Large-Scale Evaluation of Constrained Bearing Elements Made of Thermosetting Polyester Resin and Polyester Fabric Reinforcement

[+] Author and Article Information
P. Samyn

 Ghent University, Laboratory Soete, Department Mechanical Construction and Production, St. Pietersnieuwstraat 41, B-9000 Gent, BelgiumPieter.Samyn@UGent.be

W. Van Paepegem, J. Degrieck, P. De Baets

 Ghent University, Laboratory Soete, Department Mechanical Construction and Production, St. Pietersnieuwstraat 41, B-9000 Gent, Belgium

J. S. Leendertz

Ministry of Transport, Public Works and Water Management, Directorate-General, Herman Gorterhove 4, NL-2700 AB Zoetermeer, The Netherlands

A. Gerber

 University of Stuttgart, Staatliche Materialprüfungsanstalt, G-70550 Stuttgart (Vaihingen), Germany

L. Van Schepdael

 SOLICO B.V., Solutions in Composites, Everdenberg 97, NL-4902 TT Oosterhout, The Netherlands

J. Tribol 128(4), 681-696 (Jun 14, 2006) (16 pages) doi:10.1115/1.2345413 History: Received February 16, 2006; Revised June 14, 2006

Polymer composites are increasingly used as sliding materials for high-loaded bearings, however, their tribological characteristics are most commonly determined from small-scale laboratory tests. The static strength and dynamic coefficients of friction for polyester/polyester composite elements are presently studied on large-scale test equipment for determination of its bearing capacity and failure mechanisms under overload conditions. Original test samples have a diameter of 250 mm and thickness of 40 mm, corresponding to the practical implementation in the sliding surfaces of a ball-joint, and are tested at various scales for simulation of edge effects and repeatability of test results. Static tests reveal complete elastic recovery after loading to 120 MPa, plastic deformation after loading at 150 MPa and overload at 200 MPa. This makes present composite favorable for use under high loads, compared to, e.g., glass-fibre reinforced materials. Sliding tests indicate stick-slip for pure bulk composites and more stable sliding when PTFE lubricants are added. Dynamic overload occurs above 120 MPa due to an expansion of the nonconstrained top surface. A molybdenum-disulphide coating on the steel counterface is an effective lubricant for lower dynamic friction, as it favorably impregnates the composite sliding surface, while it is not effective at high loads as the coating is removed after sliding and high initial static friction is observed. Also a zinc phosphate thermoplastic coating cannot be applied to the counterface as it adheres strongly to the composite surface with consequently high initial friction and coating wear. Most stable sliding is observed against steel counterfaces, with progressive formation of a lubricating transfer film at higher loads due to exposure of PTFE lubricant. Composite wear mechanisms are mainly governed by thermal degradation of the thermosetting matrix (max. 162°C) with shear and particle detachment by the brittle nature of polyester rather than plastic deformation. The formation of a sliding film protects against fiber failure up to 150 MPa, while overload results in interlaminar shear, debonding, and ductile fiber pull-out.

Copyright © 2006 by American Society of Mechanical Engineers
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Figure 1

Use of a high-loaded ball-joint in the Maeslant storm surge barrier, near Rotterdam (NL), (a) general view on the barrier closing the Nieuwe Waterweg with hemispherical gates connected by steel trusses to a ball-joint in the abutments, (b) detail of the connection between steel trusses and the ball-joint in a climate controlled room

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Figure 2

Detail of the inner structure of the ball-joint for application of composite bearing elements

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Figure 3

Detail of a polyester/polyester composite pad with nominal diameter 250mm and thickness 40mm as sliding element in the ball-joint (grey zone indicates 5mm internal lubricated top layer of polyester/polyester B) (a) free composite pad, (b) constrained composite pad

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Figure 4

Test equipment, (a) full-scale static testing (Ghent University), (b) large-scale dynamic testing (Ghent University), (c) small-scale dynamic testing (Stuttgart University) (1) composite pad, (2) counterface, (*) thermocouple

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Figure 5

Static test results for polyester/polyester B pads, (a) short-term deformation for free pads, (b) short-term deformation for constrained pads, (c) long-term deformation of constrained pads, (d) long-term deformation for free and constrained pads

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Figure 6

Evaluation of overload and failure after static loading polyester/polyester B pads of diameter 250mm and height 40mm in general top view (left) and detailed side-view (right), (a) free 150MPa, (b) constrained 150MPa, (c) constrained 200MPa

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Figure 14

Overload failure mechanisms for polyester/polyester A and B, (a) interlaminar shear failure, (b) debonding, (c) fiber pull-out

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Figure 15

Steel counterfaces after sliding, (a) separate wear debris transfer for polyester/polyester A, (b) transfer film formation for polyester/polyester B

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Figure 16

Coating adhesion and removal, (a) polyester/polyester B surface impregnated by MoS2, (b) polyester/polyester B surface with adhesion of zinc-phosphate, (c) removal of MoS2 on the steel surface, (d) wear of zinc phosphate on the steel surface

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Figure 13

Fiber wear mechanisms for polyester/polyester A, (a) fiber pull-out, (b) fiber fracture

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Figure 12

Matrix wear mechanisms for polyester/polyester B characterized by sliding film formation, (a) film covering matrix phase, (b) film covering both matrix and fiber phases with fracture through brittleness at high loads

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Figure 11

Matrix wear mechanisms for polyester/polyester A characterized by matrix removal and lack of sliding film formation, (a) matrix removal and fiber exposure, (b) matrix shear, (c) removal of degraded particles

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Figure 10

Original polyester/polyester B structure, (a) overview with distribution of PTFE, (b) detail of impregnated fiber fabric

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Figure 9

Macroscopic photograph of counterfaces after sliding with polyester/polyester B, (a) steel, (b)MoS2 coating, (c) zinc phosphate coating

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Figure 8

Evaluation of overload and failure after dynamic sliding of composite pads of diameter 250mm and height 40mm, (a) polyester/polyester A at 150MPa, (b) polyester/polyester B at 150MPa

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Figure 7

Dynamic test results for sliding of polyester/polyester B against different counterfaces at 15MPa (running-in), (a) steel St 37-2 N, (b)MoS2 coating, (c) zinc phosphate coating




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