Fibreglass Facts

The Basics

Composite Material

 Woven roving laminate being consolidated

Woven roving laminate being consolidated

  • Reinforcements for strength - glass, carbon, synthetics, fibres, flakes
  • Thermoset resin matrix protects reinforcement and transfers loads to reinforcement - isophthalic, vinyl ester, epoxy resins
  • Manufacturing methods varied - contact moulding, filament winding, spray up, resin transfer moulding, prepregs, pultrusion
  • All fibreglass pump station for residential wastewater

Features of Fibreglass

  • High strength/weight ratio
  • Ease of fabrication - eg complex shapes, coloured
  • Fibres can be placed where the loads are
  • Dimensional stability - shapes can be duplicated accurately
  • Good weathering properties - eg can be placed outside
  • Good chemical resistance - with correct resin choice
  • Proven performance worldwide in industry for over 50 years

Stress & Strain

Ultimate Strength 

  • Yield and Ultimate Strength are same
  • Ultimate Strength reduces with increasing temperature
  • When failure does occur it can be sudden and dramatic
  • Failure initiates at point of max stress

Good Design

  • Use high safety factors, SF = 5 minimum for structural FRP
  • Build to standards
  • Analyse stresses fully with FEA (Finite Element Analysis)
  • Ensure no over-stressing can occur
  • Avoid stress concentration points
  • Maintain regular inspections
  • If cracks or “weeping” occur, initiate maintenance immediately
 LEFT: Fibreglass tank failure can be sudden and dramatic. Failure initiated from stress point 3 years after installation. Tank by another manufacturer. RIGHT: Polyethylene manhole failed under buried load at temperature.

LEFT: Fibreglass tank failure can be sudden and dramatic. Failure initiated from stress point 3 years after installation. Tank by another manufacturer. RIGHT: Polyethylene manhole failed under buried load at temperature.

Creep

What Happens

fibreglass UTS over time.png
  • Ultimate Strength of FRP under load (pipes, tanks) reduces with time 
  • Can lead to failure some years after installation
  • Reduction in Ultimate Strength depends on service temp and HDT (heat distortion temp) of resin

Good Design

  • Use higher safety factors for FRP under constant load ... minimum 10, eg for tanks and pipes
  • Use resin with HDT preferably 20ºC above max service temp 
  • Avoid stress concentration points
 LEFT: FRP tank and piping by ARMATEC at Pulp & Paper site handling bleach filtrate. Tank handles over-pressurisation from filters on floor above. RIGHT: Tank by others has crack in tank bottom knuckle due to incorrect lug design

LEFT: FRP tank and piping by ARMATEC at Pulp & Paper site handling bleach filtrate. Tank handles over-pressurisation from filters on floor above. RIGHT: Tank by others has crack in tank bottom knuckle due to incorrect lug design

Chemical Resistance

Fibreglass has wide range of corrosion resistance depending on resin selection, and is ideal for industrial applications. See How do I choose the right resin for my fibreglass products for more information.

 Used for corrosive chemical storage, corrosive gases and liquids in a scrubber, and for combinations of corrosive chemicals in manholes and neutralisations sumps in an effluent stream. All the above installations are by ARMATAEC

Used for corrosive chemical storage, corrosive gases and liquids in a scrubber, and for combinations of corrosive chemicals in manholes and neutralisations sumps in an effluent stream. All the above installations are by ARMATAEC

Standards & QA

Standards to specify include:

  • AS 2634 - good all round standard used in NZ and Australia - still in use and in process of being superceded.
  • BS 4994 - for tanks and pipes especially
  • EN 13121-3-2004 - European standard
  • ASTM RTP1 - USA standard includes pressure vessels
  • AS/NZS 3751 - FRP pipe for public utilities
  • AS/NZS 2566 - for buried flexible pipelines
  • AS/NZS 1170 - for seismic and wind loads

Quality Assurance available

  • ISO 9001 Accreditation
  • Materials traceability
  • Design Audits
  • Standardised laminates tested (see table)
  • QA checks during manufacture
  • Post fabrication thickness checks
  • Post cure Barcol hardness checks
  • On site QA logs for coatings and linings
  • Coatings and linings - sparktesting
  • Coatings and linings - thickness check
 Quality Assurance Tools Used by ARMATEC: Left - Ultrasonic thickness testing of fibreglass laminates; Centre - Spark testing tank lining for pinholes; Right - Measuring thickness of applied coating

Quality Assurance Tools Used by ARMATEC: Left - Ultrasonic thickness testing of fibreglass laminates; Centre - Spark testing tank lining for pinholes; Right - Measuring thickness of applied coating

Barrier Coatings

Key Success Criteria

  • Withstand chemical attack - choose correct resin
  • Resist permeation - less than 0.1 perms (ASTM E-96) or impedance greater than 1 x 10^8 ohm-sq.cm at 0.1Hz per EIS testing 
  • Withstand other service conditions - eg abraision, flexing, cleaning, temperature fluctuations, physical abuse
  • Properly designed and prepared substrate - cleaned, steel blasted to minimum profile, concrete surface strength adequate
  • Be installed correctly - using specifications and QA procedures

Lifecycle Cost (LCC) Analysis

LCC is better than Initial Cost in evaluation that relative cost of a coating. Costs above are current day costs. No allowance is made for downtime or lost manufacturing time when coatings replaced.

 LCC is better than Initial Cost in evaluation that relative cost of a coating. Costs above are current day costs. No allowance is made for downtime or lost manufacturing time when coatings replaced

LCC is better than Initial Cost in evaluation that relative cost of a coating. Costs above are current day costs. No allowance is made for downtime or lost manufacturing time when coatings replaced

 Flakes are used to resist permeation in barrier coatings

Flakes are used to resist permeation in barrier coatings

 Motunui methanol plant demin neutralisation sump below pipework (left) lined in 1983 by ARMATEC with barrier coating (right). In daily use for over 20 years. Maintenance costs during this time have been almost zero.

Motunui methanol plant demin neutralisation sump below pipework (left) lined in 1983 by ARMATEC with barrier coating (right). In daily use for over 20 years. Maintenance costs during this time have been almost zero.