Showing papers by "Simonetta Boria published in 2018"

Axial crushing of metal-composite hybrid tubes: experimental analysis

Abstract: In the automotive sector, special attention is paid to the study of the behavior of the structural components that make the car bodies. The continuous demands on the weight saving imply the car bodies to be assembled with components made in different materials and using different manufacturing processes. Considering the making of the sacrificial structures aimed to the energy absorption, composite materials are increasingly used to replace conventional metal materials. However, the use of composites is accompanied with a change in the type of deformation obtained during the impact phenomenon. Usually, with the conventional metal materials, the crushing behavior is a progressive buckling whereas the composite materials are characterized by a brittle fracture. The combination of the traditional metal materials with the composite ones can represent a good solution to obtain high levels of performance. In this context, the structural performance of metal-composite hybrid tubes subjected to quasi-static axial crushing is experimentally evaluated in this work. The specimens, with circular cross section, were obtained with tubes made in a fully thermoplastic composite internally reinforced with aluminum tubes. The composite material used were made in polypropylene both for the matrix and for the reinforcing fibers. This material has a good axial absorption capacity but irregular behavior during crushing. The addition of a conventional material as reinforcement allowed to increase the absorption capacity by ensuring a more progressive and controlled crush. The analysis was carried out by evaluating, for various geometric configurations, different parameters (mean load, average stress, specific energy, efficiency). The results, discussed in the work, showed how the energy absorption performance of a hybrid structure are higher than the sum of the performance of the single materials.

Green sandwich structures under impact: experimental vs numerical analysis

Abstract: Nowadays, there is a growing interest for the use and development of materials synthesized from renewable sources in the polymer composites manufacturing industry; this applies for both matrix and reinforcement components. In the present research, flax fibers embedded in an epoxy resin have been proposed as an environmentally friendly alternative to traditional synthetic composites. In addition, this material system has been combined with agglomerated cork as core material for the fabrication of sandwich structures. The objective of this article is to analyze the suitability of using such green sandwich structures in applications where energy absorption due to low velocity impacts can be of importance. Therefore green sandwich specimens with flax/epoxy face sheets and agglomerated cork as core have been manufactured and subjected to low velocity impacts at different energies. After the mechanical characterization of both skin and core material, a numerical model has been implemented through the non-linear dynamic code LS-DYNA. The FE analysis has been able to reproduce with a good level of accuracy the deformation mechanisms and the load-displacement diagrams for each energy level.

Energy absorption capability of laminated plates made of fully thermoplastic composite

Abstract: The behaviour of composites materials, made of synthetic fibres embedded in a thermoplastic resin, subjected to low velocity impacts, was largely studied in the past. However, in the last years, th...

Modelling and Control of a Self-Balancing Electric Motorcycle: Preliminary Results

Abstract: The development of electronic safety systems for two-wheeled vehicles has started with considerable delay with respect to their four-wheeled counterparts because motorcycle dynamics is more complex than four-wheeled vehicles one. In fact, in-plane and out-of-plane dynamics are strongly coupled in bikes. For these reasons the design of such a riderless control system has not been thoroughly investigated at low speed and without the use of steering torque in scientific literature. In this paper a riderless self-balancing two wheel drive electric motorcycle mathematical model - based on Lagrange's equations - with a sliding mode control strategy is put forward to cover this deficiency at low speed. Moreover, the study would find out whether at low speed driving front wheel torque could help vehicle stabilization when steering handlebar can not be actuated. For these reasons, in the proposed model the steering axis is locked over time and both front and rear wheel driving torques could be chosen as control inputs. The paper also presents a model validation with a multibody software.

Self-balancing two-wheel drive electric motorcycle modelling and control: preliminary results

Abstract: In four-wheeled vehicles, electronic stability control (ESC) was introduced in the recent past to improve passengers' safety in critical driving conditions. On the other hand, the development of electronic systems for two-wheeled vehicles has started with considerable delay with respect to their four-wheeled counterparts and the design of such a riderless control system has not been thoroughly investigated at low speed and without the use of steering torque. In this paper a riderless self-balancing two wheel drive electric motorcycle mathematical model - based on Lagrange's equations - and three control strategies are put forward to cover this deficiency at low speeds. Moreover, the study would find out whether front wheel torque could help vehicle stabilization in case of steering handlebar can not be actuated. For these reasons, in the proposed model the steering handlebar is locked over time and both front and rear wheel driving torques can be chosen as control inputs. The work would also investigate whether bike stabilization can be achieved in a small bounded area.