Squeak Behavior of Plastic Interfaces

Automotive is getting advanced and increasingly comfortable with new technologies and demand from customers. Car cabins have become much quieter as compared yesteryears. Where the outside noise has gone down significantly, secondary and small noises like squeak and rattle have become more prominent. Squeak though a transient and short lived, is an unexpected noise and often considered as an irritant. There is an increasing need felt to eliminate squeak completely from the interiors of the vehicle where choice materials play dominant role. This article briefs about the work done on evaluating different plastic interfaces for squeak behavior using Stick-Slip method. Some plastic surfaces were even tested with other interfaces like leather and vinyl coated fabrics. Choice of plastic material and interfaces to be tested were shortlisted after studying many different vehicles and benchmarking. Difference in squeak was also studied with respect to external conditions like temperature, velocity of interfaces, normal force, humidity and roughness. The result of any test is measured in the form of Risk Priority Number (RPN) where higher the RPN, higher is the interface prone to squeak. The study finds that squeak in plastic interfaces is not just related to above mentioned parameters but also on static and dynamic coefficient of friction. A material compatibility matrix was derived from the study which clearly highlights material interfaces that should or that should not be used in the automotive interiors. Where polypropylene comes out as the least squeaking material, ABS and blends clearly failed in the study. Moreover, external parameters listed above do influence squeak behavior but is specific to a particular interface only and cannot be generalized for other material interfaces. Change in color for painted metal panel also gives different results as pigment and additives packages are different