The friction performance of a wet clutch for an automatic transmission (AT) depends on the interaction between the paper-based friction material (D/C), separator plate (S/P), and automatic transmission fluid (ATF). In this study, influence factors of thermosetting resin (the raw material of the D/C) on friction performance were quantified and relationship with friction coefficient was clarified. This was achieved by changing the type of thermosetting resin and its hardening conditions, which cause the friction coefficient change.
As influencing factors of the friction force, (1) the intermolecular force, (2) elastic modulus, and (3) shear stress data were extracted according to Coulomb’s friction law and the shear friction law.
For the friction test, four levels of D/C were prepared by changing the resin type/curing conditions. In the friction test, by using an SAE No.2 Testing Machine, a static test was performed at each specified cycle during the 500 cycles of the dynamic test, and the static friction coefficient (μs) was measured.
As samples for measuring the physical properties of each resin, four levels were prepared by uniformly applying a specified quantity of the thermosetting resin (which was used to prepare the D/C) on a low carbon steel plate and then cured under the specified curing conditions.
For the measurements,(1) the intermolecular force was measured by a surface forces apparatus, (2) elastic modulus was measured by a nanoindentation tester, and (3) shear stress was measured by a scratch tester.
Moreover, a regression analysis was performed for the each of the obtained results of the resin physical properties and μs. Moreover, it was clarified that the elastic modulus was positively correlated to the μs.
In contrast, for the intermolecular force, differences were notes based on the resin type. However, it was understood that during the friction, the differences in the intermolecular force did not affect the friction because the components that originated from the ATF were attached to the outermost friction surface.