3D Weaving Process : Development of Near Net Shape Preforms and Verification of Mechanical Properties

The use 3D woven composites is on the rise, especially in aircraft engine components. OEMs are recognizing the many performance and economic advantages offered by the 3D weaving process, especially in aircraft engine applications that require high damage tolerance. Near net shape preforms with high fiber volume can be produced using the 3D weaving process. 3D weaving also offers the designer with the choice of virtually unlimited fiber architectures and design possibilities. However, a good, reliable and computationally efficient design tool for 3D woven composites is a basic necessity in order to enable the designer to fully exploit the advantages offered by the 3D weaving process. A simple analytical tool like TEXCAD can provide reliable and quick estimates and parametric studies of the 3D stiffnesses and strengths over the full range of fiber architectures that are possible with 3D weaving. Challenges in the use 3D woven composites relate to the lack of structural progressive damage modeling capability, the lack of standards and methods for the quality control, inspection and process control of 3D weaving processes and a lack of a good understanding of the effects of defects and fiber architecture variability on mechanical properties.

Interest in 3D woven carbon fibre composites has increased within industries such as aerospace, automotive and marine, due to their high strength to weight ratio, their increased tailorability and their capacity to be manufactured into near net shape preforms, thereby reducing parts count, assembly time, labour intensity and costs. It is vital that critical areas of concern such as damage (and in particular damage initiation and development) are studied and understood, thereby reducing the limiting factors to their acceptance. The damage initiation and subsequent intervals of development for ILSS (Interlaminar Shear Strength) were determined experimentally. Particular focus is paid to the significance of binder edge and binder middle testing and the influence of through-the-thickness (T-T-T) reinforcement in relation to damage types and development. Control samples for binder edge and binder middle loading locations were tested to failure as a means of determining an average point of failure, allowing the generation of testing intervals. The performance and architecture of samples from each incremental interval were characterised using a combination of graphical analysis and optical microscopy with the aid of dye-penetrant to highlight fibre damage and matrix cracking. Samples displayed specific damage initiation points, thus allowing the generation of a damage guide relating to applied force. In addition, the results imply that a relationship exists between the location of applied load and subsequent damage, thus showing the significant influence played by the T-T-T binder loading location on damage development within 3D woven carbon fibre composites. Some of the preliminary data shown in this paper was presented at IMC23 at the University of Ulster, UK in August 2006 and at Texcomp 8 in Nottingham, UK October 2006.

Three-dimensional tow inclination model for calculating elastic constants of three-dimensional triaxial braided composites

Nonlinear viscoelastic multi-scale repetitive unit cell model of 3D woven composites with damage evolution

Spray forming

Near net shape preforms, minimal material consumption and tailored processes are required to increase the acceptance of fiber reinforced polymers (FRP) in industry. For this purpose, the application of hybrid yarns facilitates short flow paths of the matrix systems and thus comparatively low impregnation and consolidation pressures. Furthermore, future applications combine the advantages of metal structures with FRP. This should be accompanied by appropriate, fast and flexible processes. The remote- laser-ablation expands the area of possible kinds of processing strategies, so that the laser has the potential to be a tool for the future. Development is therefore accompanied with the understanding of the interaction between tool and material. Laser cutting of FRP is an ambitious process because of the inhomogeneity of both the reinforcement material and the polymer matrix material. The processing of metal structures leads to increased demands of the laser-system- technology, due to the high reflectivity of the material. This paper shows an experimental set up for combining beam radiation with wavelengths of 1.07 µm and 10.6 µm. Furthermore, this paper will give an outlook on future applications regarding fiber-metal laminates.

Remote Laser Processing of Composite Materials with Different Opto–Thermic Properties

This paper reports recent work on the optimisation of preform manufacture. Producing tailored textile semifinished parts, such as non-crimp fabrics (NCFs) with locally adjusted properties, and processing these in a sequence of automated cutting, handling and joining operations are a promising approach to significantly reduce costs and cycle times within preform production. Additionally, along with the enhancement of machinery, the development of simulation tools for designing efficient process chains and understanding the behaviour of reinforcement textiles along the entire production process is essential. The Institut fuer Textiltechnik (ITA) of RWTH Aachen follows this holistic approach, aiming at preforming processes suitable for mass production. In this paper, enhanced production technologies for tailored NCFs are described. Furthermore, an overview of automated technologies for converting these tailored NCFs to near net shape preforms is given. Methodical process chain development is shown in a case study, proving the possibility to significantly increase the operating efficiency of preform production by means of the introduced approach.

Powder preform forging is a technology that comprises the preparation of near net shape preforms through powder metallurgy and a subsequent hot forging in order to obtain the desired final shape. In this work, two Ti–6Al–4V powder preforms were sintered through spark plasma sintering (SPS) and then hot compressed in a horizontal dilatometer. Varying the temperature of the process, two full density preforms having different microstructures were produced: sintering at 950°C, a plate-like α was obtained, whereas sintering at 1050°C, an acicular α was obtained. The behaviour of the preforms under hot forging has been studied through hot compression tests carried out in a quenching and deformation dilatometer in a range of temperature and strain rates typically used in hot forging this alloy (850–1050°C, 0·01–1 s−1). Hot workability has been evaluated by measuring the stresses required for deformation and by analysing both the stress–strain curves recorded during testing and the microstructures after deformation. The main microstructural phenomena occurring during hot compression were individuated. The best conditions for the hot forging operation of SPS preform are temperatures above β transus, where the materials are deformed in a regime of dynamic recrystallisation, at every strain rate.

Spray forming is a single step gas atomization/deposition process which yields ferrous and non-ferrous near net shape preforms. It has proven to be a viable, cost effective alternative to conventional metal working technology for the production of material preforms with properties surpassing those of their cast and wrought counterparts. Current Navy programs are aimed at optimization of the process, certification of the spray formed products and industrialization of the technology. This includes the development of robust, real-time sensors interfaced with an automated fuzzy logic controller and expanded motion control system. The system will have the capability to manufacture low cost, improved performance, non-symmetric components currently producible only by casting or forging. In addition commercially available spray formed piping from foreign sources is currently being evaluated and certified for near term use in the fleet. Industrialization efforts are underway to establish domestic capabilities as there are no commercial facilities in the United States to date. The Navy has just initiated a manufacturing technology program, the intent of which is to develop a commercial plant in the United States capable of producing large military components. This paper will describe the process and program status. Results and comparative data will be presented and potential new applications discussed.

Approach to net-shape preforming using textile technologies. Part II: holes

Approach to net-shape preforming using textile technologies. Part I: edges

Due to advancements made in 3D weaving process [1] and, in order to develop 3D textile structure as reinforcement of composite material for aeronautic application, a good prediction of the geometry and the mechanical properties of the 3D woven unit cell is required. Due to the complexity of these textile architectures, realistic geometric representations [2] of fabrics are often difficult to obtain especially for 3D woven fabrics, but these descriptions are necessary to define meshes for finite element computation [3]. At present, existing tools which model and define, early at a mesoscopic scale [4], the architecture of 3D fabrics don’t take into account the influence of the manufacturing process on the shape modification of the textile structure. Some numerical model exists for the braiding process [5] and the knitting process [6], but not yet for the weaving process. During the manufacturing process, fibres are subjected to significant deformations due to loads from the component of the loom or from the friction with the others fibres. These significant deformations lead to mechanical strength losses of the fabric. A numerical model of the different steps of the weaving process could predict these significant deformations and their influence on the geometry of the textile architecture. Thus, the objective of the NUMTISS project is to develop a numerical model of the deformation of the yarn during the weaving process. For the numerical modelling of the weaving process developed in finite element method, we considered all loom elements like rigid solid, and we will make the assumption that yarns are transverse isotropic elastic materials. Simulations of the process for a plain weave, a twill 2-2 and a satin 8 fabric have already been performed, as well as the simulation of orthogonal warp interlock structures. Then, to understand the kinematic motions of weaving process, the tracking of some strategic elements on the industrial weaving loom (reed, heddles, rapier,..) have been carried out. The tracking obtained from the video of the high speed camera will help us to define the numerical model of the weaving kinematic closer to reality. Correlations between numerical results and specific structures in glass fibres produced on the loom will be presented. The influence of each step of the manufacturing process on the characteristics of the textile structure could be analyzed [1]X. Chen, L. W. Taylor, L. J.Tsai. ”An overview on fabrication of three-dimensional woven textile preforms for composites”. Textile Research Journal, 2011, 81(9) 932–944 [2] SV Lomov, G Perie, DS Ivanov, I Verpoest and D Marsal. “Modeling three-dimensional fabrics and three-dimensional reinforced composites: challenges and solutions”. Textile Research Journal, 2011, 81(1) 28–41 [3] E. De Luycker, F. Morestin, P. Boisse, D. Marsal. « Simulation of 3D interlock composite performing”. Composite Structures, Volume 88, Issue 4, May 2009, Pages 615-623. [4] M. Ansar, W. Xinwei, Z. Chouwei. “Modeling strategies of 3D woven composites: A review”. Composite Structures 93 (2011) 1947–1963. [5] A. K. Pickett, J. Sirtautas, et A. Erber. « Braiding simulation and prediction of mechanical properties”. Applied Composite Materials, 2009. [6] M. Duhovic, D. Bhattacharyya. “Simulating the deformation mechanisms of knitted fabric composites”. Composites Part A : Applied Science and Manufacturing, 2006.

In the production of 3D fabrics for textile-based composite material applications, the conventional 2D weaving device is employed to produce interlaced 3D fabric comprising two sets of yarns, and non-interlaced 3D fabric constituting three sets of yarns. While the process of producing interlaced 3D fabric comprising two sets of yarns complies with the principle of 2D weaving, the process of producing non-interlaced 3D fabric constituting three sets of yarns cannot be described as the process of ‘true’ 3D weaving. This is because the conventional 2D weaving process is designed to bring about the interlacement of two orthogonal sets of yarns, and not three orthogonal sets of yarns. However, an available method well-characterizes the weaving process in bringing about interlacement of three orthogonal sets of yarns and hence qualifies to be regarded as the ‘true’ 3D weaving process. The process of producing non-interlaced 3D fabric constituting three orthogonal sets of yarns does not comply with the principle of weaving, although it is generally expressed as the 3D weaving process. This unspecified process has not until now received the due appreciation as evidenced by the absence of a specific term describing the process. Interestingly, the fabric obtained through this process is referred to as a non-interlaced or a nonwoven 3D fabric. Such a terminological discrepancy calls for the evolution of a new specific term. This paper is an attempt to find clear-cut operational features in order to distinguish between the three processes in question. The discussions, which are based on the relevant fundamentals, also evolves and proposes a new term for the non-interlaced 3D fabric-forming process.

2 - Solid three-dimensional woven textiles