Interaction between Cracking and Oxidation in Organic Matrix Composites

Abstract

The thermal oxidative degradation of carbon fiber/bismaleimide (Hexel T800H/F655-2) and carbon fiber/amine-cross-linked epoxy (Cytec Fiberite IM7/977-2) unidirectional composites and their corresponding neat polymers has been studied in air at temperatures ranging from 150 to 240 C by optical microscopy, using an interferential contrast, and IR microspectrophotometry.A coarse analysis of the damaged zone allowed the determination of main kinetic characteristics in the whole degradation process (oxidation, crack propagation, and their interaction) for each principal direction of the composite materials.It has been found that cracks initiate at the sample free surfaces when a critical value of embrittlement is reached in the oxidized layer. Then, cracks propagate differently toward the core according to both the fiber orientation and the nature of the composite system. The difference in behavior between T800H/F655-2 and IM7/977-2 systems can be explained by a difference in polymer toughness and oxygen permeability of the fiber-matrix interface.

Understanding the durability of advanced fibre-reinforced polymer (FRP) composites for structural applications

“…Colin et al (2005) showed that such models can also be used to predict oxygen diffusivity in composites. More recently, roy and Singh (2009) showed that these models can be improved to take into account physical discontinuities such as highly permeable fi bre/matrix interface or fi bre/matrix debonding due to oxidative shrinkage and erosion.…”

“…Degradation gradients, resulting from diffusion control of chemical reaction kinetics, play an important role from a mechanical point of view. Schematically, an initially ductile/tough and homogeneous polymer sample is progressively transformed into a binary structure, the sample core remaining ductile/tough, whereas the superficial layer becomes brittle and thus highly sensitive to cracking (Colin et al, 2005). A superficial crack can rapidly cross the whole superficial layer thickness and reach the skin−core interface.…”

Thermo-oxidative behavior of high-temperature PMR-15 resin and composites

“…While the time-dependent physical, chemical, and damage-induced degradation mechanisms have been studied for some resin systems, polymer composite thermal oxidation studies from a mechanistic perspective are nascent. Notable exceptions to this are the recent works of Colin and Verdu [1], Colin et al [2], Wang and Chen [3], Pochiraju and Tandon [4], Tandon et al [5], and past work by Skontorp et al [6], Wise et al [7], and McManus et al [8]. Equally important are the experimental characterization efforts by such groups as Bowles et al [9], Tsuji et al [10], Abdeljaoued [11], and Schoeppner et al [12].…”

The effect of reinforced structure on thermo-oxidative stability of polymer-matrix composites

“…The thermo-oxidative degradation occurs initially at the outer surface of the composite and proceeds inwards via a diffusion mechanism [8][9][10]. Simultaneously, microcracks may occur due to the mismatches in the coefficients of thermal expansion between the fibers and matrix, as well as the resin shrinkage [11] caused by the thermo-oxidative aging (TOA).…”