Structural panels with metal faces and corrugated plastic core

Abstract

A structural panel has one or more face sheets bonded by adhesive layers to a core body having two outer plastic liner sheets fusion-bonded to linear ends of inner plastic truss elements spaced apart with open spaces therebetween extending in a plane direction of the plastic liner sheets. The sheet-to-sheet adhesive bonding provides a high-strength laminate bonding that is very resistant to delamination, simple and inexpensive, and can be carried out by a preferred continuous sheet bonding technique. The all-plastic core body is highly resistant to moisture attack, and the open spaces between truss elements provide flexibility to accommodate thermal expansion and contraction. The truss construction of the core body provides high compressive and shear strength, while minimizing the amount of material required to be used. In one preferred embodiment, two metal face sheets are used, and the core body has plastic liner sheets fusion-bonded to a corrugated plastic core sheet. The corrugated plastic core sheet can be formed by a continuous plastic extrusion technique. Diagonal plastic webs or perpendicular plastic I-beams may also be used for the truss elements. Another preferred embodiment has two metal face sheets bonded to two plastic core bodies which in turn are bonded to a center foam core layer. A further embodiment has only one metal face sheet bonded to one side of the plastic core body, allowing it to be used as veneer or curved around rounded structures.

Description

FIELD OF THE INVENTIONThis invention generally relates to a fabrication method and product of a lightweight structural panel, in particular, a panel that is a laminate of metal face sheets and a plastic core body.BACKGROUND ARTLightweight structural panels are used in the construction industry, and are particularly desirable for outdoor use. The ideal panel is lightweight and relatively inexpensive to manufacture, has good insulation value, and is weather resistant. Panels that are durable, weather-resistant, and have high compressive and shear strength are particularly useful for outdoor applications. Structural panels having metal face sheets laminated with a plywood or wood composite core have been used, but are known to have the problem of being vulnerable to damage from moisture which can seep into the core. The moisture can cause the plywood or composite core to swell or rot. It is therefore preferable to replace the plywood or wood composite cores in structural panels for out...

AI Technical Summary

Benefits of technology

Accordingly, it is a principal object of the invention to provide a lightweight structural panel that is resistant to swelling from moisture, weathering, and freezing and thawing cycles, is easy to fabricate and makes optimum use of materials so as to obtain the highest utility for the lowest material and fabrication costs, and at the same time has good rigidity and compressive and shear strength. In particular, it is desired to produce a structural panel that can survive the rigors of outdoor exposure and wide temperature changes, and meet the stress and load requirements for architectural and industrial use.

The adhesive bonding of the plastic liner sheets of the core body to the face sheet(s) provides a high-strength laminate bonding that is very resistant to delamination. The use of sheet-to-sheet bonding with an adhesive layer is simple and inexpensive. The all-plastic core body is highly resistant to moisture attack, and the open spaces between truss elements provide flexibility to accommodate thermal expansion and contraction. The use of a core body made of plastic truss elements fusion-bonded to plastic liner sheets provides high compressive and shear strength, while minimizing the amount of material required to be used, thereby keeping the cost low. The fusion-bonding of plastic face sheets and truss elements can be accomplished readily with conventional plastic extrusion techniques.

Metal face sheets are preferred because of their high tensile strength, although plastic and fiber-reinforced skins may also be used for specific applications. A preferred core body has the two plastic liner sheets fusion-bonded to the convex surfaces of a corrugated plastic core sheet formed by a conventional plastic extrusion technique. Use of the corrugated plastic core sheet for the truss elements provides the best combination of high strength, ease of fabrication, and low material cost. However, diagonal plastic webs or perpendicular plastic I-beams may also be used for the truss elements.

In a preferred embodiment, two metal face sheets are bonded adhesively to the outer sides of the plastic core body. In another preferred embodiment, two metal face sheets are bonded to two plastic core bodies which in turn are bonded adhesively to a center foam core layer. Yet another embodiment has one metal face sheet bonded to an outer side of a plastic core body, allowing it to be used as veneer or curved around rounded structures.

Problems solved by technology

Structural panels having metal face sheets laminated with a plywood or wood composite core have been used, but are known to have the problem of being vulnerable to damage from moisture which can seep into the core.

The moisture can cause the plywood or composite core to swell or rot.

While metal-faced panels with foam cores have been used successfully, they have insufficient shear strength for some high-load applications.

Also, moisture collected in the foam core that is subjected to cycles of freezing and thawing can damage the panels by causing the layers to delaminate.

On the other hand, use of a solid plastic core sheet is costly and wastes material in excess of what is necessary to provide adequate compressive and shear strength.

However, the fabrication costs of honeycomb cores are relatively high.

Therefore, honeycomb-core laminates, for example, as sold by Unida Corp. and Ciba Geigy Corp., are typically used in aircraft and other high-priced constructions, but are too costly for widespread use as construction material.

This is a disadvantage since very careful gluing procedures and expensive high-strength adhesives are required.

However, this type of corrugated all-plastic laminate does not have sufficient rigidity for many construction applications.

While such plastic foam-core panels are resistant to weathering, they do not have sufficient shear strength for many construction applications.

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