Filament Winding Technology Research Articles

Experimental characterization and modeling of cylindrical CFRP structures under quasi-static multiaxial loading conditions

An experimental and numerical investigation of the cylindrical carbon fiber reinforced polymer (CFRP) structures under various loads including tension/torsion loading conditions has been conducted. Various boundary conditions and parameters were taken into account to check the impact of the shear component to obtain the result. The nonlinear shear model proposed by Chang has been implemented to take into account the softening effect of the stress-strain curve caused by damage accumulation. The computational model of the thin-walled tubes contains the geometrical architecture of the material, such as interweaving, which are characteristic of the parts made by filament winding technology. The studies were preceded by preliminary tests of the individual components to predict elastic properties based on the Abolin'sh micromechanical approach. The strength parameters were empirically delivered on the basis of the experimental results and used to determine the failure of the structure. The accuracy of the calibrated nonlinear shear model was validated using strain gauges and digital image correlation techniques. The strain distribution obtained from FEA was compared with that of the optical method. The damage distribution provided by FEA is exhibited in a similar manner to the real one captured by DIC. The proposed model provides a precise prediction of the CFRP tubes under quasi-static loading conditions proven by the experiments.

FEA and experimental ultimate burst pressure analysis of type IV composite pressure vessels manufactured by robot-assisted radial braiding technique

Composite pressure vessels (CPVs) are lightweight and high-strength containers that can be used for the storage of compressed gases, including hydrogen. While hydrogen is a promising alternative energy source, storage of hydrogen comes with its significant challenges which requires a need for the efficient production of CPVs. Most commonly, CPVs are manufactured using filament winding technology. Due to the rise in the need for pressure vessels, there is a need for alternative high-throughput manufacturing techniques. Braided, in comparison to filament winding, has a high throughput and is less research manufacturing technology for CPVs. In this study, the applicability of braiding for the manufacturing of CPV is researched. Two types of 2D braids, namely the conventional and unidirectional, braiding were studied for their application in such structures, 24K and UD tanks, respectively. Dry carbon fiber (T700S – 24K) and HDPE liner were used to manufacture two different types of composite pressure vessels (CPVs), by robot-assisted radial braiding technique. After the preform of the braiding process was finished, CPVs were cured with a vacuum infusion process (VIP) by using a mold system. Produced braided CPVs were subjected to a hydrostatic burst test in order to determine their ultimate burst pressure point. Finite element analysis (FEA) was used to optimize and correlate experimental burst pressure test results. Ansys ACP was utilized to design composite structures by dividing both tanks’ domes into sub-sections. Results suggest that the experimental burst pressure test of 24K and UD tanks were identified as 200 bar and 150 bar, respectively. UD vessel ruptured close to the dome, whereas the 24K fracture point was located in the center of the dome. UD braided CPV was shown to have a smaller apparent burst deformation (rupture) scale than 24K CPV. In comparison to 24K, the UD braided CPV is 5.7% lighter and requires 20.9% less carbon fiber in production. FEA results were consistent with experimental results in terms of the burst pressure point. For both 24K and UD, the fiber failure starts at the point where the cylinder section and boss system are connected under pressure, and fiber failures continue to progress steadily as the pressure increases.

Effect of Process Parameters on Thermal and Mechanical Properties of Filament Wound Polymer-Based Composite Pipes.

The aim of this study was to investigate the mechanical and thermal properties of composite pipes based on epoxy resin and glass fibers produced by filament winding (FW) technology. Epoxy resins are widely used polymers in FW composite structures. The thermal characterization of the neat epoxy resin, curing, and post-curing characteristics for the determination of polymerization and glass transition temperature was performed, which is important for the mechanical properties of polymer composite pipes. In the present work, the applicability of the full factorial experimental design in predicting the hoop tensile and compressive strengths of glass fiber/epoxy resin composite pipes was investigated. The composite pipes in accordance with the 23 full factorial experimental design by using of three parameters and two levels of variation were prepared. The winding speed of the composites was taken to be the first factor, the second was the fiber tension, and the third was winding angle. To approximate the response, i.e., the mechanical properties of the composite pipes within the study domain, the first-order linear model with the interaction was used. The influence of each individual factor to the response function was established, as well as the influence of the interaction of the two and three factors. Additionally, those results were completed with the thermal characterization of the polymer composite pipes. From received results from mechanical and thermal characterization, it was concluded that the properties of composite specimens were highly affected by the analyzed parameters in filament winding technology. It was found that the estimated first-degree regression equation with the interaction gave a very good approximation of the experimental results of the hoop tensile and the compressive strengths of composite pipes within the study domain.

Techno-economic and environmental sustainability analysis of filament-winding versus pultrusion based glass-fiber composite technologies.

In the era of sustainable development, glass-fiber reinforced polymer (GFRP) composites have made their way into modern engineering, construction, and building sectors due to their exponential characteristics. While considering the rapid growth and development in this sector, this research has assessed the relative environmental and techno-economic sustainability of two sorts of GFRP composite technologies: (a) filament winding and (b) pultrusion to effectively appraise their application, merits, and demerits. This study will help low-middle-income countries like Pakistan toward cleaner production, environmental management, and sustainable industrial development. The techno-economic sustainability is determined by using life cycle costing and techno-economic indicators, i.e., benefit-cost (B/C) ratio, net present value (NVP), internal rate of return (IRR), and payback period. The B/C ratio depicts the relationship between the relative cost and benefits of a technology, and NVP expresses the calculated present value of the future payback stream of a technological investment, while the IRR is an effective techno-economic indicators which can predict the efficacy of an investment, and the payback period is the time forecast for a technology to recover its investments. These techno-economic analytics showed that the net life-cycle cost performance, B/C ratio, and IRR are 5%, 7%, and 15% higher respectively for filament winding-based GFRP technology than the pultrusion-based manufacturing technology, whereas overall net life cycle benefits are about 80% greater for filament winding. Similarly, the payback time is shorter for filament winding compared to pultrusion. The environmental sustainability is determined, by employing a relative life cycle analysis (LCA) for both technologies. The system boundary for the study is "gate to gate," i.e., manufacturing phase, where these technologies are assessed for their environmental externalities. The functional unit of "1kg finished product," i.e., manufactured by pultrusion and filament winding technology, and eight life cycle impact assessment (LCIA) categories; climate change potential (CCP), terrestrial eco-toxicity potential (TETP), ozone depletion potential (ODP), fossil resource depletion potential (FDP), acidification potential (AP), eutrophication potential (EP), particulate matter (PM) formation, and water consumption potential (WCP) have been selected. The significant ecological impact scores are determined in the categories of CCP (kg CO2 eq.) as 10.8E + 00 and 5.01E + 00 and ETP (kg. 2,4-D eq.) as 1.26E-02 and 9.47E-03 and FDP (kg Oil eq.) as 3.96E + 00 and 2.59E + 00 for filament winding and pultrusion-based GFRP technologies, respectively. These LCIA results depicted that the ecological performance of filament winding technology is specifically better than pultrusion technology in the categories of EP, PM, and WCP, while, for all other life cycle impact categories, the pultrusion technology has depicted significantly lower impact potential and is environmentally more sustainable. The outcomes of this research will be greatly assistive for researchers, developers, manufacturers, and policymakers to effectively appraise the externalities and selection of a more sustainable GFRP technology.

Jute yarn-wound composites: optimization of methods for evaluating mechanical properties and improvement of mechanical properties

Filament winding (FW) technology is an important molding technology to obtain high-performance filament-wound composites. However, current methods for evaluating the mechanical properties of plant fibers for FW are directly borrowed from those of synthetic fibers, which may not be appropriate due to the heterogeneity of plant fibers and the unique twisting structure of plant fiber yarns. Herein, jute yarn Naval Ordnance Laboratory (JY-NOL) composites were prepared by FW technology using jute yarns (JYs) and epoxy resin (EP) to propose suitable methods for evaluating mechanical properties. Moreover, the improvement mechanism of mechanical properties of JY-NOL composites was elucidated by exploring the effects of the impregnation method, resin mass fraction and winding tension on the mechanical properties of JY-NOL composites. The results showed that the methods for evaluating the mechanical properties of JY-NOL composites with different JY specifications based on a five-layer winding structure were more scientific and reliable than the methods for evaluating the mechanical properties based on a 3-mm thickness. With the increase in the metric count and the decrease in the number of yarn strands of JYs, the glue loading of JYs gradually increased, and JYs had a unique twisting structure, making it difficult for the interiors of JYs to be impregnated with EP. Therefore, the winding parameters related to the impregnation method, resin mass fraction and winding tension were optimized, aiming at improving the impregnation effect of EP on JYs and reducing the voids in JY-NOL composites, thus strengthening the mechanical properties of JY-NOL composites.

The effect of mosaic pattern and winding angle on radially compressed filament-wound CFRP composite tubes

In this paper, the two key parameters of the filament winding technology process are investigated using both experimental and numerical approaches. While the winding angle is a commonly discussed issue, the mosaic pattern is widely disregarded. To examine its influence, nine configurations of the tubular specimens were manufactured (three winding angles and three mosaic patterns). The novelty of the work is that special attention was paid during the manufacturing process to produce comparable one-layered tubular specimens with 100% degree of coverage, which was so far disregarded in the literature. The radial compression test according to ASTM D2412 was performed. Numerical simulations in the elastic regime were carried out using the finite element method (FEM) as a reference for the experimental results. The calculations of corrected stiffness showed a statistically significant difference between the mosaic patterns for a particular winding angle. Compared to the basic mosaic pattern 1/1, for 45° winding angle the growth was 6.3% and 20.9%, for 55° it was 25.1% and 32.2%, and for 75° the increase was 16.5% and 13.5%, for 2/1 and 3/1 mosaic pattern in each winding angle, respectively. Scanning electron microscopy (SEM) revealed characteristic fracture modes depending on the mosaic pattern and winding angle.

A Low-Cost Filament Winding Technology for University Laboratories and Startups.

This paper systematically explains the methodology and results of empirical work on the development of a low-cost filament winding technology for manufacturing axisymmetric polymer composite structures with a high length-to-diameter ratio, such as tubes, motor casings, and pressure vessels. The principal objective was to examine the experiences and most optimal practices in the development of computer-controlled equipment and auxiliary tooling for the wet filament-winding process. To preclude expensive commercial software for the automated control of a winding machine, analytical equations were derived for the winding trajectory of a four-axis filament-winding machine. The feasibility of the proposed equations was successfully validated by laying the fiber along the geodesic path marked on the surface of a cylindrical mandrel with hemispherical ends. Moreover, the carbon/epoxy cylindrical casings with hemispherical ends and port openings of the same diameter were wound to determine the thickness distribution in the hemispherical dome. The fiber volume ratio in the wound composite parts was evaluated using an optical technique.

Hibridne mokronamotane kompozitne cevi (aramidno vlakno/stakleno vlakno)-epoksi smola i (ugljenična vlakna/stakleno vlakno)-epoksi smola - zapreminske, mehaničke i hidraulične karakteristike

In this paper volumetric, mechanical and hydraulic characteristics of filament wound composite one fiber tubes and hybrid tubes are presented. Composite hybrid materials, produced by filament winding technology, are categorized according to different ways of classification of hybrid materials. Four fibrous reinforcement agents (glass G600, polyamide aromatic K49, carbon T300 and carbon T800) and two impregnation agent systems (epoxy 0164 and epoxy L20) are used for manufacturing of filament wound tubes. Density, tensile strength, specific tensile strength, hydraulic burst pressure and specific hydraulic burst pressure of two filament wound glass fiber/epoxy resins tubes (as starting materials) and of twelve filament wound hybrid tubes are investigated. Four highest values of tensile strength and hydraulic burst pressure are of the next schedule: hybrid tubes mark G600-T800/L20 (the highest), hybrid tubes mark G600-T800/0164, hybrid tubes mark G600-T300/L20 and hybrid tubes mark G600-K49/L20. Also, a row of four highest specific tensile strength and highest specific hydraulic burst pressure begins with hybrid tubes mark G600-T800/L20, but the schedule of the next three tubes is different due to density of aramide composite materials (hybrid tubes mark G600-K49/L20, hybrid tubes mark G600-T800/0164 and hybrid tubes mark G600-K49/0164). All filament wound tubes (single fiber tubes and hybrid tubes) with epoxy L20 have a slightly lower density value but higher values of tensile strength, specific tensile strength, hydraulic burst pressure and specific hydraulic burst pressure than appropriate tubes impregnated with epoxy 0164. Obtained results in this testing indicate and emphasize the importance of advanced reinforcing agents (aramide roving and carbon fibers), of impregnating agents (epoxy resin systems) and of the density of hybrid tubes, especially with aramide roving.

Damage Detection of CFRP Filament Wound Tubes Using Electrical Resistance Measurement

The electrical resistance measurement method was used for damage detection of Carbon Fiber Reinforced Polymer (CFRP) tubes during torsion and flexural loading. The symmetrical convex octagon shape specimens were manufactured using a filament winding technology. The specimens were manufactured with Integrated Loop Technology (ILT) joints at the ends in a single production step. This configuration of tubes with ILT joints allows very effective load transfer and it is also efficient from the manufacturing point of view. This type of components could be used in construction of robotic arms for automated processes. Possible collisions and resulting overloading can cause damage to the composite tubes. Such damage could be overlook due to cabling, coating and casing covering the surface of the robotic arms. In addition to the above, the requirement for a smooth surface must also be met. Therefore, possible way how to easily detect serious damage of CFRP tubes was investigated, together with a testing of a novel approach to an electrical contact manufacturing. The electrical contacts for damage monitoring were made of carbon fiber tows with electrically connected endings. They were integrated to the composite structure during filament winding process. Four specimens were loaded by flexural loading and two specimens were loaded by torsional loading. All specimens were loaded by three cycles of operational loading and then loaded to final fracture. It was shown that the presented type of electrical connection to the structure is feasible, does not disturb the surface of the sample and does not affect the ultimate strength of the specimen. According to our measurements, operational loading could be monitored only to a limited extend using the electrical resistance measurement. This is because the fracture damage caused significant change in measured electrical resistance of the specimen for both torsional and flexural loading. The presented measurement configuration with electrodes made of integrated carbon fibers is suitable for further investigation in the field of fracture damage detection of carbon fiber wound profiles.

Development of a topology optimization method for the design of composite lattice ring structures

Composite lattice ring structures are known for their lightweight and high efficiency, which have a strong attraction in the aeronautical and aerospace industries. The general manufacturing process for such structures is to use wet filament winding technology. Due to the anisotropic properties of continuous fibers, the filament winding trajectory determines the mechanical properties of the composite lattice ring structures. In this work, a topology optimization method is proposed to generate the efficient filament winding trajectory, which follows the load transfer path of the composite part and can offer higher mechanical strengths. To satisfy the periodicity requirement of the structure, the design space is divided into a prescribed number of identical substructures during the topology optimization process. In order to verify the effectiveness and capability of the proposed approach, the topological design of ring structures with the different number of substructures, the ratio of outer to inner radius and the loading case is investigated. The results reflect that the optimal topology shape strongly depends on the substructure numbers, radius ratio and loading case. Moreover, the compliance of the optimized structures increases with the total number of substructures, while the structural efficiency of the optimized structures decreases with the radius ratio. Finally, taking the specified topological structure as the object, the conceptual design of a robotic filament winding system for manufacturing the composite lattice ring structure is presented. In particular, the forming tooling, integrated deposition system, winding trajectory and manufacturing process are carefully defined, which can provide valuable references for practical production in the future

A Non-Geodesic Trajectory Design Method and Its Post-Processing for Robotic Filament Winding of Composite Tee Pipes.

With the advantages of high specific strength and well corrosion resistance, polymer-matrix composite tee pipes are widely used in aerospace and civilian fields. The robotic filament winding technology is suitable for forming complex shape parts. This paper aims to provide a novel non-geodesic trajectory design method to get a continuous trajectory for tee pipe winding. Furthermore, post-processing methods are proposed for realizing the full coverage of tee pipes by robotic filament winding. The CAD/CAM software is then designed to simulate the winding process and realize the cover of the whole tee pipe. Finally, experiments of winding a tee pipe with a desktop winding machine and a six-axis winding robot are carried out. The results show that the tee pipe is fully covered, verifying the accuracy of the design method and post-processing methods.

Detection and evaluation of the fibers' deposition parameters during wet filament winding

AbstractWet filament winding technology has been extensively used for the manufacture of rotationally symmetric parts made of fiber‐reinforced plastics (FRP). As the design and modeling of FRP‐parts require numerous assumptions, deviations between calculated and achieved mechanical properties are expected. One aspect that contributes to this discrepancy is the assumption of a homogeneous rectangular cross‐section of the fiber‐band. In this work, the fiber‐band geometry in a wet‐winding process of carbon fiber cylinders is analyzed. An Infrared‐optical system for the detection of the fiber bandwidth and winding‐angle is implemented. The influence of the winding speed and the resin temperature is analyzed. An image processing algorithm for the automatic measurement of the fiber's bandwidth and winding‐angle is developed. Manual and adaptive gamma corrections are implemented to improve image quality. A parameter study for the suitable selection of image processing parameters is performed.

Design and hydraulic tests of a metal liner composite overwrapped pressure vessels with seamless connection technology

In industries such as aerospace, automobile, and petro-chemical, the composite overwrapped pressure vessels (COPV) have become a popular technique with the features of high stiffness-to-weight ratios and the advantages of leak-before-break. Based on the characteristics of filament winding process, a new technology of weldless connection of metal-lined COPV was proposed. The new technology used filament winding technology instead of welding forming process and designed a sealing groove on skirt length of the head to solve the problems of continuity and sealing between the head and the cylinder body. And an auxiliary forming tool was invented to apply filament winding process on this novel liner structure successfully. Then, the feasibility of the new structure was verified by hydraulic test. And the vessel could withstand the blasting design pressure about 110 MPa. Three damage modes were obtained by macroscopically inspecting of the vessel profile. Finally, based on a Chang-Chang failure criterion and the cohesive model, the finite element model of the novel structure was established by writing a user material subroutine VUMAT. The results show the delamination damage is the main damage mode and the fiber tensile fracture at the transition region of the head and cylinder is the main failure mode of the novel structure.

Highly efficient CFRP anisogrid lattice structures for central tubes of medium-class satellites: Design, manufacturing, and performance

A design and manufacturing method for highly efficient CFRP anisogrid lattice shells aiming at central tubes for medium-class satellites is presented in the paper. Central tubes are designed to withstand high inertial forces that are induced by the supported satellite mass and equipment during the launch phase. This requires buckling and material strength other than adequate stiffness. In addition, the typical structure includes several interfaces that are subjected to significant load transfer and need to be properly integrated in the body of the shell. A specifically adapted version of the filament winding technology showed itself to be particularly suitable for this application. The modified process implements a “parallel winding” deposition strategy in conjunction with high modulus dry carbon fibers and resin infusion. However, design and manufacturing issues need to be investigated as a whole in order to minimise the structural weight and be competitive with conventional CFRP structures. In order to demonstrate the performance achievable with an optimal lattice structure, a comprehensive testing campaign was built around two full-scale prototypes: 1) the Technological Model (TM), aimed at the manufacturing process setup and mechanical properties characterization, and 2) the Demonstrator (DM), aimed at global stiffness and strength evaluations culminated with the collapse of the structure.

Experimental investigation on the effects of glass fiber hybridization on the low-velocity impact response of filament-wound carbon-based composite pipes

Recently, the incorporation of several different types of fibers into a single matrix has led to the development of superior hybrid composite properties at a cheaper cost. Fiber hybridization is one of the active strategies to toughen composites and improve impact damage resistance. However, the extraordinary high strength and stiffness of the carbon fiber as well as its lower damage tolerance make it more susceptible under the impact loading. This article mainly aims to improve impact damage resistance of carbon fiber pipes through fiber hybridization strategy with glass fibers under low-velocity impact. The composite pipes reinforced with thin internal liner of high-density polyethylene were fabricated through filament winding technology. Eight pipe configurations with different stacking sequences and fiber content ratios with a constant winding angle of [Formula: see text] were fabricated and tested under impact energies, 50 and 100 J. The damage characterization was evaluated using the optical imaging and mechanical micrograph sectioning technique. Results indicate that the hybrid configurations showed better energy absorption than reference carbon fibers specimen under 50 J impact energy. Specifically, specimens with glass fibers on the exterior side and alternative configuration of carbon–glass fibers showed better impact resistance with less damage observed. Meanwhile, the specimens with glass fiber on the exterior side suffered from extreme damage with increase in the energy absorption and maximum displacement for both fiber content ratios under 100 J of impact energy.

Vibration characteristics of carbon-fiber reinforced composite drive shafts fabricated using filament winding technology

The metal connector and tube of the composite drive shaft were bonded together generally. However, the glued shafts showed numerous risks due to the instability of chemical glues. To avoid potential risks, filament winding with integrated flanges was proposed to prepare carbon fiber-reinforced composite (CFRP) drive shafts in this study. The natural frequency and damping of CFRP shafts were investigated by FEA and experiment. Results revealed that the natural frequency of CFRP shafts embedded in metal flanges is slightly lower than that of the glued CFRP shafts. The metal flanges did not affect the changing trend of the natural frequency with various fiber ply angles or thicknesses, and the damping had little effect on the natural frequency. The natural frequency of CFRP tubes and drive shafts was predicted using FEA and agreed well with the experimental results. The results of this study will be of great significance in the design and application of CFRP drive shafts.

Robotic filament winding: An innovative technology to manufacture complex shape structural parts

The robotic filament winding (RFW) technology consists of an industrial robot that is equipped with a feed and deposition systems; they are suitable for placing a tape along the stress directions the part is subjected to during operation. RFW cell replaces the human operator that is the only system that has been previously used to manufacture complex shape parts. It represents an advantage as regards process control, repeatability and manufacturing times. The present work focuses on the family of structural parts whose shape may be obtained as a result of a full section sweeping along a closed non auto-intersecting 3D curve. The aim of the paper is to present a design methodology for the forming process of complex shape structural parts by RFW, in order to obtain structural homogeneity and fibre content uniformity, and so to demonstrate the potential of an innovative robotic cell for manufacturing these parts.

Mokro namotano kućište filtera - ključ za racionalno prečišćavanje jako korozivnih rastvora

Practical and realistic approach for a successful use of filament wound filter housing based on bisphenol A polyester resin for purification of highly corrosive contaminated solutions is presented in this paper. Filament winding technology and basic terms about polyester and polymeric composite materials are described. Data about modes of producing neat (no reinforced) bisphenol A polyester resin specimens and composite material specimen, based on mentioned resin and glass fiber, are presented. Neat resin specimens were exposed to the single influence of aqueous solution of calcium hypochlorite, of sodium hydroxide, of sulphuric acid, of citric acid and liquid detergent for a period of 360 hours each, separately, and to the cumulative influence of all mentioned aqueous solutions for in overall period of 1440 hours. Tested properties of these specimens (mass change, hardness and impact resistance) showed that there is no negative influence on neat bisphenol A polyester resin quality. Filament wound composite reinforced glass fiber/bisphenol A polyester resin-based rings and cylinders were exposed to the influence of calcium hypochlorite aqueous solution for 1128 hours. Results of testing mass change, tensile breaking force and tensile strength of composite reinforced rings and hydraulic burst pressure of composite reinforced cylinders indicated that these specimens have high resistance to mentioned purification agent. It is concluded that the filter housing for purification of highly corrosive contaminated solutions can be produced by filament winding technology using bisphenol A polyester resin and glass fiber.

3D truss structures with coreless 3D filament winding technology

A coreless manufacturing process for generic 3D rigid frame topologies will be introduced in this paper. The aim is to extend the field of filament winding from mainly 2D-shells and some exceptional cases of 3D rigid frames. This manufacturing process employs a coreless translation cross-winding method in order to continuously deposit a roving around deflection points in space. On this basis, a design methodology is being created and deductively verified by designing a beam for a three-point bending load case. The composite beam is designed on a macro level simulation approach to match the stiffness of a reference aluminum profile, which is commonly employed as structural component for robotic gripper systems in automotive assemblies. The performance of the beams is subsequently compared by three-point bending experiments. This demonstrates that the composite beam offers equivalent stiffness and strength properties with a weight-reduction potential of nearly 50% for bending loads.

Shape retainability and reusability investigation of bottle-shaped SMP mandrel

Shape memory polymer (SMP) mandrel, a kind of mandrel for fabrication of composite structures, has attracted great attention due to the advantages of low cost, simple operation and easy demoulding. In this paper, a type of styrene-based SMP with good shape retainability and recoverability were synthesized and examined by uniaxial tensile test and dynamic mechanical analysis test. Then, a bottle-shaped smart mandrel with shape memory effect was prepared by inflation method. Short/long-time shape retainability and reusability were characterized. Finally, the SMP mandrel was used to form a bottle-shaped composite structure model by filament winding technology. The excellent demoulding property and good reusable ability of SMP mandrel provided potential applications in the composite part production.