Xavier Legrand

Analysis of the Blank Holder Force Effect on the Preforming Process Using a Simple Discrete Approach

Simulation of the dry reinforcement preforming, first step of the Resin Transfer Moulding process, become necessary to determine the feasibility of the forming process, compute the fiber directions in the final composite component, and optimize process parameters during this step. Contrary to geometrical approaches, based on fishnet algorithms, finite element methods can take into account the actual physical parameters, the real boundary conditions and the mechanical behavior of the textile reinforcement. The fabric can be modeled either as continuum media with specific material behavior [5, 6], or using discrete structural elements to describe the textile structure at the mesoscopic scale. A semi-discrete approach, which is a compromise between the above continuous and discrete approaches, is also used for simulation. A discrete approach for the simulation of the preforming of dry woven reinforcement has been proposed and presented in a previous paper. This modelling is based on a “unit cell” formulated with elastic isotropic shells coupled to axial connectors. The connectors, which replace bars or beams largely studied in other discrete approaches, reinforce the structure in the yarn directions and naturally capture the specific anisotropic behavior of fabric. Shell elements are used to take into account the in-plane shear stiffness and to manage contact phenomena with the punch and die. The linear characteristic of the connectors, has been extended to a non linear behaviour in the present paper to better account for fabric undulation. Using this numerical model, we propose, in this work to study the effect of process parameters on the woven fabric deformation during the performing step. The emphasis will be placed on the analysis of the influence of the blank holder pressure on the shear angle distribution.

A Complex Shaped Reinforced Thermoplastic Composite Part Made of Commingled Yarns With Integrated Sensor

This paper focuses on the design and one shot manufacturing process of complex shaped composite parts based on the overbraiding of commingled yarns. The commingled yarns contain thermoplastic fibres used as the matrix and glass fibres as the reinforcement material. This technology reduces the flow path length for the melted thermoplastic and aims to improve the impregnation of materials with high viscosity. The tensile strength behaviour of the material was firstly investigated in order to evaluate the influence of the manufacturing parameters on flat structured braids that have been consolidated on a heating press. A good compatibility between the required geometry and the braiding process was observed. Additionally, piezo-resistive sensor yarns, based on glass yarns coated with PEDOT: PSS, have been successfully integrated within the composite structure. The sensor yarns have been inserted into the braided fabric, before consolidation. The inserted sensors provide the ability to monitor the structural health of the composite part in a real time. The design and manufacture of the complete complex shaped part has then been successfully achieved.

Analysis of the preforming behaviour of the braided and woven flax/polyamide fabrics

Natural flax fibres have been extensively recognized by automotive industries to reduce the weight of vehicles and obtain recyclable composite parts. Most of composite parts are produced by using resin transfer moulding or thermoforming processes. As the first step of these two composite manufacturing processes, the preforming is quite important. Braided and woven fabrics are widely used as textile reinforcements to manufacture the advanced composite parts. But few research works concern the preforming of the reinforcements based on natural fibres and also there is no analysis of dry braided fabrics forming. In the present work, the studies of formability behaviour of braided and woven fabrics made of the same flax/polyamide 12 commingled yarns are performed. Furthermore, an experimental comparison between the preforming behaviour of braided and woven flax/polyamide fabrics is investigated under identical preforming conditions. The different formability behaviour and the defects developed during preforming stage are analysed. First results obtained on hemispherical shape show a higher deformability for the braided reinforcements, which can generate some forming defects, in particular buckles.

MULTIRATE PREDICTIVE CONTROL WITH NONLINEAR OPTIMIZATION APPLICATION TO A THERMAL PROCESS FOR BATCH DYEING

In this paper, we present a new approach to multirate predictive control with a multiple reference model in order to control commercial processes with nonlinear models, such as batch dyeing thermal processes. The time delay problem is resolved successfully by using multirate predictive control, and we introduce nonlinear optimization based on an augmented Lagrangien objective function to minimize the multirate predictive control quadratic criterion in the case of the nonlinear plant model. Moreover, the multirate approach improves predictive control robustness. The results of our study are used to simulate nonlinear thermal plant control with very good results. For this reason, our future work will use this method to control a batch dyeing process.

Investigation about the Manufacturing Technique of the Composite Corner Fitting Part

Abstract Textile composite reinforcement forming has been employed in many aeronautic industries as a traditional composite manufacturing process. The double-curved shape manufacturing may be difficult and can lead to defects when the composite parts have high curvatures and large deformations. Compared with the textile composites forming, surface 3D weaving can demonstrate directly the geometry of final composite part without the stages involved in 2D product. The weaving in three directions is completely designed and warp and weft yarns are always perpendicular to the surfaces of the final 3D ply. These two manufacturing techniques are applied to produce an important piece of aircraft: the corner fitting. The 3D weaving results are compared with the experimental forming by a punch as same geometry as the corner fitting part. The conveniences and limits of each technique are investigated. The comparisons show particularly a perfect final 3D fabric with homogeneous fibre volume fraction performed by the surface 3D weaving technique.

Structural and tensile behaviors of braided reinforcements: Characterization and model

Abstract The tensile behavior of braid reinforcement is classically described by the behavior of composite elaborated from these reinforcements. Few studies concern the tensile behavior of dry braids. In this chapter biaxial and triaxial braids are manufactured on a braiding loom. The evolution of key parameters as linear mass and braiding angle in function of process parameters is presented. Dry braids are characterized by uniaxial tensile behavior. The mechanical behavior is analyzed and compared in function of the braiding angle, but also different kinds of braid are considered. A specific behavior, called “double-peak,” is identified for triaxial braids, which have a higher braiding angle. The evolution of the braiding angle measured during tensile tests gives understanding of the mechanical behavior of dry braids. Associated with this experimental study, an analytical model is also proposed, to predict the modulus of dry braided reinforcements.

Innovative geometrical pre-mesh modelling strategy for 3D fibre preform manufacturing

A novel braiding–weaving system (BWS) is developed offering broad design and manufacturing possibilities based on hybridisation of weaving and braiding. In order to understand and optimize this machine and to be able to explore all the possibilities regarding complex 3-dimensional (3D) structures design, a new modelling strategy has been developed to generate geometrical skeleton of those structures. This strategy is based on the collision detection and kinematic aspects of the machine itself. Hypothesis given by kinematics allows to simply change the structure type (i.e. braiding or weaving) by changing the yarns paths. Those hypotheses are introduced in the article followed by the model that has been used and the collision detection method. Modelled 3D textile preforms are compared with manufactured samples in order to evaluate the accuracy of the modelling and simulation approaches.

Experimental and Numerical Investigation of Triaxial Braid Reinforcements

Triaxial braided reinforcements are extensively used as main constituent materials in various biomedical and composite applications. The material parameters, and the choice of process parameters during the braiding process, have a significant influence on the geometrical and mechanical properties of these reinforcements. In this study, the manufacturing on a braiding loom of triaxial braids with a large range of braiding angle is presented. On these samples geometrical properties, as bias yarn length, crimp, linear mass, are experimentally identified in function of the braiding angle. From uniaxial tests, the specific tensile behavior of these braided fabrics is characterized. These results are compared with analytical models described in the literature. Associated to this experimental approach, the geometry of these triaxial braids is numerically modeled thanks to TexMind Braider software dedicated for three-dimensional creation of braided structures. Comparison between characteristics experimentally identified and computed is analyzed.

Experimental investigation of braided fabric forming

Woven and braided textile structures are largely used as the composite reinforcements. Forming of the continuous fibre reinforcements and thermoplastic resin commingled yarns can be performed at room temperature. The “cool” forming stage is well-controlled and more economical compared to thermoforming. Many studies have been addressed for carbon and glass fibres / thermoplastic commingled yarns reinforced composite forming for woven structure. On the contrary, few research works has deal with the natural fibre reinforced textile forming and none concerns the braided fabrics forming. In this present work, the Flax/Polyamide 12 commingled yarns are used to produce braided fabric and then to analyze their deformability behaviour.

Formability of tufted 3-dimensional composite reinforcement

In the aerospace industry, more and more complex preform for composite parts are needed. Traditionally, laminated reinforcement is largely used as the method. The development of tufting technology has now advanced to a stage whereby it can be employed to produce the 3D textile composite reinforcements. Because the tufting technology is user-friendly, in this study, the tufting parameters (tufting density, tufting length, tufting yarn orientations…) are varied, in order to improve the understanding of formability of the tufted 3D fabric during manufacturing, in particular the influence of the tufting yarns, the present work is performed to analyse the preforming behaviours of tufted 3D reinforcement in the hemispherical stamping process. The preforming behaviours are also compared with the ones of the multilayered forming. Interply sliding and winkling phenomenon during forming are fully influenced by tufting yarns on the material draw-in, by the orientations of tufting yarn, …In the aerospace industry, more and more complex preform for composite parts are needed. Traditionally, laminated reinforcement is largely used as the method. The development of tufting technology has now advanced to a stage whereby it can be employed to produce the 3D textile composite reinforcements. Because the tufting technology is user-friendly, in this study, the tufting parameters (tufting density, tufting length, tufting yarn orientations…) are varied, in order to improve the understanding of formability of the tufted 3D fabric during manufacturing, in particular the influence of the tufting yarns, the present work is performed to analyse the preforming behaviours of tufted 3D reinforcement in the hemispherical stamping process. The preforming behaviours are also compared with the ones of the multilayered forming. Interply sliding and winkling phenomenon during forming are fully influenced by tufting yarns on the material draw-in, by the orientations of tufting yarn, …