This invention relates to composite sandwich panels comprising rigid skins separated by and bonded to generally lower density core materials. More specifically, the invention relates to sandwich panels having core panels comprising strips and/or blocks of at least two low density cellular materials of differing properties, and those strips and blocks extend between the panel skins in alternating configuration. The structural and other properties of the core panel are a composite of the differing properties of the cellular materials.
Low density cellular materials commonly used as cores in structural composite sandwich panels are frequently not optimized for performance and/or cost for a given application. Variations in natural materials, such as balsa wood, require structural designers to assume the minimum properties of the material, and those cores usually have higher than required properties and also often have excessive weight. Additionally, the minimum structural properties of balsa wood sometimes greatly exceed the requirements of many weight sensitive composite applications, for example, the blades of wind turbines used to produce electrical energy, and these excess properties are accompanied by excess weight. Engineered foams such as PVC foams having generally isotropic properties are often over-designed for applications which do not require the same properties in all directions. The present invention provides a means of optimizing performance, weight and cost by combining two or more low density cellular materials to form a core panel having composite properties.
The core panels of the present invention comprise a plurality of alternating strips and/or blocks of at least two low density cellular materials which are adhesively connected to each other. Each of the strips and/or blocks extends between the side surfaces or faces of the core panel for connection by a hardenable adhesive resin to rigid sandwich panel skins, for example fiberglass reinforced plastic, aluminum or plywood, to form a composite sandwich panel.
In one embodiment of the invention, a core panel comprises strips of end grain balsa wood which are oriented with grain direction perpendicular to the faces of the core panel. These end grain strips alternate with strips of low density cellular plastics foam material having substantially lower structural properties and generally lower cost than the balsa wood. This assembly achieves composite structural properties lower than those of balsa wood alone but sufficient to satisfy the requirements of the intended application, which may include reduced cost and/or weight not attainable with balsa wood alone. The proportions and configuration of the balsa wood and low density foam are selected to achieve a specific resultant set of finished core panel properties. Engineered foam having substantial structural properties may be substituted for balsa wood. In an alternate embodiment of the invention, strips comprising plastics foam of low structural properties but having integral structural facers, such as fiberglass, extend between the faces of the core panel and may be substituted for the balsa wood or the high-performance foam strips.
Referring to
A particular economic advantage of the bi-directional core panel shown in
While the forms of a core panel herein described constitute preferred embodiments of the invention, it is to be understood that the invention is not limited to these precise forms of a core panel, and that changes may be made therein without departing from the scope and spirit of the invention as defined in the appended claims.
Number | Name | Date | Kind |
---|---|---|---|
2053173 | Astima | Sep 1936 | A |
2062590 | Lundquist | Dec 1936 | A |
2493032 | Rheinfrank, Jr. | Jan 1950 | A |
3192099 | Beckman et al. | Jun 1965 | A |
3230995 | Shannon | Jan 1966 | A |
3243492 | Voelker | Mar 1966 | A |
3246058 | Voelker | Apr 1966 | A |
3264153 | Rodman et al. | Aug 1966 | A |
3298892 | Lippay | Jan 1967 | A |
3339326 | Derr et al. | Sep 1967 | A |
3472728 | Hitch | Oct 1969 | A |
3526556 | Berner | Sep 1970 | A |
3544417 | Corzine | Dec 1970 | A |
3549449 | Windecker | Dec 1970 | A |
3567541 | Kaczerginski | Mar 1971 | A |
3697633 | Edgar | Oct 1972 | A |
3708385 | Immethun | Jan 1973 | A |
3733235 | Light et al. | May 1973 | A |
3734811 | Small et al. | May 1973 | A |
3750355 | Blum | Aug 1973 | A |
3773604 | Desai et al. | Nov 1973 | A |
3841958 | Delorme | Oct 1974 | A |
3867238 | Johannsen | Feb 1975 | A |
3906137 | Bauer | Sep 1975 | A |
4042746 | Hofer | Aug 1977 | A |
4048365 | Hoover | Sep 1977 | A |
4093762 | Kiefer | Jun 1978 | A |
4119750 | Porter | Oct 1978 | A |
4179540 | Smarook | Dec 1979 | A |
4196251 | Windecker | Apr 1980 | A |
4223053 | Brogan | Sep 1980 | A |
4262052 | Kannan et al. | Apr 1981 | A |
4292369 | Ohaski et al. | Sep 1981 | A |
4330494 | Iwata et al. | May 1982 | A |
4361613 | Bogner et al. | Nov 1982 | A |
4380253 | Mead et al. | Apr 1983 | A |
4411939 | Hawkins et al. | Oct 1983 | A |
4412880 | Wintermantel | Nov 1983 | A |
4498941 | Goldsworthy | Feb 1985 | A |
4521266 | Careddu | Jun 1985 | A |
4536427 | Kohn | Aug 1985 | A |
4608103 | Aldrich | Aug 1986 | A |
4617217 | Michaud-Soret | Oct 1986 | A |
4670338 | Clemino | Jun 1987 | A |
4687691 | Kay | Aug 1987 | A |
4807969 | Shimodaira et al. | Feb 1989 | A |
4808461 | Boyce et al. | Feb 1989 | A |
4823534 | Hebinck | Apr 1989 | A |
5039567 | Landi et al. | Aug 1991 | A |
5060291 | Albertelli | Oct 1991 | A |
5087500 | Kasper et al. | Feb 1992 | A |
5108810 | Williams | Apr 1992 | A |
5182150 | Carlos et al. | Jan 1993 | A |
5186776 | Boyce et al. | Feb 1993 | A |
5197928 | Mishima et al. | Mar 1993 | A |
5234969 | Clark et al. | Aug 1993 | A |
5237737 | Zigler et al. | Aug 1993 | A |
5462623 | Day | Oct 1995 | A |
5466506 | Freitas et al. | Nov 1995 | A |
5589015 | Fusco et al. | Dec 1996 | A |
5589243 | Day | Dec 1996 | A |
5624622 | Boyce et al. | Apr 1997 | A |
5625999 | Buzza et al. | May 1997 | A |
5721034 | Seemann, III et al. | Feb 1998 | A |
5741574 | Boyce et al. | Apr 1998 | A |
5794402 | Dumlao et al. | Aug 1998 | A |
5834082 | Day | Nov 1998 | A |
5904972 | Tunis, III et al. | May 1999 | A |
5958325 | Seemann, III et al. | Sep 1999 | A |
6159414 | Tunis, III et al. | Dec 2000 | A |
6191414 | Ogle et al. | Feb 2001 | B1 |
6655633 | Chapman | Dec 2003 | B1 |
6676785 | Johnson et al. | Jan 2004 | B2 |
6740381 | Day et al. | May 2004 | B2 |
6824851 | Locher et al. | Nov 2004 | B1 |
7056567 | O'Neill et al. | Jun 2006 | B2 |
7393577 | Day et al. | Jul 2008 | B2 |
20040247856 | Sikorski et al. | Dec 2004 | A1 |
20050019549 | Tai et al. | Jan 2005 | A1 |
Number | Date | Country |
---|---|---|
446910 | Feb 1948 | CA |
658023 | Feb 1963 | CA |
2 725 735 | Dec 2009 | CA |
1951310 | Apr 1970 | DE |
1949209 | Apr 1971 | DE |
19715529 | Aug 1998 | DE |
0 569 846 | Nov 1993 | EP |
1 596 868 | Jun 1970 | FR |
245458 | May 1926 | GB |
548027 | Sep 1942 | GB |
559 527 | Feb 1944 | GB |
1 265 835 | Mar 1972 | GB |
1 375 877 | Nov 1974 | GB |
Number | Date | Country | |
---|---|---|---|
20110081518 A1 | Apr 2011 | US |
Number | Date | Country | |
---|---|---|---|
61278075 | Oct 2009 | US |