Method and apparatus for evaluating fold endurance and surface adhesion of sheet materials

A device capable of testing the endurance of a sheet and the endurance and adhesion of surface treatments on the sheet, said device comprising:

• a) a first directionally porous plate slidably mounted to a first vacuum box;
• b) a second directionally porous plate slidably mounted to a second vacuum box;
• wherein a fold is created at a preselected position on a sheet when the sheet is held by said first and second plates;
• c) means for sliding said first plate relative to said second plate, said sliding means permitting a fold in a sheet held by said first and second plates to move over a preselected area of the sheet;
• and
• d) means for maintaining a preselected spacing between said plates, the spacing of said plates determining the radius of a fold in a sheet held by said plates.

A method capable of testing the endurance of a sheet and the endurance and adhesion of surface treatments on the sheet, said method comprising:

• a) applying a pressure differential to a preselected section of a first slidable directionally porous surface;
• b) applying a pressure differential to a preselected section of a second slidable directionally porous surface;
• c) maintaining a preselected spacing between said surfaces;
• c) securing a portion of a sheet to said first surface;
• d) securing a different portion of said sheet to said second surface, thereby creating a fold at a preselected position on said sheet, the radius of said fold being determined by the spacing between said first and second surfaces;
• and
• e) selectively sliding said first surface relative to said second surface, thus permitting said fold to move over a preselected area of said sheet.