Composite and carbon fibre surface preparation for bonding and coating

Wet blasting (also known as vapor blasting) gives the best overall result for carbon fibre and CFRP bonding preparation. In comparative testing it achieves the lowest water contact angle: 43–48°, against 76–88° for peel ply, manual sanding and dry grit blasting. It also delivers high fracture toughness (757 J/m² GIC) and no fibre damage at recommended pressures. Cleaning, abrading and static removal happen in one dust-free pass, so results are repeatable from part to part.

Yes. Wet blasting removes release agents, waxy residues and the resin-rich surface layer left by the autoclave, in the same pass that creates the bonding profile. The water continuously rinses the surface, so contamination is carried away rather than smeared or driven into the laminate. The water also eliminates the static charge that would attract fresh contamination. The surface changes from hydrophobic to hydrophilic, which can be confirmed with a simple water-break test (see video above).

In Vapormatt testing, wet-blasted carbon fibre held a water contact angle of 43–54° for 17 days after blasting, so the surface stays bond-ready for over two weeks when stored clean. By comparison:

• dry grit-blasted surfaces attract recontamination through static charge
• manually sanded surfaces need cleaning immediately
• peel ply surfaces degrade on exposure to the atmosphere

Always work within the time limit set by your bonding specification.

Aluminium oxide, typically 120–220 mesh at 2.5–4 bar, is the standard choice for wet blasting carbon fibre and CFRP. It removes the resin-rich layer and creates a controlled roughness profile without fracturing fibres. In aerospace testing, a single pass raised roughness from Ra 0.28 µm to Ra 1.45 µm. Fibre damage has only been observed above 4.5 bar, outside the recommended range. A Vapormatt applications engineer sets the media grade and pressure to match your bonding specification.

Read our abrasive blast media guide

Laser ablation removes resin and contamination without contact. However, it needs significantly higher capital investment and careful control to avoid thermal damage to fibres, and it is typically slower over large surface areas. Wet blasting produces a hydrophilic, bond-ready surface (43–48° water contact angle) at lower equipment cost and higher throughput. It also has an established production track record in aerospace and Formula One.

Yes, with parameters tailored to the material. Wet blasting is well established for thermoset composites such as autoclave-cured CFRP. For thermoplastic composites with PEEK, PEKK or PAEK matrices, the media grade and pressure are adapted to three things:

• the matrix hardness
• the fibre architecture
• the downstream process, whether adhesive bonding or welding

A sample trial confirms the right parameters before production.

Contact us to organise a sample trial

The right machine depends on part size, production volume and how tightly the process must be controlled:

• Vapormate compact manual cabinet: R&D, process trials and small components.
• Puma manual machine: teams finishing medium-sized parts every day.
• Automatic Cougar+: repeatable, recipe-controlled results at production volumes.
• Five-axis Sabre: high-value parts with complex geometry.

Vapormatt also engineers bespoke automatic cells for composite production lines.

Yes. Vapormatt runs sample trials on customers’ own composite components at our R&D facility. Send us representative panels or parts with your bonding specification. We will process them, confirm the surface with a water-break test, and return them for your own bond-strength testing. A trial lets you compare wet blasting against your current method before investing in a wet blasting machine. 

Arrange a composite sample trial