Damien Soulat

Experimental Investigation About Stamping Behaviour of 3D Warp Interlock Composite Preforms

Forming of continuous fibre reinforcements and thermoplastic resin commingled prepregs can be performed at room temperature due to its similar textile structure. The “cool” forming stage is better controlled and more economical. The increase of temperature and the resin consolidation phases after the forming can be carried out under the isothermal condition thanks to a closed system. It can avoid the manufacturing defects easily experienced in the non-isothermal thermoforming, in particular the wrinkling [1]. Glass/Polypropylene commingled yarns have been woven inside different three-dimensional (3D) warp interlock fabrics and then formed using a double-curved shape stamping tool. The present study investigates the in-plane and through-thickness behaviour of the 3D warp interlock fibrous reinforcements during forming with a hemispherical punch. Experimental data allow analysing the forming behaviour in the warp and weft directions and on the influence of warp interlock architectures. The results point out that the layer to layer warp interlock preform has a better stamping behaviour, in particular no forming defects and good homogeneity in thickness.

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.

Analysis of moisture evaporation from underwear designed for fire-fighters

Abstract In this study we analysed the effect of moisture on the thermal protective performance of fire-fighter clothing in case of routine fire-fighting conditions. In the first stage of this research we investigated simultaneous heat and moisture transfer through a single-layer fabric, used as underwear for fire-fighters, at different moisture conditions. In the second stage of the study, the underwear in dry and wet state was tested together with protective clothing systems for fire-fighter consisting of three or four layers. It was found that during the evaporation of the moisture, a temperature plateau appeared during which temperatures hardly rose. The energy consumption used for the phase change of moisture located in the assembly dominated the heat transfer process as long as there was moisture present. As soon as all water had evaporated, the temperatures approached the temperatures measured for dry samples. The moisture within the clothing assembly did not lead to increased temperatures compared with the measurements with dry samples. This research has confirmed that moisture can positively affect the thermal protection of a clothing system.

Moisture management of underwear fabrics and linings of firefighter protective clothing assemblies

Thermal comfort of firefighters is strongly dependent on moisture management of clothing layers closest to the skin. This study centers on liquid moisture and moisture vapor transfer across various types of underwear fabrics and innermost layers of the firefighter intervention jacket (linings). Importance of the underwear neighboring layer in liquid moisture and moisture vapor transfer and hence, in thermal comfort of a firefighter is underlined and discussed. Moisture management tester is employed as an efficient tool in evaluating a transfer of liquid moisture not only through individual underwear fabric but also through bi-layers underwear lining. Moisture vapor transfer properties of mono- and bi-layer fabrics were investigated by evaporative dish method. The results show that moisture management performances of tested mono- and bi-layer fabrics are related to their composition and the general physical properties. Composition of both underwear and lining has a crucial impact on liquid moisture transfer through bi-layers. Transfer of moisture vapor is mainly governed by fabric physical properties. Combination of natural and synthetic fibers results in best performing fabrics with regard to the moisture management.

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.

Thermo-Mechanical Characterisations of Flax Fibre and Thermoplastic Resin Composites during Manufacturing

The flax fibre reinforced composites with advanced structure, which can be regarded as recyclable parts, are potential and promising materials in the automobile industry. During their manufacturing, the reinforcements or prepregs should be performed to the desired shape beforehand. Mechanical behaviours accordingly play an important role during this process. However, this preforming process is usually under high temperatures, thus, the mechanical behaviours could be modified under this state. Especially for reinforcements produced by flax yarns, has barely been studied. To fill this gap, in this paper the thermos-mechanical characterization of Flax/Polyamide12 (PA12) commingled yarn and prepreg woven fabric is analysed using tensile and in-plane shearing tests under different temperatures and tensile speeds. The results conclusively show that strength can be improved by increasing the temperature below the PA12 melting value on woven fabrics, which is inverse tendency for single yarn. Moreover, increasing tensile speed could increase the strength of the single yarn and fabric. This reveals that the PA12 fluidity has great influence on tensile behaviour. The characterisation results would be employed as prescriptive recommendations in the process of manufacturing flax fibre-reinforced composite parts.

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.

Innovative monitoring of 3D warp interlock fabric during forming process

The final geometry of 3D warp interlock fabric needs to be check during the 3D forming step to ensure the right locations of warp and weft yarns inside the final structure. Thus, a new monitoring approach has been proposed based on sensor yarns located in the fabric thickness. To ensure the accuracy of measurements, the observation of the surface deformation of the 3D warp interlock fabric has been joined to the sensor yarns measurements. At the end, it has been revealed a good correlation between strain measurement done globally by camera and locally performed by sensor yarns.