Andrea Zucchelli

Influence of electrospun nanofibers on the interlaminar properties of unidirectional epoxy resin/glass fiber composite laminates

Nylon 6,6 nanofibers were interleaved in the mid-plane of glass fiber/epoxy matrix composite laminates for Mode I and II fracture mechanic tests. The present study investigates the effect of the nanofibers on the laminates’ mechanical response. Results showed that Nylon 6,6 nanofibers improved specimen’s fracture mechanic behavior: the initial energy release rates GIC and GIIC increased 62% and 109%, respectively, when nanofibrous interlayer was used. Scanning electron microscope micrographs showed that nanofiber bridging mechanism enhances performances of the nanomodified specimens, still able to link the layers when the matrix is broken.

Clustering of acoustic emission signals collected during drilling process of composite materials using unsupervised classifiers

Conventional methods of analysis for drilling of composite materials usually study the amount of damaged area, thrust force, and effective parameters. However, these methods do not provide the investigator with sufficient information about drilling mechanisms. In the current investigation, a procedure for diagnosing different drilling mechanisms based on the analysis of the signals of acoustic emission is presented. According to the number of time domain acoustic emission parameters, using multi-variable methods of analysis is unavoidable. In this work, unsupervised pattern recognition analyses (fuzzy C-means clustering) associated with a principal component analysis are the tools that are used for the classification of the recorded acoustic emission data. After classification of acoustic emission events, the resulting classes are correlated with the different drilling stages and mechanisms. Acoustic emission signal analysis provides a better discrimination of drilling stages than mechanic-based analyses.

Poly-m-aramid nanofiber mats: Production for application as structural modifiers in CFRP laminates

Poly(m-phenylene isophtalamide) electrospun nanofibrous membranes were produced to be used as structural reinforcements for carbon fiber reinforced composites production. In order for the polymer to be electrospun, it needs however to be fully solubilized, so the addition of some salts is required to help disrupt the tight macromolecular packing based on intra- and inter-molecular hydrogen bonding. Such salts may also contribute to the electrospinnability of the overall solution, since the provide it with a higher conductivity, whatever the solvent might be. The salt haobwever stays in the final nanofibrous mat. The membranes containing the salt are also observed to be highly hygroscopic, with a water content up to 26%, in the presence of 20%wt LiCl in the nanofibrous mat. When those membranes were interleaved among prepregs to produce a laminates, the obtained composite displayed thermal properties comparable to those of a reference nanofiber-free composite, though the former showed also easier delaminat...

Electrospinning: A versatile technique for energy storage and sensor applications

The possibility to produce materials for energy storage and piezoelectric sensor applications through the electrospinning technique is here investigated. Electrospun lithium-ion battery separators, piezoelectric sensors are characterized and tested in order to exhibit the outstanding properties of such nanostructured materials which can be successfully implemented on the market.

Electrospun PVdF with enhanced piezoelectric behavior

This paper deals with electromechanical response of piezoelectric nanofibrous materials based on PVdF-TrFe co-polymer obtained by means of electrospinning. This technique, providing electrical poling and mechanical stretching during material processing, should increase the beta crystalline phase and thus piezoelectric effect. Two fiber patterns were analyzed, i.e. aligned and random. Experimental results showed that the electric response to mechanical vibrations, in the frequency range from 30 Hz to 200 Hz, is significantly larger for samples with aligned fiber pattern with respect to both commercial films and random fiber specimens. These latters, in fact, show lower beta phase with respect to the aligned-fiber samples.