Name: China Customized Fiberglass Square Tube Manufacturers Suppliers - Factory Direct Wholesale - Enbuess
Brand: Enbuess
SKU: 316869776

Henan Enbuess Composite Materials Co., Ltd. is one of the leading manufacturers and suppliers of fiberglass square tube in China. We are committed to providing high quality customized service for global clients. If you're going to buy high strength fiberglass square tube made in China, welcome to get free sample from our factory.

01 Standard sizes

Every row below runs on tooling we already hold - no die charge, no tooling lead time. Sizes outside this table need a new die.

Nominal (mm)	Wall (mm)	Weight (kg/m)	Resin	Tooling
16 × 16	2	0.22	Polyester	Existing
19 × 19	2	0.27	Polyester	Existing
25 × 25	2	0.35	Polyester	Existing
25.4 × 25.4	1.8	0.37	Polyurethane	Existing
28 × 28	2	0.33	Polyester	Existing
30 × 30	3	0.64	Polyester	Existing
30 × 30	3.1	0.71	Polyurethane	Existing
32 × 32	2	0.45	Polyester	Existing
34 × 34	2	-	Polyester	Existing
38 × 38	3.5	1.02	Polyester	Existing+ walls
40 × 40	3	0.9	Polyester	Existing+ walls
40 × 40	4	1.14	Polyester	Existing
45 × 45	4	-	Polyester	Existing
50 × 50	3	1.17	Polyester	Existing+ walls
50 × 50	4	1.52	Polyester	Existing
50 × 50	8	2.83	Polyester	Existing
58 × 58	4	1.75	Polyester	Existing
60 × 60	4	1.75	Polyester	Existing+ walls
63 × 63	5	2.39	Polyester	Existing+ walls
70 × 70	4	2.2	Polyester	Existing
75 × 75	6	3.4	Polyester	Existing
75 × 75	6	3.66	Polyurethane	Existing
80 × 80	3	1.79	Polyester	Existing+ walls
90 × 90	6.35	4.44	Polyester	Existing
100 × 100	3	2.13	Polyester	Existing
100 × 100	5	3.83	Polyester	Existing
102 × 102	4	3.19	Polyester	Existing
115 × 115	5	4.6	Polyester	Existing
120 × 120	4	3.8	Polyester	Existing+ walls
150 × 150	3.5	4.2	Polyester	Existing
200 × 200	4	6.37	Polyester	Existing
260 × 260	2.5	-	Polyester	Existing

01-standard-sizes

+ walls means we hold further tooling at that outside dimension in a wall thickness not listed. Tell us the wall you need and we will confirm it.

Section properties - second moment of area and section modulus - are calculated for the specific size and wall you order and supplied with the quotation. We do not publish a generic table, because the figure changes with the wall you actually buy.

02 The questions buyers actually ask

Four groups. Everything here is answered on this page - jump to the section you came for.

Sizing

What size do I need for a given span?
Is this size in stock or made to order?
What is the tolerance on straightness?
How much does it weigh per metre?

Machining

What blade should I use?
Will it split when I drill it?
Can I tap a thread into it?
How do I join two lengths?

Performance

What about load across the tube, not along it?
Will it sag under a constant load?
Does it go brittle in the cold?
Does the surface fray after a few summers?
How does it beat steel, stainless and aluminium?

Ordering

How does the price compare with aluminium?
Can I get a sample length?
Do you supply test certificates?
What is the MOQ on a custom die?

02-buyer-questions

03 Along the tube vs across it

The part most suppliers skip, and the part that decides whether the profile works in your application.

Pultrusion pulls continuous glass roving lengthwise through the die. Strength follows the fibre direction. On a high-specification section - multilayer roving with continuous filament mat and multi-axial reinforcement across the wall:

Longitudinal tensile strength

≥ 800 MPa
Along the pultrusion direction. Compression ≥ 600 MPa.

Transverse tensile strength

≥ 50 MPa
Across the direction of pull. Compression ≥ 100 MPa.
≈ 6% OF LONGITUDINAL

That gap is not a defect - it is how the process works, and it is true of every pultruded profile on the market. On a standard section without multi-axial reinforcement the transverse figure can fall to around 3% of the longitudinal one, so the layup matters as much as the outside dimension. What the gap means for your design:

Load along the tube: excellent. Posts, columns, chord members, long spans.
Load across the tube: weak. Anything bearing on the wall - a bolt, a clamp, a point load - works against the weak direction.
Concentrated loads crush the wall locally before the section reaches its bending capacity. In three-point bending tests on pultruded square sections, ultimate capacity was governed by local crushing of the web under the load point, not by the section's bending strength.

03-along-vs-across-tube

The fix is simple and cheap: spread point loads with a backing plate or saddle, and size bolted joints for bearing rather than for the bolt's shear capacity. Bearing values for each wall thickness are available on request.

04 Cutting, drilling and joining

Cutting

Use a carbide-tipped or diamond blade. A standard wood blade tears the fibres and leaves a ragged edge; an abrasive disc overheats the resin and glazes the cut face. Support the profile on both sides of the kerf so the offcut does not break away and split back along the tube.

Extract the dust and wear a rated mask. Glass dust is not something you want in your lungs, and that applies to every supplier's product, not just ours.

Drilling

Drill with a sharp HSS bit at moderate speed and light feed. Heavy feed is what breaks out the far wall and causes the splitting people complain about. Back the exit face with a scrap block and the problem largely disappears.

Hole diameter should run 1–2 mm over the fastener, and holes should sit at least two diameters from the edge. Do not tap threads directly into the wall - the transverse strength is not there to hold a thread. Use a threaded insert, a through-bolt, or a rivet nut.

Joining - it cannot be welded

Mechanical. 316 stainless or hot-dip galvanised bolts, with a backing plate or large-diameter washer to spread the bearing load. Preload drops over time because the material relaxes under a clamped joint, so serrated flange nuts or wedge-lock washers hold better on anything subject to vibration.

Adhesive. Two-part epoxy or MMA. The strongest route for permanent joints, and the one used for bonded multi-tube assemblies. Surface preparation matters more than adhesive choice: abrade, degrease, then bond.

Moulded connectors. FRP gussets, corner plates and internal splices keep the whole assembly non-conductive and corrosion-free. This is what we recommend for handrail and platform work.

Sealing cut ends

Cut ends expose the fibre architecture to moisture. For outdoor or wet installations, seal the cut face with the same resin system or a compatible paint. End caps are available for exposed terminations.

04-cutting-drilling-joining

05 Against the metals you are replacing

You are probably holding a steel or aluminium specification and wondering whether to switch. This section goes through each metal, what you gain, and where you give something up.

The full comparison

Property	Pultruded composite	Carbon steel Q235	Galvanised steel	Stainless 304	Stainless 316	Aluminium 6061-T6
Density (g/cm³)	1.8–2.2	7.85	7.85	8	8	2.7
Weight, same section	~25% of steel	Baseline	Baseline	~102%	~102%	~34%
Tensile strength (MPa)	≥ 800	370–500	370–500	515	515	310
Specific strength	≈ 400	≈ 51	≈ 51	≈ 64	≈ 64	≈ 115
Modulus (GPa)	≥ 40	~200	~200	~193	~193	~69
Salt / chloride	No mechanism	Rusts through	Zinc gone in 2–3 yrs	Pitting, SCC	Good	Pitting
Acid and alkali	Resin-dependent, excellent	Poor	Poor	Fair	Good	Poor in alkali
Galvanic corrosion	Not a failure mode	Yes	Yes	Yes	Yes	Yes
Electrical	Insulating	Conductive	Conductive	Conductive	Conductive	Conductive
Thermal conductivity (W/m·K)	0.3–0.5	~50	~50	~16	~16	~167
Expansion, longitudinal (10⁻⁶/°C)	6–10	~12	~12	~17	~16	~23.6
Magnetic / RF	Non-magnetic, RF transparent	Magnetic	Magnetic	Near non-magnetic	Near non-magnetic	Non-magnetic
Site work	Cut, drill, no hot work	Weld, hot work	Weld, then re-protect	Weld	Weld	Weld or bolt
Maintenance, 25 yrs	None	Paint 3–4 times	1–2 times	Inspect in chloride	Low	Oxidation control
Scrap value at end	Low	High	High	Very high	Very high	High

Where it wins by the widest margin: strength per kilogram

Strength on its own does not mean much - a steel beam is strong because it is heavy. Divide tensile strength by density and the picture changes. This is the number that matters wherever weight is a cost: transport, lifting, foundations, rooftops, anything a person has to carry.

05-strength-per-kilogram

Pultruded composite

≈ 400
MPa per g/cm³

Aluminium 6061-T6

≈ 115
MPa per g/cm³
3.5× lower

Stainless 304 / 316

≈ 64
MPa per g/cm³
6× lower

Carbon steel Q235

≈ 51
MPa per g/cm³
8× lower

Kilogram for kilogram, the profile carries roughly eight times what mild steel carries and three and a half times what aluminium carries. Steel still wins on stiffness and on price per metre, which is why the section below matters more than this table.

One metal at a time

vs carbon steel Q235 Clear win in corrosive service

What you gain
A quarter of the weight at the same section, so foundations, lifting plant and crew size all come down. No rust, so no blast-and-paint cycle every few years. Electrically insulating, so no bonding or earthing near DC runs and near live equipment. And it cuts and drills with hand tools - no hot-work permit, which on a chemical site or a shutdown window is often the deciding factor rather than the material price.

What you give up
Stiffness, and the lowest purchase price on the market. Mild steel is the cheapest structural material there is.

When not to switch
Dry inland sites, indoor framing, or anything where the structure is heavily loaded in bending and the span is short enough that weight is not a cost. In those cases steel is genuinely the right answer.

vs galvanised steel Clear win in coastal and industrial air

What you gain
Galvanising protects steel until it is cut, drilled or welded - and every one of those happens on site. The zinc layer is consumed around the cut edge, and the usual fix is cold-galvanising spray applied by whoever is on the ladder that day. It is the most commonly skipped step in a metal installation and the reason galvanised structures start rusting at the joints rather than in the middle of a member. In coastal or industrial air the coating itself is typically gone in two to three years.

Composite has no coating to damage. Cut it and the remaining length performs exactly as it did before - the only recommendation is sealing the cut face against moisture on outdoor work.

What you give up
Stiffness. Nothing else - galvanised steel offers no advantage over carbon steel except the coating, and the coating is what fails.

vs stainless 304 and 316 Depends entirely on chloride

Where the assumption breaks
Stainless is widely specified for coastal work on the assumption that it does not corrode. Grade 304 does corrode in chloride - pitting and stress corrosion cracking near the sea, on roads treated with de-icing salt, around swimming pools and in much chemical plant. It is the right grade indoors and the wrong grade within a few kilometres of the coast.

Grade 316 adds molybdenum and handles chloride properly. It also costs roughly five to eight times what carbon steel costs per kilogram.

What you gain
Composite has no chloride pitting mechanism and no stress corrosion cracking, at a material cost closer to 304 than to 316. In a coastal or de-icing-salt environment, that is usually the whole argument.

What you give up
Temperature capability, surface hardness, and scrap value - stainless has the highest recovery value of any common structural material. If the project accounts for end-of-life recycling revenue, stainless gives some of it back.

When not to switch
Service above about 120 °C, food-contact or hygienic finishes, or where the client wants the appearance of metal.

vs aluminium 6061 and 6063 Clear win, with one real exception

What you gain
Aluminium corrodes in alkali - concrete, alkaline soil, some industrial cleaning agents - and it forms a galvanic couple with any dissimilar metal it touches, so a steel bolt through an aluminium member needs isolation. It conducts both electricity and heat, at roughly 167 W/m·K, which makes it a thermal bridge and a condensation site on cold-side framing, and it means the structure has to be earthed. It also expands at about 23.6 × 10⁻⁶/°C, nearly three times the longitudinal figure for composite, so long runs need more generous expansion detailing.

Composite removes all four: no alkali attack, no galvanic couple, no earthing, no thermal bridge, and roughly a third less thermal movement to design for.

What you give up - this is the real one
Aluminium's modulus is about 69 GPa against composite's 40. If your design is stiffness-governed - long span, tight deflection limit, small section - aluminium will reach the same deflection with a shallower member. Aluminium also carries meaningful scrap value and a mature recycling market.

When not to switch
Stiffness-governed designs where section depth is constrained, or where the client has a metallic appearance requirement.

What it costs over 25 years
Purchase price is one line in a 25-year budget. This is where the comparison usually turns:

Cost line	Composite	Carbon steel	Galvanised	304	316	Aluminium
Initial material	Medium	Lowest	Low	High	Very high	Medium-high
Transport and lifting	Low	High	High	High	High	Medium
Installation labour	Low	High	High	High	High	Medium
Repainting cycles	None	3–4 times	1–2 times	None	None	None
Inspection and repair	None	Periodic	Periodic	Needed in chloride	Low	Oxidation control
Replacement within 25 yrs	No	Likely	Likely	Possible in chloride	Unlikely	Unlikely
Production downtime	None	Painting needs shutdown	Painting needs shutdown	-	-	-

On a plant where repainting means a shutdown, or on a structure where access requires scaffolding or a boat, the maintenance line usually outweighs the purchase price difference within the first two cycles. On an indoor frame in a dry building with easy access, it never does. That distinction, not the datasheet, is what decides it.

A correction on thermal expansion
You will see figures around 25×10⁻⁶/°C quoted for this material. That is the transverse value, or a blend of the two. Along the pultrusion direction the coefficient is typically 6–10×10⁻⁶/°C - closer to steel than to aluminium. The distinction matters in practice: a long run of tube expands along its length, so use the longitudinal figure for expansion joints and the transverse figure only for across-width clearance.

What the metals do better, stated plainly. Three things. Steel and stainless are far stiffer, so a stiffness-governed design needs a deeper composite section. Steel yields visibly before it fails - it sags and buckles and gives you warning - whereas composite fails in a more brittle mode with less visible warning, which is why we insist on the safety factors in section 07. And every metal on this table has a scrap value at end of life while composite does not. If your project books recycling revenue, that is real money we cannot match.

06 Which resin

Resin	Chemical resistance	Service temp	UV	Cost	Specify for
Isophthalic polyester	Good	−20 to +65 °C	Moderate	Lowest	General framing, indoor, dry
Polyurethane	Good	−30 to +80 °C	Good	Medium	Higher stiffness and toughness
Vinyl ester	Excellent	−20 to +80 °C	Good	Medium	Chemical plants, marine splash zone
Epoxy	Excellent	−30 to +100 °C	Good	Highest	High stiffness, higher temperature

What is actually on the tooling. Our existing square-tube tooling runs isophthalic polyester as standard, with polyurethane held on selected sizes - 25.4 mm, 30 mm and 75 mm. Vinyl ester and epoxy are produced to order on the same profiles. If your specification calls for vinyl ester or epoxy, tell us at enquiry stage and we will confirm the size and the run length.

06-which-resin

On UV and cheap quotes

UV protection comes from a surface veil and resin-integrated stabiliser, not a paint layer. It is what prevents fibre bloom - the whitening and surface fraying you see on cheap pultrusions after a couple of summers. If one quote comes in noticeably below the others, ask whether a surface veil is included. It usually is not.

07 Load data and how to use it

Tensile strength, longitudinal	≥ 800 MPa · ASTM D638	Compressive strength, longitudinal	≥ 600 MPa · ASTM D695
Tensile modulus, longitudinal	≥ 40 GPa · ASTM D638	Interlaminar shear	≥ 40 MPa · ASTM D2344
Tensile strength, transverse	≥ 50 MPa · ASTM D638	Density	1.8–2.2 g/cm³ · ASTM D792
Flexural strength, longitudinal	≥ 800 MPa · ASTM D790	Water absorption	< 0.5% · ASTM D570
Flexural modulus, longitudinal	≥ 35 GPa · ASTM D790	Barcol hardness	≥ 55 HBa · ASTM D2583

Do not design against the table above

Those are short-term coupon values measured in a test machine. A structure carrying load for 25 years behaves differently, so design against these instead:

Bending stress σ = M / S ≤ F_allowable ≈ 100–150 MPa continuous
Deflection δmax ≤ L / 200
Column buckling Pcr = π² E I / L² (pinned-pinned)
Safety factors 3.0 permanent · 2.5 temporary

The allowable figure sits well below the 800 MPa coupon value because it already carries the creep allowance, the fatigue allowance and the factor of safety. That gap is intentional - a supplier quoting allowable stress close to their coupon strength is not leaving room for 25 years of sustained load.

07-load-data-and-creep

Creep, or the sag nobody budgets for

Under a sustained load, composite keeps deforming slowly - more than steel does. Over a long span carrying constant weight, that shows up as gradual sag. We recommend using a creep-modified modulus for anything under permanent load, which means designing to a lower effective E than the datasheet figure.

Tell us the load and the span, and we will size it with the creep allowance included and show you predicted deflection at 1 year and at 25 years.

08 Where it gets specified

●

Industrial platforms, walkways, handrails
Maintenance-free in chemical and coastal air; insulating; cut on site without hot work.

●

Agricultural greenhouses
Resists ammonia and moisture without corroding.

●

Marine and docks
Salt spray tolerance, no rot, no water absorption.

●

Solar mounting and tracker frames
Weight reduction lowers tracker torque requirements.

●

Electrical and telecom
Non-conductive and signal-transparent - antenna shrouds, substation structures, 5G frames.

●

Transport and municipal
Noise barrier posts, signage supports, de-icing salt exposure.

●

Cooling towers and wastewater
Structural members in permanent heat and humidity.

●

Architectural and canopies
Colourable, stable appearance, no repainting.

●

Warehouse racking and machine frames
Light, rust-free, dimensionally stable.

●

Modular and temporary structures
Bonded multi-tube decks, fast assembly, reusable.

08-where-it-gets-specified

09 Custom, cut to length, ordering

Existing tooling	Sizes in table 01, no die charge	Colour	Integral pigment, RAL matched
New die	4–6 weeks, MOQ 1,000 m	Standard colours	Safety yellow · grey · green
Cut to length	±1 mm, both ends square	Lengths	3 m / 6 m, up to 12 m
Fabrication	Drilling, slotting, notching, mitring	Samples	Free samples
Surface	Smooth · gritted anti-slip · concave	Certificates	ISO 9001; test reports available on request

09-custom-cut-to-length

10 Production Process

Organize the Yarn

Threading Yarn

Heat Curing

Traction Pultrusion

Cut

Quality Inspection

11 FAQ

What size do I need for a given span?

Send the span, the load and how it is supported, and we will size it. Working it backwards from the tables above: check deflection at L/200 first. With a modulus around a fifth of steel's, deflection governs before strength does in most composite beam cases.

Is this size in stock or made to order?

Table 01 marks it. Stock sizes ship in 7–10 days. Made-to-order sizes need a die, 4–6 weeks.

What blade should I use, and will it split when drilled?

Carbide-tipped or diamond, with the profile supported on both sides of the kerf. For drilling, a sharp HSS bit at moderate speed and light feed, with the exit face backed by a scrap block - heavy feed is what splits the far wall.

Can I tap a thread into it?

No. Transverse strength is roughly 3% of longitudinal, so a cut thread will not hold. Use a threaded insert, a through-bolt, or a rivet nut.

How much load does it take across the tube?

Far less than along it - see section 03 for the measured numbers. If your load bears on the wall rather than along the length, spread it with a backing plate and size the joint for bearing.

Will it sag over time?

Under sustained load, yes, more than steel. We size with a creep-modified modulus and can give predicted deflection at 1 and 25 years for your load case.

Does it go brittle in the cold?

The resin governs low-temperature behaviour. Standard grades are specified to about −20 °C to −30 °C; below that we would look at epoxy. Tell us the minimum service temperature if it is below −20 °C.

Does the colour fade or the surface fray?

A surface veil plus resin-integrated UV stabiliser prevents fibre bloom. Pigment runs through the section rather than sitting on it, so chips do not expose a different colour underneath. Cheap pultrusions without a veil whiten and fray after a few summers.

We currently use 304 stainless near the coast. Would this actually be better?

In chloride exposure, usually yes - and this is the most common specification mistake we see. Grade 304 pits and can suffer stress corrosion cracking near the sea, on de-icing-salt roads, around pools and in much chemical plant. It is an indoor grade. The grade that handles chloride is 316, which typically costs five to eight times carbon steel per kilogram. Composite has no chloride pitting mechanism and lands closer to 304 on material cost. Sections 05 covers the full comparison, including where stainless still wins - temperature, surface hardness and end-of-life scrap value.

Can it replace aluminium in a design I already have?

Only if you re-check deflection first. Aluminium's modulus is around 69 GPa against composite's 40, so a straight size-for-size swap will deflect more. Strength is not the problem - composite is stronger on both absolute tensile and on strength per kilogram - stiffness is. Send us the span, the load and the section you are using now, and we will tell you what depth you need and whether it still fits the space you have.

How does the price compare with aluminium square tube?

Material cost is usually below aluminium and above carbon steel, but it moves with size, resin and volume. What tends to close the gap is the absence of maintenance and coating renewal in corrosive environments. Give us your size and quantity and we will quote against the specific aluminium section you are comparing to.

Do you supply test certificates?

ISO 9001; test reports available on request. We also supply lot traceability, and for structural orders we recommend requesting a sample coupon for independent testing.

10-faq-at-a-glance

Tell us the span and the load

Send the size you are currently using, or the span and load you need to cover. We will come back with a section recommendation, the deflection figures, and a price. If the answer is that aluminium or steel is the better call for this job, we will say that.

Request a quotation Back to size table

Hot Tags: fiberglass square tube, China fiberglass square tube manufacturers, suppliers, factory