Fibre Reinforced Plastic

Adhesive Joint and Bonding in FRP

noreply@blogger.com (Mr Joe) — Wed, 08 Feb 2012 04:00:00 +0000

Image below shows a series of typical bonded joint configurations. Adhesive joints in general are characterized by high stress concentrations in the adhesive layer. These originate, in the case of shear stresses, because of unequal axial straining of the adherents, and in the case of peel stresses, because of eccentricity in the load path. Considerable ductility is associated with shear response of typical adhesives, which is beneficial in minimizing the effect of shear stress joint strength. The response of typical adhesives to peel stresses tends to be much more brittle than that to shear stresses, and reduction of peel stresses is desirable for achieving good joint performance.

From the standpoint of joint reliability, it is vital to avoid the condition where the adhesive layer is the weak link in the joint, i.e. that the joint be designed to ensure that the adherents fail before the bond layer whenever possible. This is because failure in the adherents may be controlled, while failure in the adhesive is resin dominated, and thus subject to effects of voids and other defects, thickness variations, environmental effects, processing variations, deficiencies in surface preparation and other factors that are not always adequately controlled.

This is a significant challenge, since adhesives are inherently much weaker than the composite or metallic elements being joined. However, the objective can be accomplished by recognizing the limitations of the joint geometry being considered and placing appropriate restrictions on the thicknesses the adherents for any given geometry.

Adhesive joint / bonding types

BMW Carbon Fiber Reinforced Plastic Manufacturing Plant and Process Video

noreply@blogger.com (Fariezul Jaafar) — Wed, 01 Feb 2012 14:54:00 +0000

Radiography Testing For Fibre Reinforced Plastic & Composite

noreply@blogger.com (Mr Joe) — Wed, 11 Jan 2012 04:26:00 +0000

Radiography is a well-established production process with many variables in image formation and interpretation. The equipment performance, personnel qualifications and certification, test criteria, and test procedure scope must be identified and documented, if reliable and repeatable test results are to be achieved. Well-defined test criteria and high-quality reference images are needed to separate unacceptable material from acceptable materials with confidence.

Radiography can be used with composite materials. It provides a permanent record of the test specimen in the image, reveals fabrication, assembly, and structural defects, and often suggests a corrective action in the process used. Digital data files can be easily communicated and shared. Digital data can be rescaled to accurately reconstruct engineering values of material density and size. Radiographic testing involves exposing a media to x-ray radiation that has penetrated the specimen of interest, developing an image from the media, and interpreting the image developed.

Radiographic testing can be applied to assure the maximum reliability of fibre reinforced composite products and bonded assemblies, both with and without honeycomb. It is complementary to ultrasonic inspection, in that these methods can detect different types of defects, and data from one method can often be used to help interpret results from the other.

Existing processes involve tube-type constant potential or rectified radiation sources for production radiography, and many systems are capable of operating at low energy (< 50 kV).Radiographs are normally produced on a high contrast, small-g rain- size medium capable of meeting the flaw detection requirements of the applicable product inspection and acceptance specification. Film radiography typically uses the human eye for a detector. Films are interpreted by passing sufficient quantities of light through the film during observation. If the radiograph has sufficient contrast and spatial resolution, it will be possible to detect small variations within the specimen. Contrast variations of 2% and spatial details of 0.50 to 1.25 mm (0.020 to 0.050 in.) are easily detected in most fibre reinforced plastic and composite materials.

Radiation cell for composites material inspection

Ultrasonic Inspection for Fibre Reinforced Plastic & Composite

noreply@blogger.com (Mr Joe) — Wed, 04 Jan 2012 04:17:00 +0000

The most common method of NDT for fibre reinforced plastic and composite materials is ultrasonic inspection. The measurement of ultrasonic parameters can provide a wealth of information on the quality of composites.

Ultrasonics can generally detect delaminations, inclusions, matrix macro-cracks, and voids in composites structures. The ultrasonic method itself uses longitudinal, shear, Lamb, Rayleigh, or guided waves for various measurements on composite materials. Wave parameters, including acoustic attenuation and speed, can be used to determine materials properties and characteristics, such as void fraction, stiffness, and, if the density is known, moduli. The reader is referred to other texts and articles to obtain detailed information on the fundamental aspects of ultrasonics as well as advanced methodologies for measurements using ultrasound.

Table 2 provides some typical acoustic characteristics of materials, and Table 3 gives the relative wavelength as a function of the frequency. For example, at the interface between water and a graphite/epoxy interface, the transmission and reflection of sound energy will be 152% and 52%, respectively.

The sound energy in the fibre reinforced plastic and composite material will be greater than in the water. At an interface between graphite/epoxy and air, the transmission is 0.017%, and the reflection is 100%. It is this change in the acoustic impedance that allows ultrasound to be used to detect defects in materials. Delaminations and cracks represent air interfaces that transmit very little sound and provide a large reflection. Inclusions must have a sufficient difference in acoustic impedance from the composite material in order to be detected.

In solid homogeneous material, both longitudinal (compression) and transverse (shear) waves can be created and monitored independently. In composite materials, however, the separation of longitudinal and transverse waves is much more difficult. Composites are anisotropic media. The plane waves moving through the anisotropic media are often only quasi-longitudinal or quasi-transverse (containing both longitudinal and shear characteristics), because of the wave interactions at the many matrix and the reinforcing material interfaces. In fiber-reinforced composites, the ultrasonic waves can travel along fibers, and therefore, the technique can be highly sensitive to the fiber orientation in the structure. This feature can be used as a means of characterization of the structure. However, for the general inspection of fiber-reinforced composites, the most common inspection is with ultrasonic waves perpendicular to the fiber tape or fabric planes. As the ultrasonic beam passes through a material, it will be attenuated due to scattering, absorption, and beam spreading.

The anisotropic properties of composites can make them strong scatters of ultrasound, depending on the wavelength. As shown in Table 3, for ultrasonic frequencies between 1 and 10 MHz, the wavelength will be between 0.3 and 0.03 mm (0.01 and 0.001 in.). Features in the composite larger than one-tenth the wavelength will contribute to scatter. Features smaller than this will not be detectable. Absorption occurs due to the conversion of the sound energy into heat. Beam spreading is due to the geometric principles of the ultrasonic beam size, frequency, angle, and distance

The most common inspections of composite structures are through-transmission (TT) ultrasonics and pulse echo (PE) ultrasonics. The TT method uses two transducers, one on each side of the part, to measure the acoustic attenuation through the structure. One transducer is the transmitter and is electronically pulsed to produce an ultrasonic signal, and the other transducer is the receiver, typically aligned opposite to the pulser. The coupling media of the ultrasound to the composite is usually water. This may be performed by immersing the sample in a water tank or by using water-squirter systems.

For TT examinations, the pulser often employs a tone burst (several cycles of the waveform), so that significant ultrasonic power is available. Through transmission is the most common ultrasonic examination method for fiber-reinforced composites. Trough transmission is relatively simple to implement, much more forgiving than automated PE on alignment of the transducers to the part under test, typically has a wide dynamic range (>120 dB on some systems), and easily detects problems in multilayered structures. By comparing TT signal loss in adjacent good areas, porosity, unbonds, wrinkles, delaminations, and most inclusions can be detected. In the case of porosity, the signal loss can be correlated to standards. For example, porosity in the 1 to 2% range corresponds to a change of 4 to 8 dB in signal level for approximately 6 mm (0.25 in.) of graphite/epoxy material at 2.25 MHz.

Through transmission methods cannot determine the depth or layer of detected defects. This must be accomplished using pulse-echo ultrasonic methods. However, data from TT methods are normally presented in the C-scan mode, which presents an image of the part with gray scale or color values relating to the attenuation experienced. This is perhaps the easiest ultrasonic presentation to interpret. Pulse-echo ultrasonic methods typically use a single transducer as both the pulser and receiver of the ultrasound signal. The ultrasound is commonly coupled into the part using a couplant, such as water, glycerin, and other materials. Typical noncontact systems used to couple PE transducers to the parts are hand-held devices,immersion tanks, water-bubbler systems, or water-squirter systems.

Automated ultrasonic scanning systems take many forms and sizes. They range from small tabletop immersion tanks to large overhead gantry systems.

Automated ultrasonic two-channel flat panel through-transmission system

Overhead gantry automated ultrasonic scanning system

Type of FRC Moulds : Matched-Mould

noreply@blogger.com (Mr Joe) — Wed, 28 Dec 2011 07:35:00 +0000

Where matching moulds are required for processes such as resin injection, foam reservoir moulding or cold press moulding, a full size pattern of the final moulding is generally required. If this is a vaila ble the two halves of the mould can be made in a similar way to making a split mould but incorporating appropriate injection and vent tubes along the join between the two halves. The dictates of the process will govern which attachments are necessary. Locating dowels must also be accurately positioned.

With thin mouldings an alternative procedure is to make a pattern of the outside of the moulding and then make the negative mould. This negative mould, after full cure, is then used as a base on which to construct a model of the moulding using sheets of pattern maker's wax. When the required thickness of wax has been applied the positive mould is constructed on top. During construction of the wax pattern due consideration must be given to the provision of drainage channels and vent/injection points. The positive mould must be accurately made, allowing for resin shrinkage, so that the mould cavity is of the correct size. An oversize mould will only waste expensive materials each time a moulding is made.

For cold press moulding the back of the mould should be filled with a material capable of withstanding continuous loading in a press. One such material is concrete, although a filled resin system may also be used. Here, after the final layer of glass reinforcement has been applied to the mould, a further layer of resin is applied at a rate of about 400 gjm2, into which is sprinkled a layer of broken stone chips. After the resin has been fully cured the back of the mould is filled with the concrete or resin mix which bonds around these stone chips. Both halves of the mould should be similarly treated.

Where fibre reinforced plastic (FRP) moulds are used for cold press moulding the moulding cannot be trimmed as part of the moulding cycle. To maintain pressure on the resin and prevent it from being squeezed out leaving air bubbles in the moulding, the mould should be constructed with a pinching area. During final closure of the mould this allows air to escape but retains the resin. For mouldings up to about 5 mm in thickness, the pinching area should be sufficient to compress two layers of glass mat in a gap of 0-4-0· 5 mm. For thicker mouldings the pinching area should accommodate three or four mat thicknesses. In addition, it is useful to incorporate a drainage channel into which surplus resin can drain. An example of such a design is shown in the image.

When not in use, moulds should be stored flat to prevent distortion and protected from dust and moisture. In use, continuous scrutiny is necessary so that any imperfections which occur can be immediately rectified.

Sharp instruments must always be kept away from mould surfaces.

Properly treated, FRP moulds can give excellent service.

Pinch Area for Cold Press Moulding

Type of FRC Moulds : Split Mould

noreply@blogger.com (Mr Joe) — Wed, 21 Dec 2011 07:15:00 +0000

Where deep draw mouldings or ones with undercuts are to be produced which would be difficult or impossible to remove from a one-piece mould, split moulds can be used. Here a temporary barrier should be fitted to the pattern so that the first half of the mould can be made with a flange (image below).

The flange area should be about 50% thicker than the mould shell to ensure adequate life. The first half of the mould is left in place, the temporary barrier removed and the second half of the mould manufactured using the suitably released flange as former. A metal plate can then be laminated onto either side of the flange to assist in supporting the bolts used to clamp the flange halves together. Once the resin has cured, holes can be drilled to take fixing bolts. These should be spaced at about 150 mm intervals.

The mould should not be removed from the pattern until all necessary work has been carried out. Mould release can be assisted by using compressed air carefully applied between the mould and the pattern. Release can also be assisted by filling the gap between the mould and the pattern with water to soften and dissolve the polyvinyl alcohol release agent. If the mould has to be struck in any way, extreme care should be taken to ensure that this does not result in star patterns forming in the gelcoat.

Any imperfections in the mould surface can be removed by rubbing with fine abrasive such as grade 600 wet emery paper followed by a fine cutting paste or by using a metal polish. Before use, the mould surface must be thoroughly polished to a high gloss finish using a silicone-free wax polish applied in several thin coats.

Method of Constructing a Split Mould

PVA Release Agent

Type of FRC Moulds : Opened Mould

noreply@blogger.com (Mr Joe) — Wed, 14 Dec 2011 07:02:00 +0000

In this type of mould, only one mould surface is used in open mould process. This single mould represents either the positive (male plug) or negative (female cavity) surface as shown in image below.

Types of open mould: (a) Positive and (b) Negative

In order to produce large fibre reinforced plastic and composite components and structures, (for instance swimming pools, boat hulls, etc.) very large moulds are usually used. The main matrix materials used are thermosetting resins of epoxy and polyester, while E-glass fibres are the most widely used reinforcement material. Depending on the desired thickness, matrix resins and reinforcement fibres are applied to the mould surface layer by layer. The fibre reinforcement can be used in the form of mats, woven roving or yarns. The use of prepregs may simplify the laying process. After the lay-up process, curing treatment will be necessary for rigid thermoset matrices. Depending on the type of resin used, little or no pressure will be necessary during curing.

Open mould processes have several advantages over closed mould composite manufacturing processes. Since a single mould is used in open mould processes, mould costs will be much less than using two moulds in the closed mould processes.

Another advantage is that very large and complex structures of fibre reinforced plastic and composite, may be produced in open mould processes, which is difficult in closed mould processes. Depending on the component to be produced, a variety of materials (e.g., metals, plaster, woods, fibre reinforced composites) are available for cheaper open moulds, whereas expensive metallic moulds should be designed for closed mould processes. Therefore, it may be concluded that open mould processes have better design flexibility compared with closed mould processes. However, open mould processes have some disadvantages as well. Firstly, only one surface of the product will be finished and smooth. This is because the other surface will be not in contact with the open mould surface. Moreover, to achieve a good surface finish on at least one surface of the component, the surface of the open mould must also be very smooth.

The second disadvantage of open mould processes is that they are very labor intensive. Therefore, for the production of components with higher quality, the personnel working in the process should be adequately skilled. There have been many advances in the automation of open mould processes, which helps to solve the skilled personnel problem. Automation in open mould processes is increasing not only the quality of the product, but also the number of the parts manufactured per unit time. Another disadvantage of open mould processes is the much longer curing periods required compared with other methods. Normally, application of heat will decrease curing time. However, it is difficult to heat treat components which are very large. Open mould processes are usually classified according to the methods of resin and reinforcement application to the mould, or according to the curing methods. If the matrix and reinforcement is applied by hand, then it is named hand lay-up, if it is by a spray gun, then it is called spray-up. Similarly, if the curing is accomplished in a bag, then it is called bag moulding, if it is performed in an autoclave, then it is termed autoclave moulding, etc. However, in order to use the advantages of each method, generally two or more of these methods are combined during manufacturing.

Light Weight Carbon Fibre Cases

noreply@blogger.com (Fariezul Jaafar) — Wed, 07 Sep 2011 05:45:00 +0000

These feather-light cases manufactured by ECS using compression moulding method. The material being used is carbon fibre and DuPont Kevlar reinforcement materials with enhanced thermoset resin.

These rack mount cases are ultra-lightweight and show exceptional structural rigidity. They can be moulded in a variety of wall thickness to meet unique performance and weight requirement for military application. Additional layers of carbon fibre and/or optional ballistic reinforcement material can provide enhanced performance characteristic for challenging application.

ESC also produce other FRP cases. For more info do visit http://www.ecscase.com

Carbon Fibre Rackmount Cases

Carbon-Carbon Composite (CCC)

noreply@blogger.com (Mr Joe) — Mon, 14 Mar 2011 03:02:00 +0000

One of the most advanced and promising engineering material is the carbon fiber reinforced carbon-matrix composite, often termed a carbon–carbon composite; as the name implies, both reinforcement and matrix are carbon. These materials are relatively new and expensive and, therefore, are not currently being utilized extensively. Their desirable properties include high-tensile moduli and tensile strengths that are retained to temperatures in excess of 2000oC (3630F), resistance to creep, and relatively large fracture toughness values. Furthermore, carbon–carbon composites have low coefficients of thermal expansion and relatively high thermal conductivities; these characteristics, coupled with high strengths, give rise to a relatively low susceptibility to thermal shock. Their major drawback is a propensity to high-temperature oxidation.

Application of Carbon Carbon Composites

The development of Carbon Carbon materials began in 1958 and was nurtured under the US Air Force space plane program, Dyna-Soar and NASA's Apollo projects. It was not until the Space Shuttle Program that CC material systems were intensively researched. The criteria that led to the selection of CC composites as a thermal protection system were based on the following requirements:

1. Maintenance of reproducible strength levels at 1650°C (3002°F);
2. Sufficient stiffness to resist flight loads and large thermal gradients;
3. Low coefficient of thermal expansion to minimize induced thermal stresses;
4. Oxidation resistance sufficient to limit strength reduction;
5. Tolerance to impact damage;
6. Manufacturing processes within the state of the art

An example of CC composite applications is a one-piece, bladed turbine rotor that, in service, is coated to prevent oxidation. The rotor offers higher temperature performance without cooling; low weight and use of low-cost, non-strategic materials. Other gas turbine engine applications using CC composites include exhaust nozzle flaps and seals, augmenters, combustors and acoustic panels. CC material systems using coatings, TEOS and additions to the basic CC recipe have improved the oxidation resistance of products made of CC composites by an order of magnitude.

These composites are being used in products such as the nozzle in the F-100 jet engine afterburner, turbine wheels operating at >40 000 rpm, non-wetting crucibles for molten metals, nose caps and leading edges for missiles and for the Space Shuttle, wind-tunnel models and racing car and commercial disk brakes.

Carbon Carbon Composite Plate from SINOTEK MATERIALS

Gelcoat and Gelcoating - Method, Procedure and Tips

noreply@blogger.com (Mr Joe) — Sun, 06 Mar 2011 02:23:00 +0000

Gel coating is usually polyester resin that formulated to give a protective layer of waterproof color coat. Its main function is to protect the subsequent layer from defects. Some gelcoating resin is colored while it also available in original clear form, and pigment can be added according to users need.

Gelcoating method and procedures

The composite work is started with the preparation of the mould . The mould shall first be cleaned, followed by polishing that normally end up with shiny surface. The suitable wax is then applied to the mold surface that will help to release the finished component when cured. The wax usually applied between two to three times before the application of gel coat. When the release agent is completely dry, the gelcoat is applied by brush or spray. When choosing brush, a wide brush with long soft hairs is preferred. Two coats are generally necessary to prevent brush marks from showing. The second coat being applied once the first has sufficiently cured .

Gel coat is applied to about 0.3-0.5mm (Thickness vary manufacturer to manufacturer and from user to user) one to two layers. The operator must ensure the coat in total contact with the contour before starting the lay-up. Gel time of the gelcoat in bulk should preferably be about 15 minutes.

The condition of the gelcoat can be determined by touching it, once it feel tacky and not easily removed by finger, the next coat resin system is ready. In some cases, surfacing tissue may be used to reinforce the gelcoat.

After the tackiness has been achieved, the first layer of reinforcement (fibre) and impregnation of resin can be start.

Tips on Gelcoating :

1. To avoid uneven colour of the finish product, pigment can also be added to the resin – same pigment colour that being used in the gelcoat. (If you are using it)

2. Please refer to the Materal Data Sheet to determined the ratio of catalyst that will be mix with gelcoat / resin.

That shiny surface is a layer of gelcoat. The person in the image is repairing the gelcoat surface. (Image from http://continuouswave.com/ )

Honeycomb Core Terminology

noreply@blogger.com (Mr Joe) — Tue, 01 Mar 2011 06:16:00 +0000

Honeycomb Core Terminology

An example of Honeycomb Core

Hand Lay Up / Wet Lay Up Procedure and Tips

noreply@blogger.com (Mr Joe) — Thu, 24 Feb 2011 05:01:00 +0000

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

Reinforced Plastic System Composite Beam

noreply@blogger.com (Mr Joe) — Mon, 07 Feb 2011 00:07:00 +0000

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/

RTM Variant : Light RTM

noreply@blogger.com (Mr Joe) — Wed, 02 Feb 2011 07:54:00 +0000

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.

RTM Moulding Prosess / Procedure for FRP

noreply@blogger.com (Mr Joe) — Sun, 30 Jan 2011 23:50:00 +0000

For simplicity in understanding the complete Resin Tranfer Moulding (RTM) process, the basic steps for the fabrication of a composite component are describe as below.

1. A thermoset resin and catalyst are placed in tanks A and B of the dispensing equipment.

2. A release agent is applied to the mold for easy removal of the part. Sometimes, a gel coat is applied for good surface finish.

3. The preform is placed inside the mold and the mold is clamped.

4. The mold is heated to a specified temperature.

5. Mixed resin is injected through inlet ports at selected temperature and pressure. Sometimes, a vacuum is created inside the mold to assist in resin flow as well as to remove air bubbles.

6. Resin is injected until the mold is completely filled. The vacuum is turned off and the outlet port is closed. The pressure inside the mold is increased to ensure that the remaining porosity is collapsed.

7. After curing for a certain time (6 to 20 min, depending on resin chemistry), the composite / FRP part is removed from the mold.

Honeycombs Produced By Laser Welding

noreply@blogger.com (Mr Joe) — Sat, 01 Jan 2011 02:11:00 +0000

A customized honeycomb can now be made out of any thermoplastic material supplied in the form of a thin sheet reinforced or not with fibres or webs. The sheet can be watertight, porous or even perforated. It is first folded into a semi hexagonal shape and then welded with an array of very homogenous laser lines onto another sheet along the adjacent nodes.

The welding speed is very high and the weld is as resistant as the constituting material itself, demonstrating the same properties. A honeycomb block is thus assembled automatically on a compact machine with impressive production rates. The length of the honeycomb block can also be chosen with the accuracy of half a cell width.

The honeycomb is mainly used as a core for sandwich panels. Which achieve a construction with unique resistance/weight ratio. A lot of application are to be found in automotive, aerospace, boating, building, energy, furnishing, construction, packaging, trains, etc.

PVC Honeycomb

PEEK Honycomb

Source : http://www.plasticell-honeycomb.com/

CFRP Component for BMW

noreply@blogger.com (Mr Joe) — Sat, 25 Dec 2010 01:41:00 +0000

Last June, BMW has announced a trio of new aero components for the M3 family, including a small rear lip spoiler, mirror caps and a new front splitter.

These components are made from carbon fibre reinforced plastic - the same super-light and super-tough material used in the M3's roof panel - the new BMW Performance parts are also coated in an ultraviolet-resistant laminate, protecting against yellowing, cracking and degradation.

Composite Fabrication : Resin Transfer Molding (RTM)

noreply@blogger.com (Mr Joe) — Sun, 19 Dec 2010 07:04:00 +0000

RTM or Resin Transfer Molding is a closed mold process. In this process, matched male and female molds are being used. Before the process injection, fiber pre-form is places in the mold cavity. Then the molds are clamped. Resin mix then is injected or transferred into the cavity through injection ports at a relatively low pressure.

Schematic diagram of RTM process

Injection pressure is normally less than 690 kPa (or 100psi). The displaced air is allowed to escape through vents to avoid dry spots. Cure cycle is dependent on part thickness, type of resin system and the temperature of the mold and resin system. The part cures in the mold, normally heated by controller, and is ready for its removal from the mold when sufficient green strength is attained.

RTM offers the promise of producing low cost FRP parts with complex structures and large near net shapes. Relatively fast cycle times with good surface definition and appearance are easily achievable. The ability to consolidate parts allows the saving of considerable amount of time over conventional lay-up processes.

Example of RTM Machine

Since RTM is not limited by the size of the autoclave or by pressure, new tooling approaches can be utilized to fabricate large, complicated structures. However, the development of the RTM process has not fulfilled its full potential. For example, the RTM process is yet to be automated in operations such as preforming, reinforcement loading, demolding, and trimming. Therefore, RTM can be considered an intermediate volume molding process.

Several unresolved issues in RTM encountered by composite engineers are in the areas of process automation, preforming, tooling, mold flow analysis and resin chemistry. During the last decade, rapid advances in RTM technology development have demonstrated the potential of the RTM process for producing advanced fibre reinforced plastic and composite parts.

RTM Simulation

Product of RTM Process

Oscar With His CFRP Composite Legs

noreply@blogger.com (Mr Joe) — Mon, 13 Dec 2010 16:39:00 +0000

Carbon Fibre Reinforced Plastic (CFRP) composite legs is a product that composite researchers and designers can be proud of. Made from carbon fibre and being design for disabled person.

And who doesnt know Oscar Pistorius, gold medalist in paralympic, a double amputee, who uses carbon fibre composite legs. He is also known as the "Blade Runner" and "the fastest man on no legs".

He is better than a normal person, thanks to fibre reinforced and composite technology. He’s already considered one of the fastest men in the world.

Oscar Pistorius with CFRP Legs

Also read :
Carbon Fiber Composite Running Legs - Composite Material Blog

Sandwich Composite and Core Material

noreply@blogger.com (Mr Joe) — Sun, 12 Dec 2010 04:05:00 +0000

Sandwich composite, considered to be a class of structural composites consist of two strong outer sheets or faces separated by a layer of less dense material or core, which has lower stiffness and lower strength. The faces bear most of the in-plane loading and also any transverse bending strength. Typical face material include aluminum alloys fiber reinforced plastics titanium steel and plywood.

Structurally the core serves two functions. First it separates the faces resist deformations perpendicular to the face plane. Secondly it provides a certain degree of shear rigidity along planes which are perpendicular to the faces. Various materials and structures are utilized for cores including foamed polymers synthetic rubber inorganic cements as well as balsa wood.

Another popular core consist of a honeycomb structure-thin foil that have been formed into interlocking hexagonal cells with axes oriented perpendicular to the face planes. The material of which the honeycomb is made may be similar to the face material. Sandwich panels are found widely in a wide variety of applications they include roofs floors and wall of building and in aircraft for wing fuselage and tail plane skins.

Structural sandwich construction is one of the first forms of composite structures to have attained broad acceptance and usage. Virtually all commercial airliners and helicopters and nearly all military air and space vehicles make extensive usage of sandwich construction. In recent years, most commercial space vehicles have also adopted this technology for many components

Example of Sandwich Composite, Using Honeycomb Core

Kaizen : From Composite Technology to Fibre Reinforced Plastic

noreply@blogger.com (Mr Joe) — Thu, 09 Dec 2010 00:00:00 +0000

Lately we have made some improvement to our weblog. We changed our name from CompositeTechnology.blogspot to Fibre-Reinforced-Plastic.com. This is we think a best name for this weblog as this resource centre only talk about plastic/polymer composite, while composite represent a wide range of material including metal matrix composite and ceramic matrix composite.
Besides that, we redesign this page to look more attractive and more visitors friendly.

Next step, we will create a Fibre Reinforced Plastic community on facebook, to discuss and share our knowledge concerning polymer composite and fibre reinforced plastic (FRP) issues. We hope to hear comments from all students, researchers and FRP engineers out there!

- Mr Joe Jeff

Laminate Structure and Classification in FRP

noreply@blogger.com (Mr Joe) — Mon, 06 Dec 2010 03:41:00 +0000

The last post we discuss about lamina and laminate terminology and definition. This post will talk about laminate classification. Laminates can be classified according to the fiber orientation :

• Unidirectional Laminate- The fiber angle in any ply is parallel to the fiber angle in every other ply. This is a thick lamina from a mechanics point of view.

• Cross Ply Laminate - The fiber angle in any ply is normal to at least one other ply and parallel to any other ply or plies (i.e., contains only 0 and 90E plies).

• Angle Ply Laminate - Fiber angle of any ply is not restricted to parallel and normal directions. These definitions have different consequences depending upon whether the fiber directions are defined by their fabrication direction or loading direction. For the purposes of composite design the fiber directions relative to the loading directions are relevant. For, instance if laminate is fabricated by laying up 0 and 90E plies, it can be used as cross ply or an angle ply laminate. Laminates can also be classified based on stacking sequence.

• Symmetric Laminate – In a symmetric laminate all plies above the midplane have the same angle as the ply in the equivalent position below the midplane (i.e., the midplane of the laminate is a plane of symmetry).

• Antisymmetric Laminate - All plies above the midplane have the opposite (negative) angle as the ply in the equivalent position below the midplane. (The midplane is a plane of antisymmetry)

• Asymmetric Laminate - The midplane is not a plane of symmetry or antisymmetry.

Lamina and Laminate, What Is That?

noreply@blogger.com (Mr Joe) — Fri, 03 Dec 2010 03:34:00 +0000

So, what is lamina? What is laminate? What is the different?
Let us talk about lamina first.

A lamina is a flat (or sometimes curved) arrangement of unidirectional (or woven) fibers suspended in a matrix material. A lamina is generally assumed to be orthotropic, and its thickness depends on the material from which it is made.

For example, a graphite/epoxy (graphite fibers suspended in an epoxy matrix) lamina may be on the order of 0.127 mm thick. For the purpose of analysis, a lamina is typically modeled as having one layer of fibers through the thickness. This is only a model and not a true representation of fiber arrangement. Both unidirectional and woven laminas are schematically shown below.

Schematic illustration of lamina composite

While a laminate is a stack of lamina, as illustrated below, oriented in a specific manner to achieve a desired result. Individual lamina is bonded together by a curing procedure that depends on the material system used. The mechanical response of a laminate is different from that of the individual lamina that forms it. The laminate’s response depends on the properties of each lamina, as well as the order in which the lamina are stacked.

Schematic of laminate composite

So, to construct a product (laminate) we have to use a several lamina with determined orientation to achieve properties that we want. Usually, lamina is not used without stacking it to create a laminate. These lamina is being hold together thanks to the resin that we choose depending on service conditon of the product.

Pultrusion Process of Kenaf Fibre

noreply@blogger.com (Mr Joe) — Fri, 26 Nov 2010 17:32:00 +0000

Recently I visited an institute that doing research on Kenaf fibre / fiber. Kenaf is a natural fibre that came from hibiscus family plant. The process involve here is pultrusion. Here are some pictures during my visit there :

Kenaf Fibre

Impregnated with Polyester Resin

Into The Heated Die

Exiting The Die

The Pullers

Finish Product After Cutting Process

Suggested Application

Fiberglass Grating

noreply@blogger.com (Mr Joe) — Tue, 23 Nov 2010 16:37:00 +0000

Typical Layers in FRP Grating

Fiberglass is one of the most lightweight materials used by man today, and there are so many applications for fiberglass gratings today.

Fiberglass grating or FRP grating is products that involve pultrusion of glass fiber. This process include of a pulling mechanism of fiberglass roving and continuous mats. The fiber then being impregnated with resin in resin bath and being pulled into a heated die to get the shape that customer need.

The main reason of using fiberglass grating instead of steel is the ability of fiberglass to withstand corrosion. Other than that, fiberglass grating are maintenance free, long service life and non conductive.

Resin that being used to produce this fiberglass grafting usually are Vinylester and Isopthalic Polyester.

The grating can be used in either new application or for replacing existing application which is exposed to corrosive environment. The application can be found in all type of industries such as offshore, oil and gas, power plants, waste treatment, public facilities etc.

Example Application of Fiberglass Grating