How Honeycomb Cell Geometry Affects Composite Performance

Honeycomb core composites play a key role in all sorts of manufacturing and construction applications. They are appreciated for their high strength-to-weight ratios and excellent stiffness-to-mass. Aerospace is among a small number of industries that rely heavily on honeycomb core materials.

At the heart of the honeycomb core are the individual cells that make up its mass. What many people do not know is that cell geometry is crucial to product design. It affects how a honeycomb core composite performs. Therefore, cell geometry must match application demands.

Cell Size and Wall Thickness

Engineers are always concerned about tensile strength, compressive strength, and stiffness. When choosing honeycomb core composites, they pay attention to the ratio between cell size and wall thickness.

Cell size is measured by the length of a single cell side. By optimizing the ratio of size to wall thickness, engineers can maximize stiffness. They can improve load-bearing capacity as well. Stiffness and strength can both be increased through thicker walls and smaller cells.

Cell Shape and Regularity

A typical honeycomb core is designed around the classic hexagonal shape. This shape allows for optimal load distribution and subsequent stiffness. However, cell imperfections are normal. To the extent that a cell deviates from a pure hexagonal shape, honeycomb cores offer less compressive and sheer strength.

Essentially, irregularities weaken a honeycomb core’s structural stability. A weakened core is more likely to buckle, or even collapse, under load. Therefore, it is crucial to maintain consistent cell size and shape throughout manufacturing.

Directional Behavior

Honeycomb cores are subject to directional behavior. In simple terms, this means that the mechanical properties of a core depend highly on load direction relative to cell orientation.

The strongest and stiffest honeycomb cores are those in which the load direction is parallel to the walls. Other orientations are possible, and even desired when greater compliance is the goal. The most important thing here is that directional behavior can be tailored to each application.

Poisson’s Ratio

Differences in cell geometry impact how a material deforms under load. This is described by something known as the Poisson effect. We measure this effect using Poisson’s ratio. Simply put, we measure how a honeycomb material deforms relative to the perpendicular direction of an applied load.

If you were to observe this with the naked eye, you would see a honeycomb core composite contract horizontally when being stretched and laterally when being compressed. Different cell shapes demonstrate different Poisson’s ratios, thereby affecting multiple properties including compressive performance, fracture toughness, stiffness, and energy absorption.

Energy Absorption and Load Bearing

Speaking of energy absorption, hexagonal cells are known for their ability to efficiently distribute stress by absorbing maximum energy. It explains why honeycomb cores with hexagonal cells resist deformation so well.

With this knowledge, engineers can design all sorts of cell shapes depending on a particular application’s mechanical needs. An optimized cell geometry will minimize stress concentrations and prevent deformations. You wind up with a material that is both durable and fracture resistant under both compressive and impact loads.

Thoughtful and Intentional Cell Design

Everything we know about cell geometry and how it impacts performance leads us to one obvious conclusion: cell design needs to be thoughtful and intentional. Honeycomb core composites are the right choice for so many applications. But if cell geometry doesn’t align with application demands, engineers do not achieve the best results.

Axiom Materials specializes in honeycomb core composites. We would appreciate the opportunity of introducing them to you and your engineering team. They could ultimately prove to be your best choice for a number of composite applications.