Affiliation:
1. Laboratoire de Tribologie et Dynamique des Systèmes, UMR CNRS 5513, Ecole Centrale de Lyon, Université de Lyon, 36 Avenue Guy de Collongue, 69134 Ecully, France
2. Valeo Matériaux de Friction, Rue Barthélémy Thimonnier, 87020 Limoges, France
Abstract
The clutch facing is a complex organic matrix composite in dry clutch systems. When the clutch engages, there is a sliding contact between the clutch facing and the mating surfaces, resulting in temperature increases of up to 300 °C. These thermal cycles activate several mechanisms that can have consequences on such material: cracking and, more generally, the ageing of the polymer. The thermomechanical properties of the material therefore evolve according to the number of thermal cycles. This study focused on investigating the local and average evolution of the coefficients of thermal expansion (CTE) of clutch facing as a function of thermal cycles. Several techniques were employed, including image stereocorrelation for determining the CTE, Dynamic Mechanical Analysis (DMA) tests for monitoring the ageing of the material and acoustic emission for highlighting the damage. The results showed that the average CTE decreased as a function of the temperature and the number of loading cycles, while locally, it increased in some areas and decreased in others. These differences appear to be the result of material heterogeneity (actual yarn tracing, etc.) and interaction between cracking and ageing mechanisms in the polymer matrix. Indeed, thermal cycling led to cracking and additional crosslinking, which is influenced by ageing conditions.
Subject
General Materials Science
Reference117 articles.
1. Effect of Sliding Speed on the Thermal Stresses of Single-Disk Friction Clutches;Abdullah;J. Fail. Anal. Prev.,2020
2. Numerical and Finite Element Contact Temperature Analysis of Friction Material’s Type Effect on a Thermal Transient Behavior of a Single-Disc Dry Clutch;Tribologia,2017
3. Biczó, R., Kalácska, G., and Mankovits, T. (2021). Effects of Automotive Test Parameters on Dry Friction Fiber-Reinforced Clutch Facing Surface Microgeometry and Wear. Polymers, 13.
4. The Temperature Distribution in Friction Clutch Disc under Successive Engagements;Tribol. Ind.,2018
5. Biczó, R., Kalácska, G., and Mankovits, T. (2020). Micromechanical Model and Thermal Properties of Dry-Friction Hybrid Polymer Composite Clutch Facings. Materials, 13.