Fracture characterization of C/C composites under various stress modes by monitoring both mechanical and acoustic responses

Abstract

IntroductionCarbon/carbon (C/C) composites recognized also as carbon fiber reinforced carbon are characterized by their higher specific strength and stiffness of up to 3000°C in non-oxidizing atmospheres, as compared to other ceramic matrix composites. In addition, the low coefficient of thermal expansion, high thermal conductivity and high thermal shock resistance, have made this material an excellent candidate for aerospace and defence applications for more than three decades. The most popular applications that this unique composite is being used for are: brake discs, rocket nozzles, leading edges of re-entry vehicles, furnace heating, and thermal management components in space vehicles [1].The severe environmental conditions (mechanical and thermal) which critical engineering structures such as those made of C/C composites have to face, require special attention from manufacturing processes to improve their service in performance [2] aspects. As well-known, defects and flaws may be initiated and may grow as a result of the above conditions and this can upset the mechanical balance of fiber, matrix and interface that gives composites their high performance profile. For the first, the determination of the optimal parametric process, quality control using destructive and non-destructive techniques and mutual properties becomes important. For the second, damage degree development, degradation in performance residual strength, etc., have to be assessed from the structural integrity and life prediction points of view. EVA-STAR (Elektronisches Volltextarchiv -Scientific Articles Repository)

Damage evolution and fracture events sequence in various composites by acoustic emission technique

“…Full details of both mechanical testing and more on the AE set-up are reported elsewhere [17]. Table 1 summarizes the test conditions for the three composites including the number of tested specimens.…”

A Global Method for the Identification of Failure Modes in Fiberglass Using Acoustic Emission

“…In particular, Gang Qi studied the fracture behavior of composite materials using wavelet based signal processing [17]. Bussiba et al used AE technique to track the mechanical threshold parameters for density changes in C/C composites, so that AE parameters, such as counts, amplitude, duration, peak frequency, etc., were analyzed in order to point out the possible fracture sequence events [18][19][20]. Since AE signals in composite materials are transient, time-frequency behavior has also been studied by Fast Fourier Transform (FFT) [21,22].…”

Initial and final fracture behaviors of woven fabric composites

“…Bussiba et al [17] studied the fracture characterization of C/C composites under various stress modes by monitoring both mechanical and acoustic responses and showed a good relation between the mechanical properties and acoustic responses. Higher AE counts rate resulted in higher fracture stress.…”