Carbon Fiber Reinforced Polymers (2nd Edition)

Dear Colleagues,

The current demand for lightweight and high-performance structures leads to increasing applications of carbon fiber reinforced polymers (CFRPs), made possible also by novel production methods, automation with repeatable quality, reduced cost of carbon fibers, out-of-autoclave processes like resin transfer molding and resin infusion technologies, re-use of waste fibers, development in preform technology, high-performance fast curing resins, etc.

Moreover, the diffusion of multi-material design, where metallic and non-metallic materials are used together to fabricate the same component, has driven the research towards efficient joining technologies of metals to carbon fiber-reinforced composites. More recently, the introduction of nanofillers into conventional carbon fiber reinforced polymers offers the opportunity for combining the potential benefits of nanoscale reinforcement with well-established fibrous composites to create multi-scale or hierarchical composites, characterized by enhanced structural and functional properties.

This Special Issue aims to present recent advances in carbon fiber reinforced polymers, focusing on the emerging trends both in carbon fibers and matrix development and in composite manufacturing technologies. Original articles and review papers will deal with the following themes without being limited to them:

• Processing and characterization of fibers (from low-cost precursors or re-use of waste or recycled carbon) and polymer matrices;
• Microstructure evaluation;
• Physical and structural characterization and testing;
• Optimization of properties and processes including simulation over different length-scales;
• Novel applications of carbon fibers reinforced polymers;
• Multiscale composites;
• Advanced manufacturing processes;
• Novel joining methods, cutting-edge joining and assembly processes;
• Applications of CFRPs in different fields, also including renewable energy, infrastructure, and transportation;
• Durability of carbon fiber reinforced polymers.
• recycling of carbon fibers and new end of use solutions
• innovative matrices for CFRPs
• life cycle assessment.

I kindly invite you to submit a manuscript for this Special Issue. Full papers, communications, and reviews are all welcome.

Dr. Francesca Lionetto
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Materials is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

• carbon fibers
• thermosetting resins
• thermoplastic matrix composites
• manufacturing technologies
• joining
• multiscale composites
• recycling
• sustainability

• Carbon Fiber Reinforced Polymers in Materials (32 articles)

Title: Investigation of Fiber-Matrix Interface Strength via Single Fiber Pull-out Test in 3-D Printed Thermoset Composites: A Simplified Methodology
Authors: Neyton Baltodano; Kaan Nuhoglu; Emrah Celik
Affiliation: Mechanical and Aerospace Engineering Department, University of Miami, Coral Gables, FL 33146, USA
Abstract: The emergence of additive manufacturing technologies for fiber-reinforced thermoset composites has greatly bolstered their utilization, particularly within the aerospace industry. However, the ability to precisely measure the interface strength between the fiber and thermoset matrix in additively manufactured composites has been constrained by the cumbersome nature of single fiber pullout experiments and the need for costly instrumentation. This research aims to introduce a novel methodology for conducting single-fiber pullout tests aimed at quantifying interface shear strength in additively manufactured thermoset composites. Our findings substantiate the viability of this approach, showcasing successful fiber embedding within composite test specimens and precise characterization of fiber pullout strength using a conventional mechanical testing system. Test outcomes reveal an average interfacial strength value of 2.4 MPa between carbon fiber and thermoset epoxy matrix, aligning with similar studies in existing literature. The outcome of this research study offers an affordable and versatile test methodology to revolutionize composite material fabrication for superior mechanical performance.

Title: Optimising Recycling Processes for Polyimine-Based Vitrimer Carbon Fibre-Reinforced Composites: A Comparative Study on Reinforcement Recovery and Material Properties
Authors: Ákos Pomázi; Dániel István Poór; Norbert Geier; Andrea Toldy
Affiliation: Department of Polymer Engineering, Faculty of Mechanical Engineering, Budapest University of Technology and Economics, Műegyetem rkp. 3., H-1111 Budapest, Hungary
Abstract: We investigated the recycling process of carbon fibre-reinforced polyimine vitrimer composites and compared the composites made from virgin and recycled fibres. The vitrimer matrix consisted of a two-component polyimine-type vitrimer system, and as reinforcing material, we used nonwoven felt and unidirectional carbon fibre reinforcement. Various diethylenetriamine (DETA) and xylene solvent ratios were examined to find the optimal dissolution conditions. The 20:80 DETA:xylene ratio provided efficient dissolution, and elevated temperature (80 °C) significantly accelerated the process. Scaling up to larger composite structures was demonstrated. Scanning electron microscopy (SEM) confirmed effective matrix removal with minimal residue on carbon fibre surfaces and good adhesion in recycled composites. The recycled nonwoven composite exhibited a decreased glass transition temperature due to residual solvents in the matrix, while the UD composite showed a slight increase. Dynamic mechanical analysis on the recycled composite showed increased storage modulus for nonwoven composites at room temperature, and greater resistance to deformation at elevated temperatures for UD composites. Interlaminar shear tests indicated slightly reduced adhesion strength in reprocessed composites. Overall, the study demonstrates the feasibility of recycling vitrimer composites, emphasising the need for further optimisation to ensure environmental and economic sustainability while mitigating residual solvent and matrix effects.