Thermoplastic-based Composites Research Articles

Extraction of Lightweight Platanus orientalis L. Fruit's Stem Fiber and Determination of Its Mechanical and Physico-Chemical Properties and Potential of Its Use in Composites.

Natural fibers extracted from plants are preferred as an alternative to synthetic products. The main reasons for this preference are their affordable cost, light weight and good mechanical properties. However, finding new natural raw materials is challenging due to growth limitations in different geographical areas. Platanus orientalis L. (Eastern plane tree) is a tree with abundant fruits that can grow in many regions of the world. The aim of this study was to determine the mechanical (tensile strength, tensile modulus, elongation), physical (density, fiber diameter) and chemical (cellulose, hemicellulose and lignin) properties of Platanus orientalis L. fruit's stem by fiber extraction from the stems of the tree. It was determined that the extracted fiber had good mechanical properties and cellulose content of 42.03%. As a result of thermogravimetric analysis, it was determined that the plane tree fruit's stem fiber had thermal resistance of up to 299 °C. The tensile strength value was 157.76 MPa, the tensile modulus value was 1.39 GPa and the elongation value was 22.01%. It was determined that it is suitable for use in fiber reinforcement in thermoplastic-based composites at temperatures below 299 °C. According to the results obtained by the mechanical, chemical and physical analysis of Platanus orientalis L. fruit's stem fiber (PoLfs), it could be recommended as a suitable alternative as a reinforcing fiber in thermoplastic and thermoset composites.

On digital twinning of fused filament fabrication for tensile properties of polyvinylidene fluoride composites-based functional prototypes

In the last two decades, several studies have been conducted for the process parametric optimization of fused filament fabrication (FFF) with a variety of thermoplastic composites, especially for mechanical properties. But hitherto less has been conveyed, on the development of dynamic reduced order models (ROMs) for digital twining (DT) of tensile properties (of 3D printed implants/scaffolds) with novel thermoplastic-based composites. In this study, for the generation of dynamic ROM (for hybrid analytics), the signal-to-noise (S/N) ratio was used to ascertain the best settings of parameters for tensile properties of polyvinylidene fluoride (PVDF) composite. The study suggests that the best setting of the FFF process, for the 3D printing of PVDF composite (90% PVDF, 8% hydroxyapatite (HAp), and 2% Chitosan (CS) (for maximizing the tensile properties as per ASTM-D638-Type-V) are nozzle temperature (NT) of 235°C, raster angle (RA) 45°, printing speed (PS) of 60 mm/s respectively resulting in peak load (PL) 394.87 N, peak stress (PSt) 33.92 MPa, Young’s modulus (E) 2.606 MPa. For a modulus of toughness (MOT) of 0.484 MPa, the best settings are NT 230°C, RA 90°, and PS 50 mm/s. The results are supported by the morphological analysis.

About the high temperature fatigue performance of thermoplastic-based composite laminates for aeronautical applications

The use of thermoplastic-based composites for applications in high temperature aeronautical parts is often considered contradictory with respect to the softening of the matrix and the subsequent degradation of their mechanical properties, especially when service temperature T exceeds glass transition temperature. This paper examines the fatigue performance of unidirectional (UD) carbon fibers reinforced PolyArylEtherKetone (PAEK) laminates subjected to tension-tension fatigue at different testing temperatures (Room Temperature, 120°C and 170°C). Laminates consisting of different portions of plies in 0°/+45°/−45°/90° orientations have been investigated to evaluate the contribution of each ply orientation to the fatigue performance in terms of S-N diagrams. From the evolution of life span as a function of applied stress, it appears that the influence of temperature on fatigue behaviour of C/PAEK composites depends on the temperature conditions. 0° plies behaviour is known to be temperature-independent as is dominated by the mechanical behaviour of UD carbon fibers. It is expected to reflect on the fatigue behaviour at high temperature. From the obtained results, one may conclude that the 0° plies primarily bear the tensile load in fatigue (47-67-91% in SOFT, QI and HARD laminates, respectively) and therefore dominate the fatigue behaviour. The deformation mechanisms in +/−45° plies (localized plastic-viscoplastic dissipative behaviors) favoured at temperatures higher than Tg (e.g. 143°C) are limited by the low deformation of 0° plies. SOFT (12% of 0° plies) and QI (25% of 0° plies) laminates have similar relative fatigue performance. Unexpectedly, the fatigue performance of HARD laminates (about 62% of 0° plies) is improved at T>Tg at high stress levels. A simple temperature-dependent analytical model was used to successfully predict the fatigue life of C/PAEK laminates with different stacking sequences.

Incremental design process for vehicle structural components using thermoplastic-based composites: A simulation-guided approach for door anti-intrusion beams

The design of safety-related structural components in automobiles is a critical phase. Most car manufacturers are aiming at reducing vehicle weight considering continuous fiber-reinforced thermoplastics as candidate to replace metal-based structural components. However, this replacement cannot compromise the safety level already achieved by metal-based designs. A good example is the side door anti-intrusion beam, which is a passive safety component to protect the passengers under a lateral impact. This paper presents an incremental design process to achieve a functional side door anti-intrusion beam fully made of glass fiber reinforced thermoplastic conceived to replace metal-based ones. The reader is guided along the design challenges, where the mechanic-based reasons to adapt the part geometry and composite layout are explained in detail. This incremental design process uses a fully FEM-based approach allowing to reach a standard-defined absorbed energy of 1000 J in a lateral collision. From the simulation analysis, it was found that by implementing essential modifications in the beam’s cross-section corrugation, the damage progression can be slowed down leading to an increase of absorbed energy. Additionally, the enhancement of one extra ply in the proper direction solves severe fracture in the clamping area. The final composite design not only performs similarly to its metal-based counterpart, but also considers aspects of production feasibility. This trip along the design process concludes with the production of the simulate-designed component and its effectiveness under lateral impact is demonstrated. To meet the safety regulations, the model is thoroughly validated against the real impact test by analyzing the response in force, intrusion, energy and damage.

Investigation of fiber content evaluation methods of carbon fiber reinforced thermoplastic composites

Thermoplastic-based composites are becoming the preferred material for structural and non-structural components in the composite production industries. One of the most critical elements determining the characteristics and performance of fiber-reinforced composites is the fiber content. The fiber volume fraction (Vf) of carbon/polyamide410 (C-PA410) composite is evaluated using standard acid digestion, the unique two-stage thermogravimetry (TGA) method and 2D image processing method, with Vf values of 24.0%, 23.1%, and 18.3%, respectively. For statistical purposes, a substantial number of samples from each composite batch were tested and analyzed. The two-stage TGA approach used in this study, involves measuring the constituent content of carbon fiber thermoplastic composites in nitrogen first and subsequently in air. The standard acid digestion and the two-stage TGA method used in this study provided comparable results. The 2D image processing method, on the other hand, yields a lower volume fraction of fiber. The two-stage TGA approach has been proven to be more convenient in terms of accuracy, safety, and speed. This technique has been validated by testing a control specimen of a material (Toray Cetex® TC910 PA6) with a known weight fraction.

Synergy of silica sand and waste plastics as thermoplastic composites on abrasive wear characteristics under conditions of different loads and sliding speeds

The diverse nature of polymers with attractive properties has replaced the conventional materials with polymeric composites. The present study was sought to evaluate the wear performance of thermoplastic-based composites under the conditions of different loads and sliding speeds. In the present study, nine different composites were developed by using low-density polyethylene (LDPE), high-density polyethylene (HDPE) and polyethylene terephthalate (PET) with partial sand replacements i.e., 0, 30, 40, and 50 wt%. The abrasive wear was evaluated as per the ASTM G65 standard test for abrasive wear through a dry-sand rubber wheel apparatus under the applied loads of 34.335, 56.898, 68.719, 79.461 and 90.742 (N) and sliding speeds of 0.5388, 0.7184, 0.8980, 1.0776 and 1.4369 (m/s). The optimum density and compressive strength were obtained to be 2.0555 g/cm3 and 46.20 N/mm2, respectively for the composites HDPE60 and HDPE50 respectively. The minimum value of abrasive wear were found to 0.02498, 0.03430, 0.03095, 0.09020 and 0.03267 (cm3) under the considered loads of 34.335, 56.898, 68.719, 79.461 and 90.742 (N), respectively. Moreover, the composites LDPE50, LDPE100, LDPE100, LDPE50PET20 and LDPE60 showed a minimum abrasive wear of 0.03267, 0.05949, 0.05949, 0.03095 and 0.10292 at the sliding speeds of 0.5388, 0.7184, 0.8980, 1.0776 and 1.4369 (m/s), respectively. The wear response varied non-linearly with the conditions of loads and sliding speeds. Micro-cutting, plastic deformations, fiber peelings, etc. were included as the possible wear mechanism. The possible correlations between wear and mechanical properties, and throughout discussions for wear behaviors through the morphological analyses of the worn-out surfaces were provided.

Deformation Behavior of Single Carbon Fibers Impregnated with Polysulfone by Polymer Solution Method.

Tensile deformation behavior of continuous high-strength and high-modulus single carbon fibers impregnated with a polysulfone solution was investigated. The effect of the carbon fiber type, mass fraction of the polymer, and the loading rate on the tensile strength was studied. It was observed that, whereas for high-modulus carbon fibers the magnitude of tensile strength depends significantly on the loading rate, for high-strength carbon fibers, such dependence was nearly not observed. SEM study shows that at low loading rates, elementary filaments inside the impregnated fiber are able to align themselves along the load application axis because a thermoplastic matrix can flow under the tensile stresses' force. As a result, the fiber's strength properties can be realized more effectively in the thermoplastic-based composites than in the same composite with an epoxy matrix.

Development and Characterization of Phosphate Glass Fibers and Their Application in the Reinforcement of Polyester Matrix Composites.

This study focused on the production and characterization of phosphate glass fibers (PGF) for application as composite reinforcement. Phosphate glasses belonging to the system 52P2O524CaO13MgO (11-(X + Y)) K2OXFe2O3YTiO2 (X:1, 3, 5) and (Y:0.5, 1) were elaborated and converted to phosphate glass fibers. First, their mechanical properties and chemical durability were investigated. Then, the optimized PGF compositions were used afterward as reinforcement for thermosetting composite materials. Polyester matrices reinforced with short phosphate glass fibers (sPGF) up to 20 wt % were manufactured by the contact molding process. The mechanical and morphological properties of different sPGF-reinforced polyester systems were evaluated. The choice between the different phosphate-based glass syntheses (PGFs) was determined by their superior mechanical performance, their interesting chemical durability, and their high level of dispersion in the polyester matrix without any ad sizing as proven by SEM morphological analysis. Moreover, the characterization of mechanical properties revealed that the tensile and flexural moduli of the developed polyester-based composites were improved by increasing the sPGF content in the polymer matrix in perfect agreement with Takayanagi model predictions. The present work thus highlights some promising results to obtain high-quality phosphate glass fiber-reinforced polyester parts which can be transposed to other thermosetting or thermoplastic-based composites for high-value applications.

Imidazolium Salt for Enhanced Interfacial Shear Strength in Polyphenylene Sulfide/Ex-PAN Carbon Fiber Composites.

Processing structural or semi-structural thermoplastic-based composites is a promising solution to solve the environmental issues of the aeronautic industry. However, these composites must withstand high standard specification to ensure safety during transportation. For this reason, there is a real need to develop strong interactions between thermoplastic polymers and reinforcement fibers. This paper investigates relationships between the surface chemistry, microstructure and micromechanical properties between polyphenylene sulfide and ex-PAN carbon fibers. The incorporation of ionic salt such as 1,3-Bis(4-carboxyphenyl)imidazolium chloride into neat polyphenylene sulfide was able to significantly increase the interfacial shear strength measured by microbond micromechanical test combined with different carbon fiber surfaces treatment.

A Novel Manufacturing Concept of LCP Fiber-Reinforced GPET-Based Sandwich Structures with an FDM 3D-Printed Core.

The presented research was focused on the development of a new method of sandwich structure manufacturing involving FDM-printing (fused deposition modeling) techniques and compression molding. The presented concept allows for the preparation of thermoplastic-based composites with enhanced mechanical properties. The sample preparation process consists of 3D printing the sandwich’s core structure using the FDM method. For comparison purposes, we used two types of GPET (copolymer of polyethylene terephthalate)-based filaments, pure resin, and carbon fiber (CF)-reinforced filaments. The outer reinforcing layer “skins” of the sandwich structure were prepared from the compression molded prepregs made from the LCP (liquid-crystal polymer)-fiber fabric with the GPET-based matrix. The final product consisting of an FDM-printed core and LCP-based prepreg was prepared using the compression molding method. The prepared samples were subjected to detailed materials analyses, including thermal analyses (thermogravimetry-TGA, differencial scanning calorimetry-DSC, and dynamic thermal-mechanical analysis-DMTA) and mechanical tests (tensile, flexural, and impact). As indicated by the static test results, the modulus and strength of the prepared composites were slightly improved; however, the stiffness of the prepared materials was more related to the presence of the CF-reinforced filament than the presence of the composite prepreg. The main advantage of using the developed method is revealed during impact tests. Due to the presence of long LCP fibers, the prepared sandwich samples are characterized by very high impact resistance. The impact strength increased from 1.7 kJ/m2 for pure GPET samples to 50.4 kJ/m2 for sandwich composites. For GPET/CF samples, the increase is even greater. The advantages of the developed solution were illustrated during puncture tests in which none of the sandwich samples were pierced.

Effect of natural carbon filler on thermo-oxidative degradation of thermoplastic-based composites

Thermo-oxidative degradation of thermoplastic-based composites filled with two types of carbon filler including bituminous (Pittsburgh No.8, P8) and sub-bituminous (Powder River Basin, PRB) coals were investigated using differential scanning calorimetry (DSC) and thermogravimetric analysis. Oxidation induction time (OIT) and activation energy (AE) for coal plastic composites (CPCs), HDPE, and commercially available wood plastic composites (WPCs) were determined using isothermal and isoconversional kinetic methods. OIT values for CPC increased with coal content, indicating higher thermo-oxidative stability. AE values obtained using isothermal method were 52–116 kJ/mol for all CPC formulations, 32 kJ/mol for HDPE, and 33–114 kJ/mol for WPCs. AEs for CPCs obtained using isoconversional methods were not constant but rather dependent on the degree of degradation with CPC/ P8 coal possessing higher overall AE. Incorporating coal into HDPE increased thermo-oxidative stability of the resulting composite, indicating coal potentially acts as a natural primary and secondary antioxidant for polymer materials.

Flammability and thermal stability of thermoplastic-based composites filled with natural carbon

This investigation characterized flammability and thermal stability for a novel sustainable composite engineered for use in building applications. Flammability and thermal stability of coal plastic composites composed of coal (40–60 wt.%) and high-density polyethylene were compared to commercial wood–plastic composites. Pyrolysis thermogravimetric analysis results indicated that coal plastic composites possessed a single-step decomposition and higher char residue, while wood–plastic composites had two-step decomposition, with the first peak occurring at much lower temperatures. Thermogravimetric analyses in air suggest coal plastic composites, compared to wood–plastic composites and neat high-density polyethylene, were more thermally stable. Flash ignition temperatures for coal plastic composites were higher than high-density polyethylene and wood–plastic composites, while self-ignition temperatures were in the same range as wood–plastic composites. Rate of burning data indicated coal plastic composites were slower burning than wood–plastic composites, with increasing coal content slowing burning rate by 19.9%–27.6%. Cone calorimeter testing showed 27% and 59% reduction in total heat release and total smoke release as coal content increased while coal plastic composite with 60 wt.% coal possessed lower overall flammability in comparison with predominant commercially available wood–plastic composite products. Coal improved composite overall thermal stability and flammability by acting as char former and foaming agent.

Experimental and numerical analysis of the defects induced by the thermoforming process on woven textile thermoplastic composites

In the present work, a parallel numerical and experimental analysis of a critical type of defect is conducted, the shear deformation which is caused by the thermoforming process of thermoplastic-based composites reinforced with glass fiber textile. The numerical analysis is conducted a priori using a commercial finite element software, developed for this specific process. In parallel, an experimental thermoforming test was conducted using the exact same parameters used for simulating the process and, consecutively, measurements of the component characteristics such as the fiber relative deformation of the textile are taken. Aiming to validate the simulation and to obtain crucial information about this phenomenon, a comparison between the finite element process simulation and the measurements output is conducted revealing a satisfying agreement between them, leading also to useful conclusions about the validity of the simulation method as well as about the detection and measurement of the shear textile deformation using optical systems.

Review: Filament Winding and Automated Fiber Placement with In Situ Consolidation for Fiber Reinforced Thermoplastic Polymer Composites.

Fiber reinforced thermoplastic composites are gaining popularity in many industries due to their short consolidation cycles, among other advantages over thermoset-based composites. Computer aided manufacturing processes, such as filament winding and automated fiber placement, have been used conventionally for thermoset-based composites. The automated processes can be adapted to include in situ consolidation for the fabrication of thermoplastic-based composites. In this paper, a detailed literature review on the factors affecting the in situ consolidation process is presented. The models used to study the various aspects of the in situ consolidation process are discussed. The processing parameters that gave good consolidation results in past studies are compiled and highlighted. The parameters can be used as reference points for future studies to further improve the automated manufacturing processes.

Effect of crystallinity on the mechanical behavior of carbon fiber reinforced polyethylene-terephthalate (CF/PET) composites considering temperature conditions

Thermoplastic differs in crystallinity depending on the manufacturing conditions such as temperature and cooling rate, which affect the mechanical properties of the thermoplastic-based composites. In this work, the crystallinity of polyethylene terephthalate (PET) was varied according to the cooling rate to investigate the mechanical properties of PET matrix-based carbon fiber (CF)/PET composites. The thermal characteristics and crystallinity were analyzed through the differential scanning calorimetry (DSC) and X-ray diffraction (XRD) analysis. The mechanical behavior of CF/PET composites with different degrees of crystallinity was studied with varied temperature conditions. The failure modes of the fractured CF/PET composites were observed by using a digital microscope and scanning electron microscope (SEM). As a result, the crystallized CF/PET composites were improved 11.6 times higher in in-plane shear (±45° laminated) strength and 3.78 times higher in shear modulus than that of amorphous CF/PET composites at high temperature.

On the sensitivity of ultrasonic welding of epoxy- to polyetheretherketone (PEEK)-based composites to the heating time during the welding process

This study aims at assessing the sensitivity of the ultrasonic welding process for joining epoxy- to thermoplastic-based composites sensitivity to the heating time. For that, carbon fibre (CF)/epoxy adherends with a co-cured PEI coupling layer were ultrasonically welded to CF/polyetheretherketone (PEEK) adherends at different heating times. Process-induced changes in the meso and microstructure of these welds were identified and correlated to the weld strength. Subsequently, a processing interval, i.e., a range of heating times resulting in less than 10% decrease of weld strength, was defined. As, expected, the dissimilar composite welded joints were more sensitive to the heating time than the CF/PEEK to CF/PEEK welded joints. However, this effect was less pronounced than expected, since a relatively wide processing interval could be obtained provided that the coupling layer had a sufficient thickness.

Implementation of the modified V-Notched Rail Shear method for characterizing glass fibre thermoplastic composites at sub-zero and elevated temperatures

In the recent years, the thermoplastic-based composites are being increasingly used in a variety of industrial applications such as the automotive due to the unique features they exhibit, mainly their recyclability and their interesting capacity to be formed and produced in high volume rate. Among the most interesting categories utilized extensively in these sectors, the short fibre composites are an attractive solution to non-critical load carrying structures while the textiles are utilized in more critical components. Nevertheless, all of them are implemented into a varying service temperature range, from sub-zero up to higher temperatures than the ambient. Thus, the definition of their mechanical performance with respect to their material and fabrication characteristics is a crucial procedure. Among them, the shear properties are the most challenging due to the complexity of the standardized mechanical tests. Moreover, these properties are greatly dependent on the matrix quality and, in general, to the overall composite's quality. In the present work, presented is an experimental campaign implementing temperatures from −30 °C up to 80 °C that includes both short and textile thermoplastic based composites, fabricated with different processes. In addition, introduced is a modified testing apparatus based on the standardized one that aims to overcome some of the drawbacks observed so far.

A comparative study for shear testing of thermoplastic-based composites and metal-composite hybrids

This study presents the novel application of the compression shear test (CST) for characterising bonding strength of metal-composite hybrids made of steel and carbon fibre/polyamide 6 (CF/PA 6). An automated laser-assisted tape placement (ATP) process was used to lay-up the CF/PA 6 tapes on laser textured steel substrates. CST is of interest due to the ease of sample manufacturing as a relatively small test specimen is required. The results were compared with standardised single lap shear tests (ASTM D3165), which requires manufacturing of a double-notched test specimen. For benchmarking purposes, the compression shear test was also used to characterise the interlaminar shear strength of a plain CF/PA 6 composite. The results showed equivalent shear strength and similar failure modes for both tests of the metal-composite hybrid specimens. Grooved texturing of the steel substrate in the hybrid specimens promoted a mixed-mode (cohesive and adhesive) failure and a higher shear strength than for the composite-only specimens. Overall, the results showed that the compression shear test is a valid and efficient method to characterise the bonding strength of metal-composite hybrids and composites.

Polystyrene nanocomposites reinforced with phenyl isocyanate-treated cellulose nanofibers

Cellulose nanofibers (CNFs) have attracted much attention as eco-friendly natural nanofillers for thermoplastic-based composites. In this work, we present one possible route to fabricating such a composite based on polystyrene (PS) polymer reinforced with chemically modified CNFs. To achieve a uniform dispersion of CNF fillers in the PS matrix and simultaneously ensure interfacial strength between CNFs and PS in the composite, the surface of CNFs was functionalized with phenyl isocyanates. The composite beads of PS and iCNF were produced by coagulation, followed by thermocompression of the composite beads to produce PS-iCNF composites. Three-point bending flexural tests were performed on the composites to evaluate their mechanical properties according to the CNF loading. The elastic modulus of the PS-iCNF composite increased gradually, while the fracture bending strength decreased as the loading increased, compared to those for the pure PS film. SEM analysis of the fracture surface revealed that the failure behavior of the composite changed from ductile to brittle fracture with increasing iCNF loading. Optical transmittance of the composites was also investigated as a function of the iCNF loading.

Influence of specific mechanical energy during compounding in a co-kneader on electrical and rheological properties of multiscale composite materials

Abstract This paper focuses on the effect of different scales of fillers, from nano to macrometer, on the rheological and electrical behaviour of thermoplastic-based composites. Composites based on poly (etherimide) matrix (PEI) with multiscale reinforcement are processed by melting in a co-kneader to disperse homogeneously carbon nanotubes and glass fibers. We clearly demonstrate the strong link between the liquid-solid transition and the electrical conductivity. We show that the specific mechanical energy is a key parameter. Glass fibers allow to increase the electrical conductivity of blends based on carbon nanotubes and to obtain a lower decreasing of conductivity at the liquid transition which takes place in the same time as rheological and electrical parameters.