Accelerated aging versus realistic aging in aerospace composite materials. II. Chemistry of thermal aging in a structural composite

Abstract

Samples of an aerospace structural epoxy composite (8552/IM7) were subject to long-term (% 1 year) thermal aging at temperatures of 708, 1208, 1708, and 2008C (in air). The changes to the chemical and physicochemical structure of the composite were analyzed by a range of different techniques, including gravimetric analysis, Fourier transform infrared (FTIR), and dynamic mechanical analysis (DMA) to compare the effects of different severities of degradation treatment. The results highlighted the large differences in chemical effects between the surface and the interior of the composite with very minor changes in the latter even at quite high aging temperatures and long aging times. The oxidative changes at the surface, however, varied from highly selective molecular changes for particular chemical groups at the lower aging temperatures (708 and 1208C), to quite general and extensive oxidative degradation at the higher aging temperatures (1708 and 2008C). The results indicated that the mechanical changes in an aged composite of this type will vary greatly with the material thickness and surface protection as well as the aging temperature the composite is exposed to.

Long‐term aging in a commercial aerospace composite sample: Chemical and physical changes

“…C for approximately 3000 h. 6 This chemistry was in considerable contrast to our studies of the same composite at higher temperatures and our 45, 65, and 85% relative humidity conditioning studies (at 70 C for up to 7500 h). 7 …”

Effect of Ultraviolet Absorber on Photo-Degradation of Epoxy Coating Studied by Slow Positron Beam

“…Meanwhile, the C-H bond in methylene group near 2923 and 2852 cm −1 decreases. The result suggests a new amide is generated as a result of the oxidization of C-H bond in α-position of nitrogen atom on amino groups [8,9]. However, for the sample with ultraviolet absorber, the peak of -C=O in amide group moves from 1639 cm −1 to 1656 cm −1 , which is narrower than the unmixed one (from 1639 cm −1 to 1664 cm −1 ), indicating a suppressed effect of ultraviolet absorber on generation of the new amide group.…”

Environmental Degradation of Carbon Nanotube Hybrid Aerospace Composites

“…Many of these systems have been aerospace type formulations (although generally highly simplified) and a very good library of peak positions for each molecular structure has been built up (Dao et al 2006a). Differential scanning calorimetry (DSC) on the other hand is useful since it measures the exothermic energy of any residual reactions present in a composite material.…”

“…In this chapter we will focus on those conditions that are present in typical aerospace applications, where polymer composites are employed. Polymer matrix composites (PMCs) find use in both civil and military aircraft, where the effect of the environment on their structural performance is part of the certification process (Dao et al 2006a). PMCs, such as GFRPs, are being used in spacecraft.…”