Tailored Fiber Placement Research Articles

Waviness and fiber volume content analysis in continuous carbon fiber reinforced plastics made by tailored fiber placement

In this paper, the influence of Tailored Fiber Placement (TFP) processing-related parameters on in-plane waviness and fiber volume content of unidirectional carbon fiber reinforced plastic (UD-CFRP) composites is experimentally investigated. Twelve UD-CFRP laminates, whose preforms are produced via TFP, are manufactured by considering different values of stitch width, stitch distance and stitch sequence as well as two different stitching yarn types by resin transfer molding (RTM). The investigated TFP parameters are representative of the producing capability of a typical TFP machine. Based on calibrated high-resolution photographic images and manual recognition of the roving orientation on the laminate surface, the in-plane waviness is qualitatively and quantitatively measured using Fourier analysis. With this approach, the dominant waviness, in-plane wavelengths, and amplitudes of different stitching parameters can be evaluated. Both mean fiber volume content within the roving and within the TFP layer are determined through optical micrographs of the produced laminates. Experimental results reveal that the resulting waviness and the fiber volume content in the roving and within the TFP layer strongly dependent on TFP process parameters. In particular, the stitch width plays a major role on both fiber volume contents, whereas the stitch distance is less relevant.

Buckling optimization of composite cylinders for axial compression: A design methodology considering a variable-axial fiber layout

Fiber steering is an outstanding capability for producing composite structures with spatially tailored properties. The ability of tailoring the reinforcement arbitrarily in the space generates laminate with variable-stiffness, possessing substantial scope for outperforming traditional constant-stiffness laminates. This investigation presents a methodology to optimize composite cylinders with a variable-axial (also known as variable angle-tow and variable-stiffness) layout under axial compression for the adopted design space, loads and boundary conditions, using a novel optimization concept based on the manufacturing characteristics of the Tailored Fiber Placement (TFP) process. Next, a post-buckling analysis is carried out in order to make a first assessment of the imperfection sensitivity of the cylinders. The current approach locally optimizes both thickness and fiber angle of each finite element (FE), where thickness accumulation is reached through a smooth overlapping of rovings, a typical characteristic of TFP process. The optimized cylinders have significantly higher linear buckling loads than the corresponding initial layouts and are less sensitive to affine initial geometrical imperfections. The current work on optimization of the linear buckling behavior of variable-axial (VA) shells shows both the potential of using VA-configurations to exploit their tailoring ability and the capabilities of the current optimization framework to improve and optimize the behavior of VA structures.

Optimizing Variable‐Axial Fiber‐Reinforced Composite Laminates: The Direct Fiber Path Optimization Concept

The concept of aligning reinforcing fibers in arbitrary directions offers a new perception of exploiting the anisotropic characteristic of the carbon fiber‐reinforced polymer (CFRP) composites. Complementary to the design concept of multiaxial composites, a laminate reinforced with curvilinear fibers is called variable‐axial (also known as variable stiffness and variable angle tow). The Tailored Fiber Placement (TFP) technology is well capable of manufacturing textile preforming with a variable‐axial fiber design by using adapted embroidery machines. This work introduces a novel concept for simulation and optimization of curvilinear fiber‐reinforced composites, where the novelty relies on the local optimization of both fiber angle and intrinsic thickness build‐up concomitantly. This framework is called Direct Fiber Path Optimization (DFPO). Besides the description of DFPO, its capabilities are exemplified by optimizing a CFRP open‐hole tensile specimen. Key results show a clear improvement compared to the current often used approach of applying principal stress trajectories for a variable‐axial reinforcement pattern.

CFRP manufacturing method by using electro-activated deposition and the effect of reinforcement with carbon fiber circumferentially around the hole

For the efficient manufacturing of carbon fiber reinforced plastics (CFRP), the electro-activated deposition resin molding (ERM) method is developed. The carbon fiber fabric is immersed in an electro-activated deposition solution containing polymer with epoxy groups. By energization, an epoxy resin is precipitated on the surface of the carbon fiber, and impregnation occurred in the solution. In this study, applying the ERM method, CFRP specimen with the hole was manufactured. Furthermore, the reinforcement by arranging the fiber circumferentially around the hole was installed. The carbon fiber fabric was sewn using the tailored fiber placement (TFP) machine. As a results, the effect of the reinforcement was confirmed. The tensile strength of CFRP with the hole and the reinforcement was the same as in the case without the hole. From the finite element analysis, it was confirmed that the reinforcement around the hole reduced the stress concentration.

Effect of configuration in intermediate materials on textile processability by TFP technology

Continuous fiber reinforced thermoplastic (c-FRTP) has been focused on because of not only the excellent specific rigidity and strength but also the recyclability and the secondary workability due to a feature of the thermoplastic resin as the matrix. However, unlike the thermosetting resin, it is very difficult to impregnate thermoplastic resin into continuous fiber bundles because of its high melt viscosity. In order to solve this problem, various intermediate materials have been developed. On the other hand, Tailored Fiber Placement (TFP) is a textile manufacturing technology for continuous fiber preforming. Compared to other textile manufacturing processes, the continuous fiber material can be placed in any direction according to the requirement. From this characteristic, it is possible to change the local fiber orientation in the fiber reinforced composite material, so that mechanical properties of reinforcing fibers can be utilized to maximum. Applying fibrous intermediate material for c-FRTP to TFP technology, the high cycle c-FRTP molding with optimized fiber orientation can be achieved. However, in order to prepare a preform of c-FRTP, textile processability (flexibility) is needed for fibrous intermediate materials as dry fiber. Therefore, to develop fibrous intermediate material with both better impregnation property and flexibility for TFP technology is required. In this study, the effect of fabrication condition of newly developed fibrous intermediate material called PCY (Partially Impregnated Commingled Yarn) on preforming by TFP technology was investigated. The textile processability was evaluated by measuring the deformation resistance of various PCYs. The unidirectional (UD) preforms were prepared using PCY with better textile processability and impregnation property. In order to investigate the effect of stitch yarn on impregnation property during molding, the impregnation state was quantified by cross-sectional observation of various specimens. In addition, a tensile test using UD specimen was carried out to investigate the effect of stitch yarn on mechanical properties.

Tailored Fiber Placement in Thermoplastic Composites

Fiber path optimization methods combined with the Tailor Fiber Placement (TFP) technology provide the optimum correlation between load case and fiber orientation and therefore lead to unmatched component performance with endless fiber composite materials. The aim of this work is the development of an innovative manufacturing technology for thermoplastic composites (TPC) including sizing-adapted commingled glass fiber (GF) / thermoplastic yarns (SpinCom yarns) to be processed by TFP to textile preforms with a variable-axial, load adapted fiber design. Furthermore, these preforms will be consolidated in a low energy and resource consuming process using novel light and low cost forming tools produced by incremental sheet metal forming technology. Finally, a low cost solution for thermal processing even for complex shaped TPC parts will be presented. Heading towards optimized resource and cost efficiency of the whole process chain, first results of SpinCom yarns, fiber path optimization, tool manufacturing and forming procedure are presented and demonstrated using GF/PBT (polybutylene therephthalate) SpinCom yarns and the geometry of a bicycle saddle.

Press Forming of Thermoplastic Composite Fabricated by Tailored Fiber Placement Machine

Press Forming of Thermoplastic Composite Fabricated by Tailored Fiber Placement Machine

Development of 2D and 3D structured textile batteries processing conductive material with Tailored Fiber Placement (TFP)

In recent years smart textiles have gained a significant increase of attention. Electrotherapeutic socks, light emitting dresses or shirts with integrated sensors, having the ability to process data of vital parameters, are just a few examples and the full potential is not yet exhausted: Smart textiles are not only used for clothing purposes. Sensors for the care of the elderly, light applications for home textiles and monitoring systems in the automotive section are promising fields for the future. For all these electrical and electronic features, the supply of power is needed. The most common used power supplies, however, are not flexible, often not lightweight and therefore a huge problem for the integration into textile products. In recent projects, textile-based batteries are being developed. Metal-coated fabrics and yarns (e.g. silver, copper, nickel, zinc) as well as carbon based materials were used to create textile based energy sources. This article gives an overview of textile based electrochemical cells by combining different conductive yarns and a gel-electrolyte. The available materials will be processed by embroidering utilizing tailored fiber placement (TFP). The electrical characteristics of different embroidered patterns and material combinations are examined.

Development of adaptive hinged fiber reinforced plastics based on shape memory alloys

This paper presents the development of adaptive hinged fiber reinforced plastics based on structurally integrated shape memory alloys. To realize this novel smart structure, hinged preforms are realized, shape memory alloys are converted into actuating hybrid yarns with tailored adhesion properties using the friction spinning technology, the hybrid yarns are integrated on the surface of the hinged preforms by tailored fiber placement and finally the hybrid yarn integrated hinged preform is infiltrated by a suitable thermoset resin. Additionally, the deformation behavior of adaptive hinged fiber reinforced plastics is tested and results are evaluated with regard to quasi-static and dynamic aspects. The maximum deformation and the deformation speed on the heating as well as on the cooling cycle strongly depend on the hinge width of adaptive fiber reinforced plastics and the meander distance of the hybrid yarn embedded in it.

Evaluation of fiber-spacing and vibration characteristics of CFRP plates fabricated by Tailored Fiber Placement Machine

Evaluation of fiber-spacing and vibration characteristics of CFRP plates fabricated by Tailored Fiber Placement Machine

Integration of excess material into a semi-finished product to form complex composite parts

With a view to minimizing production costs of carbon fiber-reinforced plastics (CFRP), a contoured, variable-axial reinforcing fabric, so-called “CoCo – contoured composites,” has been developed for complex, primary structural components,. Thereby, scrap in the production of lightweight high-performance components out of CFRP is reduced. Furthermore, components can be designed in an anisotropic way, thus lighter and adapted to the fiber properties. Moreover, production speed will be by far higher than that of conventional variable-axial textiles, like tailored fiber placement and fiber patch preforming. Furthermore, these textiles will show higher drapability than conventional production techniques, like tape-laying or standard textiles. The main focus of this paper is the investigation of draping mechanisms of variable-axial, tailored textiles and their feasibility. To reach high drapability of these semi-finished products, a new draping strategy has been developed. Reinforcing rovings are laid in meander way onto a carrier material holding excess material available for draping. For the textile “CoCo” new draping characteristics have been investigated, showing a kind of stretch forming of the carrier material and a straightening of the reinforcing fibers previously laid in meander. Due to this draping mechanism the material has the ability to form over very complex shapes without showing draping defects, like loops, gaps, or waviness. The calculation of the excess material and the draping mechanism are investigated on a complex form and proven by draping trials.

Meso-scaled finite element analysis of fiber reinforced plastics made by Tailored Fiber Placement

In this paper the effect of the embroidery based textile manufacturing technology Tailored Fiber Placement (TFP) on the stiffness and stress behavior of continuous fiber reinforced plastics is analyzed. Therefore the geometrical impact of the used stitching yarn on the fiber waviness is experimentally determined in a single unidirectional carbon fiber reinforced plastic layer made by TFP. Based on experimental data a parametrical three-dimensional representative unit cell (RUC) is developed to numerically determine the local fiber volume content as well as the stress and strain distribution under uniaxial loading. The numerical results are found in good agreement with the results obtained from tensile tests. A significant variation of local strain is found in fiber direction within the RUC while due to the effect of TFP the variation of global strain is observed to be insignificant.

ファイバー縫付機による熱可塑性複合材料の作製

ファイバー縫付機による熱可塑性複合材料の作製

ファイバー縫付機により作成した曲線状複合材の振動特性

The present study fabricates fibrous composite with curvilinear fiber shape by using tailored fiber placement machine which is an application of embroidering machine. The composite with curved fibers has variable mechanical properties depending on fiber curvature. First the relationships among fiber density, thickness and curvature are revealed by experimental study with test specimens that has various curvatures. Then, regression equations for stiffness and fiber volume fraction in terms of fiber curvature are estimated by using the mixture rule. Finally, natural frequencies and mode shapes are calculated by finite element analysis with estimated mechanical properties, and those are compared with experimental results. The present calculated results indicated better agreement with experimental results than those without estimated values. Therefore, it was found that the obtained regression equation is effective to predict mechanical behavior of composite with curvilinear fiber.

Prospects of applying the tailored fiber placement (TFP) technology for manufacture of composite aircraft parts

A prospective technological process of manufacturing dry performs using tailored fiber placement (TFP) technology is considered. A possibility is assessed to enhance structural and processing properties of composite parts due to application of tailored reinforcement. A prospect of reinforcement perform production with optimal fiber arrangement is demonstrated. We present the examples of parts produced using TFP.

Effect of reinforcement volume fraction and orientation on a hybrid tissue engineered aortic heart valve with a tubular leaflet design

Transcatheter aortic valve implantation of fibrin-based tissue engineered heart valves with a tubular leaflet construct have been developed as an alternative to invasive traditional surgical heart valve implantation. In general, they are well suited for the pulmonary position, but display insufficient mechanical properties for the aortic position. To enable the application of tissue-engineered valves in the systemic circulation, the tissue is reinforced with a textile scaffold. The current study seeks to compare the effect of varying the fiber volume fraction and orientation of bidirectional textile reinforcement on the closed-valve configuration. An anisotropic large deformation material model based on structural tensors was chosen and the materials were characterized. A finite element model was constructed of the heart valve, and the pinching and suturing of the corners along with application of pressure was simulated. Virtual experiments were conducted with fiber volume fractions of 0.1, 0.01, 0.001, and 0.0001 for ±45° fiber orientations. Furthermore, volume fraction was held at 0.01 and fiber orientations of 0°, ±15°, ±30°, ±45°, ±60°, ±75° and 90° from the tube’s axial direction were simulated and compared. It was shown that increasing the fiber volume fraction decreased the maximum principle strain in the valve, but lead to less closure. Additionally, the effect of fiber orientation affected the strains differently at different locations, depending on the local deformed geometry. This indicates that a non-uniform fiber distribution using tailored fiber placement could be used to optimize reinforcement design.

Path Definition for Tailored Fiber Placement Structures Using Numerical Reverse Draping Approach

The properties of fiber reinforced materials are depending on the fiber direction. During draping processes - which are necessary to form complex structures - the fiber direction and therefore the resulting properties of the final part are changing.To ensure that the fibers in the final complex structure are placed exactly in the direction needed, a new approach is investigated.The idea is to define the orientation of the reinforcement fibers based on the distribution of forces in a complex structure under certain loading determined by a structural simulation. Best lightweight behavior is achievable in the final complex structure. A three-dimensional mesoscopic model of the directed fibers is created using FEM-software. In reverse draping simulations the three-dimensional fibers are formed from complex shape to a two-dimensional flat sheet.In manufacturing the two-dimensional patches can be created using the tailored fiber placement process. With this process it is possible to place the fibers orientated to the required paths. The patches are formed to the necessary three-dimensional shape by a real draping process. The relative sliding behavior of crossing fibers can be achieved by varying the stitch during the TFP process.Using that approach it is possible to create lightweight structures in which fibers are orientated directly along the load paths of the three-dimensional application.

Innovative tailored fiber placement technique for enhanced damage resistance in notched composite laminate

Abstract Composites have recently gained considerable acceptance in the transportation sector such as the aerospace and automotive industries, as these materials offer the ability to reduce weight, greenhouse gas emissions and associated fuel cost. Conversely, problems related to material behavior, cost, manufacturing process, assembly and choice of joining technique pose challenges that limit the wide acceptance and implementation of the composite materials. Specifically, a major problem related to joining is the use of mechanical/fastener joints with drilled holes that can damage the continuous fibers and cause considerable reduction in the load carrying capacity of resulting composite structures. To address this issue, an innovative solution that manufactures fabric laminates using ‘tailored placement’ of fibers around the holes/notch was proposed. This eliminates the need for drilling and machining of holes thereby eliminating the sources of delamination. The tensile performance of notched composites from the novel tailored fiber placement (TFP) approach was compared to conventional notched composites. Additionally, the effect of various fiber placement patterns and machining processes on the strength, damage initiation and fracture mode of notched composite laminates were studied. Specifically, the stress and strain fields around the notch were thoroughly evaluated. The experimental results for notched specimens were compared with the damage initiation and strength predictions obtained from the Hashin failure criteria as available in commercially available FEA package (ABAQUS®). A good agreement between experimental results and numerical predictions was observed. Overall, the proposed approach shows great promise in the use of tailored fiber placement technique to eliminate delaminations, maintain continuous fiber alignments and reduce associated stress concentrations in a wide range of composite applications including but not limited to mechanical fastening.

Influence of fiber paths on buckling load of tailored conical shells

The purpose of this paper is to propose a method for evaluation of varying stiffness coefficients of tailored conical shells (TCS). Furthermore, a comparison between buckling loads of these shells under axial load with the different fiber path is performed. A circular truncated conical shell subjected to axial compression is taken into account. Three different theoretical path containing geodesic path, constant curvature path and constant angle path has been considered to describe the angle variation along the cone length, along cone generator of a conical shell are offered. In the TCS with the arbitrary fiber path, the thickness and the ply orientation are assumed to be functions of the shell coordinates and influencing stiffness coefficients of the structure. The stiffness coefficients and the buckling loads of shells are calculated basing on classical shells theory (CST) and using finite-element analysis (FEA) software. The obtained results for TCS with arbitrary fiber path, thickness and ply orientation are derived as functions of shell longitudinal coordinate and influencing stiffness coefficients of structures. Furthermore, the buckling loads based on fiber path and ply orientation at the start of tailored fiber get to be different. The extent of difference for tailored fiber with start angle lower than 20 degrees is not significant. The results in this paper show that using tailored fiber placement could be applied for producing conical shells in order to have greater buckling strengths and lower weight. This work demonstrates the use of fiber path definitions for calculated stiffness coefficients and buckling loads of conical shells.

刺繍機によるCFRPドライプリフォームの最適繊維配置

A design method for an embroidery-based TFP (tailored fiber placement) was proposed, in which fiber bundles were placed along desired directions by an embroidery machine. To verify availability of the method a CFRP laminate plate optimized for a bending-torsion problem was processed and they were evaluated by the calculation and the experiment. Result showed that the stiffness of the plate could be improved by the TFP both in the calculation and the experiment although the difference between them was significant quantitatively. It was found from discussions that consideration of damage of the fiber bundles plays important roles on prediction of the properties of composites with the TFP layers.