What is the difference between chopped strand mat and woven roving?

The key difference between chopped strand mat (CSM) and woven roving (WR) lies in their structure, strength, and applications in fiberglass-reinforced composites. Here’s a detailed comparison:

          

1. Structure & Manufacturing

Chopped Strand Mat (CSM)	Woven Roving (WR)
Made from randomly oriented short glass fibers (typically 1–3 inches long) bonded with a resin-soluble binder (powder or emulsion).	Made from continuous glass fibers woven into a heavy, coarse fabric (like a burlap sack).
Non-woven, isotropic (equal strength in all directions).	Woven, anisotropic (stronger in the direction of the fibers, usually 0° and 90°).
Lower fiber density, fluffy and easy to cut/shape.	Higher fiber density, stiff and harder to drape over complex shapes.

 

2. Mechanical Properties

CSM	WR
Lower strength but provides uniform reinforcement in all directions.	Higher tensile strength (especially along the weave direction) but weaker at angles.
Good for stiffness and impact resistance but not for high-load applications.	Used where high strength-to-weight ratio is needed (e.g., boat hulls, tanks).
Typically used in layers with resin for general-purpose laminates.	Often paired with CSM in hybrid laminates for better interlaminar bonding.

3. Resin Absorption & Layup

CSM	WR
Soaks up more resin (higher resin-to-fiber ratio, ~2:1 by weight).	Uses less resin (more fiber-dense, ~1:1 resin-to-fiber ratio).
Easier to wet out (good for hand layup).	Harder to wet out (may require rollers/brushes to remove air pockets).
Often used as a first layer for better adhesion to molds.	Used in structural layers for added strength.

 

4. Common Applications

Chopped Strand Mat (CSM)	Woven Roving (WR)
✔ General-purpose fiberglass parts (e.g., shower stalls, panels). ✔ Repair work (easy to conform to curves). ✔ Used with polyester resin (binder dissolves).	✔ High-strength structures (boat hulls, wind turbine blades). ✔ Automotive parts (truck bodies, trailers). ✔ Tanks and pipes requiring directional strength.

5. Global Suppliers

Owens Corning (USA)

One of the largest manufacturers of fiberglass and composite materials, supplying high-performance CSM for marine, automotive, and construction industries.

Jushi Group (China)

One of the world’s largest fiberglass producers, supplying cost-effective CSM and WR for global markets.

Saint-Gobain Vetrotex (France)

A global leader in glass fiber reinforcements, offering premium chopped strand mats and woven roving.

Ruifiber (China)

Known for high-quality fiberglass products, including CSM and WR for construction and industrial application.

 

6. Cost & Handling

CSM is cheaper and easier to handle but requires more resin.

WR is stronger and lighter but harder to work with on complex shapes.

Hybrid Use Case (CSM + WR)

Many composites combine both:

First layer: CSM for mold adhesion and smooth finish.

Middle layers: WR for strength.

Final layer: CSM for a clean surface.

Which One to Choose?

Use CSM for low-cost, isotropic, easy-to-shape parts.

Use WR for high-strength, directional reinforcement.

Combine both for optimized cost, strength, and workability.