1 / 14

Effects of mesostructure on the in-plane properties of tufted carbon fabric composites

Effects of mesostructure on the in-plane properties of tufted carbon fabric composites. CompTest 2011, 14 th February 2011 Johannes W G Treiber Denis D R Cartié Ivana K Partridge j.treiber@cranfield.ac.uk. Tufting process. - Modified one-sided stitching process

mindy
Download Presentation

Effects of mesostructure on the in-plane properties of tufted carbon fabric composites

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Effects of mesostructure on the in-plane properties of tufted carbon fabric composites CompTest 2011, 14th February 2011 Johannes W G Treiber Denis D R Cartié Ivana K Partridge j.treiber@cranfield.ac.uk

  2. Tufting process - Modified one-sided stitching process - Automated insertion of carbon, glass or aramid thread - For dry composite preforms 0.5% carbon tufted NCF Top Automated KSL KL150 tufting head Hollow needle Presser foot Dry fabric Bottom Tuft thread loop Support foam Tufting process Meso-structure Exp. database FE-Models

  3. Introduction Main purpose: Through-the-thickness reinforcement technique + 460%/+60% mode I/II delamination toughness for only 0.5% areal tuft density (Cranfield) Tuft bridging Delamination crack DCB of 0.5% carbon tufted NCF Drawback: Potential reduction of in-plane properties Stitching: - considerable database Stiffness: -15% to +10% Tensile strength: -25% to +25% Tufting: - to date only 3 experimental studies (KU Leuven, Cranfield) Tensile strengths: -14% to +10% no agreement Need for detailed testing database on wider range of tufted materials Tufting process Meso-structure Exp. database FE-Models

  4. Materials - Carbon Preforms: Uni-weave - [0°]7 , [0°]10 balanced NCF - [(0°/90°)s]2 - Tufted with 2k HTA carbon thread in at sx = sy = 5.6 mm (0.5%) /2.8 mm (2%) Square arrangement • Cross-over • Pattern shift Free loop height: 3.5 – 5 mm - RTM injection of epoxy resin (ACG MVR 444) for dimensional control Tufting process Meso-structure Exp. database FE-Models

  5. In-plane tension behaviour Tensile tests (BS EN ISO 527-4:1997): Property changes depend on fabric and tuft morphology Tufting process Meso-structure Exp. database FE-Models

  6. Meso-structure In-plane disturbance (x-y): Triangular UD 4° w ,φ UD: 6° NCF: 10° Resin pocket Fabric deviation Tuft 0.5% 2.0% Square w Thermal crack Square w,φ 2φ UD: 3° NCF: 4° 7° NCF Tufting process Meso-structure Exp. database FE-Models

  7. Meso-structure Out-of-plane disturbance (x-z/y-z): Thread seam Surface crimp z x Vf = f(wi,tloop, tthread) Thread layer tth Loop layer tl • Surface seam causes local fabric crimp • Resin rich layers and pockets affect global and local Vf z y Tufting process Meso-structure Exp. database FE-Models

  8. Numerical Unit Cell model φ= cosine fct. Loop Vf= f(tl,tth,wi) ¼ UC Resin channel Tuft y Thread y x wi ‘Smeared’ UD x Parametric 3D Unit Cell model (Marc): UD, NCF, square and triangular arrangement Isotropic, linear elastic material + ‘Rule of mixtures’ (Chamis) Failure and degradation: Ply: Puck (FF + 3 modes of IFF) Resin: Maximum strength Knops, Comp. Sci. Tech. 2006 Tufting process Meso-structure Exp. database FE-Models

  9. Failure prediction – NCF 0° Ply ¼ UC A Transverse tension failure A Longitudinal splitting 0.5% NCF|| Cracks • Accurate modulus and strength, also for 2% density (error < 2/4%) • Fabric straightening leads to transverse tension failure in fabric and longitudinal splitting of resin pocket Longitudinal splitting Tufting process Meso-structure Exp. database FE-Models

  10. Failure prediction – NCF 0° Ply B ¼ UC B Fibre failure initiation 0.5% NCF|| Rupture Tuft 0° • Ultimate fabric fibre failure in close vicinity of tuft Tufting process Meso-structure Exp. database FE-Models

  11. Vf distribution 0.5% NCF|| • Local fabric fibre distribution affects both stiffness and strength prediction • Gradient Vf model agrees best with true morphology and tension results Tufting process Meso-structure Exp. database FE-Models

  12. Fibre misalignment φ 0.5% square wmin • Fabric fibre deviation critical on tensile strength, effect on modulus negligible • UD strength more sensitive to fabric deviation Tufting process Meso-structure Exp. database FE-Models

  13. Tuft arrangement UD|| • Upper and lower strength bounds defined by square and triangular pattern • Triangular pattern causes most critical strength reduction Tufting process Meso-structure Exp. database FE-Models

  14. Conclusions • Tuft introduces structural complexity into Z-reinforced composite • Critical meso-structural tuft defects: resin rich pockets, fibre deviation, matrix cracking and local fibre compaction • Tufting has no effect on longitudinal tensile stiffness of UD and biaxial NCF composite, but surface loops increase matrix dominated transverse stiffness • Reduction in longitudinal tensile strength most prominent for UD (<-19%) • Fibre undulation most critical contributing factor, fibre breakage limited effect on tensile strength • High quality experimental morphology data allows accurate tensile stiffness and strength prediction of tufted composites

More Related