Sandwich panel

A sandwich panel comprising:

• a hollow columnar core;
• a middle material layered on a first surface of the hollow columnar core and layered on a second surface of the hollow columnar core;
• and
• a surface material layered on the middle material layered on the first surface of the hollow columnar core and layered on the middle material layered on the second surface of the hollow columnar core,
• wherein said middle material comprises:
• a first unidirectional fiber body having a resin content ratio of 30% or lower, said first unidirectional fiber body having fibers that are aligned in a direction that is substantially parallel to an edge of the sandwich panel;
• a second unidirectional fiber body having a resin content ratio of 30% or lower, said second unidirectional fiber body having fibers that are aligned in a direction that is substantially orthogonal to an edge of the sandwich panel;
• a first bonding layer having a resin content ratio of 50% or higher provided between the first unidirectional fiber body and the second unidirectional fiber body;
• and
• a second bonding layer having a resin content ratio of 70% or higher provided between the first and second surfaces of the hollow columnar core and the second unidirectional fiber body, and
• wherein:
• said first and second bonding layers comprise woven fiber bodies in which fibers are used for a warp yarn and a woof yarn, and the yarns are woven,
• the woven fiber bodies are formed so that the warp yarn and the woof yarn are each tilted approximately 45° in relation to said edge of said sandwich panel,
• a polyvinylidene fluoride film or a non-woven cloth that includes glass fibers is employed as said surface material, and
• the sandwich panel has a weight per unit area of 1.79 kg/m2 or less, a maximum bending load of 520 N or greater, a peel strength of 80 N·in/3 in or greater, and an in-plane shear strength of 20 kN or greater, and
• the resin content ratio is a ratio between a weight of resin in a bonding layer or a fiber body and a weight of the bonding layer or the fiber body containing the resin.

A sandwich panel comprising:

• a hollow columnar core;
• a middle material layered on a first surface of the hollow columnar core and layered on a second surface of the hollow columnar core;
• and
• a surface material layered on the middle material layered on the first surface of the hollow columnar core and layered on the middle material layered on the second surface of the hollow columnar core,
• wherein said middle material comprises:
• a first unidirectional fiber body, said first unidirectional fiber body having fibers that are aligned in a direction that is substantially parallel to an edge of the sandwich panel;
• a second unidirectional fiber body, said second unidirectional fiber body having fibers that are aligned in a direction that is substantially orthogonal to an edge of the sandwich panel;
• a first bonding layer having a resin content ratio of 50% or higher provided between the first unidirectional fiber body and the second unidirectional fiber body;
• and
• a second bonding layer having a resin content ratio of 50% or higher is provided between said first and second surfaces of said hollow columnar core and the second unidirectional fiber body, and
• wherein:
• said first and second bonding layers comprise woven fiber bodies in which fibers are used for a warp yarn and a woof yarn, and the yarns are woven,
• the woven fiber bodies are formed so that the warp yarn and the woof yarn are each tilted approximately 45° in relation to said edge of said sandwich panel,
• wherein a polyvinylidene fluoride film or a non-woven cloth that includes glass fibers is employed as said surface material, and
• wherein the sandwich panel has a weight per unit area of 1.79 kg/m2 or less, a maximum bending load of 520 N or greater, a peel strength of 80 N·n/3 in or greater, and an in-plane shear strength of 20 kN or greater
• wherein said resin comprises a resol-based phenol resin, said resol-based phenol resin having a five-minute peak heat release rate (HRR) of 30 kW/m2 or less in a heat release test, a two-minute heat release integral of 30 kW min/m2 or less, and a smoke density of 200 or less during combustion, and
• the resin content ratio is a ratio between a weight of resin in a bonding layer and a weight of the bonding layer containing the resin.

A sandwich panel comprising:

• a hollow columnar core;
• a middle material layered on a first surface of the hollow columnar core and layered on a second surface of the hollow columnar core;
• and
• a surface material layered on the middle material layered on the first surface of the hollow columnar core and layered on the middle material layered on the second surface of the hollow columnar core,
• wherein said middle material comprises:
• a first unidirectional fiber body having a resin content ratio of 30% or lower, said first unidirectional fiber body having fibers that are aligned in a direction that is substantially parallel to an edge of the sandwich panel;
• a second unidirectional fiber body having a resin content ratio of 30% or lower, said second unidirectional fiber body having fibers that are aligned in a direction that is substantially orthogonal to an edge of the sandwich panel;
• a first bonding layer having a resin content ratio of 50% or higher provided between the first unidirectional fiber body and the second unidirectional fiber body;
• and
• a second bonding layer having a resin content ratio of 70% or higher provided between the first and second surfaces of the hollow columnar core and the second unidirectional fiber body, and
• wherein:
• said first and second bonding layers comprise woven fiber bodies in which fibers are used for a warp yarn and a woof yarn, and the yarns are woven,
• the woven fiber bodies are formed so that the warp yarn and the woof yarn are each tilted approximately 45° in relation to said edge of said sandwich panel,
• a polyvinylidene fluoride film or a non-woven cloth that includes glass fibers is employed as said surface material, and
• the sandwich panel has a weight per unit area of 1.79 kg/m2 or less, a maximum bending load of 520 N or greater, a peel strength of 80 N·in/3 in or greater, and an in-plane shear strength of 20 kN or greater,
• wherein the resin comprises a specific resol-based phenol resin having a five-minute peak heat release rate (HRR) of 30 kW/m2 or less in a heat release test, a two-minute heat release integral of 30 kW min/m2 or less, and a smoke density of 200 or less during combustion, and
• the resin content ratio is a ratio between a weight of resin in a bonding layer or a fiber body and a weight of the bonding layer or the fiber body containing the resin.