Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Patent
1998-01-05
2000-04-04
Dawson, Robert
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
428241, 523440, 523466, 525107, 525523, B32B 700
Patent
active
060458984
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an epoxy resin composition suitable as a matrix resin composition of a fiber reinforced composite material, and also to a prepreg. In more detail, it relates to a prepreg which has good self adhesiveness to a honeycomb core and gives a construction of a honeycomb structure, skin panels of which are of low porosity and also relates to its matrix-resin composition. Furthermore, it relates to a prepreg which is excellent in tackiness, less in temporal change of tackiness, and gives a construction with skin panels having less pits and dents on the surfaces, and also relates to its matrix resin composition. Moreover, it relates to a honeycomb structure obtained from the foregoing.
BACKGROUND ART
Fiber reinforced composite materials consisting of reinforcing fibers and a matrix resin are widely used for airplanes, automobiles and other industrial applications, since they are excellent in mechanical properties. In recent years, as the fiber reinforced composite materials may become more widely adopted, they are required to have more excellent properties to meet more severe requirements. To let the fiber reinforced composite materials manifest their mechanical properties and durability sufficiently, it is important to decrease the defects resulting in the decline of strength. Especially for structural materials of airplanes, in view of weight reduction, it is more frequently practiced to use a fiber reinforced composite material as skin panels to be incorporated into a honeycomb sandwich panel. Honeycomb cores are made of aramid or aluminum. In particular, it is general practice to produce a honeycomb sandwich panel by laminating prepreg layers on both sides of a honeycomb core, and co-curing to cure the prepreg layers and to bond the prepreg layers and the honeycomb core simultaneously.
In this case, the bonding strength between the honeycomb core and the prepreg layers laminated as skin panels is important. Conventionally it is popular practice to use a structural adhesive film between the honeycomb core and each of the prepreg layers, for co-curing. However, to further reduce the weight of the honeycomb sandwich panel and to reduce the cost of fabricating, it is desired to self-bond the honeycomb core and the prepreg layers without using any adhesive film.
However, if they are bonded without using any adhesive film, the resin existing in the prepreg layers must migrate into the honeycomb core to sufficiently wet the honeycomb walls, instead of the resin in the adhesive films, and it has been a very difficult problem to achieve a high bonding strength. The cured portions of the resin sinking or rising along the honeycomb walls in the thickness direction of the honeycomb core from the laminated prepreg layers are called fillets, and it is difficult to form the fillets sufficiently between the honeycomb core and the skin panels. If the viscosity of the resin is too low, the resin of the top skin panel tends to flow down too much along the honeycomb walls, and as a result, the bonding strength between the top skin panel and the honeycomb core becomes insufficient. On the other hand, if the resin viscosity is too high, the resin cannot sufficiently wet the honeycomb walls, and especially the bonding strength between the bottom skin panel and the honeycomb core is liable to be insufficient.
On the other hand, since the resin existing in the prepreg layers must be distributed toward the honeycomb core walls, the absolute amount of the resin in the laminated prepreg layers becomes insufficient, and, disadvantageously, pores are likely to be formed in the skin panels. In the case of honeycomb structure, since the pressure for fabricating it does not act on the prepreg layers at the portions above and below the hexagonal voids of the honeycomb core, pores are more likely to be formed as compared with a case of fabricating an ordinary prepreg laminate.
Furthermore, conventionally it is popular practice to stick a structural adhesive film on the surface of each prepreg l
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Hayashi Masahiko
Higashi Toshiaki
Kishi Hajime
Odagiri Nobuyuki
Aylward D.
Dawson Robert
Toray Industried, Inc.
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