jinjiudingFrp

Some of the products developed successfully under the Mission have already recorded significant milestone achievements and reached the threshold of commercialization. The salient Mission achievements include the following :
FRP Gear-Case for Railway Locomotives

Under the project FRP gear-cases for diesel & electric locomotives have been successfully developed and field-tested extensively. Against a development order received from Indian Railways, 60 nos. FRP gear-cases, have been fitted in the diesel locomotives and these are now fully operational. Another development order has been received from OEM supplier for the induction of 108 nos. FRP gear-cases in diesel locos.

FRP gear-cases for electric locomotives (Hitachi model) has also been developed. 36 nos. FRP gear-case for electric locomotives have been supplied against an order from Railways. The Indian Railways plan to induct FRP gear-cases for locomotives in a big way for regular use.

With the use of FRP beam , there has been a weight saving of 430 kgs. per loco. These gear-cases are expected to last for over 6 years in service as against merely 2 to 3 years of conventional steel gear-case. The cost benefit analysis has proved the superiority of FRP gear-case over MS ones on life-cycle basis.

 

No.	Tests	Observed Values (Avg.)	Specified Values
1.	Flexural Strength (MPa)	460	450
2.	Tensile Strength (MPa)	330	300
3.	Hardness (Rc)	119	115
4.	Izod Impact (Kg-Cm)	135	As Declared
5.	Water Absorption	0.12	0.5 Max
6.	Glass Content	64%	60% Min
7.	Specific Gravity	1.94	1.7-2.0
8.	Resistance to spread of flame	Passed (2 Sec)	To Pass (30Sec)
9.	Resistance to Boiling Water % Water Absorption % Reduction in Cross Breaking Strength	0.224 12.7	2% Max 20% Max

 

Extended life-cycle for the products along with a considerable weight savings, better maintainability makes it attractive against steel gear-cases.
Jute-Coir Composite Boards as Wood Substitutes

The project aimed at developing boards with oriented jute face veneer and coir/rubber wood waste inside as wood substitute. The jute-coir composite boards, being positioned as plywood & MDF substitutes have been developed & tested successfully.

Two major categories of composite boards namely, coir-ply boards (jute + rubber wood + coir) as plywood substitute and natural fibre reinforced boards (jute + coir) as MDF substitute have been developed under the project with superior performance, properties and great price advantages. The detailed properties of jute-coir boards tested as per IS-12406 against the specified values of MDF boards are given in Table 3.0.

 

Sl. No.	Tests	Observed Values (Average)			Specified Values
		Board Thickness
		8 mm	6 mm	4 mm	Exterior Grade	Interior Grade
1.	Cross Breaking Strength (Kgs./cm2) - Perpendicular to Grain Direction
a)	Before Boiling	318	391	373	275 (min.)
b)	After 8 Hrs. Boiling	266	270	240	150 (min.)
2.	Bulk Density (Kgs./cm3)	700	739	760	500-900
3.(a)	Moisture Content (%)	5.73	5.90	5.92	5-15	5-15
(b)	Variation from mean moisture content (%)	-2.1	+0.9	+1.2	+3.0	+3.0
4.	Max. water absorption (%)
(a)	After 2 Hrs. soaking	4.5	5.1	2.9	6	9
(b)	After 24 Hrs. soaking	9.1	9.2	6.8	12	18
5.	Max. linear expansion (% swelling in water)
(a)	Due to general absorption after 24 Hrs. soaking
i.	Thickness	Average value : 1.0			4	7
ii.	Length	Average value : 0.13			0.3	0.4
iii.	Width	Average value : 0.21			0.3	0.4

 

Two major categories of composite boards namely, coir-ply boards (jute + rubber wood + coir) as plywood substitute and natural fibre reinforced boards (jute + coir) as MDF substitute have been developed under the project with superior performance, properties and great price advantages. The detailed properties of jute-coir boards tested as per IS-12406 against the specified values of MDF boards are given in Table 3.0.Detailed evaluation of the jute-coir board samples has been carried out by Indian Railways for their applications as berth backings & partitions in railway coaches; the results conform to the railways' requirements. Based on the initial success of using 500 nos. jute-coir boards as MDF substitute in the railway coaches, the Indian Railways decided to induct 4000 nos. boards.

The industry partner has been offering the technology know-how (hard board grade, MDF grade, plywood grade & doors) for transfer to other industries to enable replication of the benefits accrued. The panel & flush doors made of jute-coir composite boards have also been introduced. These are fast gaining the market acceptance by construction agencies and others.

The project aiming at improving fan design to provide optimum efficiency suitable for specific air-flow and system pressure applications was launched in 1998 with technology support from IIT-Bombay, Mumbai. Five types of fans for cooling towers, mine ventilation, textile humidification, radiator cooling for diesel locomotives & air heat-exchangers were developed & tested successfully; an efficiency differential of around 20-30% with commensurate energy saving was achieved over conventional fans with aluminium impellers.

The test results of FRP grating vis-a-vis metallic fans are listed in Table 4.0. These fans promise a pay-back period of 2-3 months at current energy rates. Based on extensive field trials of two radiator cooling FRP fans fitted in diesel locomotives, the Indian Railways have inducted 10 nos. fans for such application.

The energy efficient FRP axial flow fans have been inducted for cooling tower, mine ventilation and other applications by leading Indian industries. The axial flow fans enjoy good export potential especially in the neighbouring countries, as there are very few manufacturers of FRP grating, mostly located in Europe and USA.

 

Sl. No.	Type of FRP Fan	Flow Rate M3/Sec.	Total Pressure mm water gauge	Shaft Power kW	FRP Fan Efficiency as Certified by User Agencies	Efficiency Improvement over Conventional Fan	FRP Fan Energy Savings over Conventional Fan
1.	Cooling Tower Fan+	240.47	8.48	23.24	86.06%	Superior	Superior
2.	Textile Mill Humidifier Fan *	19.04	34.83	-	78.01%	24.58%	Superior
3.	Mine Ventilation Fan+	48.60 to 81.00	92.83	89.63	59.40%	8.22%	21.96%
4.	Radiator Cooling Fan for Railway Diesel Locomotives*	49.76 to 60.21	88.56 to 102.98	74.95 to 78.60	65.67% to 70.24%	2.33% to 9.62%	1.86% to 4.60%
5.	Air-heat Exchanger Fan+	91.43 to 96.94	8.26 to 8.56	10.1 to 10.17	74.01% to 80.04%	20.79% to 21.09%	28.96% to 34.93%

 

FRP Pultruded Profiles

The project aimed at developing FRP profiles for industrial gratings, solid rods for electrical insulation, cable trays, ladders etc. These products have been developed successfully with excellent surface finish and flame retardancy as per international standards. The comparison chart of the properties of FRP Pultruded Profiles sections and other structural materials are listed in table 5.0 & 6.0.

 

Properties	Pultruded FRP	Rigid PVC	Mild Steel	Stainless Steel	Wood
Tensile Strength (N/mm2)	382	44	340	340	80
Flexural Strength (N/mm2)	468.3	70	380	380	12
Flexural Modulus (N/mm2)	22489	2400	196000	196000	700
Izod Impact (Kg.m/cm)	2.15	0.09	1.5	0.53

 

Properties	Pultruded FRP	Rigid PVC	Mild Steel	Stainless Steel	Wood
Specific Gravity	1.8	1.38	7.8	7.92	0.52
Thermal Conductivity (Kcal/hr/m2/° C)	24.4	6.4	1220	732.00	0.4
Coeff. of Linear Expansion (cm/cm° C) x 10-6	5.2	37	8	10	1.7
Safe Working Temp. (° C)	130	55	600	600	160
Flame Resistance	Good*	Poor	Excellent	Excellent	Poor
Corrosion Resistance
a. Acidic	Excellent	Good	Poor	Excellent	Poor
b. Alkaline	Good	Fair	Good	Excellent	Poor
c. Solvents	Fair	Poor	Good	Excellent	Fair
d. Coastal Environment	Excellent	Good	Poor	Excellent	Fair
e. Outdoor Exposure	Excellent	Poor	Fair	Excellent	Fair
f. Effluent Water	Excellent	Good	Poor	Excellent	Fair
g. Steam	Good	Poor	Fair	Excellent	Fair

 

Towards the market seeding for commercialisation of the pultruded product, the Company targeted three major segments viz. new projects, replacement market in industrial & non-industrial applications. Cable trays, gratings, channels & strips & other accessories are being supplied regularly to various industries in India. 

 

 

from:tifac.com

Composites for Railways

    * FRP Gear-Case for Railway Locomotive
    * Jute-Coir Composite Boards for Coach Interiors
    * FRP Pultruded Profiles
    * Jute-Glass Composites for Coaches
    * FRP Sleepers for Railway Girder Bridges
    * FRP Modular Toilet Units for Railway
    * Coaches Composite Main Door for Passenger & EMU Coaches
    * Radiator Cooling FRP Fan for Diesel Locomotives

Composite for Automobiles

    * Composite CNG Cylinders for Automobiles
    * Jute-Coir Composite Boards for Bus Interiors

Composites for Bio-Medical Applications

    * Carbon Fibre External Ring Fixators for Orthopaedics
    * Endoskeleton Type Tomposite Artificial Limbs for Physically Handicapped

Composites for Industrial Applications

    * Energy Efficient Axial Flow FRP Fans for various applications
    * Vacuum Forming Press for CompositesFabrication
    * FRP ArmouredOptical Fibre Cables
    * FRP Pultruded Profiles
    * Double-Walled FRP Vessels for Chemical Storage

Composites for Building & Construction

    * Jute-Coir Composite Boards for wardrobes, furniture, paneling, doors
    * FRP Doors & Windows
    * FRP Pultruded Profiles

The Mission targeted the aspect of energy conservation & energy saving in the sectors like transportation (automobiles & railways), process equipment etc. Lightweight coupled with high strength composites can replace conventional components such as metals, wood etc. in transportation thus directly contributing to energy savings.

The Mission has launched a few projects based on natural fibre composites especially for partial replacement of high-cost glass fibres for low load bearing applications such as partitions, door, panels and other interiors. Commercial exploitation of jute composites for non-structural applications has provided an excellent application & market potential.

Natural fibre composites reinforced with quickly renewable natural fibres such as jute, coir, sisal etc. as wood substitute can help preventing depletion of precious forest resources. Simultaneously, such natural fibre composites can be excellent value-addition avenues for the farmers and converters for novel applications far from the traditional means of using the FRP grating . With increasing emphasis on fuel efficiency, jute composites enjoy wider applications in automobiles and railway coaches.

The Mission has made a visible impact on Indian Railways by launching nine projects having direct relevance to railways. A few products have gone in a big way towards commercialization. The product has catered to stringent technical and safety requirements. The painstaking and concerted efforts over a prolonged period have gone in the conceptualization, design & development and further improvement of these composite products for the railways.

Towards an industry oriented technology incubation process, the Mission attempted to source the knowledge from various centres of excellence across the country and catalyzed an active partnership with the industries for technology absorption, development & dissemination.

An industry partner was involved in the projects for bridging the gap between the product development and market penetration. The Mission thus enhanced the confidence levels in the industries as well as R&D agencies to promote commercialization of composite technologies.
The material characterization, design methodology, product development, process parameters, quality control, testing & certification of Fiberglass mat products are of utmost importance for accepting the products by the end users. This can be met by in-house development of such facilities meeting Indian & international standards. The Mission has identified the prime need for creating such in-house testing capabilities for the industries.

Under the projects supported by the Advanced Composites Mission, the industries have set up automated in-house production, testing & quality control facilities for manufacturing composite products meeting the international standards & quality norms.

This has contributed significantly to the upgradation of composite technology in terms of basic design parameters, raw material selection, process of fabrication, testing, quality assurance and certification resulting in the development of novel composite products for a wide array of applications.

This aspect generated confidence among industry & the user. The products developed with upgraded technology are successful in replacing some of the imported ones with better efficiency & enhanced life. This has paved the way for good business potential in the domestic market as well as avenues abroad.

 

 

from: tifac.com

The Mission targeted the aspect of energy conservation & energy saving in the sectors like transportation (automobiles & railways), process equipment etc. Lightweight coupled with high strength composites can replace conventional components such as metals, wood etc. in transportation thus directly contributing to energy savings.

The Mission has launched a few projects based on natural fibre composites especially for partial replacement of high-cost glass fibres for low load bearing applications such as partitions, door, panels and other interiors. Commercial exploitation of jute composites for non-structural applications has provided an excellent application & market potential.

Natural fibre composites reinforced with quickly renewable natural fibres such as jute, coir, sisal etc. as wood substitute can help preventing depletion of precious forest resources. Simultaneously, such natural fibre composites can be excellent value-addition avenues for the farmers and converters for novel applications far from the traditional means of using the natural fibres. With increasing emphasis on fuel efficiency, jute composites enjoy wider applications in automobiles and railway coaches.

The Mission has made a visible impact on Indian Railways by launching nine projects having direct relevance to railways. A few Fiberglass mats have gone in a big way towards commercialization. The product has catered to stringent technical and safety requirements. The painstaking and concerted efforts over a prolonged period have gone in the conceptualization, design & development and further improvement of these composite products for the railways.

Towards an industry oriented technology incubation process, the Mission attempted to source the knowledge from various centres of excellence across the country and catalyzed an active partnership with the industries for technology absorption, development & dissemination.

An industry partner was involved in the projects for bridging the gap between the product development and market penetration. The Mission thus enhanced the confidence levels in the industries as well as R&D agencies to promote commercialization of composite technologies.

The Advanced Composites Mission also set up two stand-alone technology incubation centres. The details of such technology incubation activities are given under ‘Composites Development Cemtre’.
The material characterization, design methodology, product development, process parameters, quality control, testing & certification of Fiberglass fabric are of utmost importance for accepting the products by the end users. This can be met by in-house development of such facilities meeting Indian & international standards. The Mission has identified the prime need for creating such in-house testing capabilities for the industries.

Under the projects supported by the Advanced Composites Mission, the industries have set up automated in-house production, testing & quality control facilities for manufacturing composite products meeting the international standards & quality norms.

This has contributed significantly to the upgradation of composite technology in terms of basic design parameters, raw material selection, process of fabrication, testing, quality assurance and certification resulting in the development of novel composite products for a wide array of applications.

This aspect generated confidence among industry & the user. The products developed with upgraded technology are successful in replacing some of the imported ones with better efficiency & enhanced life. This has paved the way for good business potential in the domestic market as well as avenues abroad.

Milestone Achievements

Some of the products developed successfully under the Mission have already recorded significant milestone achievements and reached the threshold of commercialization. The salient Mission achievements include the following :

Under the project FRP gear-cases for diesel & electric locomotives have been successfully developed and field-tested extensively. Against a development order received from Indian Railways, 60 nos. FRP gear-cases, have been fitted in the diesel locomotives and these are now fully operational. Another development order has been received from OEM supplier for the induction of 108 nos. FRP gear-cases in diesel locos.

FRP ladder for electric locomotives (Hitachi model) has also been developed. 36 nos. FRP gear-case for electric locomotives have been supplied against an order from Railways. The Indian Railways plan to induct FRP gear-cases for locomotives in a big way for regular use.

With the use of FRP gear-cases (six nos. per locomotive), there has been a weight saving of 430 kgs. per loco. These gear-cases are expected to last for over 6 years in service as against merely 2 to 3 years of conventional steel gear-case. The cost benefit analysis has proved the superiority of FRP gear-case over MS ones on life-cycle basis.
Extended life-cycle for the products along with a considerable weight savings, better maintainability makes it attractive against steel gear-cases.
Jute-Coir Composite Boards as Wood Substitutes

The project aimed at developing boards with oriented jute face veneer and coir/rubber wood waste inside as wood substitute. The jute-coir composite boards, being positioned as plywood & MDF substitutes have been developed & tested successfully.

Two major categories of FRP beam namely, coir-ply boards (jute + rubber wood + coir) as plywood substitute and natural fibre reinforced boards (jute + coir) as MDF substitute have been developed under the project with superior performance, properties and great price advantages. The detailed properties of jute-coir boards tested as per IS-12406 against the specified values of MDF boards are given in Table 3.0.
Detailed evaluation of the jute-coir board samples has been carried out by Indian Railways for their applications as berth backings & partitions in railway coaches; the results conform to the railways' requirements. Based on the initial success of using 500 nos. jute-coir boards as MDF substitute in the railway coaches, the Indian Railways decided to induct 4000 nos. boards.

The industry partner has been offering the technology know-how (hard board grade, MDF grade, plywood grade & doors) for transfer to other industries to enable replication of the benefits accrued. The panel & flush doors made of jute-coir composite boards have also been introduced. These are fast gaining the market acceptance by construction agencies and others.
Energy Efficient Axial Flow FRP Fans

The project aiming at improving fan design to provide optimum efficiency suitable for specific air-flow and system pressure applications was launched in 1998 with technology support from IIT-Bombay, Mumbai. Five types of fans for cooling towers, mine ventilation, textile humidification, radiator cooling for diesel locomotives & air heat-exchangers were developed & tested successfully; an efficiency differential of around 20-30% with commensurate energy saving was achieved over conventional fans with aluminium impellers.

The test results of FRP fans vis-a-vis metallic fans are listed in Table 4.0. These fans promise a pay-back period of 2-3 months at current energy rates. Based on extensive field trials of two radiator cooling FRP fans fitted in diesel locomotives, the Indian Railways have inducted 10 nos. fans for such application.

The energy efficient FRP grating axial flow fans have been inducted for cooling tower, mine ventilation and other applications by leading Indian industries. The axial flow fans enjoy good export potential especially in the neighbouring countries, as there are very few manufacturers of FRP fans, mostly located in Europe and USA.
  FRP Pultruded Profiles

The project aimed at developing FRP Pultruded profiles for industrial gratings, solid rods for electrical insulation, cable trays, ladders etc. These products have been developed successfully with excellent surface finish and flame retardancy as per international standards. The comparison chart of the properties of FRP pultruded sections and other structural materials are listed in table 5.0 & 6.0.
Towards the market seeding for commercialisation of the pultruded product, the Company targeted three major segments viz. new projects, replacement market in industrial & non-industrial applications. Cable trays, gratings, channels & strips & other accessories are being supplied regularly to various industries in India.

 

 

from:tifac

Technology incubation has been an international experience in developing and promoting the novel technology applications. The relevance of technology incubation specially assumes importance in the context of a developing economy and industry as typified by India.

From its inception, the Advanced Composites Mission had explored different ways so as to evolve the single most effective mechanism for technology development for faster & wider applications. At the initial stage, the approach had been to locate the incubation activities within the premises of a national level publicly funded R&D lab or an academic institution with the outside support of an industry partner.

The model involved carrying out all the developmental activities and creation of Fiberglass fabric in the laboratory itself supported with major funding from the Mission. The strategy was based on the premise that in the event of successful development of technology, the industry would take it up further for commercialization.

Most of the targeted areas of development were of critical technology without a large usage base, mostly concerning aerospace applications of low-volume but high-value. The strategy lacked in the direct involvement of the users/stake holders (market perspective) in technology development. The industry partners being extraneous to the entire development exercise were not too keen on the outcome. The strategy is schematically illustrated by Fig.

 

 

 

 

 

In the later experiment, while the development & incubation activities still centred around the R&D labs, the industry partners were involved directly in die development, prototype fabrication and product testing. The technology incubation became a success with the product finding bulk application.

The case of developing FRP grating for railway girder bridges involving a defence R&D lab, a medium sized entrepreneur and most importantly, the user, Indian Railways, has been successful. The project was co-funded by Indian Railways and the Mission with the promise of large-scale replication.

After a whole gamut of simulated use tests by two national agencies and year-long field trials on actual condition, the FRP sleepers have now been inducted by the Indian Railways. With the knowledge replication, there are four FRP manufacturers in the country today capable of fabricating and supplying the sleepers catering to a large demand pattern. A schematic presentation of the second strategy is given in Fig. 

 

 

The most successful strategy of technology incubation has been the latest one wherein the actions were shifted to the premise of SMEs. The SMEs were nurtured with design & technology support from the centres of excellence e.g. IITs, CSIR labs etc. The knowledge partners extended support in terms of design, material selection, process optimization, equipment specifications & procurement, prototype development and finally product testing towards user acceptance.

In all such cases, a tripartite arrangement was arrived at where the centre of excellence, entrepreneur and the Mission worked together. The Mission introduced the unique methodology of project review and monitoring with the involvement of experts mostly drawn from the user agencies.

The technology incubation attributes such as attractive scheme of financial assistance, technological risk sharing, an effective programme management and knowledge-based project monitoring by experts coupled with the market intervention by reaching to the user agencies all helped the Mission to record its achievements in a short span and arrive at a threshold. The Mission functioned more as a ‘facilitator’ than merely a funding agency. The schematic representation of the proven strategy is given in Fig.

 

 

Sectors Targeted Towards Technology Development

Under the aforesaid Mission on Advanced Composites, a number of projects on novel composite applications such as Fiberglass mat for railway locomotives, high energy efficiency FRP axial flow fan, pultruded FRP profiles , jute-coir composite boards etc.were initiated in partnership with the industries across the country. There has been an intense interaction with major user agencies from important economic sectors towards product standardization, testing, approval & acceptance for wider induction.

 

from:tifac 

FRP pultruded profiles windows were first produced in Canada in 1984, were subsequently introduced to the USA and European markets and are becoming increasingly popular. Market studies conducted on behalf of North American manufacturers predict a tenfold increase in the next few years. In the UK, pultruded fibreglass windows have been available only since the early 2000s.

Pultruded fibreglass windows offer a number of advantages over other types of window systems, as follows:

> Thermal performance. Pultruded fibreglass has a low coefficient of thermal conductivity that compares favourably with other low conductivity products like PVC or wood. Because of its great strength, profiles can be very thin, thus limiting the potential for cold bridging. Therefore, the thermal performance of the manufactured product is very good.

> Strength. As shown in Table 1, pultruded FRP profiles have greater flexural and tensile strengths than other materials used in fenestration. Therefore, they are suitable for large openings without the need for metal reinforcements.

> Dimensional stability. Pultruded fibreglass has a low coefficient of linear expansion which is very similar to that of glass. Other window materials have much higher coefficients – aluminium’s is double that of glass and PVC’s is seven times greater. As a result, pultruded FRP frames do not distort due to thermal variations.

> Resistance to moisture. Pultruded fibreglass is virtually impervious to moisture, and therefore does not rot, warp, crack or twist.

> Chemical resistance. Pultruded fibreglass is unaffected by chemicals or salt air, and is therefore suitable for coastal locations.

> Appearance. As FRP pultruded profiles are dimensionally and hydroscopically stable, they are a good base for sophisticated finishing systems.

> Cost. Initial capital expenditure is higher than for PVC, aluminium or timber windows. However, a whole life cost study conducted by the Building Research Establishment concluded that over a 30-year period, pultruded FRP was more economical than PVC.

A relatively minor limitation of the product is that FRP profiles cannot be welded, and therefore joints must be formed using adhesives.

Environmental considerations
There are a number of factors to be considered when assessing the environmental impact of pultruded FRP windows, among others:

> Resource depletion. Glass, which is silica based, accounts for approximately 65-85% of the components of FRP profiles. For all intents and purposes, sand can be considered an inexhaustible material. The polymer-based matrix is, of course, subject to the availability of oil for its production.

> Energy during manufacture. Because the main component is silica sand, this is low for FRP profiles .

> Gas release during manufacture. Unlike that of PVC, the manufacture of FRP profiles is a sealed operation, and the release of gases into the atmosphere can be closely controlled.

> Energy used during life. This is generally low, because of the good thermal performance of FRP.

> Disposal. As previously explained, the thermoset resins used in FRP are not easily recyclable, and may, in due course, steer the industry towards the use of thermoplastics.

Pultruded FRP has achieved an A rating in the latest BRE ‘Green Guide to Composites’, which is an environmental profiling system for composite materials and products published by BRE (‘A’ is the highest grade, ‘E’ the lowest). Table 2 compares the environmental impact of pultruded FRP windows with that of two alternatives.

Summary
The use of composites has been embraced wholeheartedly by the sports, aeronautic, car and maritime industries among others, but acceptance by the construction industry has been much more muted. In the UK, the BRE has created a specific forum called the Network Group for Composites in Construction with the aim of disseminating the advantages of composites throughout the building industry. Pultruded fibreglass window profiles, in particular, appear to offer the designer the opportunity of using very slim but strong and durable profiles suitable for large openings without compromising the ‘green’ credentials of the design.

 

 

from:ribajournal

Composite materials (composites for short) are engineering materials made up of two or more components which, although remaining separate and distinct, act in unison, each overcoming the deficiencies of the other. Combining the advantages of each element results in a material with broader and more attractive properties than its individual components. One of the two constituents acts as reinforcement and it is surrounded by the other, a matrix which transfers loads to it.

A very early example of composites is the use of mud bricks, with straw acting as reinforcement.

Reinforced concrete is a more modern example, where the poor compressive strength of steel is made up by the good performance of the concrete, with the opposite being true for tensile strength. Reinforcement materials used can be present in the form of particulates, discontinuous fibres (short fibres) or continuous fibres. Matrix products include metals, ceramics and plastics.

This overview of composites applied to windows will focus on glass fibre reinforced plastics (FRP grating ), where the matrix is a polymer and the reinforcement is carbon, glass or aramid fibres. Aramid is a synthetic long chain polyamide best known by its trade name Kevlar, used in the construction of bullet-proof vests. These reinforcement materials have very high tensile and compressive strengths, but in their natural form fail at levels lower than their theoretical limits because of surface flaws that cause them to crack. When the material is used in fibre form, these surface flaws are limited to a small number of fibres, whereas the remainder still behave to their theoretical limits.

The function of the matrix is to spread the load to the individual fibres, and also to protect them from damage resulting from abrasion and impact. Materials used for the matrix can be categorised as:
> Thermoset polymers, which are plastic resins that cure by chemical reaction when heated and, once cured, cannot be resoftened by heating. Their greatest advantage is that, because of their low viscosity, fibre impregnation can be carried out at low pressure. More than 90% of the polymers currently being used in composites are thermoset.

> Thermoplastic polymers, which are plastics capable of being repeatedly softened by increases in temperature and hardened by decreases in temperature. They are also tougher and FRP applications than thermosets, but are more expensive to process as this must be done at a much higher pressure. However, they are much more readily recyclable than thermosets and, in the future, this may swing the choice their way in spite of the additional costs. A recent innovation has been the development of a proprietary patented product consisting of fibreglass reinforcement fibres in a PVC-U matrix, which is a thermoplastic polymer.

Various polymers are currently used as the matrix constituent, including: polyester resin; vinyl ester resin; epoxy; polyimide; polypropylene, etc.

The properties of a composite are determined by:

> the properties of the reinforcement

> the properties of the matrix

> the ratio of fibre to matrix (called fibre volume fraction). This is adjusted accurately during the impregnation process to suit the intended product use and ensure an even distribution. Although, in theory, a very high FRP profiles volume fraction would result in higher mechanical properties, there is a practical limit because all fibres need to be fully impregnated.

> the geometry and orientation of the fibre in the composite. The diameter of the fibre is of great importance, as finer fibres have proportionally a larger surface area, and therefore the loads transferred by the matrix are spread more efficiently. Composites have anisotropic properties, ie, properties that are direction-specific as a result of the orientation of the fibres.

In the construction industry, pre-impregnated materials, ie, materials where the reinforcement has been pre-impregnated with resin before forming are the most commonly used ones, as opposed to those where the reinforcement is added to the matrix at the moulding stage. There are two basic types of pre-impregnated FRPs:

> unidirectional, where the impregnated fibres are aligned in one direction only and

> woven, which is a resin-impregnated fabric.

The composite must then be formed in the required shape/profile, generally by moulding. Until recently, this has necessitated high temperature and/or pressure, with associated high costs. However, the advent of low temperature moulding materials has simplified the process and lowered costs allowing possible on-site processing without the need for autoclaves and manufacturing shops.

The very high strength-to-weight ratio of composite materials makes them very suitable for structural long span applications, and their flexibility allows complex shapes to be formed, for example, lightweight cladding panels. Durability is also high, and life cycle and maintenance costs are low.

Fiberglass mat
Since its invention in 1938, fibreglass reinforced plastic (FRP) also known as GRP (glass reinforced plastic) has grown in popularity and now accounts for approximately 65% of composite production.

Fibreglass fibres are extruded molten glass (usually silica based, but not exclusively so) fibres, braided into bundles to form a continuous rope. FRP is produced by combining a polymer matrix with fibreglass reinforcements, either cut into short strands or woven into a cloth. The ratio between matrix and reinforcement is generally 65-85% resin and 15-35% reinforcement. All FRP products are thermosets.

Different grades of Fiberglass fabric can be produced by varying the composition of the glass used for the fibres, for example:

> E-Glass, which has good electrical properties

> C-Glass, offering the best resistance to chemical attack, etc

> R-, S- or T-Glass are not grades, they simply refer to proprietary trade names from various manufacturers.

When the FRP has been woven into a cloth, it is then moulded into shape. There are various moulding techniques, including open moulding, which produces only one good, finished surface and a rough one, and autoclave and vacuum moulding, which produce two finished surfaces. However,FRP pultruded profiles can also be formed into continuous profiles by means of a process called pultrusion.

In the extrusion process, the material to be formed is pushed through a die, but fibre-reinforced composites need to be pulled instead. This process is called pultrusion (the name is a portmanteau word derived from the words ‘pull’ and ‘extrusion’).

Figure 1 explains the pultrusion process in schematic form: the reinforcement fibres are pulled through a resin bath, where they are impregnated, through a forming plate that confers the composite its profile section and then finally into a heated die where the resin is polymerised. As it cools down, the profile solidifies and is eventually cut into the required lengths.

The process of pultrusion has several advantages:

> it is a fast, economic way of impregnating and curing materials

> volatile emissions can be limited because resin impregnation takes place in enclosed surroundings

> resin and fibre content can be accurately controlled

> structural properties of laminates can be good since the profiles have very straight fibres and high fibre volume fractions can be obtained.

An even more recent development is the process of co-pultrusion, where two or more materials pass through a single die, and the resulting product is a laminate profile, where each ply of the laminate confers to it a desired property (for example, resistance to some specific environment, stiffness, etc).

Pultruded fibreglass products are very strong, dimensionally stable and durable, and can be formed accurately into sophisticated profiles. It is therefore not surprising that they are now increasingly being used in the manufacture of windows and doors. Table 1 compares the mechanical and physical properties of pultruded profiles with those of other materials.

 

 

from:ribajournal