Thermoplastic Matrix Materials Research Articles

Experimental and numerical analysis of new thermoplastic composite mandrels

In the field of aerospace, the application of carbon fiber composite parts is increasing year by year. As an important factor in the manufacturing of composite parts, tools play a crucial role in the manufacturing accuracy of composite parts, and composite tools have higher accuracy to better meet the manufacturing requirements. In this study, the properties of the novel thermoplastic composite mandrel of the new polymethyl methacrylate matrix are further investigated and a model is proposed to simulate the curing and spring back process of the composite part with the proposed composite mandrel. In detail, the glass transition temperature test and dynamic frequency test were carried out for the thermoplastic composite mandrel. The material constitutive equation of the thermoplastic composite mandrel was constructed based on the experimental data, and the accuracy of the constitutive equation of thermoplastic matrix material was verified by tensile experiments of matrix materials under constant strain conditions. Finally, the simulation result is compared with the fabricated part, and the effectiveness of the proposed method has been verified. This proved that the developed constitutive model of thermoplastic composite mandrel can effectively predict the curing deformation of composite parts with complex structures.

Evaluating the impact of filler size and filler content on the stiffness, strength, and toughness of polymer nanocomposites using coarse-grained molecular dynamics

Their great versatility makes polymer nanocomposites an important class of engineering materials. In order to gain detailed insights into the nanoscale mechanisms underlying their macroscopic mechanical properties, molecular dynamics (MD) simulations are a valuable tool to complement experimental studies. In this work, we modify the analytical potential functions of an efficient bead–spring model representing a generic polymer nanocomposite to account for the breaking of covalent bonds. We perform uniaxial tensile simulations of double-notched specimens and validate the model using experimental trends for overall stiffness, strength, and toughness. First, we study the effects of sample size, notch geometry, strain rate, temperature, and molar mass for the pure thermoplastic matrix material. Second, we analyze the influence of filler size and filler content on the mechanical behavior of the polymer nanocomposite. With this study, we show that in both the development of new materials and the optimization of established materials, it is possible to gain important preliminary insights into the effects of pertinent material characteristics with a simple MD setup, which can then be further refined by increasing the complexity of the material description and the boundary conditions.

Modeling the anisotropic squeeze flow during hot press consolidation of thermoplastic unidirectional fiber-reinforced tapes

The anisotropic material behavior of continuous-fiber-reinforced composites that is evident in their mechanical properties should also be considered in their processing. An important step in the processing of thermoplastic unidirectional (UD) fiber-reinforced tapes is consolidation, where a layup consisting of locally welded UD tape layers is firmly bonded. Compression of the molten thermoplastic matrix material during consolidation leads to a squeeze flow, the direction of which is determined by the fibers. This work presents a model that describes the influence of fiber direction on compression and flow behavior, implemented in the computational fluid dynamics (CFD) software tool OpenFOAM®. To validate the simulation results, we performed experiments in a laboratory consolidation unit, capturing the squeeze flow with cameras and then quantifying it by gray-scale analysis. The specimens used were UD polycarbonate tapes (44% carbon fibers by volume) of various sizes and with various fiber directions. The simulation allows prediction of the changes in specimen geometry during consolidation and is a first step towards optimizing the process by avoiding extensive squeeze flow.

Hydrogen permeability of thermoplastic composites and liner systems for future mobility applications

High pressure hydrogen permeation tests were carried out and specific permeation rates of various thermoplastic matrix materials have been measured as well as of continuous fiber reinforced thermoplastic composites (PA6, PA12, PA410, PPA, PPS), considering non-crimp and crimp textile architectures. Furthermore, liners based on thermoplastic high barrier films made of EVOH were applied on PA6 composites and their effect on permeation rate were investigated. All samples were accompanied by pressure tightness tests and micrographs to determine manufacturing effects, microstructure, porosity and additional defects like microcracks. Experiments show that thermoplastic composites can reach low permeation rate as long as a damage-free microstructure is ensured. Furthermore, the influence of the matrix material can be assessed, whereby the influence of the textile architecture can only be roughly estimated and is considered to be small. EVOH layers show remarkable barrier properties and are easy to integrate into the composite structure.

Interface Characterization of Consolidated PPGF Tapes on PPGF Mat Material.

Laminated composites with thermoset matrices are already well established in major engineering fields like automotive and aviation. The primary drawbacks of such thermoset-based composites are the high cycle times required during manufacturing and their limited potential for recycling. Providing an alternative to thermoset-based composites, thermoplastic matrix materials gained more and more momentum by addressing these previously mentioned drawbacks. The preferred manufacturing technique for these materials employs fiber-reinforced thermoplastic tapes consolidated and formed together with a compatible substrate. The most critical aspect for all these applications is the stress or load transfer between the thermoplastic tapes and the substrate. If the interface is too weak and fails prior to the substrate or tape, a high amount of theoretical mechanical performance is lost. The presented research investigates the influence of variations in manufacturing parameters, within the industrially relevant process window, on the interface strength of the final composite. The investigated composite material consists of PPGF UD tapes consolidated on a PPGF mat substrate. In particular, the influence of the consolidation parameters of pressure, temperature, and time are of special interest. The results of this work reveal a 400% increase in the measured mean strain energy release rate upon increasing the consolidation time from 60 s to 120 s at a consolidation temperature of 230 °C and a pressure of one bar. In contrast to this, an increase in the consolidation pressure, at constant temperature and time, leads to a minor improvement in the GC value of 20%. For testing and characterizing the corresponding interface properties, a mandrel peel testing setup was employed.

Thermoplastic matrix material influences on the mechanical performance of additively manufactured carbon-fiber-reinforced plastic composites

Materials design and development continue to be more relevant as applications continue to rise for additively manufactured carbon-fiber-reinforced-plastic (CFRP) composites. Plastic matrixes bond and protect the fiber and help to transfer load through the composite to support intended applications. This makes it more necessary to understand the influences of thermoplastic matrixes on the mechanical performance of the composites fabricated through the additive manufacturing (AM) technique. This study investigated Acrylonitrile–Butadiene–Styrene (ABS) and Polyamide (PA) matrixes, which represent the bulk of the amorphous and semicrystalline engineering-grade thermoplastics matrixes, respectively, used in CFRP composite applications. Mechanical properties: tensile, compression, flexural, and thermal properties were examined, with the results showing the thermoplastic matrixes compositions and morphologies influences on the mechanical properties. The CF-PA was found to offer superior strength, ductility, and toughness because of their close-packed ordered lamellar matrix morphology, while the CF-ABS was found to offer superior modulus because of their loose morphology which more easily rearrange in reaction to stress upon elastic deformation. The mechanical properties results were reinforced by the fracture failure modes and the thermal analysis results which showed the CF-PA composite’s ability to withstand higher mechanical performance and temperatures before failure.

Comparison of lightning strike behavior between carbon fiber reinforced materials with thermoset resin matrix and thermoplastic resin matrix

One of the weak points of the structures made of carbon fibre reinforced materials and thermosetting matrix is its mechanical impact behavior. In order to improve it, materials reinforced with carbon fiber and thermoplastic resin matrix are under study. In addition to the mechanical properties there are other factors to consider before introducing any structural material in the manufacturing of an aircraft, such as its lightning strike behavior. Materials properties that influence this behavior are mainly electrical, thermal and also mechanical; and these properties are modified from thermoset resins to thermoplastics. Within the Clean Sky program Airbus Defense and Space has carried out preliminary tests on flat panels manufactured by Fidamc with a carbon fibre reinforced material and thermoplastic resin matrix with two different configurations, both layout and additional (with and without metallization) The tests objective was the evaluation and comparison of the damages obtained after a lightning strike in flat panels made of traditional materials (thermoset matrix) with those made with new thermoplastic matrix materials. Both the mechanical damage and the temperatures generated in the material (using a thermal camera during the test) were analyzed in order to compare the thermal behavior of the thermoplastic matrix against the thermostable. This article shows the work done as well as results and conclusions.

Automatically controlled laser-based welding process for repair of CFRP parts

Due to a high strength-to-weight ratio, carbon fiber-reinforced plastics (CFRPs) have become a standard in the lightweight industry, which results in the development of new machining and repairing methods. Specifically, CFRP with a thermoplastic matrix material is more attractive for many applications as a thermosetting matrix material. Thermoplastic matrix materials enable new joining processes due to their thermoformability and weldability. Currently, the repair process is mainly executed manually. In order to reduce repair costs, an automated, reliable, and fast process is needed. For the new laser-based repair process, first a scarf joint is prepared in a CFRP laminate consisting of a thermoplastic polyphenylene sulfide matrix material. To refill the scarf, a patch with the same matrix material and fiber setup as the original laminate is cut into shape and welded into the scarf area. In order to obtain a reliable and stable welding process resulting in high weld seam qualities, an automated controlled welding process is being used, which controls the laser power via the surface temperature, which is detected by a pyrometer. For the development of the welding process, the influence of the welding time and the surface temperature on the resulting weld seam quality were evaluated. For the analysis of the joining quality, overlap samples were welded and tested in order to determine the weld seam strength. In addition, cross sections were prepared and analyzed with a microscope. Finally, the measured results were correlated in order to determine a parameter set generating a high-quality weld seam.

ТЕХНОЛОГИИ ПОЛУЧЕНИЯ ПОЛИМЕРНЫХ КОМПОЗИЦИОННЫХ МАТЕРИАЛОВ НА ОСНОВЕ ТЕРМОПЛАСТИЧНОЙ МАТРИЦЫ (обзор)

Various technologies for the production of prepregs based on a thermoplastic matrix and composite materials based on them are considered. Their advantages over the technologies of manufacturing polymer composite materials based on a thermosetting matrix are presented. It is shown that the use of melt technology allows the production of fiberglass with the highest level of strength characteristics. An algorithm for estimating residual stresses in a thermoplastic composite to optimize the technological process of producing complex products is described.

Quasi-static and high strain rate response of Kevlar reinforced thermoplastics

The present study deals with the quasi-static and high strain rate characterization of Kevlar-129 based thermoplastic composites. Two different thermoplastic matrices, namely, Polypropylene (PP) and Polyetherimide (PEI) were used to manufacture composite laminates. Quasi-static compression tests were performed at strain rates of 0.041 s−1 and 0.045 s−1. High strain rate tests were performed using a split Hopkinson pressure bar apparatus within the strain rates ranging from 2548 s−1 to 4379 s−1. Stress-strain relations reveals the rate-sensitive behaviour of composites. Kevlar/PP (K-PP) showed higher peak stress under quasi-static loading as compared to the high strain rate test. Comparable peak stresses were revealed under quasi-static and high strain rate loading for Kevlar/PEI (K-PEI) composite. Also, high strain rate compression properties such as peak stress, peak strain and toughness of K-PP were 25%, 27% and 6% higher than that of the K-PEI composite. The failure mechanisms of both the composites were characterized through macroscopic and scanning electron microscopy. K-PP failed majorly due to matrix crush and fibre failure while K-PEI failed due to shear cracking. Damage study reveals that a single fibre based composite system can be tailored to act as an energy-absorbing or dissipating material system by varying the thermoplastic matrix materials.

An anisotropic creep model for continuously and discontinuously fiber reinforced materials

AbstractThe present study is concerned with the formulation, implementation and validation of anisotropic creep laws for neat thermoplastic matrix materials, discontinuously long fiber reinforced thermoplastic (LFT) composite materials with process dependent fiber preference directions as well as unidirectionally fiber reinforced thermoplastic tapes. Based on a simple three term Kelvin‐Voigt approach, an anisotropic model is formulated and implemented into a finite element program. The model is validated against an experimental data base of creep experiments on continuously and discontinuously fiber reinforced materials.

Characterization of tanalith E treated wood flour filled polylactic acid composites

In this study, it was investigated the feasibility of wood-plastic composites (WPCs) made of polylactic acid (PLA), as a biobased thermoplastic matrix material and treated wood flour (Pinus sylestris L.) with Tanalith E, as organic reinforcement of matrix material. The wood flour amounts in composites were 30, 40 and 50 wt% by weight fiber loadings. Maleic anhydrid grafted polyethylene (MAPE) as a coupling agent was also used to improve the compatibility between the fiber and plastic matrix. Density, void content, water absorption, thickness swelling, tensile test, flexural properties, impact strengths, thermal properties, microstructural and morphological characterization and durability against white rot (Trametes versicolor (MAD-697) (L:Fr.) Pilat) and brown rot (Coniophora puteana ((Schumach.: Fr.) P. Karst (Mad-15)) were used to characterize the WPCs properties. Results revealed that WPCs with untreated wood flour had higher densities compared to those of WPCs with treated wood flour for the same wood contents due to higher void content of treated wood flour-PLA composites. In addition, water absorption and thickness swelling rate of WPCs increased with an increasing the fiber content in WPCs. Regarding to mechanical properties, PLA composites with treated wood flour content of 40 wt% showed best mechanical performance among the different fiber contents. The percentage of weight loss and residual ratio increased with increases in both the wood flour content and the temperature. All tested WPCs had lower weight losses than that of control (untreated wood) samples due to encapsulation of wood by biobased thermoplastic matrix.

In Situ Joining of Unidirectional Tapes on Long Fiber Reinforced Thermoplastic Structures by Thermoplastic Automated Fiber Placement for Scientific Sounding Rocket Applications

Automated Fiber Placement allows the automated lay-up of tailored laminates in aerospace quality. For thermoplastic matrix materials, the use of closed-loop temperature control enables an in situ consolidation. This makes autoclave curing superfluous and increases the overall process efficiency. Scientific sounding rockets typically consist of several aluminum modules carrying the scientific payload. The design of a module includes a cylindrical outer shell and two load input rings with a defined assembly interface. Reducing the structural weight would allow higher payloads, higher apogees or reduced fuel consumption. A new manufacturing concept using the Thermoplastic Automated Fiber Placement (TP-AFP) process was developed to manufacture a lightweight composite module.This paper presents the developed concept and focuses on the characterization of an in situ joint of TP-AFP tapes on a long fiber reinforced thermoplastic (LFT) structure. This represents the joint of the cylindrical shell on the load input rings of the rocket module. The joint was characterized with single lap shear tests for two different sample extraction areas at room temperature and at elevated temperature on pre-treated and untreated LFT surface.The variations did not show significant effects on the resulting shear strength. The results were considered for the design of the composite module allowing a weight reduction of more than 40 % compared to the aluminum modules. The new module proved its airworthiness as part of the sounding rocket mission REXUS-23 in March 2019. Beyond sounding rockets, the concept of in situ bonded TP-AFP tapes on complex LFT structures has many potential applications within aerospace but also automotive structures.

Mechanical properties of composite parts manufactured in FDM technology

PurposeThis paper aims to study strength properties and accuracy of a new type of composites, in which matrix is manufactured additively, whereas infill is a polyurethane resin. The process of manufacturing these composites is invented and patented by authors.Design/methodology/approachThe authors developed a method of manufacturing composites, which was then used to build samples for tensile and bending tests (according to ISO 572 and ISO 178 standards), as well as measurements of accuracy.FindingsIt was found that the method of composite manufacturing designed by the authors allows obtaining both stronger and cheaper parts in comparison with the traditional acrylonitrile butadiene styrene FDM parts.Research limitations/implicationsThe research was limited to static tests only, and no dynamic tests were performed on the manufactured samples. The accuracy analysis is only a basic one.Practical implicationsDeveloped method allows to shorten the FDM process with simultaneous decrease of costs (in professional processes) and increase of strength of obtained products.Originality/valueApplication of composite materials presented in the paper will significantly expand possibilities of using FDM method to manufacture functional, strong parts able to carry higher loads. Application of different combinations of thermoplastic matrix materials with different resin infills will allow to control properties of obtained composites. The solution is currently subject of a patent.

INFLUENCE OF COCONUT SHELL ADDITION ON PHYSICO-MECHANICAL PROPERTIES OF WOOD PLASTIC COMPOSITES1

ABSTRACT In this study, composites with three types of thermoplastic matrix and cellulosic material in a proportion of 40% were produced. The three thermoplastic matrices were high density polyethylene (HDPE), polypropylene (PP) and low density polyethylene (LDPE), and the cellulosic materials were pure wood flour (Pinus taeda L) or a mixture of wood flour and coconut shell flour (Cocus nucifera L) in equal ratios. The objective was to evaluate the influence of addition of coconut shell on the physico-mechanical properties (density, strength and rigidity) and the distribution of the cellulosic material in the thermoplastic matrix of the manufactured composites. It was found that the composites had a satisfactory distribution of wood flour in thermoplastic matrices, but the addition of coconut shell promoted bubble formation in the resulting pieces and, thus, interfered with the material properties. The use of a coupling agent promoted interfacial adhesion (cellulose - thermoplastic matrix), which was better in high density polyethylene composites, followed by polypropylene and low density polyethylene. In general, the coconut shell addition caused a decrease of all properties compared to composites made with Loblolly Pine. In addition, the interactions between thermoplastic type and cellulosic matrix type have been statistically confirmed, which caused variations in the studied properties

Methodological approach to investigate the behavior of the structure under dynamic loading using multiple criteria decision-making method

The main objective of this article is to develop a support approach for designers in the concept phase of the design process. In this paper, two different structures are investigated with metal, composite and hybrid material under dynamic loading with multiple strain rates. The optimum choice of material and structural combination is found by a methodological approach using a Multi Criteria Decision Making Method (MCDM). It uses a stepwise procedure in evaluating the significance of each criterion and ranks the different alternatives. This method is applied to solve various problems in the field of economics, engineering, management. In this article, COPRAS is used to rank different material and structural combination.Cylindrical and rectangular structures are investigated under axial and 3-point bending load. Moreover, three different constellations of material widen the comparison; they are steel and aluminum, composite material with carbon fiber and thermoplastic matrix and hybrid material, with a combination of composite and metal. The output parameters from the simulation such as energy absorption and force, are further mathematically converted to specific energy absorption (SEA), crash-force-efficiency (CFE) and load non-uniformity (LU). PAM-Crash is used as a solver for simulation.

Aplicaciones de caucho reciclado: Una revisión de la literatura

La generación de residuos de caucho se ha convertido en una preocupación global por su impacto negativo en el medio ambiente y en la salud humana. La legislación ambiental sobre la disposición de este tipo de residuos ha venido aumentando las exigencias a los fabricantes, comercializadores y usuarios, con lo cual se ha acelerado la búsqueda de alternativas para el reaprovechamiento de los residuos de caucho. Este artículo presenta una revisión bibliográfica acerca de las principales tendencias en la utilización del caucho reciclado, incluyendo aplicaciones actualmente comercializadas y otras derivadas, tanto de estudios terminados, como de líneas de investigación en desarrollo. Las aplicaciones con mayor potencial de volumen consumido son del sector infraestructura y construcciones civiles, especialmente asfaltos, concretos y materiales aislantes para construcción liviana. Algunas aplicaciones con potencial en el futuro cercano son los filtros para la limpieza de aguas contaminadas y como componente en materiales compuestos con matriz termoplástica o en poliuretano. Por último, se evidencia la pertinencia de continuar investigando sobre esta temática que posee unos retos científicos de alta relevancia, los cuales ameritan la mayor atención por el problema ambiental significativo asociado al manejo de los residuos de caucho.

Simultaneous Grasping and Heating Technology for Automated Handling and Preforming of Continuous Fiber Reinforced Thermoplastics

Nowadays large-scale production systems for lightweight car-bodies made of composite materials become increasingly important. Especially, the use of thermoplastic matrix materials makes these composites worthwhile for large quantities. However, these so-called organo-sheets must be heated above melting temperature before manufacturing. In this state, the composite becomes form unstable, which complicates the handling in an automated process. To simplify the handling, this paper presents an approach, which allows the handling, heating and preforming of organo- sheets. This includes the introduction of a robot-tool, which is composed of heatable vortex-grippers and a folding mechanism, as well as a analysis of its automation potential.

Intrinsic Hybrid Composites for Lightweight Structures: Tooling Technologies

The increasing use of hybrid materials requires efficient manufacturing processes. With the concept of the intrinsic hybrids the shaping or forming of the part is combined with the hybridization in the same process step and thereby the same tool. Hence new tooling concepts, which realise the process requirements, are necessary. This paper describes tooling concepts and design methods for the manufacturing of intrinsic hybrid parts. Different solutions for rotational and planar parts with thermosetting or thermoplastic matrix material are presented. Additionally the integration of inserts in such tools is discussed. Finally the main challenges for the design of tools for intrinsic hybrids will be presented.

High Volume Production Technology for Corrosive Resistant Long-Fiber-Reinforced Plastic Extinguishers

Portable fire extinguishers need to be reliable and fully functional at all given environmental conditions. Especially in off-shore and power plant applications a specific range of properties is necessary, e.g. corrosive resistance and electromagnetic compatibility. Hence, the application of fiber reinforced composites and fiber composite design offers an alternative to the traditional application of metallic materials.Within the scope of the development of an innovative fire extinguisher, a process-chain for manufacturing of composite fire extinguishers suitable for aggressively corrosive environmental conditions was developed. The aim of the project has been the development of a fire extinguisher with the technology of thermoplastic composite materials. Besides the intended weight reduction, a concept for the realization of a high-volume production suitable process-chain had to be developed. Using a thermoplastic matrix material allows a corrosive-free, non-magnetic and functional integrated design. Within the scope of the research project, the extinguisher container with integrated base and connection for the valve has been dimensioned and designed. The containers geometry with optimized ratio of filling volume, overall part size and material utilization was derived by applying FE analysis. Furthermore, a process-chain for high-volume production was conceived and had been verified by producing functional demonstrators for further testing.The container is made of two glass-fiber reinforced injection molding parts being thermally joined. The leakproofness and sufficient material strength after the joining process were identified as key challenges of the joining process and were overcome with an adapted design of the molded parts. Within the process development, reproducible and high quality weld joints were achieved based on a robust and cost-efficient joining technology. For reliable processing, the specific processing parameters were analyzed and regulations for each processing step deduced.