Vladan Koncar

Online Measurement of Structural Deformations in Composites

This paper describes a new approach of Nondestructive Evaluation (NDE) using fibrous sensors inserted inside composite reinforcements during their weaving. A flexible piezoresistive fibrous sensor has been developed and optimized for in situ structural deformation sensing in carbon composites. The sensor was inserted, in the weft direction, in three-dimensional warp interlock reinforcement during the weaving process on a special weaving loom. The reinforcement was then impregnated in epoxy resin and was later subjected to quasi-static tensile strain. It was found that the sensor was able to detect deformations in the composite structure until rupture since it was inserted together with reinforcing tows. The morphological and electromechanical properties of the fibrous sensors have been analyzed using scanning electron microscopy, tomography and yarn tensile strength tester. An appropriate data treatment and recording device has also been developed and utilized. The results obtained for carbon composite specimens under standard testing conditions (NF EN ISO 527-4 Plastiques, CEN, 1997) have validated in situ monitoring concept using our textile fibrous sensors.

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.

A Study of Strength Transfer from tow to Textile Composite Using Different Reinforcement Architectures

The paper proposes an experimental and analytical approach of designing composites with the predetermined ultimate strength, reinforced with warp interlock fabrics. In order to better understand the phenomena of transfer of tensile properties from a tow to the composite, intermediate phases of composite manufacturing have also been taken into account and tensile properties of tows taken from the loom and the woven reinforcements have also been tested. Process of transfer of mechanical properties of raw materials to the final product (composite) depends on various structural factors. Here the influence of weave structure, which ultimately influences crimp has been studied. A strength transfer coefficient has been proposed which helps in estimating the influence of architectural parameters on 3D woven composites. 3 woven interlock reinforcements were woven to form composites. The coefficients of strength transfer were calculated for these three variants. The structural parameters were kept the same for these three reinforcements except for the weave structure. In was found that the phenomenon of strength transfer from tow to composite is negatively influenced by the crimp. In general the strength transfer coefficients have higher values for dry reinforcements and afterwards due to resin impregnation the values drop.

Novel approach of ulcer prevention based on pressure distribution control algorithm

A long term static position, of patient lying in a bed, leads to the ulcer formation on body areas submitted to humidity, shearing and high interface skin pressure. To avoid the ulcer formation, existing static solutions are available using different material such as foam, gel etc. Dynamic solutions based on the spread of the pressure distribution using air are also available. However, the pressure distribution control is made in global way and therefore not able to detect the specific area of the human body to handle. A global and random motion of all the mattress is produced which gives a response to the ulcer formation, but without any comfort in a long term stay for the patient. To avoid the ulcer risk and ensure a comfortable position to the patient, a new control algorithm able to check and to optimize the pressure distribution of the mattress is proposed in this article. It automatically detects the shape of the human body and locally acts on the identified part to reduce and spread the pressure. The algorithm needs to converge to a safe solution leading to comfort and efficiency. Thus, the motion of the mattress will be smooth and locally adapted to human body parts. The proposed research work treats the design of a comfortable bed with an independent and automatic control system able to prevent the ulcer formation in an effective and autonomous way.

A study on the beam pattern of ultrasonic sensor integrated to textile structure

Purpose – During the past decades, several researchers have introduced devices that use sonar systems to detect and/or to determine the object location or to measure the distance to an object using reflected sound waves. The purpose of this paper is to use sonar sensor with textile structure and to test it for detection of objects.Design/methodology/approach – In this study, a sonar system based on intelligent textiles approach for detection of objects has been developed. In order to do this, ultrasonic sensor has been integrated to textile structures by using conductive yarns. Furthermore, an electronic circuit has been designed; PIC 16F877 microcontroller unit has been used to convert the measured signal to meaningful data and to assess the data. The algorithm enabling the objects detection has also been developed. Finally, smart textile structure integrated with ultrasonic sensor has been tested for detection of objects.Findings – Beam shape is presented related to identified object and compared with t...

An Algorithm Based on Neuro-Fuzzy Controller Implemented in A Smart Clothing System For Obstacle Avoidance

Abstract In this study, to overcome navigation concerns of visually impaired people, an algorithm based on neuro-fuzzy controller composed of multi-layer fuzzy inference systems (FIS) for obstacle avoidance was developed and it was implemented in a smart clothing system. The success of the proposed algorithm was tested in real environment and it was compared with one layer FIS. Results showed that the proposed algorithm is capable of guiding user to a right orientation and it presented better results than the one layer FIS.

Light properties improvement of light emitting woven textiles with optical fibres for photodynamic therapy

For an efficient and less painful photodynamic therapy (PDT), a light emitting fabric (LEF) was woven from plastic optical fibres (POF) aiming at the treatment of dermatologic diseases such as Actinic Keratosis (AK). The traditional PDT treatments applied with external light sources deliver a non-uniform light distribution on the skin surface due to the anatomical particularity of the human body (head vertex, hand, etc.). Therefore a successful PDT obligates a homogenous and reproducible light delivery. With this purpose, plastic optical fibres (POF) have been woven in textile in order to create macro-bendings and thus emit out the injected light directly to the skin. To improve the light intensity and light emitting homogeneity of the LEF, Doehlert Experimental Design is applied. Fifteen experiments performed to analyze the response surface. Light properties of the prototypes were evaluated. The proposed models fitted well with the experimental data and enabled the optimal set up the warp yarns tensions. This study showed that RSM was a suitable tool to optimize the models of light diffusion properties.

11 – Smart textiles for the protection of armoured vehicles

The requirement for weight reduction encourages the use of composite materials which are lighter than steel for similar mechanical performance. In the field of vehicle armour, existing solutions can be improved by the introduction of new composite materials in combination with steel or ceramics. One of these solutions may lie in the use of three-dimensional (3D) textile structures, in particular a multilayer fabric called 3D warp interlock, using different types of high performance fibres. A new textile composite solution is presented in this chapter. To enhance on-line measurement of mechanical stresses during impact, a fibrous sensor has been developed to better understand the in-situ behaviour of the target.