151-0548-FS2017-K3-PROCESSING THERMOSETS … · C. Lekakou, M. G. Bader, Mathematical modellingof...

||ETH Zurich, Laboratory of Composite Materials and Adaptive Structures

Paolo Ermanni9 March 2017

Processing of Thermosets Composites

09.03.2017Manufacturing of Polymer Composites - Processing of Thermosets Composites 1

Spring Semester 2017

151-0548-00L Manufacturing of Polymer Composites


Contents

Introduction

Wet-Lamination Process

Flow in porous media

Resin curing kinetics

Resin viscosity



Selection criteria for manufacturing process


InvestmentsEquipmentToolingLabour costsMaterial CostsSeries volumeCycle timeSafety and health aspects

Structural features Design and fabrication of highly

integrated monolithic structures (reduction of single parts)

Manufacturing of highly complex shapes

Easy integration of doublers, inserts damping materials and functional elements such as actuators and sensors.

Surface qualityLaminate features Mechanical properties Fibre architecture Fibre volume content

Quality and reproducibility

Economical aspects Technical aspectsSelectionCriteria


Fabrication route

Physical and chemical processes

Material properties

Top-level Process-chain from constituent materials to final part


Capillary drivenflow

Pressure drivenflow

Chemical reaction

Final part & material

properties

Manufacturing process

CuringFormingImpregnation

Layup,Preform

Constituent materials

Quality features

Fibre volume content

Flemming, M.; Ziegmann, G.; Roth S.: Faserverbundbauweisen, Halbzeuge und Bauweisen; Springer-Verlag, Berlin Heidelberg 1996

Fibre distribution Void content and distribution Delamination Fibre/matrix interface


Overview


3D-Form

TextileProcess

Multi-axial material

VernähenWirkenSticken

WebenFlechtenStricken

Textile Process

Intermediate material

Rovings

RTM, VARISCRIMP...

Preforming Preform

Prepregs

Off-line Impregnation

Filament Winding, Pultrusion,

Automated layup

AutoclavePress technologiesSMC, GMTLFI, E-LFI

Off-line Impregnation

Flow-Processes Draping Processes Injection-

ProcessesFi

bre


Contents

Introduction




Resin viscosity



Wet Lamination technique


DemoldingForming Impregnation CuringPreparation

Typical fibre material: glass fabrics vlies and mats

Resin systems: Unsaturated Polyester, Vinylester, Epoxy

Wetting of the fabric

Vacuum-bagging

Curing usually takes place at room temperature.

Post-curing at higher temperature is possible after removal from the mold.

Demolding

Post-processing

Forming takes place by laying/draping the layers in resp. on the mold

Preparation of fibre layers and cutting to desired shape and size

Preparation of the mold

Resin mixing


Wet Lamination technique


Glass fibre mats, vlies and/or fabrics Mold

Release agentSurfacing ply



Vacuum-bagging



Demolding

Post-processing


Mold reinforcement

Simple molds

No special requirements with regard to temperature resistance

Mold material: often wood or resin



Resin mixing


Wet lamination technique




Vacuum-bagging



Demolding

Post-processing




Resin mixing


Main process features

Well-suited for parts with complex geometries

Fabrication of small and very large parts

Easy integration of local reinforcements (dopplers) and inserts

Good surface quality (on the mold-side)

Typical fibre volume content: approx. 40%

Long cycle time

Low investments

‚Open‘ process Health & safety is a concern!

Mediocre laminate quality and reproducibility. Part quality stronglydepends on the skills of the technicians



Which of those parts would you fabricate in wet-lamination technique?


1. Tooling / Mold 2. Airplane structural panel 3. Boot Hull

4. Space antenna 5. F1 Chassis


How relevant are following criteria for the selectionof the appropriate fabrication process?

CriteriaGeometrical complexityTolerancesSurface qualityAchievable fibre volume contentMechanical propertiesLaminate qualityReproducibilityInvestment costsLabor expensesMaterial costsNumber of parts p.a.Cycle time


-- - = + ++Criteria is not relevant

Criteria is veryrelevant

--++++++++++++-+-=+

-==------

++-

++----

-+++

++++++++----------

+++

++----=-

++-

++----

++

++++++-----


Typical application fields

Mold construction Ship hulls

Wind energy



Wet-lamination technique: Process variants


PressureVacuum Bag

Schraubzwinge

Spannrahmen

Dichtunggelochtes Blech

Rinne für überflüssiges Harz

FolieVerstärkung mit Laminat

Trennschicht

festes Werkzeugunterteil

Vakuumbehälter für überflüssiges Harz

Ventil zur Vakuumpumpe

Druck

Druckstutzen

Druckfolie

umlaufende Dichtung

Laminat

festes Werkzeugunterteil

Überlauf

Verschraubungfester Deckel

Quellen: Ehrenstein, G.W.: Faserverbund-Kunststoffe, Werkstoffe-Verarbeitung-Eigenschaften; Carl Hanser Verlag, München 1992


Process automation example


Scobalit AG, 8604 Winterthur


Contents

Introduction




Resin viscosity




Pressure driven flow

e.g. Processes: RTM, VARTM, VARI, etc.

Darcy‘s law

Capillary driven flow

e.g. Processes:– Pultrusion, filament winding,

hand lamination, prepregging, etc.

Capillary number:


PAKQ

coslv

uCa


Flow in porous media - Background

Darcy‘s law:

Fluid flow is dependent on: material permeability (K), fluid viscosity (μ), and driving pressure ( )

Porosity is a function of compaction (required to adjust the fiber volume fraction of the composite) of the porous media


PAKQ

Fluid OutFluid In

Porous Medium

p


Injection experiment in a glass tool



Darcy’s experiment


sand

diameter D

perforated plates

piezometrictubes

1h

2h

gp1

gp2

Darcy’s experiment (1856)


Inside a composite: Computer Tomograph pictureshighlighting the dual-scale nature of the porous media

09.03.2017Manufacturing of Polymer Composites - Processing of Thermosets Composites 22Schell, J.S.U., Investigation of the Influence of Meso-scale Flow Effects in Liquid Composite Moulding Processes on the Laminate Quality, Diss. ETH Nr. 17044, 2007

Meso-scale structure showing the bundles Micro-scale structure of the bundles showing the individual fibres within

the bundles.


Dual-scale structure is influencing the impregnation process

09.03.2017Manufacturing of Polymer Composites - Processing of Thermosets Composites 23C. Lekakou, M. G. Bader, Mathematical modelling of macro- and micro- infiltration in resin transfer moulding (RTM), Composites Part A 29 (1998) 29–37.

Mode 1 of the impregnation model of woven fabrics




Fiber/Matrix interface development

Fibre-wetting is a pre-condition for developing a ‚good‘ interface!

09.03.2017Manufacturing of Polymer Composites - Processing of Thermosets Composites 24M. Connor, Consolidation Mechanisms and Interfacial Phenomena in Thermoplastic Powder Impregnated Composites, PhD-Thesis No. 1413, EPF Lausanne, 1995


Capillary pressure


Benetzung Keine Benetzung

20

2

Wetting No wetting

Gas phase (1)

Liquid phase (2)

Solid phase (3)

Gas phase (1)

Liquid phase (2)

Solid phase (3)

Capillary ascension Capillary depression


Wetting of Fibres


2313

12

3

21

“Surface tension”:

Equilibrium condition:

Capillary height:

Capillary pressure:

mN

skg

mJ

dAdW

22

12 cos 13 23

h 212 cosgr

rrr

AFP

cos2cos2 12

212


Contents

Introduction




Resin viscosity



The processing time is depending on the rheology properties of the matrix


0,000

0,100

0,200

0,300

0,400

0,500

0,600

0,700

0 60 120 180 240 300

Zeit / s

Visk

ositä

t / Pa *s isotherm bei 50°C

isotherm bei 90°C


Curing kinetics

Addition polymerisation of epoxy systems is an exothermal reaction

Kamal-Sourour model:

Coefficients can be extracted fromDSC-curves!


RTE

ii

nm

i

eATk

kkdtd 121

gesH

dtQ


Contents

Introduction




Resin viscosity



A simple viscosity model

Viscosity model:

Castro und Macosko:


C

TB

AeT ),(

DC

g

gTB

eAT

),(

With: A, B, C, D: Constantsg: Curing degree of the resin at gelpoint

151-0548-FS2017-K3-PROCESSING THERMOSETS … · C. Lekakou, M. G. Bader, Mathematical modellingof...

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