Creating a line-shaped weakening in a polymer skin/foam bilaminate sheet while minimizing read-through

When a line shaped weakening in a polymer skin/foam bilaminate is created by mechanically scoring the backside of the skin, where it is bonded to the foam, the weakness of the bilaminate is determined by the depth of the score groove. The deeper the groove, the weaker the bilaminate and the easier it is to achieve a location-controlled fragmentation-free failure. But also, the deeper the groove, the greater the tendency for read-through. Read-through is seeing on the front surface of the skin the location of the groove that was created on the back surface. This is why it is often important to minimize the groove depth required to achieve a location-controlled fragmentation-free failure and to minimize read-through for a given groove depth. The immediate application of this technology is found in the weakening of a car instrument panel to allow the passenger-side airbag to deploy through it.; This work has focused on understanding how the skin fails, how the foam fails, and what leads to a location-controlled fragmentation-free failure of the bilaminate. Quasi-shear and tensile tests were conducted to achieve this. The knowledge acquired was used to develop tests to predict how a bilaminate will fail and to make general bilaminate design recommendations to minimize the groove depth required to achieve a location-controlled fragmentation-free failure.; This work has also focused on understanding what topographical feature on the skin's surface constitutes read-through, what strains are induced by mechanical scoring, and how these strains lead to read-through. Scored and mounted skins were viewed with an optical interferometer and measured with a profilometer to better understand what topographical features constitute read-through. Skins of different color and gloss level were viewed with incident light directed in various directions to better understand the affect of incident light direction, color, and gloss on read-through. Several model systems were used to determine what strains are induced by mechanical scoring. This knowledge was used to identify factors that may affect read-through. The factors were then varied to verify their effect. It may be possible to use this increased knowledge to minimize read-through at a given score groove depth.