Editorial Type:
Article Category: Research Article
 | 
Online Publication Date: 01 Oct 2017

Impact of Pre-Strain, Initial Thermal Strain, and Viscoelasticity of Hybrid/Merged Cords on Tire Performance

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Page Range: 244 – 258
DOI: 10.2346/tire.17.450401
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ABSTRACT

Hybrid/merged cords made by blending dissimilar yarns into a single cord are commonly used in tire applications. This method is used to capture the desirable properties of each component. In nylon (PA66)/aramid (A19) cord constructions, the aramid is used for its superior strength and thermal stability. The nylon is used for its high elongation. In tire numerical modeling, the composite components require two types of input data, one related to the initial thermal strain, coefficient of thermal expansion (CTE), and one related to the growth/creep viscoelastic response, creep factor (cr_fr). The following article provides a summary of the laboratory measurements of these material properties for the commonly used hybrid/merged cords. A consumer tire with reinforcing layers was analyzed under normal inflation and loading conditions. The impact on the tire's outer contour and footprint characteristic was shown to be dependent on the type of cord materials used, its initial thermal strain, and its viscoelastic behavior.

Keywords: tires; hybrid cord; nylon 66; aramid; viscoelasticity; coefficient of thermal expansion
FIG. 1
FIG. 1

Testrite testing equipment used to measure the CTE.

FIG. 2
FIG. 2

CTE comparison for simple and hybrid cord constructions.

FIG. 3
FIG. 3

Viscoelasticity experiment.

FIG. 4
FIG. 4

Constant axial strain and correspondent modulus response.

FIG. 5
FIG. 5

Creep factor cr_fr for simple and hybrid cord constructions.

FIG. 6
FIG. 6

Ribbed tire footprint at 0.241 Mpa inflation pressure, and 1088 kgf vertical load.

FIG. 7
FIG. 7

Tensile function for the different cord constructions.

FIG. 8
FIG. 8

Impact of CTE, cr_fr, and pre-strain on (a) R1 and (b) R5.

FIG. 9
FIG. 9

Change in footprint width.

FIG. 10
FIG. 10

Center rib (R3) length change.

FIG. 11
FIG. 11

Impact of CTE, cr_fr, and pre-strain of footprint ratio FR.

FIG. 12
FIG. 12

Tire cross section profile with reinforcement cord N1 (a) CTE only; (b) cr_fr only; and (c) pre-strain only.

FIG. 13
FIG. 13

Tire cross section profile with reinforcement cord N2 (a) CTE only; (b) cr_fr only; and (c) pre-strain only.

FIG. 14
FIG. 14

Tire cross section profile with reinforcement cord H1 (a) CTE only; (b) cr_fr only; and (c) pre-strain only.

FIG. 15
FIG. 15

Tire cross section profile with reinforcement cord H2 (a) CTE only; (b) cr_fr only; and (c) pre-strain only.

FIG. 16
FIG. 16

Tire cross section profile with reinforcement cord H3 (a) CTE only; (b) cr_fr only; and (c) pre-strain only.

FIG. 17
FIG. 17

Tire inflation radius growth.

Contributor Notes

2 Corresponding author. The Goodyear Tire & Rubber Company, Akron, Ohio 44316, USA. Email: mahmoud.assaad@goodyear.com
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