Non Monotonous Effects of Noncovalently Functionalized Graphene Addition on the Structure and Sound Absorption Properties of Polyvinylpyrrolidone (1300 kDa) Electrospun Mats

Graphene is an attractive component for high-performance stimuli-responsive or 'smart' materials, shape memory materials, photomechanical actuators, piezoelectric materials and flexible strain sensors. Nanocomposite fibres were produced by electrospinning high molecular weight Polyvinylpyrrolidone (PVP-1300 kDa) in the presence of noncovalently functionalised graphene obtained through tip sonication of graphite alcoholic suspensions in the presence of PVP (10 kDa). Bending instability of electrospun jet appears to progressively increase at low graphene concentrations with the result of greater fibre stretching that leads to lower fibre diameter and possibly conformational changes of PVP. Further increase of graphene content seams having the opposite effect leading to greater fibre diameter and Raman spectra similar to the pure PVP electrospun mats. All this has been interpreted on the basis of currently accepted model for bending instability of electrospun jets. The graphene addition does not lower the very high sound absorption coefficient, α, close to unity, of the electrospun PVP mats in the frequency range 200⁻800 Hz. The graphene addition affects, in a non-monotonous manner, the bell shaped curves of α versus frequency curves becoming sharper and moving to higher frequency at the lower graphene addition. The opposite is observed when the graphene content is further increased

Statistical Modelling of Comfort Preferences and Uncertainty in Subjective Evaluations of Aircraft Seat Comfort

Aircraft seat is rated as the most unsatisfying aspect of flying; under-standing the main factors impacting on passenger’s evaluations can provide a concrete opportunity for airlines to improve seat comfort and thus enhance pas-senger satisfaction and loyalty. Although there is a great deal of interest, the re-search on effective assessment strategies for subjective comfort is still underde-veloped. In this study a model-based approach for the analysis of subjective comfort data is suggested. The model adopted can be interpreted as a parametric version of the psychological process generating comfort ratings. The proposed approach is exploited through a case study concerning comfort assessment of aircraft seats designed for regional flights

Design and analysis of comparative experiments to assess the (dis-)comfort of aircraft seating

This paper focuses on the comparative assessment of comfort and discomfort (hereafter, (dis-)comfort) for air- craft seating. Subjective and objective data of seating (dis-)comfort were collected during an experiment in- volving 20 volunteers who tested 3 aircraft double-seats in upright and reclined position. In order to minimize experimental uncertainty due to well-known noise factors (i.e. patterns of discomfort during the work week and during the work day, order of evaluation, inter-individual differences), experimental trials were performed according to a crossover design. Statistical data analysis aimed mainly at investigating (dis-)comfort differences across seat conditions; gender-based differences in perceived discomfort on different body parts; effect of sitting duration on perceived discomfort on different body parts. The experimental results show that differences across seat conditions impacted differently on perceived discomfort depending on gender, body parts and sitting duration. No significant differences in perceived discomfort across gender were evident for the lightweight seat in both upright and reclined positions. On the contrary, for both baseline configurations, perceived discomfort at head and neck areas was higher for males than for females. For all seat conditions, participants experienced a significant worsening of perceived comfort over time at shoulders, back, sacrum and thighs and, in addition, at upper body area (i.e. neck, arm and forearm) and knees only for seats in reclined position

Statistics for Safety and Ergonomics in Design

The research aims at developing robust assessment and design strategies to support industrial engineers in the selection of optimal solutions for safety and ergonomics. It is realized through a successful integration of knowledge in experimental statistics, biomechanical modelling and advanced engineering design. The robust assessment and design strategies have been applied to the context of aircraft and automotive seat design, respectively. They rely on both physical and VR simulated experiments. In the former case, seat comfort is assessed via subjective perceptions and postural responses to seat exposures measured via interface pressure maps; whereas in simulated experiments, ergonomic evaluations are based on postural indexes based on joint angles. The adoption of the proposed strategies has provided interesting results in deepening the knowledge on seat ergonomics with focus on three main critical aspects: 1) differences in postural responses to seated exposures; 2) the impact of gender-based postural differences on objective measures of seat discomfort; 3) the usefulness of postural measurements (i.e. seat-interface pressure and joint angles) in finding significant differences in seat designs across different target populations of users

INNOVATIVE SOUNDPROOFING MATERIALS THROUGH ELECTROSPINNING

Water resistant sound absorbers with reduced thickness and excellent sound-absorption properties in the low and medium frequency range, that pass the fire tests (Federal Aviation Regulation FAR 25.853 and FAR 25.855) which are mandatory in many engineering areas, were produced through an eco-friendly electrospinning process. It is shown that the produced PVP/silica samples may have better sound absorption properties, in the lower frequency range, than materials, of the same thickness, that are usually used in both the civil and aerospace engineering fields. Preliminary results suggest that the mats have potential application for thermal insulation