PP Honeycomb Core Selection & Engineering Guide
Specifying polypropylene honeycomb means choosing the right density and thickness, deciding whether you need a scrim or barrier film, and matching the core to your lamination process. The points below cover the choices that most affect performance and cost.
💡 Pro Tip: Use Scrim and Barrier Film to Control Resin
A non-woven polyester scrim gives adhesives and resins something to key into, while a barrier film keeps resin from filling the cells during infusion. Skipping the film on a vacuum-infused part can raise weight and cost through excess resin uptake.
1. How to Select the Right Density and Thickness
PP honeycomb is commonly supplied around 65 kg/m³ (4 pcf) for general panels and 100 kg/m³ (6.25 pcf) where higher compression is needed. Thickness typically runs from about 5 mm to 100 mm. Heavily loaded areas, inserts, and fastener zones benefit from the higher-density grade, while large flat panels keep weight and cost down at the lower density.
2. Typical Mechanical Performance by Density
| Density |
Compressive Strength |
Shear Strength |
| ~65 kg/m³ (4 pcf) |
~1.2 MPa (174 psi) |
~0.4 MPa (58 psi) |
| ~100 kg/m³ (6.25 pcf) |
~2.6 MPa (377 psi) |
~0.7 MPa (101 psi) |
Values are indicative for standard PP honeycomb (8 mm cell); actual figures vary with grade and test standard.
3. Scrim, Barrier Film, and Bonding Options
Most PP honeycomb is supplied with a non-woven polyester scrim on both faces so it bonds well to fiberglass, carbon-fiber, or thermoplastic skins using epoxy, polyester, polyurethane, or vinyl-ester adhesives. An optional barrier film prevents resin from migrating into the open cells during vacuum infusion, keeping the part light. PP honeycomb can also be thermally welded to thermoplastic skins for fully recyclable all-thermoplastic sandwich panels.
4. Where PP Honeycomb Core Performs Best
🚢 Marine & Transportation
Boat decks, bulkheads, and vehicle bodies where low weight, impact absorption, and moisture resistance matter.
🏗️ Industry & Energy
Wind nacelles and blades, rail floors and partitions, advertising boards, and industrial covers.
5. Thermoforming, Machining, and Recycling
PP honeycomb thermoforms well, so it can be shaped to gentle curves before lamination. It cuts and routes cleanly on standard CNC equipment, and because it is a thermoplastic it is fully recyclable. Note that the standard grade is combustible (UL94 HB); a flame-retardant, halogen-free grade (UL94 V-2) is available where fire performance is required.
Frequently Asked Questions (FAQS)
1. What density and thickness range is available for PP honeycomb core?
Common grades are around 65 kg/m³ (4 pcf) and 100 kg/m³ (6.25 pcf), with thicknesses typically from 5 mm to 100 mm. Sheets can be cut to your required dimensions.
2. What are the main engineering benefits of PP honeycomb core?
A high strength-to-weight ratio, very low water absorption, good impact and energy absorption, sound and vibration damping, corrosion resistance, and full recyclability.
3. How does PP honeycomb bond to skins, and do I need a scrim?
Most grades are supplied with a non-woven polyester scrim that bonds well to fiberglass, carbon-fiber, and thermoplastic skins using epoxy, polyester, polyurethane, or vinyl-ester adhesives. A barrier film can be added to stop resin filling the cells during infusion.
4. How does PP honeycomb behave in moisture and outdoor service?
Polypropylene is hydrophobic, so the core absorbs very little water and resists rot and common chemicals. It performs well in marine and outdoor environments, though the finished panel should still be sealed at edges and fasteners.
5. Which manufacturing processes is PP honeycomb compatible with?
Vacuum infusion, hand lay-up, RTM, compression lamination, and thermal welding for all-thermoplastic panels. It also thermoforms and CNC-machines cleanly.
6. Is PP honeycomb fire rated?
The standard grade is combustible (UL94 HB). A flame-retardant, halogen-free grade achieving UL94 V-2 is available where fire performance is required for the application.
7. How are PP honeycomb sheets packed for shipping?
Sheets are protected with film and stacked on export pallets or in crates suitable for 20ft and 40ft container freight. Custom sizes and densities can be prepared to your specifications.
