Composite SMC Material data

May 13, 2021

All of our composite access covers, manhole covers in round, square and rectangular, gully gratings and frames, gully tops, rain gratings, inspection Chambers, recessed access covers, Bridge Drainage and Tank Sumps etc are made of composite SMC(sheet moulding compound), SMC is Unsaturated polyester resins reinforced with glass fibers.

What is the Sheet Molding Compounds (SMC)

SMC is an abbreviation for Sheet Molding Compound, which is a high strength glass fiber reinforced thermoset,moulding material which is normally compression moulded. It combines glass fiber and unsaturated polyester/ phenolic/ Vinyl and Acrylic modified resins, fillers(Calcium carbonate), catalysts, pigments and stabilizers, release agents to produce a high strength moulding compound.

Glass reinforcement is between 10% and 60%, and glass length is between 1/2-inch and 1-inch (25mm).

Manufacture of sheet molding compounds is a continuous in-line process. The material is sheathed both top and bottom with a polyethylene or nylon plastic film to prevent auto-adhesion. The paste is spread uniformly onto the bottom film. Chopped glass fibers are randomly deposited onto the paste. The top film is introduced and the sandwich is rolled into a pre-determined thickness. The sheet is allowed to mature for 48 hours. Delivered as sheet usually 2.5-6mm and 1000-1200mm wide.

SMC is ideal for large structural components due to its high strength-to-weight ratio. SMC offers additional benefits in part design allowing localised rib reinforcement and bosses for fastening attachments and sub assemblies. Significant tooling investment and overall component cost savings result from part consolidation. With the same coefficient of thermal expansion as Steel and excellent corrosion resistance, SMC is an ideal alternative to Steel and can be used in the same fluctuating temperature environments. The main benefit however is a typical 25% weight reduction achieved at similar strength to Steel.

The heat stability, mechanical and electrical properties of SMC are key attributes to its success in a number of industries including the automotive sector where it is commonly used in painted body panels, lightweight structural panels such as bumpers, valve covers, and engine shields. SMC is also extensively used in the production of electrical enclosures, lighting, solar, shower bases, walls, and sinks.

SMC Manufacturing Process

Manufacturing process including pulping, premix, placing glass fibers, steeping and rolling etc.

Why SMC material is superior ?

All parts of our covers are used high strength of thermoset SMC composites which made by our company.

SMC—Sheet Moulding Compounds, Refers to the reinforced unsaturated glass fiber resin sheet molding compound  which is mainly composed of unsaturated resin, glass fiber, filler and functional additives, is one kind of high performance composites used for compression molding.

The main components including glass fiber, unsaturated polyester resin, filler and related additives.

This material use glass fiber as reinforcing material .So the SMC material has good wear proof.

The material has good fatigue resistance and long service life.

Manufacturing process: Under the condition of high temperature and high pressure, with large hydraulic equipment one-time molding, without any steel reinforced material.

Meeting the standards of EN124:1994 and Australian Standard of AS3996-2006.

SMC Features:

Standard rules the resistance on the material surface is 106-8 Ω. We actually adopted SMC material which surface resistance is 104-6 Ω to make the product has better antistatic performance.

nullChemical Resistance

SMC material has good chemical resistance (acid, alkali, salt, organic solvent, etc.), Long-term use in the environment of underground or oil gas will not result in the change of material structure or performance.


SMC material has high density and low water absorption (0.15mg). It has excellent waterproof.

nullResistance to deformation capacity and bearing capacity

By improving the mechanical properties of materials and optimizing the structural design, make the product in the process of installation and use not cause deformation, displacement and cracking phenomenon.

nullHigh and low temperature resistance

Thermal deformation temperature of SMC materials is greater than 200 ℃. It can be in -55℃~+150℃ for long-term use and the environment temperature changes will not affect product performance.

nullLow thermal expansion coefficient
SMC Material has very low thermal expansion coefficient (12 × 10-6 / ℃), same as steel material, to ensure that products in the process of temperature changes will not cause the looseness of the filled soil around.

SMC Material Performance Test
1: Material Mechanics Properties
Test Project Name Required Value Test Result Standard
Flexural Strength(Mpa) ≧170 215 GB/T1449-2005
Flexural Modulus(Gpa) ≧10.0 12
Tensile Strength(Mpa) ≧100 138 GB/T1447-2005
Impact Toughness(kJ/m2) ≧90 762 GB/T1451-2005
Barcol Hardness ﹥60 70 GB/T3854-2005
Water Absorption <0.3% 0.09% GB/T1462-2005
The Average Thermal Expansion Coefficient  (/℃) 11.9×10-6(20~105℃) GB/T9979-2005

From above table, we can find that our SMC Properties are higher standards request on all aspects. So our SMC material used on manhole covers will have better loading capacity, fatigue resistance, impact resistance.

2: Chemical Resistance
Item Flex Strength MPa Flex Mod GPa
0h 48h Retention(%) 0h 48h Retention(%)
Xylene 215 205 95.3 12 12 100
Sulfuric Acid 40% 215 220 102.3 12 12.2 101.7
Hydroxide 10% 215 210 97.7 12 11.8 98.3
Gasoline 215 210 97.7 12 10.6 88.3

From the data , we can find that SMC material has the good acid , alkali, organic matter , oil and gas resistance .Covers made with this material can be widely used in the presence of chemicals,petroleum and petrochemical industries.

3:High and Low Temperature Resistance
Test Project Name Test Result Standards
Flexural Strength Flexural Modulus
(25℃) 215 12 GB/T1449-2005
Normal Temperature
(150℃) 152 7.52
High Temperature
(-50℃) 238 12.4
Low Temperature

Covers used SMC material has a long time use between  -50℃-150℃ because of its ‘good performance under the temperature more than 200℃ and low to -50℃.

4:Anti-Static Performance
Test Project Name Required Value Test Result Standards
Oh ﹤1.0×106 1.0×104 GB16413-2009
Surface Resistivity

According to the China standards, the surface resistance of SMC should be less than 106Ω, which can be defined as passing the Anti-electrostatic test. Our SMC material have better Anti-electrostatic properties because of the surface resistance is 104 Ω with our special formulation and manufacturing process.  This kind of covers applies in variety occasions of combustible gases. Effectively prevent the explosion caused by electrostatic.

5: Ageing-Resistant Performance
ITEM Test of Heat Aging Test of Artificial Xenon Resistance Test Standard
0h 500h 1000h 0h 500h 1000h EN513-1999
with the initializer .
Flex Strength Mpa 208 200 196 208 205 191 FlexStrength change :<40%
Flex Mod GPa 11.7 10.8 11.1 11.7 12.1 11.5 FlexMod change:<30%

Above sheet shows the material has excellent weather resistance, under the long time sun and rain, it still can use long time, and the covers lifespan is up to 20 years.

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