193
7
Vacuum infusion produces composites with a uniform
resin distribution, producing high-quality composite structures. The tool cost is low in this process because open
moulds are used. In vacuum infusion technology, there is no
residue or precipitates from substantial emission reduction
compared to other open moulding or vacuum bagging
processes. In Brazil, SkyRail coaches have been made using
VI technology [18]. The construction of these coaches uses
sandwich composites with a foam core. These rail coaches are
capable of ferrying 10,000 passengers per day at a speed of 65
Km/hr.
5 Processability Parameters—The processability parameters for
vacuum infusion technology are the following.
5 Viscosity of the resin (η)—Only low viscosities of resin allow
the processability of composites. Low viscosity is essential
for the flow of resin through compacted reinforcement for
complete wetting.
5 Gelation time—Gelation time for the resin needs to be
higher than the impregnation time for the processability of
the composite.
5 Shape and profile of the product—Sharp edges and undercuts
do not favour the processability of composites by vacuum
infusion technology because sharp edges may puncture the
vacuum bag.
5 Form of reinforcement—Only fabrics and CSM are used as
reinforcements in order to allow the processability of the
composite using vacuum infusion technology.
5 Cure temperature—In general, the matrix resin used in
vacuum infusion cures at room temperature. This process
does not support high-temperature resin systems. For
high-temperature curing resins, the cost of processing goes
up due to the use of both high-temperature bagging film
and high-temperature putty. There also is a risk of warpages
and dimensional inaccuracies due to open moulding
processing.
One disadvantage of VI is that the excellent consolidation favours a
thin cross section with a high-fibre content. Thus, the composites
developed may lack sufficient stiffness. In order to combat this
problem, core materials of various types are used to increase the
stiffness. A further complication with VI is that while the lamination process itself is very quick, the setting up of the mould with the
bag and resin distribution network is time-consuming and costly, as
the materials are disposable.
Typically, vacuum infusion is used for parts where high performance and quality are the main criteria and where the extra cost
associated with the disposable materials can be supported. The process has been used particularly in the marine industry for boat hulls
and masts.
7.1 · Open Mould Processing Technologies
7
Vacuum infusion produces composites with a uniform
resin distribution, producing high-quality composite structures. The tool cost is low in this process because open
moulds are used. In vacuum infusion technology, there is no
residue or precipitates from substantial emission reduction
compared to other open moulding or vacuum bagging
processes. In Brazil, SkyRail coaches have been made using
VI technology [18]. The construction of these coaches uses
sandwich composites with a foam core. These rail coaches are
capable of ferrying 10,000 passengers per day at a speed of 65
Km/hr.
5 Processability Parameters—The processability parameters for
vacuum infusion technology are the following.
5 Viscosity of the resin (η)—Only low viscosities of resin allow
the processability of composites. Low viscosity is essential
for the flow of resin through compacted reinforcement for
complete wetting.
5 Gelation time—Gelation time for the resin needs to be
higher than the impregnation time for the processability of
the composite.
5 Shape and profile of the product—Sharp edges and undercuts
do not favour the processability of composites by vacuum
infusion technology because sharp edges may puncture the
vacuum bag.
5 Form of reinforcement—Only fabrics and CSM are used as
reinforcements in order to allow the processability of the
composite using vacuum infusion technology.
5 Cure temperature—In general, the matrix resin used in
vacuum infusion cures at room temperature. This process
does not support high-temperature resin systems. For
high-temperature curing resins, the cost of processing goes
up due to the use of both high-temperature bagging film
and high-temperature putty. There also is a risk of warpages
and dimensional inaccuracies due to open moulding
processing.
One disadvantage of VI is that the excellent consolidation favours a
thin cross section with a high-fibre content. Thus, the composites
developed may lack sufficient stiffness. In order to combat this
problem, core materials of various types are used to increase the
stiffness. A further complication with VI is that while the lamination process itself is very quick, the setting up of the mould with the
bag and resin distribution network is time-consuming and costly, as
the materials are disposable.
Typically, vacuum infusion is used for parts where high performance and quality are the main criteria and where the extra cost
associated with the disposable materials can be supported. The process has been used particularly in the marine industry for boat hulls
and masts.
7.1 · Open Mould Processing Technologies