What Is Continuous Filament Mat? CFM vs CSM Explained
What is continuous filament mat (CFM/continuous strand mat)? How swirl-laid continuous fibers differ from CSM, where CFM wins in RTM and pultrusion, and typical specs.
CFM Knowledge Hub
Continuous filament mat (CFM) — also sold and specified as continuous strand mat — is a non-woven fiberglass reinforcement in which the filaments are never chopped: continuous glass strands are laid down in a swirl pattern and bonded into a mat. This page explains what CFM is, how it differs from chopped strand mat, and where its continuous-fiber architecture wins.
Definition
Continuous filament mat is produced by depositing continuous glass filaments in a swirling, interlocking pattern onto a moving belt, then binding them with powder or emulsion binder. Because every filament runs unbroken for meters across the mat, load paths stay continuous through the reinforcement — unlike chopped strand mat (CSM), where fibers are cut to 25–50 mm and strength relies on the resin transferring stress between short random strands.
The swirl layup keeps the mat quasi-isotropic in-plane (useful strength in all directions, like CSM) while adding the tensile strength, stiffness, and fatigue resistance of continuous fiber. The trade-off: CFM drapes less readily around tight compound curves than chopped mat, and it typically carries a higher price per kilogram.
How Continuous Filament Mat Is Made
- Glass is melted and drawn into continuous filaments (typically E-glass or ECR-glass).
- Filaments are laid onto a belt in a swirl pattern through oscillating nozzles — no chopping step.
- Powder or emulsion binder is applied and cured to lock the swirl network.
- The mat is wound into rolls at 300–1200 g/m² and custom widths.
Because the fiber is never cut, CFM production runs faster and wastes less fiber than chopping lines, and the same line can serve RTM, pultrusion, and compression molding grades.
CFM vs CSM: Continuous vs Chopped
| Property | Continuous Filament Mat (CFM) | Chopped Strand Mat (CSM) |
|---|---|---|
| Fiber length | Continuous, meters unbroken | Chopped 25–50 mm |
| Architecture | Swirl-laid, interlocked | Random deposited |
| In-plane strength | Quasi-isotropic, high | Isotropic, moderate |
| Tensile/fatigue | Higher (continuous load paths) | Lower (resin-transfer between strands) |
| Conformability | Good on gentle curves; stiffer | Excellent on compound curves |
| Best process | RTM, pultrusion, compression molding, SMC | Hand lay-up, spray-up, repair |
| Typical use | Structural closed-mold parts, automotive panels, pultruded profiles | Boat hulls, tanks, repair patches, waterproofing |
| Relative price | Higher | Lower |
Both mats are binder-compatible with polyester, vinyl ester, and (powder-bound grades) epoxy — the resin selection rules in the resin guide apply to either.
Where CFM Wins
- RTM and light-RTM: preforms hold shape, fibers don't wash under injection, and the continuous network resists wash in high-flow areas — see the RTM molding guide.
- Pultrusion: the mat feeds continuously through the die and survives the high line speeds and die pressure that disrupt chopped mats — details in the pultrusion guide.
- Compression molding / SMC lines: fast wet-through plus high molded strength for automotive and structural panels.
- Class-A automotive: CFM layers appear in stacked laminates behind appearance surfaces, as covered in the Class-A surface finishing guide.
Typical CFM Specifications
| Property | Typical Range |
|---|---|
| Weight | 300 – 1200 g/m² |
| Width | custom (1270 – 2600 mm typical) |
| Binder | Powder or emulsion |
| Glass | E-glass / ECR-glass |
| MOQ | 2 tons (roll or slit) |
Frequently Asked Questions
What is continuous filament mat?
Continuous filament mat (CFM) is a non-woven fiberglass reinforcement made of continuous glass filaments laid in a swirl pattern and bonded together. Because the fibers are never chopped, it delivers higher tensile strength and fatigue resistance than chopped strand mat, especially in closed-mold processes like RTM and pultrusion.
Is continuous strand mat the same as continuous filament mat?
Generally yes — "continuous strand mat" and "continuous filament mat" usually describe the same product: a swirl-laid mat of unbroken glass filaments, and "swirl mat" also appears in catalogs. Terminology varies by supplier and is not formally standardized, so match the spec sheet rather than the name.
CFM or CSM — which do I need?
Choose CFM for structural closed-mold parts (RTM, pultrusion, compression molding) where tensile strength and fiber wash resistance matter. Choose CSM for hand lay-up, complex curved molds, repairs, and any job where conformability and cost come first. Many laminates use both.
Can continuous filament mat be used with epoxy?
It depends on the binder formulation, not just powder vs emulsion — check the TDS for the specific grade. Powder-bound grades are commonly recommended for epoxy, but binder–resin compatibility is grade-specific; verify before committing a production run. See CSM with epoxy for the same caution on chopped mat.
What weights does CFM come in?
Common CFM weights run from 300 g/m² (surface/backing layers) through 450–600 g/m² (general structural) up to 1200 g/m² for heavy pultrusion profiles. Widths are customizable per line requirement (1270–2600 mm typical).
