OUR FRP

 

At PROTECTOR we use the highest quality materials to construct every single system we have. At protector we hold ourselves and our products to the highest standards, ensuring that they meet every Standard for storm water treatment systems. As we are a company that deals with protecting the environment, putting the upmost importance of treating storm water efficiently and to maximum effect. With this being our main goal, we have a series of stringent tests and qualities that our base material must achieve. In storm water treatment strength to withstand underground installation, a long lifespan of the product, a strong resistance to corrosion, assurance of watertight barriers and to not decay at any rate to cause more harm to our environment. With all of these in mind, along with the need to appease customers with the best possible pricing we came to a solution.

FIBRE REINFORCED POLYMERS. 

FRP, known as Fibre Reinforced Polymers or Fibre reinforced Plastics, is a composite material made up of two parts – the polymer matrix which is then reinforced with fibres. These fibres are usually glass, carbon fibres, aramid or basalt each system having their own strengths and advantages. The common polymers, or matrix, usually an epoxy, vinyl ester or thermosetting plastic. The main reason in which Fibre reinforced polymers are such a useful material as it is considered a composite material, which are materials that are the result of from bonding two or more homogenous materials to derive a final material with specific required physical, mechanical and chemical properties. Currently, they have a high potential to replace conventional materials such as steel and concrete in these infrastructure systems due to their amazing high strength and stiffness, greater fatigue strength and energy absorption capacity and corrosion resistance among other advantages.

Usually the matrix system, or the binding agent, is the plastic material. The matrix is a strong but relatively weak system that has undesirable mechanical properties when considered in an application that requires long life, high strength and corrosion resistance. These systems are brittle, with low durability, deform easily under load and have a lower strength when compared to reinforced plastics. Once the matrix is reinforced with the fibres, the strength properties and elasticity are drastically altered. The overall system becomes high strength under tensile and compressive loads, more suitable for high stress, higher stiffness and will not permanently deform under working load and most importantly resists a broad range of chemicals and is unaffected by moisture making it ideal for application for water immersion systems. Fibre reinforced polymers also have a long life, which may hinder their ability to be recycled, make them great in applications that involve long life systems.

Specification of orientation of the reinforcing fibres can also increase the strength and resistance to deformation of the polymers. When the fibres are parallel to the direction of force, this is when the fibre reinforced plastic material is at its strongest. This is where the highest strength, stiffness and long life qualities of the system are excelled. However this process can also hinder the material in cases where there is a misalignment of fibres causing shear failure, tensile forces that stretch the matrix more than the fibres can also cause shear failure, in cases where the fibre separates from the matrix causing weaknesses and in cases of extremely high load the fibres themselves can shear. It is hence paramount that during the construction of any FRP system, the engineering and manufacturing processes are up to the highest standards allowing maximum strength.

Our FRP Process

At PROTECTOR, our fibre reinforced polymer systems are made using a chop hoop filament winding process. Our systems and manufacturing processes ensure that every system has the highest strength and exemplified benefits so that our systems are quality assured and of maximum strength. Protector products are constructed using the advanced chop hoop filament winding process which ensures circumferential as well as longitudinal strength. Every Protector product has a smooth moulded resin rich corrosion barrier inner layer and an external resin rich water penetration barrier. Being manufactured in FRP (fibre reinforced plastics) Protector products are light, easy to handle and easy to install. The smooth internal moulded finish provides excellent protection against scum build up, exhibit excellent corrosion resistance and are not susceptible to rust.

With the high demand and the large amounts of FRP products going out the door at PROTECTOR, we need to ensure that our manufacturing processes are at the highest standard and that there is complete control over all stages of the product cycle. At PROTECTOR we have been investing heavily in our manufacturing systems to ensure only the best products are sent out. With our complete control over every stage of the manufacturing process we can ensure quality, consistency, accurate supply and assurance of on time delivery and having maximum customer satisfaction.

Our Manufacturing Spec’s

The specified ratio for chop-hoop winding process is 43% (0.432) Chop and 57% Hoop (0.568).

There are several key corrosion layers that are used in the construction of our systems that are vital for a chemical and pollutant resistance and to keep a watertight system to ensure no effluent leaks into the environment.

  • Internal

o   Internal Corrosion Barrier, moulded with a resin rich C’veil and CSM layers

o   Resin rich Corrosion barrier constructed from Hetron 922 Vinyl Ester Resin

o   C’veil will be Regina 80gsm Surface Tissue

  • External

o   External layer will a resin rich CSM layer and C-Glass veil finished with ISO/NPG Flocoat layer for external finish to required colour

  • Reinforcement

 

o   Structural layers are constructed from Polyplex Isophthalic Resin with CSM & Hoop in accordance with Ratio’s as specified by the design.

o   Fiberglass ‘E’ glass is used for both chopped and continuous strands.

We ensure our Manway systems maintain the structural integrity of the rest of our system, ensuring maximum strength evenly over the body of the system. There are several intensive loads that are increased at the manhole and the connection points, hence special steps need to be taken to ensure the system strength and life.

 

  • Internal Corrosion Barrier Contact moulded

o   0.5mm “C” Glass Veil Surface layer with Hetron 922 (or equivalent) Vinyl Ester Resin.

  • Internal Corrosion Barrier Backing Layers

o   2.5mm ‘E’ Glass Chop Strand tie layer with Hetron 922 (or equivalent) Vinyl Ester Resin.

  • Structural Laminate

o   ‘E’ Glass reinforcement in chopped and continuous strands.

o   Minimum glass content 50% (Thickness according to Design Drawings)

  • Structural Stiffeners

o   Polyurethane Foam rib former overlaid with ‘E’ Glass reinforcement in chopped and continuous strands. Minimum glass content 50%

  • External Surface – Final surface

o   0.5mm “C” Glass Veil Surface layer with Hetron 922 (or equivalent) Vinyl Ester Resin.

  • External Surface – Sealer

o   Pigmented ISO/NPG Flowcoat for external protection.

Advantages of FRP

Fibre reinforced polymers are such highly sought after materials, and a growing day by day. Their applications are endless due to their wide range of advantages and benefits. When we consider regular plastics or polymers, before the fibres have been added, they are weaker materials not suitable for high strength and high value applications. When fibres are added to plastic polymers, these systems become much more valuable and are able to be implemented in high strength applications and can be applied to industrial or infrastructure requirements.

FRP is such a great material due to a wide range of advantages and benefits

  • Lightweight – FRP is a very lightweight material, at a fraction of the weight of steel or aluminium. Even though it is so lightweight this material is strong enough to withstand the same applied forces and loads due to its amazing strength to weight ratio. As this means that the system will be just as strong and reliable, using a lightweight material will give a plethora of advantages. The system will be much easier to install, often in cases not requiring lifting apparatus. It is sager and simpler to deliver and move and hence will reduce the amount of time spent in installation phase, reducing overall costs dramatically.
  • Easy to manufacture – due to the manufacturing processes that are available for Fibre reinforced polymers, almost any shape or configuration is available and hence a wide variety of systems can be manufactured. This means that it has a large sharping versatility and altered with different resins or fibres for various applications. Hence unlike steal or other metal products, it is simple to make complex systems our of FRP and hence the simplicity of manufacturing process allows for a reduction in overall costs for FRP making them the more suitable option for almost all applications. Furthermore, as their compositions are easily changed additives are simply added to change properties like flame resistant resin additives or temperature additives. This makes these materials easier to design and create for any application, as almost all properties are possible and almost any complex shape is able to be made making it the smart material choice.
  • High strength – fibre reinforced polymers have greater flexural strength than timber and gram for gram is a stronger material than steel and aluminium when the fibres are aligned in the force load direction. The fibre additives are able to drastically improve the strength of the material both in tension and in compression making it very applicable to high load situations such as underground installations.
  • Corrosion resistance – FRP has a resistance to a wide range of chemical and effluent and is unaffected by moisture of immersion into water making it perfect for applications in marine or chemical circumstances. Unlike steel and aluminium, which are susceptible to oxidation and corrosion, FRP is able to withstand these chemicals and makes it the perfect applications in situations of water storage or treatment.
  • High stiffness – FRP is up to 3.3 times as rigid as timber and will not permanently deform under workling loads
  • Impact Resistance – Another advantage of Fibre reinforced polymers is that it has high impact resistance, which is that they will never permanently deform or break under impact like traditional building materials. The glass material in the FRP system distributes impact load to prevent surface damage, even in low temperatures.
  • Colour – Since fibre reinforced polymer components are moulded, colour can be moulded straight through the part.  For more traditional materials, a combination of paints, stains, and coatings must be used and will require periodic re-applications.  A wide range of colours are available.
  • Thermal properties – FRP is a great insulator and hence has a low thermal conductivity, unlike metals such as aluminium and steel. Hence this means that fibreglass products maintain a constant temperature and cool to the touch and hence make it a material that is applicable to almost all applications, continuing to operate efficiently at high heat or sub zero temperatures.
  • Non-conductive – FRP is a nonconductive material and has a high dielectric capability whilst metals like steel and aluminium conduct electricity readily and must be grounded. This has led to its use in nanotechnology
  • Durability and Long term performance – Fibre reinforced plastics are considered highly durable and long life products. These FRP products have a longer design life as they are no susceptible to corrosion, degradation, decay or permanent deformation. Hence these systems are often considered to be extremely long life products and hence can be a very reliable product in the long term.
  • It is considered an Sustainable Product – Sustainable products are products that, through every phase of its life be it construction, manufacture, installation and usage, its energy usage and environmental effect do not go on at a rate that would compromise the natural environment, or that it would not affect the environment negatively over its lifespan. Its manufacturing processes are effective and efficient, minimal wastage in construction, usually does not require more energy that would compromise the natural aspects of its existence and has no environmental harm through the lifespan of its use.
  • Cost and Pricing – One of the most important thing when we consider which material to choose is pricing. When we compare these two, steel has a lower initial material cost, this is true. But when we consider a wider range of expenses over the life of the system, FRP becomes much more affordable and economically efficient when compared to steel. It has lower installation costs due to its weight, much less maintenance require and a much longer life span all contributing to a cheaper overall cost over tim

PROPERTYFRP COMPOSITESSTEELALUMINIUMHDPECONCRETE
CORROSION RESISTANCE and WATER RESISTANCEResists a broad range of chemicals and unaffected by water
FRP systems are water tight and Protectors systems have an external resin rich water tight penetration barrier
Subject to oxidation and corrosion which otherwise requires galvanisation for many complications – a expensive and difficult process.Can cause galvanic corrosionTypically made from only a single or small range of polyethylene resins, HDPE lacks the ability to be optimized for severe chemical environments and efflucentConcrete is a porous material allowing water to penetrate the surface. Even with sealants concrete can leak
Concrete often uses steel rebar for reinforcement and the rebar is susceptible to rust from water permeating the surface.
STRENGTHGram for Gram stronger than Steel and aluminium
Compressive strength – 206.5MPa (LW)
Flexural Strength – 206.5MPa (LW)
Ultimate stress –
110MPa
Yield Strength – 248.22MPa
Higher tensile strength and higher tensile modulus
Yield Strength – 241.325MPa
Higher tensile strength and higher tensile modulus
Ultimate Stress = 23MPa
Degrades over time, although initial strength of system is greater
High compressive strength, but low tensile strength – reinforcement available. Ultimate strength dependant on water-cement ratio
Modulus of ElasticityHoop Modulus = 27.58GPa
Axial Modulus = 12.4GPa
200GPa69 GPaHDPE Modulus = 0.69GPa
HDPE has higher in ground deflection and pipe bending.
Requires piping supports in some installations
Dependant on modulus of elasticity of aggregate, matric and rebar (if any)
Usually between 30-50GPa
Pressure DesignDesigns at minimum a 6:1 safety factor ratio in pressure situationsLower safety factor in designs causing extreme occasions to be big issue for HDPEN/A
WEIGHTWeights 25% of steels and 70% of aluminiumDue to high weight often requires lifting apparatus where it would not be require for FRP, lowering costs33% of the weight of steelDensity = 970 kg/m3
Hence is a lighter weight per cubic metre than FRP
Density of 2400kg/m^3, roughly twice the weight per cubic metre than FRP, pound for pound stronger than Concrete
ELECTRICAL CONDUCTIVITYNon conductiveRequires grounding due to high conductivity Requires grounding due to high conductivity Non conductiveN/A
THERMAL CONDUCTIVITYGood insulator with low thermal conductivity
0.04W/mK
Thermal conductivity
50.2 W/m
thermal conductivity
25W/mK
Low thermal coefficient of expansion
23.4 m/m/C *10^-6 K
Generally considered to be ¬ 0.5 W/mK0.04W/mK – 0.07W/mK, usually N/A property
Thermal expansion and contractionLower thermal expansion, with 1/10th of the expansion and contraction of HDPE
Low thermal coefficient of expansion
12.6 – 14.4 m/m/C *10^-6
Low thermal coefficient of expansion
13.5 – 14.4 m/m/C *10^-6 K
Low thermal coefficient of expansion
23.4 m/m/C *10^-6 K
HDPE tends to lose its mechanical properties drastically at 22 degrees. Becomes not recommended when the temperature exceeds 80 degrees.
12 x 10-5 cm/(cm °C)
Concrete expands and contracts regularly with temperate cause cracks to appear and corrosion.
OPERATING AND DESIGN TEMPERATURESFRPs mechanical properties do not degrade until roughly 83-105 CELCIUSHDPE tends to lose its mechanical properties drastically at 22 degrees. Becomes not recommended when the temperature exceeds 80 degrees.
IMPACT RESISTANCEWill not permanently deform under impactCan permanently deformCan permanently DeformRequires a high force o cause impact damage, but once concrete is damaged due to brittle nature permanent deformation occurs
COSTLower installation costs, less maintenance, longer product life cause lower lifespan costLower initial material costs, ,high installation and maintenance costs. Part Price comparable to FRPCheaper than FRP, similar lifetime costs – lifespan usually just as long under low load conditionsLower initial material costs, ,high installation and maintenance costs.
LifespanGuaranteed to last 75years, lifespan can be up to 150 yearsIn the case of underground steel installations, steel tanks usually last roughly 10-15 years before replacement – dependant on many factorsRoughly similar to FRP, due to low strength cannot be used in high load situations15-50 year expected lifespan, depending on environment.
MANUFACTURE AND FABRICATIONCan be easily manufactured, easy of complex shapes, can be fabricated with simple carpenters tools. No torches or torches requiredOften requires welding and cutting tools, with heavy equipment requiring special processes. Good machinabilityCan be manufactured to smaller diameters with HDPE being quicker to produce – uses more complex processes to create such as rotatory mouldingConcrete must be built as separate sections for ease of delivery and installation, hence joints provides weaknesses even with additional sealants. More complex systems are required in manufacture of concrete assemblies.
INSTALLATION FRP is simple to install, requiring minimal machinery operation and usually light crane systems. Due to the lightweight nature of FRP installation, transportation and the preassembled nature of the systems installation is usually quick and simpleDue to the weight of steel, systems are usually requiring heavy machinery, the likes which would not be necessary for FRP Comparable weight and usual thin sheet nature of Aluminium has comparable installation ease to FRP, with reductions in strengthComparable to FRPRequires step by step installation on site as concrete systems have to be poured and set. Requires more transportation increasing time and expenses.
MAINTENANCEMaintenance is simple with the interior coating and smooth layer make removal of sludge simple and easy and maintenance requires minimal effort. Comparable to FRP
Much more difficult in all stages of maintenance to deal with, more difficult to clean and maintain requiring higher frequency and increased cost over the life of the system.

FRP vs Concrete

For many years, Concrete has remained the favourite choice in civil systems due to a wide range of characteristics. But through recent years, Fibre reinforced Polymers have becomes a material being more and more preferred due to several characteristics.

The lightweight property of FRP gives it several beneficial aspects when considered against concrete. The first benefit of lightweight materials is the reduced installation and transport costs. With rising transportation costs and construction costs, a quick and simple installation can save a drastic amount of money. FRP materials are also much easier for installation as the processes are simple and this ease of manufacture on site allows for simple tooling to create and adjust parts on site. When considering bridge constructions, specifically bridge deck panels, FRP are easier in transport, and faster to install. Furthermore concrete requires 28 days to cure and precast concrete panels require heavy duty equipment, again providing further savings. FRP also require much less substructure (ground connections) and much less superstructure requiring a lower overall cost than concrete.

Colouring is another great example of changes. Concrete cannot be changes in colour without much difficulty and specialty products. FRP on the other hand can be easily pigmented and colour at any stage of manufacture. This allows FRP systems to blend into any environment and can provide more aesthetic options.

A major point of the differences between the two systems is variation in corrosion and decay of both systems. Concrete has a lot of weaknesses which in certain applications can become dangers to concrete structures. When concrete is exposed to a range of chemicals or water, issues may arise. Concrete is more susceptible to corrosion and decay, and is not recommended in systems that are exposed to salt water such as coastal areas. FRP is highly chemical resistant. It is highly resistant to water, salt and chemicals, hot and cold temperature extremes ad variables found in coastal environments. It is this that has led FRP to become favourable in construction and civil exercises, with the outer layers being and FRP material to be resistance to weathering and corrosion. Furthermore FRP is considered an extremely water tight system, with it concrete being porous and can form leaks. Hence in water effluent systems, FRP is a much more preferred materials

As a further point, concrete has a lifespan on anywhere between 15 to 50 years, depending on the environment – in environments with salt and coastal weather patterns even less! FRP however has an expected lifespan of over 75 years, range to up to 150 years. The lifespan alone will dramatically reduce lifetime costs, with less replacement of systems and maintenance than for FRP systems. FRP systems also have the advantage of having no degradation over time, with concrete having decay and damage over time causing sooner replacement when considered against FRP.

In fabrication concrete tanks are built in sections requiring field assembly. Each joint is a potential leak even with additional sealants. Fiberglass tanks are monolithic. FRP is easier to assemble, with even the possibility of fabrication and manufacture on site with simple tools, or more commonly having a preassembled system if possible. Furthermore in terms of maintenance fibreglass is much easier to clean and keep clean, extending the life of the interior parts such as pumping systems and valves.

PROPERTYFRPCONCRETE

Water Resistance and Leakages
FRP systems are water tight and Protectors systems have an external resin rich water tight penetration barrier.Concrete is a porous material allowing water to penetrate the surface. Even with sealants concrete can leak
Structural strengthStrong material in terms of strength, will not degrade over timeDegrades over time, although initial strength of system is greater
Lifespan75 year guaranteed lifetime, up to 150 years maxBetween 15-50 year expected lifespan
FabricationFRP systems can be made as a whole, monolithic system with no leaks usually coming pre-assembled.Concrete must be built as separate sections for ease of delivery and installation, hence joints provides weaknesses even with additional sealants. More complex systems are required in manufacture of concrete assemblies.
Expansion and contractionFibre glass has a low coefficient of expansion under heat and weather conditions.Concrete expands and contracts regularly with temperate cause cracks to appear and corrosion.
Corrosion due to Microbial Induced CorrosionResistance to all chemical corrosion typesHydrogen sulphide creates sulphuric acid when in underground water systems, a common cause of deterioration of concrete.
Bacteria resistanceFRP products are Protector are manufactured with smooth interior resistant layers and exterior waterproof layers making it perfect environment to combat bacteria and algae accumulation. Not suitable
Oxidation resistanceIs not effected by OxidationConcrete often uses steel rebar for reinforcement and the rebar is susceptible to rust from water permeating the surface.
WeightLightweight requiring smaller crane systems for loading and offloading.
Weighs approx. 1400kg per cubic m
Concrete is a heavier system. Weights approx 2400kg per cub metre.
InstallationFiberglass tanks can be transported on a single truck and are delivered to the site as a finished product making installation easier and fasterRequires step by step installation on site as concrete systems have to be poured and set. Requires more transportation increasing time and expenses.
Maintenance and RepairsAdditional appurtenances can be installed directly to the FRP tank at the job site and even after burial. Fiberglass does not require resurfacing for the life of the product. Fiberglass is easier to clean and keep clean which extends the life of pumps and filtering equipment.Much more difficult in all stages of maintenance to deal with, more difficult to clean and maintain requiring higher frequency and increased cost over the life of the system.

FRP vs Steel

Steel is a material that is widely used in almost all areas of engineering – in infrastructure, industrial, mechanical, civil applications. It has high strength and is a very reliable material, so why would we replace the modern applications of steel with the Fibre reinforced polymer materials we have available to us to day. Whilst there are many areas in which steel excels as a material, it also has a variety of drawbacks that make in not suitable to some systems, and due to FRPs ability to work with a wide range of additives to change properties.

Steel is very susceptible to corrosion and hence to failure. Oxidation and chemical corrosion are big issues for steel, and hence reduce the amount of applications that steel can be used in, especially in systems with even small risk of exposure. FRP has a resistance to a wide range of chemical and effluent and is unaffected by moisture of immersion into water making it perfect for applications in marine or chemical circumstances. Unlike steel and aluminium, which are susceptible to oxidation and corrosion, FRP is able to withstand these chemicals and makes it the perfect applications in situations of water storage or treatment. Whilst treatment is available to strengthen steel, these treatment processes can sometimes be expensive and reduce the sustainability of steel. The additives to FRP are much simpler and easier to add making it a more cost effective material for applications with corrosion and oxidation risk. Additives to FRP are also able to make its properties alter, adding stronger corrosion resistance, flame retardants and temperature resistance.

Pound to pound, FRP is actually a stronger material than steel, making it a much stronger system whilst maintaining being a very lightweight material. Hence FRP is able to maintain its high strength whilst being a very lightweight material. This means two further advantages of FRP over steel appear. Firstly FRP systems are much more lightweight than steel making it much easier to install, which has a large amount of time savings and hence cost reduction. The second point is that pound for pound, FRP is actually stronger than steel. This can mean a wide range of advantages in the construction industry, allowing for frp to be used instead of steel and being able to maintain strength whilst able to reduce weight and also cost. It also hence has a greater strength in tensile and compression as well as in shear due to the addition of fibres for added strength.

Price is probably one of the most important considerations when comparing materials for projects. When we compare these two, steel has a lower initial material cost, this is true. But when we consider a wider range of expenses over the life of the system, FRP becomes much more affordable and economically efficient when compared to steel. It has lower installation costs due to its weight, much less maintenance require and a much longer life span all contributing to a cheaper overall cost over time.

Impact resistance is another property that varies when steel is compared to FRP. FRP as a whole will not permanently deform under a working load. The matrix material distributes impact load to prevent surface damage even in low temperatures whereas steel and other metals such as aluminium deform much easily under working load creating failure where FRP would not.

The other difference between the two is their thermal and electrical conductivity. Steel has high conductivity of both heat and electricity, providing good and bad advantages. FRP however have low thermal conductivity and zero electrical conduction making them perfect for applications where this property is desired. Hence FRP becomes more suitable to more applications in manufacture and construction having the ability to function normally at high temperatures and at sub zero temperatures. With varying thermal energy steel has  a much greater fluctuation of its properties, causing it to become more unreliable in varying temperatures, whereas FRP retains its reliability and properties in varying temperature conditions.

Finally when we compare its ease of fabrication and manufacture, a large disparity appears. FRP composites can be field fabricated using a simple carpenters tooling with no welding or torches required. It is also much easier to fabricate into intricate and complex shapes with much greater ease when compared to steel. Steel often requires welding and cutting torches, with the material requiring special equipment to erect and install.

PROPERTYFRP COMPOSITESSTEELALUMINIUM
CORROSION RESISTANCEResists a broad range of chemicals and unaffected by waterSubject to oxidation and corrosion which otherwise requires galvanisation for many complications – a expensive and difficult process. Can cause galvanic corrosion
STRENGTHGram for Gram stronger than Steel and aluminium
Compressive strength – 206.5MPa (LW)
Flexural Strength – 206.5MPa (LW)
Yield Strength – 248.22MPa
Higher tensile strength and higher tensile modulus
Yield Strength – 241.325MPa
Higher tensile strength and higher tensile modulus
WEIGHTWeights 25% of steels and 70% of aluminiumDue to high weight often requires lifting apparatus where it would not be require for FRP, lowering costs33% of the weight of steel
ELECTRICAL CONDUCTIVITYNon conductiveRequires grounding due to high conductivity Requires grounding due to high conductivity
THERMAL CONDUCTIVITYGood insulator with low thermal conductivity
0.04W/mK
Low thermal coefficient of expansion
12.6 – 14.4 m/m/C *10^-6
Thermal conductivity
50.2 W/m
Low thermal coefficient of expansion
13.5 – 14.4 m/m/C *10^-6 K
thermal conductivity
25W/mK
Low thermal coefficient of expansion
23.4 m/m/C *10^-6 K
IMPACT RESISTANCEWill not permanently deform under impactCan permanently deformCan permanently Deform
COSTLower installation costs, less maintenance, longer product life cause lower lifespan costLower initial material costsPart Price comparable to FRP
MANUFACTURE AND FABRICATIONCan be easily manufactured, easy of complex shapes, can be fabricated with simple carpenters tools. No torches or torches required
Often requires welding and cutting tools, with heavy equipment requiring special processes.
Good machinability