MONOFILAMENT TECHNICAL TEXTILES FOR SCREEN PRINTING: EXPERIMENTAL - PowerPoint PPT Presentation

MONOFILAMENT TECHNICAL TEXTILES FOR SCREEN PRINTING: EXPERIMENTAL AND NUMERICAL INVESTIGATION OF THE MECHANICAL BEHAVIOUR Valter Carvelli Politecnico di Milano

SCREEN PRINTING Printing technique, also known as serigraphy , involving stencils to transfer pictures. The ink is applied to the textile and penetrates areas of the screen not filled by the stencil. Exposure of the stencil Frame preparation tension and tie Plain screen-printing Deposit of the stencil a) frame b) stencil c) ink d d) squeegee a b c e) substrate e

SCREEN PRINTING DRY TEXTILE FILLED TEXTILE (textile composite) The mechanical response of the textile tied in the frame involves both the mechanical properties of the DRY TEXTILE and  the mechanical properties of the FILLED WITH STENCIL TEXTILE 

OUTLINE 70  m 70  m  Experimental Results 34  m 34  m 30  m 30  m on dry textiles 45  m 45  m  Numerical Modelling • First-Scale Numerical Modelling • Second-Scale Numerical Modelling  Numerical applications and comparisons  Analytical model  Open discussion

ANALIZED TECHNICAL TEXTILES Two polyester plain weave monofilament textiles Textile A Textile B  150 polyester fibres per cm  62 polyester fibres per cm  34  m fibre nominal diameter  64  m fibre nominal diameter B A 200  m 200  m

EXPERIMENTAL INVESTIGATION OF THE DRY TEXTILES Carvelli V., Corazza C., Poggi C. Computational Materials Science, 2008

EXPERIMENTAL RESULTS: dry textiles Geometric parameters Textile A Scansion Electronic Microscopy (SEM) 30  m 20  m 20  m Optical Microscopy (OM) 70  m 70  m 70  m 70  m 33  m 33  m 28  m 28  m 34  m 34  m 30  m 30  m 40  m 40  m 45  m 45  m Cross-section of warp fibres Cross-section of weft fibres

EXPERIMENTAL RESULTS: dry textiles Geometric parameters Textile B Scansion Electronic Microscopy (SEM) 30  m 30  m 100  m Optical Microscopy (OM) 148  m 148  m 146  m 146  m 47  m 47  m 48  m 48  m 62  m 62  m 56  m 56  m 70  m 70  m 73  m 73  m Cross-section of weft fibres Cross-section of warp fibres

EXPERIMENTAL RESULTS: dry textiles MTS Fibres mechanical properties (0.1kN load cell) R : 32.44  m R : 26.58  m R : 17.77  m Fibres extracted from R : 24.99  m R : 25.14  m the textile diameter 34  m diameter 64  m 800 800 weft weft 600 600 Stress [MPa] Stress [MPa] warp 400 400 warp 200 200 warp warp weft weft 0 0 0 10 20 30 40 50 0 10 20 30 40 Strain [%] Strain [%]

EXPERIMENTAL RESULTS: dry textiles Uniaxial and Biaxial tensile tests of textiles digital camera for DIC Home made biaxial tensile device 145 60 145mm 25 145 25mm r=20  Two independent servo-motors 15 15 60  Speed range: 1÷280mm/min load cells 145mm  Maximum load per direction: 5kN markers clamping zones

EXPERIMENTAL RESULTS: dry textiles UNIAXIAL TENSILE TESTS 500 500 textile A textile B 400 400 force [N] force [N] 300 300 200 200 warp warp 100 100 weft weft 0 0 -10 -8 -6 -4 -2 0 0 10 20 30 40 -10 -8 -6 -4 -2 0 0 10 20 30 40 longit. strain [%] transv. strain [%] transv. strain [%] longit. strain [%] 500 textile A 400 force [N] 300 200 fibres oriented ±45 o 100 to the load direction 0 0 20 40 60 80 shear strain [%]

EXPERIMENTAL RESULTS: dry textiles UNIAXIAL TENSILE TESTS Textile A weft strain component in-plane shear strain component 15 15 23 10 10 3 weft direction weft direction 5 5 22 0 2 0 -5 -5 21 1 -10 -10 -15 -15 -15 -10 -5 0 5 10 15 -15 -10 -5 0 5 10 15 warp direction warp direction

EXPERIMENTAL RESULTS: dry textiles BIAXIAL TENSILE TEST (displacement speeds ratio = 1) 500 textile A 400 force [N] 145 60 145mm 300 25 200 145 25mm r=20 15 warp 100 15 60 weft 0 145mm markers clamping zones 0 3 6 9 12 15 strain [%] 200 500 textile A textile B weft direction [pixels] 400 100 force [N] 300 0% 0 8.5% 200 -100 warp 100 weft -200 0 -200 -100 0 100 200 warp direction [pixels] 0 3 6 9 12 15 strain [%]

EXPERIMENTAL RESULTS: dry textiles BIAXIAL TENSILE TEST (displacement speeds ratio = 1) 145 60 145mm Map of the strain components 25 145 25mm r=20 15 15 15 60 10 weft direction [mm] 145mm markers clamping zones 5 15 0 15 10 weft direction [mm] -5 10 weft direction [mm] 5 -10 5 0 -15 0 -15 -10 -5 0 5 10 15 -5 warp direction [mm] -5 -10 strain in the -10 -15 warp direction -15 -10 -5 0 5 10 15 -15 -15 -10 -5 0 5 10 15 warp direction [mm] warp direction [mm] strain in the in-plane shear strain weft direction

EXPERIMENTAL RESULTS: dry textiles STATIC FRICTION COEFFICIENT In the numerical model, Coulomb friction for fibre-fibre contact interaction static friction coefficient  s  5  d = 0.56 dynamic friction coefficient Test according to ASTM D3412 Experimental device Yarn Tension Gages   T    1 2     ln Yarn Guide   d T   1 Yarn helix Adjustable Input tension Yarn Takeup T 1 mean input tension Yarn Guide Yarn T 2 mean output tension PacKage  wrap angle average dynamic friction coefficient 0.112 coefficient of variation (%) 3.2

NUMERICAL MODELLING AT TWO SCALES Carvelli V., Corazza C., Poggi C. Computational Materials Science, 2008

BACKGROUND FUNDAMENTALS OF HOMOGENIZATION THEORY FOR PERIODIC MEDIA Representative Volume Heterogeneous Material Homogenized Material

NUMERICAL MODELLING Hypothesis: periodic distribution of REPRESENTATIVE VOLUMES (RV) the fibres in the textile FILLED WITH DRY TEXTILE STENCIL TEXTILE Heterogeneous Periodic Material FIRST-SCALE NUMERICAL MODELLING (HOMOGENIZATION at the yarn scale) SECOND-SCALE NUMERICAL MODELLING (textile structure scale)

PROBLEM FORMULATION FOR THE HOMOGENIZATION The homogenized constitutive law is predicted solving the incremental problem defined on the RV Microscopic stress   div 0 in V  Microscopic strain Volume of the RV    F ( u ( )) in V    Microscopic constitutive law Periodic part of ~  the microscopic      u u E x periodic on V   displacement Boundary      t n anti - periodic on V  of the RV 1      V dV  V Macroscopic stress 1   Macroscopic strain   E V dV  V

FIRST-SCALE NUMERICAL MODELLING KINEMATIC BOUNDARY CONDITIONS GENERAL 3D MICROSCOPIC DISPLACEMENT FIELD position vector ~        0 u ( x ) u x E x u ( x ) rigid displacement periodic displacement component antisymmetric symmetric tensor strain tensor Macroscopic   Ψ Ω E displacement gradient Carvelli V, Taliercio A. Mechanics Research Communications, 1999

FIRST-SCALE NUMERICAL MODELLING FINITE ELEMENT MODEL: KINEMATIC BOUNDARY CONDITIONS ~        0 u ( x ) u x E x u ( x ) no rigid         2 1 displacement   2 2 A ( 0 , , 0 ) B ( , , 0 )  1 u 0 = 0 periodic displacement   C ( , , 0 ) D ( 0 , , 0 )  2 A no rigid rotation  = 0 D C B in the textile plane      C D A B ( u u ) ( u u ) 0 1 1 2 2  H  K  A  B u u u u (H , K) – ( Y , X) couples of nodes    Y X C D u u u u corresponding in the periodicity

FIRST-SCALE NUMERICAL MODELLING FINITE ELEMENT MODEL: CONSTITUTIVE BEHAVIOUR OF THE FIBRES 800 Experiment: diameter 64  m Material of fibres is considered: 600 Stress [MPa]  isotropic 400  nonlinear 200 warp weft Approximation of the fibres 0 0 10 20 30 40 constitutive behaviour by Strain [%] Ramberg-Osgood nonlinear model hardening n exponent      | | strain         stress 0  E E   Young’s 0 modulus stress at linear limit offset parameter

FIRST-SCALE NUMERICAL MODELLING FINITE ELEMENT MODEL: CONSTITUTIVE BEHAVIOUR OF THE FIBRES Fitting of the experimental data by the Ramberg-Osgood model 800 800 fibres 34  m fibres 64  m experimental experimental 600 600 stress [MPa] stress [MPa] 400 400 analytical analytical 200 200 warp warp weft weft 0 0 0 10 20 30 0 10 20 30 40 strain [%] strain [%]

FIRST-SCALE NUMERICAL MODELLING FINITE ELEMENT MODEL: two DRY TEXTILE representative volumes RV1 RV2 70  m 70  m 34  m 34  m 30  m 30  m Hypothesis: 45  m 45  m constant elliptic fibre cross section Kinematic conditions: • no penetration between fibres • no adhesion at the fibres crossovers (due to the thermal treatment) • Coulomb friction contact between fibres.

FIRST-SCALE NUMERICAL MODELLING FINITE ELEMENT MODEL: two DRY TEXTILE representative volumes RV1 RV2 Textile Elements Nodes Textile Elements Nodes A 25920 6380 A 19200 5330 B 26880 6612 B 26880 7410 ( 4-nodes tetrahedral elements)