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Impact events are common in every-day life and can severely compromise the integrity and reliability of high-performing structures such as sandwich composites that are widespread in different industrial fields. Considering their susceptibility to impact damage and the environmental issues connected with their exploitation of synthetic materials, the present work aims to propose a bio-based sandwich structure with an agglomerated cork core and a flax/basalt intraply fabric as skin reinforcement and to address its main weakness, i.e. its impact response. In-service properties are influenced by temperature, therefore the effect of high (60 °C) and low (−40°C) temperatures on the impact behavior of the proposed structures was investigated and a suitable comparison with traditional (polyvinyl chloride) (PVC) foams was provided. The results highlighted the embrittlement effect of decreasing temperature on the impact resistance of the sole cores and skins and of the overall structures with a reduction in the perforation energy that shifted, in the last case, from 50–60 J at – 40 °C up to more than 180 J at 60 °C. A maleic anhydride coupling agent in the skins hindered fundamental energy dissipation mechanisms such as matrix plasticization, determining a reduction in the perforation threshold of all composites. In particular, neat polypropylene (PP) skins displayed a perforation energy of 20 J higher than compatibilized (PPC) ones at 60 °C, while agglomerated cork sandwich structures at 60 °C were characterized by a perforation threshold higher of at least 50 J.
Claudia Sergi; Fabrizio Sarasini; Pietro Russo; Libera Vitiello; Enrique Barbero; Sonia Sanchez-Saez; Jacopo Tirillò. Effect of temperature on the low-velocity impact response of environmentally friendly cork sandwich structures. Journal of Sandwich Structures & Materials 2021, 1 .
AMA StyleClaudia Sergi, Fabrizio Sarasini, Pietro Russo, Libera Vitiello, Enrique Barbero, Sonia Sanchez-Saez, Jacopo Tirillò. Effect of temperature on the low-velocity impact response of environmentally friendly cork sandwich structures. Journal of Sandwich Structures & Materials. 2021; ():1.
Chicago/Turabian StyleClaudia Sergi; Fabrizio Sarasini; Pietro Russo; Libera Vitiello; Enrique Barbero; Sonia Sanchez-Saez; Jacopo Tirillò. 2021. "Effect of temperature on the low-velocity impact response of environmentally friendly cork sandwich structures." Journal of Sandwich Structures & Materials , no. : 1.
Low-velocity impacts can severely jeopardize the structural reliability of polymer composites. In view of this, the present work provides a thorough overview of the impact response of polypropylene (PP) composites reinforced with an ecofriendly intraply flax/basalt hybrid fabric, assessing the effect of different parameters: energy level, temperature, and number of impacts. Indeed, high-energy single impacts are as dangerous as low-energy repeated impacts for the structural integrity of laminates. Moreover, considering the poor interfacial adhesion between hydrophobic polyolefin matrices and hydrophilic vegetable fibers, the effect of a maleic anhydride coupling agent was evaluated. A detrimental effect of coupling agent on composites impact response was observed, determining a reduction of the impact life (impacts to failure from 83 to 63 at 10 J and from 30 to 9 at 15 J) because several energy dissipation mechanisms were prevented. Decreasing temperatures (−40°C) caused an embrittlement effect on neat PP composites with an increase between 7.3% and 20.3% of maximum force and a decrease between 7.5% and 10.9% of maximum displacement, whereas increasing temperatures (80°C) led to a softening of compatibilized composites with a decrease between 13.8% and 27.5% of maximum force and an increase between 28.1% and 34.4% of maximum displacement.
Luca Ferrante; Claudia Sergi; Jacopo Tirillò; Pietro Russo; Andrea Calzolari; Fabrizio Sarasini. Temperature effect on the single and repeated impact responses of intraply flax/basalt hybrid polypropylene composites. Polymer Composites 2021, 1 .
AMA StyleLuca Ferrante, Claudia Sergi, Jacopo Tirillò, Pietro Russo, Andrea Calzolari, Fabrizio Sarasini. Temperature effect on the single and repeated impact responses of intraply flax/basalt hybrid polypropylene composites. Polymer Composites. 2021; ():1.
Chicago/Turabian StyleLuca Ferrante; Claudia Sergi; Jacopo Tirillò; Pietro Russo; Andrea Calzolari; Fabrizio Sarasini. 2021. "Temperature effect on the single and repeated impact responses of intraply flax/basalt hybrid polypropylene composites." Polymer Composites , no. : 1.
Sandwich structures are widespread in all the industrial applications where a high stiffness-to-weight ratio is required. Despite the unique bending performance, they feature two major drawbacks: the massive exploitation of synthetic materials and a strong susceptibility to impact damage. This work addresses both problems, investigating the puncture impact response of bio-based sandwich structures with an agglomerated cork core and intraply flax/basalt hybrid skins. A preliminary campaign of impacts was performed on three agglomerated corks with different densities and on three traditional polyvinyl(chloride) foams with comparable densities. Based upon the results obtained, one agglomerated cork (NL25) and one PVC foam (HP130) were selected to realize a finite element analysis (FEA) on the sole core and to produce the whole sandwich composites. FEA results show a good agreement with experimental ones ensuring a reliable prediction of cores dynamic response. The tests performed on sandwich structures proved the feasibility of agglomerated cork as an effective core, able to provide an improved damage tolerance to the structure. NL25 sandwiches impacted at 20-30J showed a permanent indentation 60-67% lower than HP130 ones. The coupling agent in skins has a detrimental effect reducing composites perforation threshold from 80 to 60J.
Claudia Sergi; Simonetta Boria; Fabrizio Sarasini; Pietro Russo; Libera Vitiello; Enrique Barbero; Sonia Sanchez-Saez; Jacopo Tirillò. Experimental and finite element analysis of the impact response of agglomerated cork and its intraply hybrid flax/basalt sandwich structures. Composite Structures 2021, 272, 114210 .
AMA StyleClaudia Sergi, Simonetta Boria, Fabrizio Sarasini, Pietro Russo, Libera Vitiello, Enrique Barbero, Sonia Sanchez-Saez, Jacopo Tirillò. Experimental and finite element analysis of the impact response of agglomerated cork and its intraply hybrid flax/basalt sandwich structures. Composite Structures. 2021; 272 ():114210.
Chicago/Turabian StyleClaudia Sergi; Simonetta Boria; Fabrizio Sarasini; Pietro Russo; Libera Vitiello; Enrique Barbero; Sonia Sanchez-Saez; Jacopo Tirillò. 2021. "Experimental and finite element analysis of the impact response of agglomerated cork and its intraply hybrid flax/basalt sandwich structures." Composite Structures 272, no. : 114210.
Thanks to the unique flexural properties, sandwich composites are considered as irreplaceable structures in many industrial fields, but their susceptibility to impact events is still a considerable drawback that undermines their structural integrity determining a reduction of their load-bearing capabilities. Considering that the core material plays the major role to distance the skins, the knowledge of its multiple-impacts response becomes a key design parameter in order to ensure a long-term stability to the structure. In view of this, the present work addresses the multiple-impacts behavior in dynamic compression and puncture impact conditions of bio-based agglomerated cork cores taking into account the effect of density and providing a meaningful comparison with more traditional petroleum-based foams. Despite the inherently higher mechanical properties of the PVC (polyvinyl chloride) foams, agglomerated cork demonstrated to provide a higher dimensional stability to the structure after repeated impacts thanks to its unique microstructure. With a reduction lower than 25% of its initial height after 10 impacts, agglomerated cork NL25 proved to be an exceptional alternative to the common HP130 foam, which undergoes a halving of its initial height after only 3 impacts, to obtain a more eco-friendly and performing sandwich composite.
Claudia Sergi; Fabrizio Sarasini; Enrique Barbero; Sonia Sanchez-Saez; Jacopo Tirillò. Assessment of agglomerated corks and PVC foams cores crashworthiness under multiple-impact events in different loading conditions. Polymer Testing 2021, 96, 107061 .
AMA StyleClaudia Sergi, Fabrizio Sarasini, Enrique Barbero, Sonia Sanchez-Saez, Jacopo Tirillò. Assessment of agglomerated corks and PVC foams cores crashworthiness under multiple-impact events in different loading conditions. Polymer Testing. 2021; 96 ():107061.
Chicago/Turabian StyleClaudia Sergi; Fabrizio Sarasini; Enrique Barbero; Sonia Sanchez-Saez; Jacopo Tirillò. 2021. "Assessment of agglomerated corks and PVC foams cores crashworthiness under multiple-impact events in different loading conditions." Polymer Testing 96, no. : 107061.
Nowadays, infrared thermography, as a widely used non-destructive testing method, is increasingly studied for impact evaluation of composite structures. Sparse pattern extraction is attracting increasing attention as an advanced post-processing method. In this paper, an enhanced sparse pattern extraction framework is presented for thermographic sequence processing and defect detection. This framework adapts cropping operator and typical component extraction as a preprocessing step to reduce the dimensions of raw data and applies sparse pattern extraction algorithms to enhance the contrast on the defect area. Different cases are studied involving several defects in four basalt-carbon hybrid fiber-reinforced polymer composite laminates. Finally, comparative analysis with intensity distribution is carried out to verify the effectiveness of contrast enhancement using this framework.
Jue Hu; Hai Zhang; Stefano Sfarra; Claudia Sergi; Stefano Perilli; Clemente Ibarra-Castanedo; Guiyun Tian; Xavier Maldague. Enhanced Infrared Sparse Pattern Extraction and Usage for Impact Evaluation of Basalt-Carbon Hybrid Composites by Pulsed Thermography. Sensors 2020, 20, 7159 .
AMA StyleJue Hu, Hai Zhang, Stefano Sfarra, Claudia Sergi, Stefano Perilli, Clemente Ibarra-Castanedo, Guiyun Tian, Xavier Maldague. Enhanced Infrared Sparse Pattern Extraction and Usage for Impact Evaluation of Basalt-Carbon Hybrid Composites by Pulsed Thermography. Sensors. 2020; 20 (24):7159.
Chicago/Turabian StyleJue Hu; Hai Zhang; Stefano Sfarra; Claudia Sergi; Stefano Perilli; Clemente Ibarra-Castanedo; Guiyun Tian; Xavier Maldague. 2020. "Enhanced Infrared Sparse Pattern Extraction and Usage for Impact Evaluation of Basalt-Carbon Hybrid Composites by Pulsed Thermography." Sensors 20, no. 24: 7159.
The remarkable flexural properties of sandwich structures hinge on the selection of performing core materials with suitable out of plane mechanical properties, i.e. compressive ones. For this reason, this work compares the compressive behaviour of a synthetic foam (polyvinyl chloride) and an environmentally friendly agglomerated cork as a function of density, strain rate, temperature and anisotropy. The strain rate sensitivity of these cellular materials was investigated in a wide range of velocity conditions by using drop weight tower and Split Hopkinson Pressure Bar dynamic compression tests. The results highlighted a remarkable strain rate sensitivity of both materials because of their viscoelastic nature and, in particular, an increase in compressive properties with increasing strain rate. This increment was more pronounced in the medium–high strain rate range than in the low-medium one. An embrittlement effect with decreasing temperature was detected, which compromises core materials crashworthiness determining a reduction of the percentage absorbed energy. Despite a remarkable anisotropy induced by the production processes, this work confirms the feasibility of agglomerated cork as a sustainable alternative to petroleum-based cellular core materials especially in consideration of the significant recovery capabilities that ensure a higher dimensional stability of the sandwich structure.
Claudia Sergi; Fabrizio Sarasini; Jacopo Tirillò; Enrique Barbero; Sonia Sanchez-Saez; Marco Sasso; Edoardo Mancini. Temperature, strain rate and anisotropy effects on compressive response of natural and synthetic cellular core materials. Composite Structures 2020, 260, 113268 .
AMA StyleClaudia Sergi, Fabrizio Sarasini, Jacopo Tirillò, Enrique Barbero, Sonia Sanchez-Saez, Marco Sasso, Edoardo Mancini. Temperature, strain rate and anisotropy effects on compressive response of natural and synthetic cellular core materials. Composite Structures. 2020; 260 ():113268.
Chicago/Turabian StyleClaudia Sergi; Fabrizio Sarasini; Jacopo Tirillò; Enrique Barbero; Sonia Sanchez-Saez; Marco Sasso; Edoardo Mancini. 2020. "Temperature, strain rate and anisotropy effects on compressive response of natural and synthetic cellular core materials." Composite Structures 260, no. : 113268.
This study deals with the development and optimization of hybrid composites integrating microcrystalline cellulose and short basalt fibers in a polypropylene (PP) matrix to maximize the mechanical properties of resulting composites. To this aim, the effects of two different coupling agents, endowed with maleic anhydride (MA-g(grafted)-PP) and acrylic acid (AA-g-PP) functionalities, on the composite properties were investigated as a function of their amount. Tensile, flexural, impact and heat deflection temperature tests highlighted the lower reactivity and effectiveness of AA-g-PP, regardless of reinforcement type. Hybrid formulations with basalt/cellulose (15/15) and with 5 wt. % of MA-g-PP displayed remarkable increases in tensile strength and modulus, flexural strength and modulus, and notched Charpy impact strength, of 45% and 284%, 97% and 263%, and 13%, in comparison with neat PP, respectively. At the same time, the thermo-mechanical stability was enhanced by 65% compared to neat PP. The results of this study, if compared with the ones available in the literature, reveal the ability of such a combination of reinforcements to provide materials suitable for automotive applications with environmental benefits.
Claudia Sergi; Francesca Sbardella; Matteo Lilli; Jacopo Tirillò; Andrea Calzolari; Fabrizio Sarasini. Hybrid Cellulose–Basalt Polypropylene Composites with Enhanced Compatibility: The Role of Coupling Agent. Molecules 2020, 25, 4384 .
AMA StyleClaudia Sergi, Francesca Sbardella, Matteo Lilli, Jacopo Tirillò, Andrea Calzolari, Fabrizio Sarasini. Hybrid Cellulose–Basalt Polypropylene Composites with Enhanced Compatibility: The Role of Coupling Agent. Molecules. 2020; 25 (19):4384.
Chicago/Turabian StyleClaudia Sergi; Francesca Sbardella; Matteo Lilli; Jacopo Tirillò; Andrea Calzolari; Fabrizio Sarasini. 2020. "Hybrid Cellulose–Basalt Polypropylene Composites with Enhanced Compatibility: The Role of Coupling Agent." Molecules 25, no. 19: 4384.
Considering the major role played by sandwich structures in many fields where high stiffness-to-weight ratio is required, the selection of a suitable core material is of paramount importance. In order to face the environmental problems related to waste disposal, the selection of an eco-friendly core material is now included in the design criteria of sandwich structures. Agglomerated cork is recognized as a good solution that combines satisfactory mechanical performances and eco-sustainability. Many research studies individually addressed cork’s morphological, thermal, and mechanical features without providing a comprehensive overview of the relationships that exist between them. In this work, the investigation of the peculiar cork morphology allowed learning more about its good insulation capacity and its impressive recovery capability. The use of dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA) clarified the influence of temperature on both flexural and compressive performances. The effect of testing parameters such as temperature and speed on agglomerated cork properties was validated through statistical analysis. Moreover, to highlight agglomerated cork advantages and drawbacks, the work provides also a comparison with more traditional polyvinylchloride (PVC) foams commonly used in industrial applications.
Claudia Sergi; Jacopo Tirillò; Fabrizio Sarasini; Enrique Barbero Pozuelo; Sonia Sanchez Saez; Christoph Burgstaller. The Potential of Agglomerated Cork for Sandwich Structures: A Systematic Investigation of Physical, Thermal, and Mechanical Properties. Polymers 2019, 11, 2118 .
AMA StyleClaudia Sergi, Jacopo Tirillò, Fabrizio Sarasini, Enrique Barbero Pozuelo, Sonia Sanchez Saez, Christoph Burgstaller. The Potential of Agglomerated Cork for Sandwich Structures: A Systematic Investigation of Physical, Thermal, and Mechanical Properties. Polymers. 2019; 11 (12):2118.
Chicago/Turabian StyleClaudia Sergi; Jacopo Tirillò; Fabrizio Sarasini; Enrique Barbero Pozuelo; Sonia Sanchez Saez; Christoph Burgstaller. 2019. "The Potential of Agglomerated Cork for Sandwich Structures: A Systematic Investigation of Physical, Thermal, and Mechanical Properties." Polymers 11, no. 12: 2118.
The Achilles heel of thermoplastic natural fibre composites is their limited durability. The environmental degradation of the mechanical properties of hemp and hemp/basalt hybrid-reinforced high-density polyethylene (HDPE) composites has been investigated with a special focus on the effects of water ageing and accelerated ageing, including hygrothermal and UV radiation. Modification of the matrix was carried out using a maleic anhydride high-density polyethylene copolymer (MAPE) as a compatibilizer. Hybridization of hemp fibres with basalt fibres and the incorporation of MAPE were found to significantly decrease the water uptake (up to 75%) and increase the retention of mechanical properties after accelerated ageing. Secondary crystallization phenomena occurring in the composites, as confirmed by differential scanning calorimetry (DSC) analysis, were able to counteract the severe combined effects of hygrothermal stress and UV radiation, with the exception of hemp-fibre composites where permanent damage to the fibres occurred, with 2% and 20% reduction in tensile strength and modulus, respectively, for a 30 wt % hemp fibre-reinforced HDPE.
Claudia Sergi; Jacopo Tirillò; Maria Carolina Seghini; Fabrizio Sarasini; Vincenzo Fiore; Tommaso Scalici. Durability of Basalt/Hemp Hybrid Thermoplastic Composites. Polymers 2019, 11, 603 .
AMA StyleClaudia Sergi, Jacopo Tirillò, Maria Carolina Seghini, Fabrizio Sarasini, Vincenzo Fiore, Tommaso Scalici. Durability of Basalt/Hemp Hybrid Thermoplastic Composites. Polymers. 2019; 11 (4):603.
Chicago/Turabian StyleClaudia Sergi; Jacopo Tirillò; Maria Carolina Seghini; Fabrizio Sarasini; Vincenzo Fiore; Tommaso Scalici. 2019. "Durability of Basalt/Hemp Hybrid Thermoplastic Composites." Polymers 11, no. 4: 603.
In an attempt to increase the low-velocity impact response of natural fiber composites, a new hybrid intraply woven fabric based on flax and basalt fibers has been used to manufacture laminates with both thermoplastic and thermoset matrices. The matrix type (epoxy or polypropylene (PP) with or without a maleated coupling agent) significantly affected the absorbed energy and the damage mechanisms. The absorbed energy at perforation for PP-based composites was 90% and 50% higher than that of epoxy and compatibilized PP composites, respectively. The hybrid fiber architecture counteracted the influence of low transverse strength of flax fibers on impact response, irrespective of the matrix type. In thermoplastic laminates, the matrix plasticization delayed the onset of major damage during impact and allowed a better balance of quasi-static properties, energy absorption, peak force, and perforation energy compared to epoxy-based composites.
Fabrizio Sarasini; Jacopo Tirillò; Luca Ferrante; Claudia Sergi; Pietro Russo; Giorgio Simeoli; Francesca Cimino; Maria Rosaria Ricciardi; Vincenza Antonucci. Quasi-Static and Low-Velocity Impact Behavior of Intraply Hybrid Flax/Basalt Composites. Fibers 2019, 7, 26 .
AMA StyleFabrizio Sarasini, Jacopo Tirillò, Luca Ferrante, Claudia Sergi, Pietro Russo, Giorgio Simeoli, Francesca Cimino, Maria Rosaria Ricciardi, Vincenza Antonucci. Quasi-Static and Low-Velocity Impact Behavior of Intraply Hybrid Flax/Basalt Composites. Fibers. 2019; 7 (3):26.
Chicago/Turabian StyleFabrizio Sarasini; Jacopo Tirillò; Luca Ferrante; Claudia Sergi; Pietro Russo; Giorgio Simeoli; Francesca Cimino; Maria Rosaria Ricciardi; Vincenza Antonucci. 2019. "Quasi-Static and Low-Velocity Impact Behavior of Intraply Hybrid Flax/Basalt Composites." Fibers 7, no. 3: 26.