Interlaminar crack propagation in MWCNT/fiber reinforced hybrid composites

Abstract

Abstract. In this work carbon fiber/epoxy composites and MWCNT (multiwalled carbon nanotube)/carbon fiber/epoxy hybrid composites with 0.1, 0.3, 0.5 and 1 weight% nanotube filling of the matrix have been prepared and compared in terms of interlaminar properties. For the dispersion of the carbon nanotubes in the epoxy resin three roll milling has been utilized. The mechanical characterization has been carried out using standard DCB (double cantilever beam) tests assisted by acoustic emission. The test results have been evaluated by the conventional method provided by the standard and a novel method implementing acoustic emission signal localization for crack propagation tracing. According to the tests carbon nanotube filling of the matrix of the composites has a beneficial effect on their interlaminar properties: the interlaminar fracture toughness values of the composites have increased by a maximum of 13 and 33% at a 0.3 weight% carbon nanotube content of the matrix according to the conventional and AE based evaluation method respectively.

Enhancement of mechanical performance of epoxy/carbon fiber laminate composites using single-walled carbon nanotubes

“…Since the SWCNT toughening mechanisms postulated above are expected to be more ''active'' during propagation, this supports the idea that these are indeed the source of the increased toughnesses observed. A similar increase of 13% in Mode I fracture toughness was reported by Romhany and Szebenyi [27] for a MWCNT loading of 0.3 wt%, suggesting that SWCNT may be more effective than MWCNT for a given loading. In another work, Karapappas et al [31] demonstrated that 1 wt% loading of MWCNT can result in a 60% improvement in Mode I fracture toughness; however, for small loading of 0.1 wt% (similar to this work) slight reductions in both Mode I and Mode II fracture toughness values were reported.…”

“…7. This compares to other published results based on MWCNT [26,27] in which the fracture toughness values vary considerably as crack length increases. It seems reasonable that this may be attributable to a more uniform dispersion of SWCNT within epoxy due to a lower loading of SWCNT and the effective functionalization to maintain the dispersion.…”

“…10 shows SEM images of the fracture surfaces of a baseline and a nano-modified specimen. Two dominant toughening mechanisms involved with Mode II fracture tests are micro-cracks and hackles, which are both related to microscale matrix failure modes [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37]. A comparison between the two SEM images shows that the hackles are larger for the nanocomposites.…”

Effects of graphene oxides on the cure behaviors of a tetrafunctional epoxy resin

“…CNT-and CNF-reinforced epoxy nanocomposites have shown improved mechanical, electrical and thermal properties [2][3][4][5]. However, the high cost of CNTs and CNFs and the poor dispersion in the epoxy limits their range of practical applicability.…”

Wavelet-based acoustic emission characterization of damage mechanism in composite materials under mode I delamination at different interfaces

“…Several studies were already conducted on the mode I fracture to determine the surface energies of composite materials by creating a crack propagation effect [3,4]. To find correlation between AE parameters and damage mechanism several studies have been carried out [5][6][7][8][9]. Most studies so far have used AE descriptors such as counts, amplitude, energy and also multiparameter method to characterize the development of failure mechanisms.…”