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Thursday, February 24, 2011

Hand Lay Up / Wet Lay Up Procedure and Tips

Hand lay-up is the simplest process in the low end composite products, require low investment, higher operating skill, and versatile shapes of product that need single high quality surface finish.

Hand lay-up is the process that starts with the application of gel coating onto a completely polished and waxed mould. (gelcoating is an optional step. We will discuss about gelcoating next time)


A coat of laminating resin (resin that being mixed with catalyst / hardener, or else your part will not cure) is then being applied by brush or roller. Follow by the first layer of chopped strand mat (preferably 300 gs/m2 or less), or if desire a surface tissue.

The laminating resin is then applied to the reinforcement (the fiberglass) so that all trap air can be force out using roller.


Continue doing this for your next layer of fiberglass, until desired thickness is achieved.


Once finished, allow the resin to cure. You can feel the reaction taken place when your product is producing heat.

Finally, remove your product from the mould (demould) and next step is trimming the fiberglass product.

Hand Lay Up Tips

1. Make sure the mould is properly waxed. 5-6 layer of paste wax should be apply to the newly use mould. This is to make sure the product can be easily be demould.

2. Refer to Material Data Sheet on ration for resin-catalyst. Make sure laminating process can be finish before the resin start gelling. This is called the resin gel time.

3. Use compress air to help you demould the product.

4. Quickly wash the brush and roller with acetone if you wish to reuse it.

Brushes for resin impregnation process and metal rollers to force the air buble out.

Paint rollers can be use as alternative to brushes depending on mould size and profile

Monday, February 7, 2011

Reinforced Plastic System Composite Beam

RPS composite beams are solving corrosion problems in the Flue Gas Desulphurization Industry. The environment inside SO2 absorber towers is very corrosive and can be problematic for metals. Due to the abrasive and corrosive atmosphere and chloride concentrations, these environments often require very expensive alloy materials for a variety of components including support beams. Composites beams developed by RPS are now being installed in FGD absorber towers.

RPS is currently supplying 120 composite beams to be installed in 4 FGD absorber towers. The beams are being shipped in lots of 30 to be assembled in a 35 ft x 135 ft rectangular scrubber in two layers of 15 beams each.

The beams will support the mist eliminators and associated ME wash pipe. The beams were designed to a customer defined envelope and were modeled by structural and composite engineers using RISA structural engineering software to meet the end-users performance criteria. The beams are of 3 specific designs: 8"W x 19"D x 26'L, 8"W x 19"D x 38'L with 1" camber, and 12"W x 25"D x 36'L with 1" camber. These beams are manufactured using RPS Flow Core infusion technology with vinyl ester resins and proprietary multi 3 dimensional fabrics that produce a laminate with a modulus of elasticity of > than 6 million psi. These laminates are incorporated in the top and bottom flanges of the beam. This high stiffness fabric is complimented with interlaced 45 degree bi directional fabrics that optimize load distribution between the compression and tension side of the beams in bending.

RPS vacuum infusion technology ensures consistently high quality parts with repeatable and predictable properties.

Once the vacuum infused beam is removed from the mold the beam is de burred of any resin flashing, visually inspected, and is moved to a test fixture.
Each beam is performance tested using a 4 point bending test fixture that deflects the beams to full operational limits and from this the bending stiffness (EI) is determined and checked against specified stiffness.
 
For this application the inherent corrosion resistance of RPS Composite beams was enhanced by the addition of an exterior proprietary erosion resistant liner which is applied after visual inspection and testing are complete. Attachments for pipe supports, guides, etc., are manufactured with traditional vacuum infusion laminates and are attached to the beams by contact molded secondary bonds. The overall assembly of 15 beams for each layer is shop trial fit as a system prior to beam shipment.

RPS Composite Beams

For more information on RPS Composite Beam or other FRC product, please visit : http://www.reinforcedplasticsystems.com/

Wednesday, February 2, 2011

RTM Variant : Light RTM

LRTM process for composites is best described as a complimentary process to RTM (Resin Transfer Moulding). LRTM mould costs are basically half the price of equivalent RTM moulds but they produce, at best, at half the rate of RTM however the process provides molders an attractive introductory route into closed mould production.


In LRTM, resin flow rates cannot be speeded up above an optimum level in order to fill the mould more quickly as the recommended LRTM mould construction and the atmospheric mould clamping pressures limit overall in-mould pressures to less than 0.5 bar (8 psi).

As with any composite closed mould production technique LRTM is no exception to the rule in demanding high quality accurate composite moulds in order to provide good mould life and consistent production of good parts.

LRTM is now well established as an alternative FRP/GRP moulding technique and we encourage any traditional hand lay moulder starting up in LRTM to ensure their mould build technology, equipment and parts for LRTM are acquired from professional sources.

The advantages of closed molding for either true RTM or RTM Light, offers working environments for the molding operators that are far more comfortable and healthy. They then are willing to apply their skills of quality and productivity at a consistently higher level each day. Even though it is true that RTM Light will not yet meet the production rates that are enjoyed in traditional RTM, RTM Light will provide a 300 to 400% increase in per square foot productivity over open mold, with significant improvement of bill of material compliance and lower operator employment turnover.

Process Flow of Light Resin Transfer Moulding (LRTM)

Source : Magnum Venus Plastech (MVP), their website is http://www.plastech.co.uk/

Ps: I have attended training organized by MVP on building a RTM mould. It was very helpful and informative. Their trainer, Mr Charles is a very friendly and skillfull person. I also met him at JEC composite Asia Show in Singapore while he at MVP booth.