal decomposition temperature are changed. Physical aging mechanisms areanalyzed through SEM photos. Infrared spectroscopy and XPS are also used to find thechemical reaction of functional groups which after aging tests. By testing the glassfiber/phenolic composite’s mechanical properties under various conditions, thechanging rule of mechanical properties is obtained. At last, we establish the predictionmathematical model of artificial accelerated aging life to estimate the glassfiber/phenolic composite’s storing life and compare it with the natural stored samples.The results show that the presence of water can accelerate the aging process ofglass fiber/phenolic composites. Aging causes the decrease of tensile strength while ismore destructive than condition. After aging tests under different conditions all thesamples’ thermal decomposition temperature are lower but not the Tghas the samechange: hot-oxygen aging can postcure the composite and increase its free volume, bothof these make the Tghigher; the hot-humid condition aggravate the swelling ofcomposite which make Tgdown. We infer that the composite is mainly due to thedilated defects from the remain of volatile gases which are manufactured during thepostcure and some other chemical reactions. The other physical aging failure mode isdebonding because the fiber and matrix have different degrees of substitution whichcauses interfacial stress. Two chemical reactions are accused of chemical aging failure:methylene group, ether bond, hydroxymethyl group are all oxidized by oxygen thatproducing carbon-oxygen double bond under dry conditions; methylene ether oxygenbond is oxidized that producing carbon-oxygen double bond under humidityenvironment. Natural aging include both physical and chemical aging process. Wepredict the storage life of glass fiber/phenolic composite is67.8years through ouraging model. Tensile strength which is extrapolated from the prediction curve iskeeping with the natural aging’s.