Fiber Thermoplastic Composites Research Articles

Carbon nanotube-induced localized laser heating toward simultaneously enhanced laydown efficiency and fracture toughness of in-situ consolidated glass fiber thermoplastic composites

Thermoplastic composites suffer from weak inter-tape bonding during high-rate laser-assisted automated fiber placement (L-AFP). Here, we propose a strategy to simultaneously enhance the laser heating efficiency and fracture toughness of glass fiber-reinforced polypropylene prepreg tape for L-AFP process by depositing carbon nanotubes (CNTs) on the tape surface by a low-cost bath coating process. CNTs function as efficient light absorbing and photothermal coating to promote molecular inter-diffusion and interfacial healing between successive tapes, as well as toughen the weak interface by CNT pull-out and rupture. A 56 % increase in the near-infrared laser absorption of tapes results in a 946 % improvement in the laydown rate. CNTs also remarkably improve transverse temperature uniformity. Furthermore, double cantilever beam and pants tearing tests show that 0.5 wt% CNTs improve the mode I interlaminar fracture toughness and mode III fracture strength by 17 % and 52 %, respectively, attributed to the enhanced molecular inter-diffusion and CNT bridging effect.

Microstructural evolution of highly aligned discontinuous fiber composites during longitudinal extension in forming

The longitudinal extensional viscosity of a highly aligned discontinuous fiber (ADF) thermoplastic matrix composite is investigated to develop a model and validate microstructural evolutionary mechanisms. Samples stretched at constant temperature and strain rate are shown to exhibit a strain softening behavior. X-ray CT analysis and optical micrographs show that the composite microstructure deconsolidates before forming and evolves with deformation. The conventional unit cell micromechanical model includes the effects of matrix viscosity, fiber aspect ratio and fiber volume fraction. This model is modified to include the stiffening effect of fiber spacing variability, and the softening effects of porosity and decreasing fiber overlap length with elongation. Calibration of the model reveals that matrix shear strain rate is an order of magnitude higher than previously predicted due to local fiber spacing. This effect is captured by a fiber spacing variability parameter which scales average spacing down by an order of magnitude. The observed strain softening behavior is described and a combinations of fiber overlap length reduction and local fiber spacing increase.

Preparation and properties of hybrid specific length carbon fiber thermoplastic composites by suspension method

AbstractCarbon fiber reinforced thermoplastic composites have such advantages as low density, high strength, high temperature resistance, impact resistance, and good ductility, but due to the density difference between carbon fibers and resin fibers, it is difficult to mix them uniformly. Hence, it is difficult to prepare the composites with the uniform properties. In order to solve this problem, a preparation process based on solid phase mixing of carbon and resin fibers by suspension method is proposed in this paper. The carbon fiber reinforced thermoplastic composites (CFRTPs) can be prepared by dispersing carbon fibers of a certain length (~50 mm) and resin fibers in suspension through ultrasound‐assisted and churn‐combing methods. The effects of carbon fiber length, content and molding process on the mechanical properties of the CFRTPs were studied. The results show that the carbon fiber content and length are the main factors affecting the mechanical properties as well as void ratio of CFRTP. The performance of composites is significantly improved with the increase of carbon fiber length. While the length of carbon fiber is 50 mm and the content is 30 wt%, the prepared CFRTP has the best performance, with the tensile strength of 182.1 MPa, the bending strength of 354.3 MPa, the impact strength of 67.2 KJ·m−2, and the material void ratio of 0.65%. The study shows that the suspension method is feasible for the preparation of the CFRTPs. It is beneficial to improve production efficiency and decrease cost of production for the CFRTPs.Highlights Carbon fiber reinforced thermoplastic composites can be prepared by dispersing carbon fibers of a certain length (~50 mm) and resin fibers in suspension through ultrasound‐assisted and churn‐combing methods. Through the cooling‐high pressure molding process, the porosity of CFRTP is reduced and the mechanical properties of CFRTP are improved. The tensile strength, bending strength, and notch‐free impact strength properties of CFRTP are best when the carbon fiber content is 30% and the CF length is 50 mm. The method is characterized by simple process, low cost and high mechanical properties.

Effect of reparation on the mechanical behavior of glass fibers/Elium acrylic laminate composites: Experimental and numerical approaches

AbstractElium® Acrylic/Glass Fiber thermoplastic laminate composites are liable to develop irreversible local defects under quasi‐static loading. To reinforce the damaged material, repair is a cost‐effective mechanical alternative. The present study investigates the tensile behavior of an Elium® glass‐fiber‐based acrylic laminate composite panel, repaired by vacuum bonding with Elium® repair resin and double overlap of external patches (DP). The results obtained for all repaired laminate composites E190/GF_D(10, 20, 30)R with diameters 10, 20, and 30 mm showed an improvement in the mechanical properties of the repaired panels, compared with the drilled and pristine samples. Average load recovery rates were significant for E190/GF_D10R (7.9%, 3.55%, 13%) E190/GF_D20R (23%, 18%, 3.32%), E190/GF_D30R (7.2%, 9.36%, 32.37%) at strain rates of 0.001, 0.01, and 0.05 s−1 respectively. Finite element (FE) models for the virgin, drilled, and repaired composite, performed by coupling the Hashin criteria with the cohesive zone model (CZM), provided a relevant prediction of intra‐ and interlaminar failures of these woven laminated composites.Highlights The effect of vacuum bonding repair with Elium E351 EOT resin was studied. Symmetrical repair of acrylic laminate drilled by fiberglass patches. Tensile strength of the repaired laminates was investigated. Intra‐ and interlaminar damage was predicted by finite elements modeling.

Non-contact heating methods of carbon fiber thermoplastic composites based on Joule thermal properties: Optimization and validation

Carbon fiber matrix composites have garnered significant attention due to their exceptional properties, finding wide-ranging applications in industries such as aerospace, transportation, and military. In this study, a novel approach involving the addition of nickel was explored to fabricate carbon fiber-reinforced thermoplastic polymer composites and composite materials filled with nylon 12, utilizing nickel foam as matrix. Subsequently, electromagnetic-thermal multiphysics coupling models were established to analyze the induction heating process. The study investigated the effects of nickel content, spatial location of the main heat source, coil current, and coil frequency on the temperature rise and heat generation. Additionally, a linear fit was applied to determine the material surface temperature and related factors during induction heating. Furthermore, a theoretical formula was derived for induction heating under ideal conditions, elucidating the heat transfer mechanism and the influence of various factors on heat generation. The findings of this research serve as a reference for optimizing the utilization of Joule heat in composites, thereby expanding the application of carbon fiber-reinforced polymer composites in temperature regulation and operational control.

Characterization Approach for Compression Molded Discontinuous Fiber Thermoplastic Composites

Thermoplastic composites show potential in increasing the manufacturing production rate of composite aerospace structures. This is largely due to their ability to be consolidated quickly using automated processes. A variety of reinforced thermoplastic material forms are offered that can be processed multiple ways in order to meet structural performance requirements at the necessary production volumes without substantial compromise. Intrinsically, this requires generating a significant amount of statistically-based material property data for each unique material and process combination. Currently, the National Institute for Aviation Research (NIAR) and the Federal Aviation Administration (FAA) are developing a material qualification framework for compression molded discontinuous fiber thermoplastic composites in consensus with industry experts. To aid in the development of the qualification framework, a screening test matrix was formed to identify the key processing parameters and evaluate the appropriate test methods and specimen sizes. Three main variables were considered in the trial testing: reinforcement size, material flow behavior and panel thickness. The effect of these key processing parameters on the mechanical properties are discussed along with guidelines for testing and characterization.

Short Jute Fiber Preform Reinforced Polypropylene Thermoplastic Composite: Experimental Investigation and Its Theoretical Stiffness Prediction.

Natural-based lignocellulose fibrous materials can be used as a sustainable alternative to conventional fossil-based fibers such as glass fibers, in lightweight fiber-reinforced thermoplastic composites for marine, automotive, aerospace, or other advanced applications. However, one of the main challenges in using natural fiber-based thermoplastic composites is the low mechanical performance of composite structures. This can be improved significantly through the development of an optimized novel fiber architecture with enhanced fiber packing properties, following a low-cost production process. In this context, this study demonstrates a less energy-consuming and cheaper manufacturing process, for developing highly individualized short jute fiber-based dry fiber preform architecture, with an improved fiber packing property. Short jute fibers were chemically treated with alkali and PVA sizing treatments in the processing of new fiber preform architectures, and they were used in manufacturing of ultimate short jute fiber/polypropylene (PP) thermoplastic composites. The newly developed short fiber thermoplastic composites showed a significant improvement in mechanical properties (tensile, flexural, and impact) compared to any other natural fiber architecture-based (woven, knitted, nonwoven, unidirectional, etc.) composites found in the literature. Due to the use of new fiber architecture, the developed composites' fiber content was observed to increase. In addition, the compatibility of jute fibers with the polypropylene matrix was strengthened with the application of chemical treatments on highly individualized jute fibers. These reasons were responsible for the enhancement of mechanical properties of developed composites. Micromechanics of the fibers in composites were evaluated using the modified rule of the mixture and Halpin-Tsai equations for stiffness prediction of the composites in order to develop a theoretical understanding of newly developed composites' mechanics. It is thought that the improved mechanical performance of short jute fiber/PP thermoplastic composites can extend the use of these composites in many load-demanding applications, wherein normally synthetic fiber composites are used.

Assessing the shear viscous behavior of continuous carbon fiber reinforced PEKK composites with squeeze flow measurements

Out-of-autoclave processes of carbon fiber thermoplastic composites are gaining interest as they can drastically reduce the economic cost. To optimize consolidation, the flow behavior of these highly filled composites has to be characterized. Here, we propose to measure viscosity of carbon fiber/polyetherketoneketone through squeeze flow experiments in a rheometer. A modified Stefan's law assuming a power law fluid behavior with full anisotropy is developed for square and circular geometries to model the data. Values of the power law parameters K and n are obtained, on the order of 15,000 Pa.sn and 0.02 at 1 bar. Though as expected independent of the samples' geometry and tapes' stacking, K and n depend on the applied pressure and plate size. This is due to localized shear which results in a shear-banding-like phenomenon. Finally, squeeze flow is compared to dynamic measurements and invalidate the Cox-Merz rule for such materials.

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.

Developing fire retardant composites of biodegradable polyethylene reinforced with agricultural wastes

Developing novel natural fiber thermoplastic composites is twofold effective. The Added-value of local agricultural wastes is enhanced and the environmental burden is reduced by less use of imported synthetic fibers and more recycling of agricultural waste. Material selection, parametric optimization, and characterization of biodegradable natural fiber thermoplastic composites with flame retardant properties are carried out in this work. Thermoplastic matrix is linear aliphatic low-density Polyethylene PE. [0–30 wt%] natural fibers of locally produced jute, corn silk, and Bagasse are used for reinforcing. Fibers are cut to different lengths after being alkali-treated. 16–24 % ammonium polyphosphate APP is used for fire retarding at different loadings. A coupling agent is added to link the polymer matrix with the fiber. 3% Ferric Stearate is used for biodegradability activation. The samples are produced using a compounding kneader at 180 °C. Mechanical, water absorption, and flame-retardant properties are characterized. The biodegradability index, which is an indication to what extent the products manufactured from the composite are eco-friendly, is being measured. Jute composites show the highest mechanical properties of 11 MPa ultimate strength and 8 GPa modulus of elasticity, whereas the corn silk composites have better performance of V-2 according to the UL94 flame retardancy test. Water absorption of 15% fiber content is reduced to 1%.

Using long fiber thermoplastic composites as substitutes for metal: design considerations

Long fiber thermoplastic (LFT) composite design studies often emphasize fiber content but are sketchy on fiberorientation, fibermatrix interface, and mold design. At PlastiComp we use an all-inclusive approach to successfully deploy LFT materials in metal replacement applications. Examples show how long carbonfiber compounds were successfully substituted for die-cast magnesium by redesigning the application for injection molding production, achieving tailored fiber architectures at key stress locations through strategic gate locations, as advised through finite element analysis (FEA) and mold flow analysis (MFA), and maximizing mechanical properties through optimized molding processes.

Analysis of Mechanical Properties Related to Fiber Length of Closed-Loop-Recycled Offcuts of a Thermoplastic Fiber Composites (Organo Sheets).

Increasing demand for energy-efficient means of transport has steadily intensified the trend towards lightweight components. Thermoplastic glass fiber composites (organo sheets) play a major role in the production of functional automotive components. Organo sheets are cut, shaped and functionalized by injection molding to produce hybrid components, such as those used in car door modules. The cutting process produces a considerable amount of production waste, which has thus far been thermally recycled. This study develops a closed mechanical recycling process and analyzes the different steps of the process. The offcuts were shredded using two shredding methods and implemented directly in the injection-molding process. Using tensile tests and impact bending tests, the material properties of the recycled materials were compared with the virgin material. In addition, fiber length degradation via the injection-molding process and the influence of the waterjet-cutting process on the mechanical properties are investigated. Recycled offcuts are both comparable to new material in terms of mechanical properties and usability, and are also economically and ecologically advantageous. Recycling polypropylene waste with glass fiber reinforcement in a closed loop is an effective way to reduce industrial waste in a sustainable and economical production process.

Mechanical Properties of High Fiber Volume Fraction Continuous Carbon Fiber Thermoplastic Composites Made by Material Extrusion

Mechanical Properties of High Fiber Volume Fraction Continuous Carbon Fiber Thermoplastic Composites Made by Material Extrusion

Tensile and charpy impact properties of CNTs integrated PET/ Glass Fiber thermoplastic composites with commingled yarn

Tensile and charpy impact properties of CNTs integrated PET/ Glass Fiber thermoplastic composites with commingled yarn

A Study on the Aging Resistance of Injection-molded Glass Fiber Thermoplastic Composites

A Study on the Aging Resistance of Injection-molded Glass Fiber Thermoplastic Composites

Predictions of the Mechanical Performance of Leaf Fiber Thermoplastic Composites by FEA

The available potential plant waste could be worthy material to strengthen polymers to make sustainable products and structural components. Therefore, modeling the natural fiber polymeric-based composites is currently required to reveal the mechanical performance of such polymeric green composites for various green products. This work numerically investigates the effect of various fiber types, fiber loading, and reinforcement conditions with different polymer matrices towards predicting the mechanical performance of such natural fiber composites. Cantilever beam and compression schemes were considered as two different mechanical loading conditions for structural applications of such composite materials. Finite element analysis was conducted to modeling the natural fiber composite materials. The interaction between the fibers and the matrices was considered as an interfacial friction force and was determined from experimental work by the pull out technique for each polymer and fiber type. Both polypropylene and polyethylene were considered as composite matrices. Olive and lemon leaf fibers were considered as reinforcements. Results have revealed that the deflection resistance of the natural fiber composites in cantilever beam was enhanced for several reinforcement conditions. The fiber reinforcement was capable of enhancing the mechanical performance of the polymers and was the best in case of 20 wt.% polypropylene/lemon composites due to better stress transfer within the composite. However, the 40 wt.% case was the worst in enhancing the mechanical performance in both cantilever beam and compression cases. The 30 wt.% of polyethylene/olive fiber was the best in reducing the deflection of the cantilever beam case. The prediction of mechanical performance of natural fiber composites via proper numerical analysis would enhance the process of selecting the appropriate polymer and fiber types. It can contribute finding the proper reinforcement conditions to enhance the mechanical performance of the natural fiber composites to expand their reliable implementations in more industrial applications.

Damage propagation in short fiber thermoplastic composites analyzed through coupled 3D experiments and simulations

Due to the complex nature of the heterogeneous microstructures of short fiber composites, computationally predicting their mechanical behavior, especially past the elastic regime and into the damage initiation and progression regimes, is very challenging. Matrix cracking has notably been difficult to predict because it can propagate in different manners, such as fiber mediated interfacial cracking and conoidal cracking, which have not been well understood. Therefore, this work couples in-situ X-ray micro tomography experiments with a finite element simulation of the exact microstructure to enable a sub-fiber 3D microstructural study by tracking damage propagation and computing the local stresses and strains in the microstructure. Here we show the role of shear stress in interfacial cracking (and how it differs from debonding), the role of hydrostatic stress in conoidal cracking, and the role of environmental damage in longitudinal fiber breakage. In doing so, this work gives insight into the stress states resulting in non-linear damage propagation in thermoplastic fiber composites.

Fabrication of Porous Carbon Films and Their Impact on Carbon/Polypropylene Interfacial Bonding

Porous carbon films were generated by thermal treatment of polymer films made from poly(acrylonitrile-co-methyl acrylate)/polyethylene terephthalate (PAN/PET) blend. The precursor films were fabricated by a dip-coating process using PAN/PET solutions in hexafluoro-2-propanol (HFIP). A two-step process, including stabilization and carbonization, was employed to produce the carbon films. PET functioned as a pore former. Specifically, porous carbon films with thicknesses from 0.38–1.83 μm and pore diameters between 0.1–10 μm were obtained. The higher concentrations of PET in the PAN/PET mixture and the higher withdrawal speed during dip-coating caused the formation of larger pores. The thickness of the carbon films can be regulated using the withdrawal speed used in the dip-coating deposition. We determined that the deposition of the porous carbon film on graphite substrate significantly increases the value of the interfacial shear strength between graphite plates and thermoplastic PP. This study has shown the feasibility of fabrication of 3D porous carbon structure on the surface of carbon materials for increasing the interfacial strength. We expect that this approach can be employed for the fabrication of high-performance carbon fiber-thermoplastic composites.

Characterisation of tape-based carbon fibre thermoplastic discontinuous composites for energy absorption

ABSTRACT Tape-based discontinuous composite is a relatively new type of composite material that offers improved mechanical properties for similar process-ability compared to Sheet Moulding Compound or Bulk Moulding Compound. This makes it potentially attractive for the automotive industry. In this paper, a thin-ply carbon fibre reinforced polypropylene-based discontinuous composite is studied. Mechanical tests are performed to obtain the tensile, compression and shear behaviour of the material. The energy absorption via tearing is also studied to assess the suitability of the material for energy absorption applications, such as crash-boxes. The tearing test results show a large degree of plastic deformation and an advancing damage front leading to higher specific energy absorption via tearing compared to conventional composite materials.

WITHDRAWN: Development of long fiber thermoplastic composites for industrial applications

WITHDRAWN: Development of long fiber thermoplastic composites for industrial applications