Honeycomb Core Materials

Highest stiffness-to-weight, conductive

Expanded aluminium, stainless steel, brass and tin steel. Metallic cores give the best shear and compressive strength per unit density of any family, and are the reference the others are measured against. Conductivity is the deciding factor either way — essential for EMI shielding, disqualifying under an RF aperture.

Density

16 – 190 kg/m³ (1.0 – 12.0 pcf)

Service temp

to ~175 °C (aluminium); far higher for stainless

Moisture-immune, recyclable, impact-tolerant

Polypropylene cores, supplied bare or skinned with FRP. They absorb essentially no moisture and are chemically inert, which suits wash-down and marine environments where paper-based cores degrade. They crush progressively rather than failing abruptly, making them the usual choice for energy absorption.

Density

30 – 130 kg/m³ (1.9 – 8.1 pcf)

Service temp

to ~100 °C (PP)

Non-metallic, dielectric, flame-resistant

Phenolic-dipped aramid paper and woven fiberglass. The resin coating sets the mechanical properties as much as the substrate does, so the same paper at a heavier dip yields a stiffer, denser core. Non-conductive and transparent to RF, which makes this the default family under radomes and antenna structures.

Density

24 – 144 kg/m³ (1.5 – 9.0 pcf)

Service temp

to ~180 °C with phenolic resin