Core Material Selection
Choosing the Right Foam Core Material
(1) Price:
There are significant price differences among PU, PVC, and PMI foams. At the same density, PMI foam typically costs 2–3 times more than PU, and 1.5–2 times more than PVC.
(2) Mechanical Properties:
Compared to PU and PVC, PMI foam offers superior specific mechanical properties. Even at low densities, it meets structural requirements, enabling lightweight design. This reduces energy consumption during operation and increases payload capacity.
(3) Processability:
Thanks to PMI’s high thermal resistance, production processes can be accelerated by increasing the curing temperature and shortening curing cycles. This improves equipment utilization and lowers processing costs.
(4) Additional Properties:
PMI foam features excellent dielectric properties, a very low aluminum equivalent, and outstanding fatigue resistance. It is also suitable for use as a functional material in demanding applications.
PMI Foam vs. Honeycomb Core
(1) Price:
Honeycomb cores are generally less expensive than PMI foam. However, in high-performance sectors such as aerospace, premium-grade honeycomb materials can be even more costly than PMI foam.
(2) Mechanical Properties:
Honeycomb is anisotropic, providing high strength mainly in the out-of-plane direction. In contrast, PMI foam is isotropic, offering high strength in all directions. This isotropy gives designers greater freedom and eliminates the need to consider material orientation in the design phase.
(3) Processability:
Honeycomb requires specialized equipment and labor-intensive preparation, such as splicing and secondary bonding. It also needs large amounts of potting compounds due to its open-cell and anisotropic structure. These characteristics make it unsuitable for modern composite manufacturing trends such as liquid molding, out-of-autoclave curing, and low-cost rapid production.
PMI foam, on the other hand, can be processed with standard CNC equipment. Its rigid closed-cell microstructure allows for the machining of intricate features and complex surfaces without potting or secondary bonding.
