Mr. Meechai Sriwiboon, Compact International(1994) Co.,Ltd., THAILAND

Ms. Kritsana Kaewlob, Compact International(1994)Co.,Ltd., THAILAND

Mr. Seong Rhee, SKR Consulting, UNITED STATES

Disc pads of one low-copper formulation and one high-copper formulation were made and cured under 4 different cure conditions. These pads had no backing layer (underlayer) and no scorching in order to minimize experimental variables. Pad thickness, dynamic modulus and resonant frequencies were continuously monitored over a period 12 months. After 12 months at room temperature, pad thickness, dynamic modulus and resonant frequencies all increased to higher values. The low-copper formulation exhibited relatively rapid property changes during the first 60 days, and the copper-free formulation exhibited relatively rapid changes during the first 90 days, followed by slow changes thereafter. Two competing processes were found to be taking place; internal residual stress relief leading to pad expansion and cross-linking of the resin leading to pad shrinkage. In addition, pad property changes due to testing were measured. As the properties are changing with time, a question rises regarding the timing of measurement for quality control. Implications of these property changes will be discussed for correlating pad properties with friction, wear, brake squeal and squeal modeling/simulation.