Abstract
The extensive production of polymer composites reinforced by carbon nanotube is limited by the absence of non-destructive evaluation (NDE) methods capable of assessing product quality to guarantee compliance with specifications. It is well known that the level of dispersion of carbon nanotubes (CNTs) in the polymer matrix is the parameter that, much more than others, can influence their enhancement capabilities. Here an active Infrared Thermography Non Destructive Testing(IR-NDT) inspection, joined with pulsed phase thermography (PPT), were applied for the first time to epoxy-CNT composites to evaluate the level of dispersion of the nanoparticles. The PPT approach was tested on three groups of epoxy nanocomposite samples with different levels of dispersion of the nanoparticles. The phasegrams obtained with the presented technique clearly show clusters, or bundles, of CNTs when present, so a comparison with the reference sample is not necessary to evaluate the quality of the dispersion. Therefore, the new NDE approach can be applied to verify that the expected dispersion levels are met in products made from epoxy and Multi-Walled Carbon Nanotubes (MWCNTs). The mechanisms underlying the effects of the dispersion of carbon nanotube on the thermal response of polymer composites have been identified.
Highlights
Carbon nanotubes (CNTs) have exceptional mechanical properties, which combined with high geometrical aspect, stiffness to weight and strength to weight ratios, give them the potential to be the ideal reinforcing agents in composites e.g., [1,2,3,4,5,6,7,8,9]
Testing (IR-NDT) inspection technique was applied for the first time to epoxy-CNTs composites to evaluate the level of dispersion of the nanoparticles
In a previous work [29], a novel non-destructive evaluation (NDE) technique based on infrared thermography, able to test the dispersion of the added nanoparticles in nanocomposites, was presented
Summary
Carbon nanotubes (CNTs) have exceptional mechanical properties, which combined with high geometrical aspect, stiffness to weight and strength to weight ratios, give them the potential to be the ideal reinforcing agents in composites e.g., [1,2,3,4,5,6,7,8,9]. By adding CNTs, thermal e.g., [10,11,12,13,14], electrical e.g., [15,16,17,18], and optical properties e.g., [19,20,21,22] of formed composites can be improved These high potentials collide with some issues that considerably hinder the use of polymeric composites enhanced by CNTs. One of the most important is the absence of non-destructive evaluation (NDE) techniques able to and at low cost, control the quality of the products made, in order to ensure compliance with their specifications. An NDE technique based on the impulse acoustic microscopy method, and that was able to control the quality of the graphene dispersion has been presented in literature [26,27] They were used to control bulk microstructure in carbon nanocomposite samples with different levels of dispersion; this NDE method is slow and can only scan small samples, limiting possible industrial applications. In [28], a technique based on dynamic scanning calorimetry (DSC) measurement data was proposed to represent the Materials 2020, 13, 5649; doi:10.3390/ma13245649 www.mdpi.com/journal/materials
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