how and Why of FOAM cores
08-22-2003, 12:31 AM
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how and Why of FOAM cores
This is from an article about metal foams, probably see them in cars soon, but I thought it a pretty good explanation.
Structural Material
Foams intrinsically combine relatively high stiffness with lower density than their parent material. It is important to note that, if only the direct strength is considered, foams often have a similar or slightly worse performance than solid material of the same weight. The advantage of foams becomes apparent when bending stresses are considered as a function of weight. The mass distribution of cellular structures increases the overall moment of inertia of the material, giving a far higher specific bending stiffness and strength than for the corresponding weight of bulk metal. This makes foams useful as high-strength, low-density load-bearing components in automotive and aerospace applications. This could be in the form of direct load-bearing components, but most uses envisage some form of bonded structure, where foam is used as a central element encased in an outer metal sheet. Sandwich constructions have been produced where foam serves as a honeycomb-type material, encased between solid outer plates. Compared with typical honeycomb materials, these are easier to mass-produce, and have increased resistance to shear due to the isotropic nature of foams. Some of the production methods (including the one I'm working on) also allow the filling of irregular moulds or shapes with foam - for example to make complex shapes, or to fill beams or pipe structures with foam, to provide increased rigidity without significantly increasing the weight. Compared with solid metal components, structures produced using foam cores have been shown to be significantly lighter, while offering notably increased structural rigidity.
Structural Material
Foams intrinsically combine relatively high stiffness with lower density than their parent material. It is important to note that, if only the direct strength is considered, foams often have a similar or slightly worse performance than solid material of the same weight. The advantage of foams becomes apparent when bending stresses are considered as a function of weight. The mass distribution of cellular structures increases the overall moment of inertia of the material, giving a far higher specific bending stiffness and strength than for the corresponding weight of bulk metal. This makes foams useful as high-strength, low-density load-bearing components in automotive and aerospace applications. This could be in the form of direct load-bearing components, but most uses envisage some form of bonded structure, where foam is used as a central element encased in an outer metal sheet. Sandwich constructions have been produced where foam serves as a honeycomb-type material, encased between solid outer plates. Compared with typical honeycomb materials, these are easier to mass-produce, and have increased resistance to shear due to the isotropic nature of foams. Some of the production methods (including the one I'm working on) also allow the filling of irregular moulds or shapes with foam - for example to make complex shapes, or to fill beams or pipe structures with foam, to provide increased rigidity without significantly increasing the weight. Compared with solid metal components, structures produced using foam cores have been shown to be significantly lighter, while offering notably increased structural rigidity.
