Polymer-based composites reinforced with nanocarbonaceous materials can be tailored for functional applications. Poly(vinylidene fluoride) (PVDF) reinforced with carbon nanotubes (CNT) or graphene with different filler contents have been developed as potential piezoresistive materials. The mechanical properties of the nanocomposites depend on the PVDF matrix, filler type, and filler content. PVDF 6010 is a relatively more ductile material, whereas PVDF-HFP (hexafluropropylene) shows larger maximum strain near 300% strain for composites with CNT, 10 times higher than the pristine polymer. This behavior is similar for all composites reinforced with CNT. On the other hand, reduced graphene oxide (rGO)/PVDF composites decrease the maximum strain compared to neat PVDF. It is shown that the use of different PVDF copolymers does not influence the electrical properties of the composites. On the other hand, CNT as filler leads to composites with percolation threshold around 0.5 wt.%, whereas rGO nanocomposites show percolation threshold at ≈ 2 wt.%. Both nanocomposites present excellent linearity between applied pressure and resistance variation, with pressure sensibility (PS) decreasing with applied pressure, from PS ≈ 1.1 to 0.2 MPa−1. A proof of concept demonstration is presented, showing the suitability of the materials for industrial pressure sensing applications.

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It is believed that the acoustic emissions (AE) signal contains potentially valuable information for monitoring precision cutting processes, as well as to be employed as a control feedback signal. However, AE stress waves produced in the cutting zone are distorted by the transmission path and the measurement systems. In this article, a bicepstrum based blind system identification technique is proposed as a valid tool for estimating both, transmission path and sensor impulse response. Assumptions under which application of bicepstrum is valid are discussed and diamond turning experiments are presented, which demonstrate the feasibility of employing bicepstrum for AE blind identification. r

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This paper is aimed at investigating the influence of nonviscous modes on the vibrational response of viscoelastic systems. Thus, exponential damping models are considered. Provided that nonviscous modes disappear with time, they have influence on only the transient response of the system. Thus, the system response is obtained by means of modal superposition in order to examine the contribution of each mode. The analysis is carried out on two lumped parameter systems; systems involving a single degree and three degrees of freedom are studied. For the former, the analytic solution is derived via modal superposition and Laplace transformation. For the latter, the analytic response is contrasted with that provided via two numerical direct methods. From this investigation, it can be concluded that the system may present no oscillations, even if elastic modes are underdamped modes.

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The main objective of this paper is to investigate a way to characterize experimentally the mechanical behavior of low modulus adhesives. In this context, the relaxation and complex moluli master curves of a SIKAFLEX 1 505 adhesive are obtained by means of dynamic mechanical thermal analysis. Firstly, the procedure carried out to prepare and to validate the test specimens is explained. Next, the influence of the test specimen thickness and strain level is studied. Finally, the relaxation and dynamic master curve sunder tension strain are constructed via a procedure based on the time-temperature superposition principle.