Text 1. Cored CompositesThe essenti

Text 1. Cored Composites
The essential idea behind cored-composite structures is to maximize the stiffness-to-weight ratio. Since flexural stiffness of a beam is proportional to the cube of its thickness, it would at first seem desirable to make everything thick—but if the material is solid, that can become absurdly heavy. Fortunately, we can play a trick: use a lightweight core to add thickness. When you try to bend something made this way, the stresses resolve into three separate cases, so we can optimize the materials to handle them. Imagine pushing down on a piece of my cardboard-core bicycle trailer:
The upper fiberglass skin is in compression across its surface, focused at the point of contact. The lower skin is in tension. The core is loaded in “shear,” which tries to split it along the middle as the faces move like hands rubbing together.
Since everything is bonded nicely together, the characteristics of the long glass fibers work to our advantage (they are oriented at right angles in a normal cloth weave in this particular case, but there’s nothing sacred about that; in optimized structures, the majority of the fibers may be oriented along the lines of maximum anticipated loading). As long as the core maintains a constant thickness and doesn’t start to crush or split longitudinally, the whole assembly is resistant to bending and the skins don’t wrinkle or buckle; failures, when they do occur, are generally catastrophic. It’s analogous to an I-beam, where the skins correspond to the flanges and the core corresponds to the web. This approach also cuts weight, with the sum of the skins thinner and lighter than a “single skin” structure of equivalent stiffness (and it has better insulating properties).
Of course, cardboard is a wimpy core material, and would never be used in a real application (especially in a marine environment—one crack and the whole thing would turn to mush). Old boxes were a cheap option back in 1989 when I was bicycle-hacking, but I graduated to professional materials when moving on to boatbuilding; instead of cellulose, the Microship uses Divinycell, a closed cell rigid PVC foam with a density of 5 pounds per cubic foot. This is one of a wide range of materials that are made specifically for this purpose, varying in shear modulus, density, permeability, fabrication difficulty, and cost.
One familiar core material is end-grain balsa wood (from Baltek Corporation), oriented with the fibers running from skin to skin to resist shear loads and add compressive strength.
Balsa is particularly good at handling attachment points without crushing, something that is more of a pain with foam. But as with the cardboard, damage to one of the skins (or even a hidden leak around a fastener) can eventually cause the structure to become waterlogged.
Foams are available in many flavors, ranging from cross-linked types like Divinycell (and Klegecell) to linear types that are more flexible (Airex). They can be had in a wide range of densities as indicated by the application—where flotation is an issue (as in surfboards) a very light core would be used, but that is of course more prone to impact damage if the skins are too thin.

Figure1: A sampling of core materials. Gray surface and scrap at upper-right are the Divinycell used throughout the Microship project; various honeycombs are also shown. [12]

Результаты (английский) 1:

Text 1. Cored CompositesThe essential idea behind cored-composite structures is to maximize the stiffness-to-weight ratio. Since flexural stiffness of a beam is proportional to the cube of its thickness, it would at first seem is desirable to make everything thick — but if the material is solid, that can become absurdly heavy. Fortunately, we can play a trick: use a lightweight core to add thickness. When you try to bend something made this way, the stresses resolve into three separate cases, so we can optimize the materials to handle them. Imagine pushing down on a piece of my cardboard-core bicycle trailer:The upper fiberglass skin is in compression across its surface, focused at the point of contact. The lower skin is in tension. The core is loaded in "shear," which tries to split it along the middle as the faces move like hands major together. Since everything is nicely bonded together, the characteristics of the long glass fibre work to our advantage (they are oriented at right angles in a normal cloth weave in this particular case, but there's nothing sacred about that; in optimized structures, the majority of the fibre may be oriented along the lines of maximum anticipated loading). As long as the core maintains a constant thickness and doesn't start to crush or split longitudinally, the whole assembly is resistant to bending and the skins don't wrinkle or buckle; failures, when they do occur, are generally catastrophic. It's analogous to an i-beam, where the skins correspond to the flanges and the core corresponds to the web. This approach also cuts weight, with the sum of the skins thinner and lighter than a "single skin" structure of equivalent stiffness (and it has better insulating properties). Of course, cardboard is a wimpy core material, and would never be used in a real application (especially in a marine environment — one crack and the whole thing would turn to mush). Old boxes were a cheap option back in 1989 when I was bicycle-hacking, but I graduated to professional materials when moving on to boatbuilding; instead of cellulose, the Microship uses Divinycell, a closed cell rigid PVC foam with a density of 5 pounds per cubic foot. This is one of a wide range of materials that are made specifically for this purpose, varying in shear modulus, density, permeability, difficulty of fabrication, and cost.One familiar core material is end-grain balsa wood (from Baltek Corporation), oriented with the fibre running from skin to skin to resist shear loads and add compressive strength. Balsa is particularly good at handling attachment points without crushing, something that is more of a pain with foam. But as with the cardboard, damage to one of the skins (or even a hidden leak around a we) can eventually cause the structure to become waterlogged.Foams are available in many flavors, ranging from cross-linked types like Divinycell (and Klegecell) to linear types that are more flexible (Airex). They can be had in a wide range of densities as indicated by the application is where flotation is an issue (as in surfboards) a very light core would be used, but that is of course more prone to impact damage if the skins are too thin. Figure1: A sampling of core materials. Gray surface and scrap at upper-right are the Divinycell used throughout the Microship project; various honeycombs are also shown. [12]

Результаты (английский) 2:

1. Cored Composites Text
The essential idea behind-cored composite structures is to maximize the stiffness-to-weight ratio. Since flexural stiffness of a beam is proportional to the cube of its thickness, it would at first seem desirable to make everything thick-but if the material is solid, that can become absurdly heavy. Fortunately, we can play a trick: use a lightweight core to add thickness. When you try to bend something made ​​this way, the stresses resolve into three separate cases, so we can optimize the materials to handle them. Pushing down on Imagine Imagine a piece of cardboard my bicycle trailer-core:
The upper fiberglass skin is in compression across its surface, focused at the point of contact. The lower skin is in tension. The core is loaded in "shear," which tries to split it along the middle as the faces move like hands rubbing together.
Since everything is bonded nicely together, the characteristics of the long glass fibers work to our advantage (they are oriented at right angles in a normal cloth weave in this particular case, but there's nothing sacred about that; in optimized structures, the majority of the fibers may be oriented along the lines of maximum anticipated loading). As long as the core maintains a constant thickness and does not start to crush or split longitudinally, the whole assembly is resistant to bending and the skins do not wrinkle or buckle; failures, when they do occur, are generally catastrophic. It's analogous to an I-beam, where the skins correspond to the flanges and the core corresponds to the web. This approach also cuts weight, with the sum of the skins thinner and lighter than a "single skin" structure of equivalent stiffness (and it has better insulating properties).
Of course, cardboard is a wimpy core material, and would never be used in a real application (especially in a marine environment-one crack and the whole thing would turn to mush). Old boxes were a cheap option back in 1989 when I was bicycle-hacking, but I graduated to professional materials when moving on to boatbuilding; instead of cellulose, the Microship uses Divinycell, a closed cell rigid PVC foam with a density of 5 pounds per cubic foot. This is one of a wide range of materials that are made ​​specifically for this purpose, varying in shear modulus, density, permeability, fabrication difficulty, and cost.
One familiar core material is end-grain balsa wood (from Baltek Corporation), oriented with fibers running from the skin to skin to resist shear loads and add compressive strength.
Balsa is particularly good at handling attachment points without crushing, something that is more of a pain with foam. But as with the cardboard, damage to one of the skins (or even a hidden leak around a fastener) can eventually cause the structure to become waterlogged.
Foams are available in many flavors, ranging from cross-linked types like Divinycell (and Klegecell) to linear types that are more flexible (Airex). They can be had in a wide range of densities as indicated by the application-where flotation is an issue (as in surfboards) a very light core would be used, but that is of course more prone to impact damage if the skins are too thin . Figure1: A sampling of core materials. Gray surface and scrap at upper-right are the Divinycell used throughout the Microship project; various honeycombs are also shown. [12]

Результаты (английский) 3:

text 1. Cored Composites
the essential idea behind cored - composite structures is to maximize the stiffness - to - weight ratio. since flexural stiffness of a beam is proportional to the cube of its thickness, it would at first seem desirable to make very thick, but if the material is solid, that can become absurdly heavy. there, we can play a trick:use a lightweight core to add thickness. when you try to bend something made this way, the stresses resolve into three separate cases, so we can optimize the materials to handle them. imagine pushing down on a piece of my cardboard core bicycle excluding:
upper fiberglass skin is in compression across its surface, focused at the point of contact. the lower skin is in tension.the core is loaded in the "shear," which tries to split it in the middle of the faces move like hands rubbing together.
since everything is bonded walk together, the characteristics of the long glass fibers work to our advantage (they are oriented at right angles in a normal cloth weave in this particular case, but there 's nothing sacred about that; in the optimized structures.the majority of the fibers may be oriented along the lines of maximum anticipated loading). as long as the core maintains a constant thickness and doesn't start to crush or split longitudinally, the whole assembly is resistant to bending and the skins don't wrinkle or buckle; failures when they do occur, are generally catastrophic. it's analogous to an i - beam,where the skins correspond to the flanges and the core corresponds to the web. this approach also cuts weight, with the sum of the skins thinner and is in a "single," the structure of equivalent stiffness (and it has better insulating properties).
of course, cardboard is a wimpy core material.and i would never be used in a real application (especially in a marine environment, a crack and the whole thing would turn to mush). old boxes were a cheap option back in 1989 when i was bicycle - hacking, but i graduated to professional materials and moving on to boatbuilding; instead of cellulose, the Microship uses Divinycell,a closed cell rigid pvc foam with a density of 5 pounds per cubic foot. this is one of a wide range of materials that are made specifically for this purpose, varying in shear modulus, density, permeability, fabrication price and cost.
one from core material is end in balsa wood (from Baltek corporation)oriented with the fibers running from skin to skin to resist shear loads and add compressive strength.
Balsa is particularly good at handling attachment points without crushing, something that is more of a pain with foam. but as with the cardboard, damage to one of the skins (or even a hidden nothing but a fastener) can eventually cause the structure to become waterlogged.
Foams are available in many flavors, ranging from cross - linked types like Divinycell (and Klegecell) to linear types that are more flexible (Airex). they can be had in a wide range of densities as indicated by the application - where flotation is an issue (as in surfboards) a very light core would be used, but that is of course more prone to impact damage if the skins are too thin.

Figure1:a sample of core materials. gray surface and only at the upper - right are the Divinycell used throughout the Microship project; various honeycombs are also shown. [12].