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Stress with Models Molecular Modelling of Thermosetting

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Stress with Models Molecular Modelling of Thermosetting Powered By Docstoc
					  Thermoplastic and
Thermosetting Polymers
    for Composites

      Dr Ian Hamerton

         Chemistry
  School of Biomedical and
     Molecular Sciences
    University of Surrey
       Outline of Presentation

•   Definition of a Composite
•   Thermosetting polymers
•   Thermoplastic polymers
•   Thermoplastic processing
•   Use of Composites in Aerospace
•   Performance Criteria
•   Application of LCA to composites
•   Conclusions
•   Questions


                                  2
Composite

  A multi-phase material in which the properties of a continuous phase
  (matrix) are enhanced by distributed sheet-like, fibrous or particulate
  fillers




                                                                     3
 Common Thermoset Polymers
Epoxy (common, industry standard, versatile)

Vinyl esters (composition, cost properties
  between epoxies and unsaturated esters)

Unsaturated polyesters (cheapest, good
  properties at lower temperature, large
  components/volume production)

Phenolics (lower mechanical properties, retain to
  high temperature, no toxic flammables)

Polyimides (expensive, but high performance)

Bismaleimides (good hot/wet properties, brittle,
  cheaper than some polyimides)

Cyanate esters (low loss properties, relatively
  expensive)                                      4
Selected high performance thermosets

 Polyimides     Bismaleimides Cyanate esters




       Epoxy                Phenolics




  Vinyl polyesters   Unsaturated polyesters


                                              5
   Thermosetting Polymers
Can offer
• Variety of physical forms and
  viscosities
• Wide choice of curing systems
• Latitude with processing conditions
• Low cure shrinkage
• Good chemical resistance
• Good mechanical properties
• Good fibre/reinforcement adhesion
• Thermal stability over wide temperature
  range
• Good resistance to moisture

But…
• Often limited outlife
• Usually need to be toughened          6
• Pose significant recycling problems
Selected high performance thermoplastics




                                      7
    Thermoplastic Polymers
• Will soften above Tg for shaping and harden in
  this form on cooling

Can offer
• Better resistance to moisture and various
  industrial solvents than thermosets
• Superior flexural and impact properties to
  thermosets

But…
• Poorer abrasion and dimensional stability to
  thermosets
• No apparent advantage in static properties or
  fatigue
• Higher processing temperatures than most
  thermosets (generally above 300oC)
• Compression strength may be inferior
                                               8
         Thermoplastic matrices
                                     Tg/oC          Tproc/oC
Poly(amide-imide)a                    275          345-355
Polyarylethersa                     220-260        310-345
Polyethersulphonea                   220           300-310
Poly(arylene sulfide)a 200-210                         345
Polyetheretherketonec 140-145                     340-350
Polyphenylenesulfidec 85-95                            330
Poly(arylene ketone)c 200-210                      370-415
Polyimidea,c                        250-280        350-360

Tg = Glass transition temperature    a = amorphous
Tproc = Processing temperature       c = crystalline

                                                             9
Thermoplastic processing methods
• Autoclave consolidation
• Press forming (rubber assisted punch
  or hydro forming)
• Double diaphragm forming
• Pultrusion
• Roll forming
• Filament and tape winding




                                    10
    Aerospace Applications
• Combinations of thermoplastics and thermosets




                                            11
Aerospace Applications




                         12
          Trade offs as composite
Property               T/sets         T/plastics
Formulations           complex        simple
Melt viscosity         very low       high
Fibre impregnation easy               difficult
Prepreg tack           good           none
Preprepg drape         good           none to fair
Prepreg stability      poor           excellent
Processing cycle       long           short to long
Processing T/P         low/moderate   high
Fabrication cost       high           potent. low
Mech. Properties       fair to good   fair to good
(-54 to 93oC, hot/wet)
Environ. Stability     good           unknown
Solvent resistance     excellent      poor to good
Damage tolerance       poor/good      fair/excellent
Database               very large     small      13
     LCA should address:

• Initial preparation

• Formulation

• Processing

• Lifetime(s)

• Recycling potential

                           14
Conclusions – potential hotspots

• Thermosets
  –   High monomer cost
  –   Long processing cycle
  –   Storage of prepreg (refrigeration)
  –   Repair (poor damage tolerance)
  –   Poor recycling potential

• Thermoplastics
  – High melt viscosity/impregnation
  – High polymerization temperatures



                                           15
Any Questions?




                 16

				
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posted:6/26/2014
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