SERVICES & FACILITIES

The activity of TEXTILESHUB focuses on testing and prototype realization, for lightweight structures, design objects and building components based on textiles and/or polymeric materials. The structures studied are: tensile structures, tents, pneumatic constructions, form-active systems and ETFE cushions, textile and polymers based lamps or design objects, tensioned ceilings, textile partitions, false walls, textile wallpapers.

We use our CLUSTEX pavilion as a unique space for research, prototyping, testing, workshops, hands on exercises, teaching. All students, collaborators and clients are highly encouraged to come to visit us and enjoy working together on innovative ideas for lightweight structures.

• characterisation of mechanical behaviour under a state of twin-axial force on: textiles and non-textiles, technical textiles, lined membranes, reinforced polymeric membranes, elastomers, polymeric materials, composites
• measurement of UV-VIS-NIR optical and spectral properties (specular and diffuse hemispherical reflectance, two-directional reflectance and transmittance)
• measurement of spectral IR properties (diffuse hemispherical reflectance and transmittance, specular reflectance of glass and normal emissivity)
• characterisation of thermal performance of macroporous and textile walls
• creation of prototypes and demonstrators for lightweight structures, design objects and construction components made from textiles and/or polymers, such as, for example: tensile structures, tent structures, pressurised structures, emergency tents, form-active structures, ETFE cushions, lamps and other design objects made from textiles and polymers, tensed false ceilings, dividers, wall linings, wallpapers, etc.
• study and assessment of the integration of photovoltaic cells into flexible substrates such as membranes and fluoropolymers

The operative core of TEXTILESHUB is the biaxial mechanical traction test station, where take place biaxial mechanical evaluations on different advanced materials for different field of application: technical textiles, non-woven fabrics, coated and reinforced membranes, elastomers, polymeric and composite materials. Since the textiles are more and more applied for creating complex forms, where the fabric are used also combined with other materials, additional needed equipments have been disposed for developing the research on these high performance “new skins”.

Both uniaxial and biaxial tensile tests can be performed with the biaxial rig set up on two squared steel frames, designed for an estimated maximum force of 175kN on each side. The actuators are based on a brushless motor, equipped with an absolute encoder. The maximum speed is 240 mm/min and the positioning resolution is equal to +/- 0.05 mm. Each actuator is equipped with a force transducer, which measures the force applied, allowing accurate control of the linear displacements of the actuator. The force transducers have been calibrated following the Quality System of the Politecnico di Milano.

Twelve electromechanical actuators, three on each side of the squared rig, compose the biaxial test machine. The actuators are free to move transversally and each one is adjustable independently from the others. The maximum load applicable is 50kN per each actuator on two opposite sides, that is 6 load cells connected with the respective 6 actuators, and 25kN for the remaining ones, while the minimum stress value is 1kN. Therefore totally 150 kN on two sides and 75kN on the other two. It provides a graphical interface that enables the system to be easily controlled by the user. The controlling system regulates the test, recording the data of mechanical stresses generated in the samples, and operates both in force and displacement control. The graphics show in real time the mean values of the applied force and the elongation of the sample. The transduction of the strain is done by four linear potentiometers or by a Digital Image Correlation system without contact, and the images post-processing allows the measurement of the full field strain, on the external surface of the sample during loading.

The biaxial machine has been designed and built with a high degree of adaptability, combining the different skills of involved researchers with different test configurations: it is possible to test different sizes of samples and high variation of polymeric films. The wide range of forces and transversal movement of engines allows to test different materials, from technical textiles or carbon fibres composites employed in construction field, which should withstand high loads, to biomedical tissues, which are tested in small samples and support lower stresses. The samples are fixed to the bars by means of special clamping system, which allows testing models from 10 to 100 cm of wide. The particular configuration of the biaxial rig offers freedom to test samples in mono- or bi- axial traction, but also other types of systems not compliant with the traditional models (e.g. mono- and biaxial test campaigns or biaxial tests for compensation value, for E-modulus investigation), as follows.

In the recent experience the experimentation has dealt with particular and customized requirements: from the application of the biaxial test procedure for the characterization of membranes with a new coating applied on traditional fabrics by an innovative industrial plant, to special and less conventional configuration tests.

- The test campaign regarding the characterization of a fabric with a new coating aimed to determine strength by biaxial tests, elongation at break of the specimens by monoaxial ones and determination of the tear strength of the specimens in the pants shape.

- In the field of tents, a campaign of mechanical tests had the objective of performing the real conditions geometry of a tent system “anchoring system - textile configuration” and the mechanical resistance of the textile reinforcements strips, aiming to characterize, verify and improve at the same type the details of the tent architecture and the textile manufacturing of new products, intended to be tested directly in the field. The reference values, imposed during the test, are the result of a previous structural analysis and calculations for the design.

- A monoaxial test campaign, with a real condition configuration, on innovative composite textiles mechanically based on rigid components, under development in an industry applied research, has been performed, in order to test and characterize the mechanical behaviour and the resistance of the new composites for architecture facades coupled with their anchoring systems.

- High resistance fibre composite multiaxial textiles have been objective of the experimental campaign in order to assess and observe the biaxial tensile mechanical response and structural integrity of a complex structure designed for aerospace: through biaxial test coupled with Digital Image Correlation (DIC), assessed the behaviour under intensive high loads, derived from preliminary analytical calculations and by a campaign of FEM structural analysis.

- A study of the integration of photovoltaic cells on flexible substrates, such as membranes and fluoropolymers, investigated and validated the performance of stretchable organic photovoltaic, their mechanical responses, through a coupled electrical-mechanical test methodology, in order to verify the effect of external loads on the electrical properties of OPV conductive layers. Through a series of tensile tests on different substrates and various conductive layers commonly employed by OPVs, this work clarified the property difference among different OPV electrode layers under stretching strains, therefore providing valuable information for subsequent building product development towards OPV integration into membrane structures.

Our lab is equipped with prototyping equipment for lightweight structures. The thermal welding torch for ETFE, which measures 600 mm in the bar length and has a temperature range between 20° and 300°C allowing the welding of different types of textile materials. Other machines include: a servo-hydraulic mechanical tester (dynamometer) and sewing machine.

At the moment the research group is focusing on the realization of prototypes for the field tests of two European Researches in which Politecnico of Milano is a partner involved. On one side the attention is put on the study and test of deployable kits for emergency situations, developed inside the project S(P)EEDKITS . On the other side the improvement is related to technical textiles and thin materials for energetic retrofitting, which is the main topic of the research EASEE .

We can perform optical and thermal characterisation of materials as well as performance simulations and optimisations of materials, composites, systems and buildings. For laboratory optical characterisation of materials we use a spectrophotomer (UV-VIS-NIR). For optical analysis we use LBNL WINDOW, OPTICS, THERM as well as other more advanced software for fluid dynamic simulation. In addition to the standard analysis and simulations we create automated workflows and optimisations to explore design search space. In special cases we also develop our own software such as Stingray - raytracing plugin for Grasshopper and Rhino 3D.

Textile Architecture Network has carried out environmental testing and monitoring for different projects, prototypes and buildings. This includes acoustics/rain noise tests, daylighting, thermal/energy, PV efficiency.

For daylighting we use world-leading Konica Minolta T10 illuminance meters for evaluating illumination metrics indoor or outdoor. The device features a very large measurement range of 0.01 to 299,900 lx and is able to perform in extremely bright or dark environments. For automatic and simultaneous measurements at several locations, we use multiple receptor heads connected through a serial port controlled by a computer with a data logging software. Additionally, we use full-scale black-box mock-up for assessing accuracy of (day)lighting simulations and evaluating performance of facades and shading devices.

For the purposes of assessing acoustical performance of ETFE cushions, particularly rain noise, we developed special raining rig.

To implement the TEXTILESHUB equipments the university has provided a financing, which will allow new arrangements of test within the year.  The research group of Polimi TEXTILESHUB has predisposed the purchase of new machineries: a climatic chamber for the biaxial machine, which allow to test textile materials under stress in extreme temperature conditions (temperature range -40°/+200°C), a double ventilated climatic chamber, which has the possibility to set different temperatures in the two-controlled environments, and a spectrophotomer FT-IR equipped with integrated sphere and optional for testing the light transmittance of membranes with a specular behaviour.