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Fiber Reinforced Thermoplastic Composites: Processing/Structure/Performance Inter-relationships

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A special issue of Polymers (ISSN 2073-4360). This special issue belongs to the section "Polymer Composites and Nanocomposites".

Deadline for manuscript submissions: closed (29 February 2024) | Viewed by 28703

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Dr. Abderrahmane Ayadi

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Centre for Materials and Processes, Institut Mines-Télécom, IMT Nord Europe, Douai, France
Interests: numerical and experimental mechanics applied to forming processes of thermoplastic materials; processing–structure–performance relationships; thermoplastic composites manufacturing; image-based structural analysis; mechanical properties of thermoplastic matrix composites; finite element analysis; numerical homogenization for composite materials analysis; structural health monitoring; kinematic full-field measurements
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Prof. Dr. Patricia Krawczak

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IMT Nord Europe, Institut Mines Télécom, University of Lille, Centre for Materials and Processes, F-59653 Villeneuve d’Ascq, France
Interests: advanced composites; polymer composites; composites manufacturing and properties; polymer processing and properties; advanced manufacturing; additive manufacturing and 3D printing; structural health monitoring; recycling; bio-based polymers and composites
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Chung Hae Park

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Co-Guest Editor

IMT Nord Europe, Institut Mines-Télécom, Univ. Lille, Centre for Materials and Processes, F-59000 Lille, France
Interests: advanced composites; polymer composites; composites manufacturing and properties; advanced manufacturing; numerical simulation and modeling
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The search for eco-responsible solutions is attracting the interest of end-use industries toward fiber-reinforced thermoplastic composites (FRT). However, numerous challenges are still limiting the development of efficient optimization approaches of FRT composites for structural parts. Such challenges emanate from complexities related to (i) the multiscale structure of reinforcement and (ii) multiphysical phenomena governing the use of thermoplastics within liquid resin transfer processes. In this context, the development of new interdisciplinary approaches for better understanding processing–structure–performance inter-relationships is encouraged to alleviate challenges related to (i) smart manufacturing, (ii) advanced microstructure characterization, (iii) numerical modeling of physical phenomena or (iv) simulation approaches. The current Special Issue aims to explore recent developments focused on FRT composites falling within the scope of the aforementioned topics. Multidisciplinary articles and review papers are encouraged to cover emerging topics such as artificial intelligence applied to manufacturing, data-driven simulations, multimodal microstructure characterization, hierarchical FRT composites, mechanical metamaterials, etc.

Dr. Abderrahmane Ayadi
Prof. Dr. Patricia Krawczak
Prof. Dr. Chung Hae Park
Guest Editors

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Keywords

high-performance thermoplastic composites
hierarchical fiber-reinforced composites
mechanical metamaterials
ultra-lightweight composites
one-shot short cycle time manufacturing processes
zero-defect manufacturing
low-cost manufacturing technologies
non-destructive image-based microstructure characterization
process-induced flaws prediction
numerical modeling and simulation
image-based full-scale simulations
data-driven simulations
artificial intelligence-based manufacturing

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Fiber Reinforced Thermoplastic Composites: Processing/Structure/Performance Inter-relationships, 2nd Edition in Polymers (1 article)

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28 pages, 21028 KiB

Open AccessArticle

Assessing Intra-Bundle Impregnation in Partially Impregnated Glass Fiber-Reinforced Polypropylene Composites Using a 2D Extended-Field and Multimodal Imaging Approach

by Sujith Sidlipura, Abderrahmane Ayadi and Mylène Lagardère Deléglise

Polymers 2024, 16(15), 2171; https://doi.org/10.3390/polym16152171 - 30 Jul 2024

Viewed by 1309

Abstract

This study evaluates multimodal imaging for characterizing microstructures in partially impregnated thermoplastic matrix composites made of woven glass fiber and polypropylene. The research quantifies the impregnation degree of fiber bundles within composite plates manufactured through a simplified compression resin transfer molding process. For comparison, a reference plate was produced using compression molding of film stacks. An original surface polishing procedure was introduced to minimize surface defects while polishing partially impregnated samples. Extended-field 2D imaging techniques, including polarized light, fluorescence, and scanning electron microscopies, were used to generate images of the same microstructure at fiber-scale resolutions throughout the plate. Post-processing workflows at the macro-scale involved stitching, rigid registration, and pixel classification of FM and SEM images. Meso-scale workflows focused on 0°-oriented fiber bundles extracted from extended-field images to conduct quantitative analyses of glass fiber and porosity area fractions. A one-way ANOVA analysis confirmed the reliability of the statistical data within the 95% confidence interval. Porosity quantification based on the conducted multimodal approach indicated the sensitivity of the impregnation degree according to the layer distance from the pool of melted polypropylene in the context of simplified-CRTM. The findings underscore the potential of multimodal imaging for quantitative analysis in composite material production. Full article

(This article belongs to the Special Issue Fiber Reinforced Thermoplastic Composites: Processing/Structure/Performance Inter-relationships)

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16 pages, 4126 KiB

Open AccessArticle

Low-Density and High-Performance Fiber-Reinforced PP/POE Composite Foam via Irradiation Crosslinking

by Hongfu Li, Tianyu Wang, Changwei Cui, Yuxi Mu and Kangmin Niu

Polymers 2024, 16(6), 745; https://doi.org/10.3390/polym16060745 - 8 Mar 2024

Cited by 2 | Viewed by 1870

Abstract

This study addresses the challenge of achieving foam with a high expansion ratio and poor mechanical properties, caused by the low melt viscosity of semi-crystalline polypropylene (PP). We systematically employ a modification approach involving blending PP with polyolefin elastomers (POE), irradiation crosslinking, and fiber reinforcement to prepare fiber-reinforced crosslinked PP/POE composite foam. Through optimization and characterization of material composition and processing conditions, the obtained fiber-reinforced crosslinked PP/POE composite foam exhibits both low density and high performance. Specifically, at a crosslinking degree of 12%, the expansion ratio reaches 16 times its original value, and a foam density of 0.057 g/cm³ is reduced by 36% compared to the non-crosslinked PP/POE system with a density of 0.089 g/cm³. The density of the short-carbon-fiber-reinforced crosslinked sCF/PP/POE composite foam is comparable to that of the crosslinked PP/POE system, but the tensile strength reaches 0.69 MPa, representing a 200% increase over the crosslinked PP/POE system and a 41% increase over the non-crosslinked PP/POE system. Simultaneously, it exhibits excellent impact strength, tear resistance, and low heat shrinkage. Irradiation crosslinking is beneficial for enhancing the melt strength and resistance to high temperature thermal shrinkage of PP/POE foam, while fiber reinforcement contributes significantly to improving mechanical properties. These achieve a good complementary effect in low-density and high-performance PP foam modification. Full article

(This article belongs to the Special Issue Fiber Reinforced Thermoplastic Composites: Processing/Structure/Performance Inter-relationships)

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10 pages, 1491 KiB

Open AccessArticle

Processing Method and Performance Evaluation of Flame-Retardant Corrugated Sandwich Panel

by Yiliang Sun, Jingwen Li and Boming Zhang

Polymers 2024, 16(5), 696; https://doi.org/10.3390/polym16050696 - 4 Mar 2024

Viewed by 1490

Abstract

In this study, in order to expand the engineering application range of thermoplastic corrugated sheets, flame-retardant thermoplastic corrugated sheets were prepared by the thermoplastic molding method. Based on our previous research results, we prepared flame-retardant prepreg tapes with the flame retardant addition accounting for 15%, 20%, and 25% of the resin matrix. Then, we prepared flame-retardant thermoplastic corrugated sandwich panels with corresponding flame retardant addition amounts. The limiting oxygen index test, vertical combustion test, cone calorimetry test, and mechanical property test were carried out on each group of samples and control group samples. The results showed that when the flame retardant was added at 25%, the flame retardant level could reach the V0 level. Compared with the control group, the flexural strength and flexural modulus decreased by 2.6%, 14.1%, and 19.9% and 7.3%, 16.1%, and 21.9%, respectively. When the amount of flame retardant was 15%, 20%, and 25%, respectively, the total heat release decreased by 16.3%, 23.5%, and 34.1%, and the maximum heat release rate decreased by 12.5%, 32.4%, and 37.4%, respectively. Full article

(This article belongs to the Special Issue Fiber Reinforced Thermoplastic Composites: Processing/Structure/Performance Inter-relationships)

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21 pages, 6773 KiB

Open AccessArticle

Using Heating and Cooling Presses in Combination to Optimize the Consolidation Process of Polycarbonate-Based Unidirectional Thermoplastic Composite Tapes

by Janos Birtha, Eva Kobler, Christian Marschik, Klaus Straka and Georg Steinbichler

Polymers 2023, 15(23), 4500; https://doi.org/10.3390/polym15234500 - 23 Nov 2023

Cited by 4 | Viewed by 1743

Abstract

The main aim of this work was to optimize the consolidation of unidirectional fiber-reinforced thermoplastic composite tapes made of polycarbonate and carbon fibers using a heating press and a cooling press in combination. Two comprehensive studies were carried out to investigate the impact of process settings and conditions on the quality of the consolidated parts. The initial screening study provided valuable insights that informed the design of the second study, in which the experimental design was expanded and various modifications, including the implementation of a frame tool, were introduced. The second study demonstrated that the modifications in combination with a high heating press temperature and elevated heating and cooling pressures successfully achieved the desired goals: the desired thickness (2 mm), improved bonding strength (23% increase), and reduced void content (down to 4.64%) in the consolidated parts. Full article

(This article belongs to the Special Issue Fiber Reinforced Thermoplastic Composites: Processing/Structure/Performance Inter-relationships)

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14 pages, 7149 KiB

Open AccessArticle

Cashew Nutshells: A Promising Filler for 3D Printing Filaments

by María José Paternina Reyes, Jimy Unfried Silgado, Juan Felipe Santa Marín, Henry Alonso Colorado Lopera and Luis Armando Espitia Sanjuán

Polymers 2023, 15(22), 4347; https://doi.org/10.3390/polym15224347 - 7 Nov 2023

Cited by 7 | Viewed by 2563

Abstract

Cashew nutshells from the northern region of Colombia were prepared to assess their potential use as a filler in polymer matrix filaments for 3D printing. After drying and grinding processes, cashew nutshells were characterized using scanning electron microscopy (SEM), attenuated total reflectance Fourier-transform infrared (ATR-FTIR), and thermogravimetric analyses (TGA). Three different filaments were fabricated from polylactic acid pellets and cashew nutshell particles at 0.5, 1.0, and 2.0 weight percentages using a single-screw extruder. Subsequently, single-filament tensile tests were carried out on them. SEM images showed rough and porous particles composed of an arrangement of cellulose microfibrils embedded in a hemicellulose and lignin matrix, the typical microstructure reported for natural fibers. These characteristics observed in the particles are favorable for improving filler–matrix adhesion in polymer matrix composites. In addition, their low density of 0.337 g/cm³ makes them attractive for lightweight applications. ATR-FTIR spectra exhibited specific functional groups attributed to hemicellulose, cellulose, and lignin, as well as a possible transformation to crystalline cellulose during drying treatment. According to TGA analyses, the thermal stability of cashew nutshell particles is around 320 °C. The three polylactic acid–cashew nutshell particle filaments prepared in this work showed higher tensile strength and elongation at break when compared to polylactic acid filament. The characteristics displayed by these cashew nutshell particles make them a promising filler for 3D printing filaments. Full article

(This article belongs to the Special Issue Fiber Reinforced Thermoplastic Composites: Processing/Structure/Performance Inter-relationships)

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14 pages, 3213 KiB

Open AccessArticle

Effect of the Chemical Properties of Silane Coupling Agents on Interfacial Bonding Strength with Thermoplastics in the Resizing of Recycled Carbon Fibers

by Hyunkyung Lee, Minsu Kim, Gyungha Kim and Daeup Kim

Polymers 2023, 15(21), 4273; https://doi.org/10.3390/polym15214273 - 30 Oct 2023

Cited by 5 | Viewed by 2176

Abstract

Upcycling recycled carbon fibers recovered from waste carbon composites can reduce the price of carbon fibers while improving disposal-related environmental problems. This study assessed and characterized recycled carbon fibers subjected to sizing treatment using N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (APS) chemically coordinated with polyamide 6 (PA6) and polypropylene (PP) resins. Sizing treatment with 1 wt.% APS for 10 s yielded O=C-O on the surface of the carbon fiber, and the -SiOH in the APS underwent a dehydration–condensation reaction that converted O=C-O (lactone groups) into bonds of C-O (hydroxyl groups) and C=O (carbonyl groups). The effects of C-O and C=O on the interfacial bonding force increased to a maximum, resulting in an oxygen-to-carbon ratio (O/C) of 0.26. The polar/surface energy ratio showed the highest value of 32.29% at 10 s, and the interfacial bonding force showed the maximum value of 32 MPa at 10 s, which is about 15% better than that of commercial carbon fiber (PA6-based condition). In 10 s resizing treatments with 0.5 wt.% 3-methacryloxypropyltrimethoxysilane (MPS), C-O, C=O, and O=C-O underwent a dehydration–condensation reaction with -SiOH, which broke the bonds between carbon and oxygen and introduced a methacrylate group (H2C=C(CH₃)CO₂H), resulting in a significant increase in C-O and C=O, with an O/C of 0.51. The polar/surface free energy ratio was about 38% at 10 s, with the interfacial bonding force increasing to 27% compared to commercial carbon fiber (PP-based conditions). MPS exhibited a superior interfacial shear strength improvement, two times higher than that of APS, with excellent coordination with PP resin and commercial carbon fiber, although the interfacial bonding strength of the PP resin was significantly lower. Full article

(This article belongs to the Special Issue Fiber Reinforced Thermoplastic Composites: Processing/Structure/Performance Inter-relationships)

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19 pages, 4620 KiB

Open AccessArticle

Short Flax Fibres and Shives as Reinforcements in Bio Composites: A Numerical and Experimental Study on the Mechanical Properties

by Sofie Verstraete, Bart Buffel, Dharmjeet Madhav, Stijn Debruyne and Frederik Desplentere

Polymers 2023, 15(10), 2239; https://doi.org/10.3390/polym15102239 - 9 May 2023

Cited by 7 | Viewed by 2714

Abstract

The complete flax stem, which contains shives and technical fibres, has the potential to reduce the cost, energy consumption and environmental impacts of the composite production process if used directly as reinforcement in a polymer matrix. Earlier studies have utilised flax stem as reinforcement in non-bio-based and non-biodegradable matrices not completely exploiting the bio-sourced and biodegradable nature of flax. We investigated the potential of using flax stem as reinforcement in a polylactic acid (PLA) matrix to produce a lightweight, fully bio-based composite with improved mechanical properties. Furthermore, we developed a mathematical approach to predict the material stiffness of the full composite part produced by the injection moulding process, considering a three-phase micromechanical model, where the effects of local orientations are accounted. Injection moulded plates with a flax content of up to 20 V% were fabricated to study the effect of flax shives and full straw flax on the mechanical properties of the material. A 62% increase in longitudinal stiffness was obtained, resulting in a 10% higher specific stiffness, compared to a short glass fibre-reinforced reference composite. Moreover, the anisotropy ratio of the flax-reinforced composite was 21% lower, compared to the short glass fibre material. This lower anisotropy ratio is attributed to the presence of the flax shives. Considering the fibre orientation in the injection moulded plates predicted with Moldflow simulations, a high agreement between experimental and predicted stiffness data was obtained. The use of flax stems as polymer reinforcement provides an alternative to the use of short technical fibres that require intensive extraction and purification steps and are known to be cumbersome to feed to the compounder. Full article

(This article belongs to the Special Issue Fiber Reinforced Thermoplastic Composites: Processing/Structure/Performance Inter-relationships)

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19 pages, 4147 KiB

Open AccessArticle

Influence of Different Hot Runner-Systems in the Injection Molding Process on the Structural and Mechanical Properties of Regenerated Cellulose Fiber Reinforced Polypropylene

by Jan-Christoph Zarges, André Schlink, Fabian Lins, Jörg Essinger, Stefan Sommer and Hans-Peter Heim

Polymers 2023, 15(8), 1924; https://doi.org/10.3390/polym15081924 - 18 Apr 2023

Cited by 3 | Viewed by 2502

Abstract

The increasing demand for renewable raw materials and lightweight composites leads to an increasing request for natural fiber composites (NFC) in series production. In order to be able to use NFC competitively, they must also be processable with hot runner systems in injection molding series production. For this reason, the influences of two hot runner systems on the structural and mechanical properties of Polypropylene with 20 wt.% regenerated cellulose fibers (RCF) were investigated. Therefore, the material was processed into test specimens using two different hot runner systems (open and valve gate) and six different process settings. The tensile tests carried out showed very good strength for both hot runner systems, which were max. 20% below the reference specimen processed with a cold runner and, however, significantly influenced by the different parameter settings. Fiber length measurements with the dynamic image analysis showed approx. 20% lower median values of GF and 5% lower of RCF through the processing with both hot runner systems compared to the reference, although the influence of the parameter settings was small. The X-ray microtomography performed on the open hot runner samples showed the influences of the parameter settings on the fiber orientation. In summary, it was shown that RCF composites can be processed with different hot runner systems in a wide process window. Nevertheless, the specimens of the setting with the lowest applied thermal load showed the best mechanical properties for both hot runner systems. It was furthermore shown that the resulting mechanical properties of the composites are not only due to one structural property (fiber length, orientation, or thermally induced changes in fiber properties) but are based on a combination of several material- and process-related properties. Full article

(This article belongs to the Special Issue Fiber Reinforced Thermoplastic Composites: Processing/Structure/Performance Inter-relationships)

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13 pages, 7600 KiB

Open AccessArticle

Modification of Polyamide 66 for a Media-Tight Hybrid Composite with Aluminum

by Fabian Lins, Christian Kahl, Jan-Christoph Zarges and Hans-Peter Heim

Polymers 2023, 15(7), 1800; https://doi.org/10.3390/polym15071800 - 6 Apr 2023

Cited by 2 | Viewed by 1977

Abstract

Metal–plastic composites are becoming increasingly important in lightweight construction. As a combination, e.g., for transmission housings in automobiles, composites made of die-cast aluminum housings and Polyamide 66 are a promising material. The interface between metal and plastic and the properties of the plastic component play an important role with regard to media tightness against transmission oil. The mechanical properties of the plastic can be matched to aluminum by glass fibers and additives. In the case of fiber-reinforced plastics, the mechanical properties depend on the fiber length and their orientation. These structural properties were investigated using computer tomography and dynamic image analysis. In addition to the mechanical properties, the thermal expansion coefficient was also investigated since a strongly different coefficient of the joining partners leads to stresses in the interface. Polyamide 66 was processed with 30 wt% glass fibers to align the mechanical and thermal expansion properties to those of aluminum. In contrast to the reinforcement additives, an impact modifier to improve the toughness of the composite, and/or a calcium stearate to exert influence on the rheological behavior of the composite, were used. The combination of the glass fibers with calcium stearate in Polyamide 66 led to high stiffnesses (11,500 MPa) and strengths (200 MPa), which were closest to those of aluminum. The coefficient of thermal expansion was found to be 6.6 × 10⁻⁶/K for the combination of Polyamide 66 with 30 wt% glass fiber and shows a low expansion exponent compared to neat Polamid 66. It was detected that the use of an impact modifier led to less orientated fibers along the injection direction, which resulted in lower modulus and strength in terms of mechanical properties. Full article

(This article belongs to the Special Issue Fiber Reinforced Thermoplastic Composites: Processing/Structure/Performance Inter-relationships)

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15 pages, 2769 KiB

Open AccessArticle

Describing and Modeling Rough Composites Surfaces by Using Topological Data Analysis and Fractional Brownian Motion

by Antoine Runacher, Mohammad-Javad Kazemzadeh-Parsi, Daniele Di Lorenzo, Victor Champaney, Nicolas Hascoet, Amine Ammar and Francisco Chinesta

Polymers 2023, 15(6), 1449; https://doi.org/10.3390/polym15061449 - 14 Mar 2023

Cited by 6 | Viewed by 1744

Abstract

Many composite manufacturing processes employ the consolidation of pre-impregnated preforms. However, in order to obtain adequate performance of the formed part, intimate contact and molecular diffusion across the different composites’ preform layers must be ensured. The latter takes place as soon as the intimate contact occurs and the temperature remains high enough during the molecular reptation characteristic time. The former, in turn, depends on the applied compression force, the temperature and the composite rheology, which, during the processing, induce the flow of asperities, promoting the intimate contact. Thus, the initial roughness and its evolution during the process, become critical factors in the composite consolidation. Processing optimization and control are needed for an adequate model, enabling it to infer the consolidation degree from the material and process features. The parameters associated with the process are easily identifiable and measurable (e.g., temperature, compression force, process time, ⋯). The ones concerning the materials are also accessible; however, describing the surface roughness remains an issue. Usual statistical descriptors are too poor and, moreover, they are too far from the involved physics. The present paper focuses on the use of advanced descriptors out-performing usual statistical descriptors, in particular those based on the use of homology persistence (at the heart of the so-called topological data analysis—TDA), and their connection with fractional Brownian surfaces. The latter constitutes a performance surface generator able to represent the surface evolution all along the consolidation process, as the present paper emphasizes. Full article

(This article belongs to the Special Issue Fiber Reinforced Thermoplastic Composites: Processing/Structure/Performance Inter-relationships)

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13 pages, 4920 KiB

Open AccessArticle

Sisal-Fiber-Reinforced Polypropylene Flame-Retardant Composites: Preparation and Properties

by Zhenhua Wang, Weili Feng, Jiachen Ban, Zheng Yang, Xiaomin Fang, Tao Ding, Baoying Liu and Junwei Zhao

Polymers 2023, 15(4), 893; https://doi.org/10.3390/polym15040893 - 10 Feb 2023

Cited by 17 | Viewed by 3155

Abstract

Natural-fiber-reinforced polypropylene (PP) composites with a series of advantages including light weight, chemical durability, renewable resources, low in cost, etc., are being widely used in many fields such as the automotive industry, packaging, and construction. However, the flammability of plant fiber and the PP matrix restricts the application range, security, and use of these composites. Therefore, it is of great significance to study the flame retardants of such composites. In this paper, sisal-fiber-reinforced polypropylene (PP/SF) flame-retardant composites were prepared using the two-step melt blending method. The flame retardant used was an intumescent flame retardant (IFR) composed of silane-coated ammonium polyphosphate (Si-APP) and pentaerythritol (PER). The influence of different blending processes on the flammability and mechanical properties of the composites was analyzed. The findings suggested that PP/SF flame-retardant composites prepared via different blending processes showed different flame-retardant properties. The (PP/SF)/IFR composite prepared by PP/SF secondary blending with IFR showed excellent flame-retardant performance, with a limited oxygen index of about 28.3% and passing the UL-94 V-0 rating (3.2 mm) in the vertical combustion test. Compared with the (PP/IFR) /SF composite prepared by a matrix primarily blended with IFR and then secondly blended with SF, the peak heat release rate (pk HRR) and total heat release (THR) of the (PP/SF)/IFR composite decreased by 11.3% and 13.7%, respectively. In contrast, the tensile strength of the (PP/SF)/IFR system was 5.3% lower than that of the (PP/IFR)/SF system; however, the overall mechanical (tensile, flexural, and notched impact) properties of the composites prepared using three different mixing processes were similar. Full article

(This article belongs to the Special Issue Fiber Reinforced Thermoplastic Composites: Processing/Structure/Performance Inter-relationships)

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27 pages, 9886 KiB

Open AccessReview

Rapid Impregnating Resins for Fiber-Reinforced Composites Used in the Automobile Industry

by Mei-Xian Li, Hui-Lin Mo, Sung-Kwon Lee, Yu Ren, Wei Zhang and Sung-Woong Choi

Polymers 2023, 15(20), 4192; https://doi.org/10.3390/polym15204192 - 23 Oct 2023

Cited by 2 | Viewed by 2634

Abstract

As environmental regulations become stricter, weight- and cost-effective fiber-reinforced polymer composites are being considered as alternative materials in the automobile industry. Rapidly impregnating resin into the reinforcing fibers is critical during liquid composite molding, and the optimization of resin impregnation is related to the cycle time and quality of the products. In this review, various resins capable of rapid impregnation, including thermoset and thermoplastic resins, are discussed for manufacturing fiber-reinforced composites used in the automobile industry, along with their advantages and disadvantages. Finally, vital factors and perspectives for developing rapidly impregnated resin-based fiber-reinforced composites for automobile applications are discussed. Full article

(This article belongs to the Special Issue Fiber Reinforced Thermoplastic Composites: Processing/Structure/Performance Inter-relationships)

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