ISO 6311:1980

Overview

ISO 6311:1980 - "Road vehicles - Brake linings - Internal shear strength of lining material - Test procedure" defines a laboratory method to measure the internal shear strength of brake lining (friction) materials used for disc brake pads and drum brake linings on road vehicles. The standard describes the required apparatus, specimen sampling and conditioning, test setup (including a schematic test rig), the controlled loading procedure to induce shear failure, and the required test reporting.

Key topics and technical requirements

• Scope: Applies to friction materials intended for vehicle brake pads and linings; the test is intended to produce rupture of the lining material under shear.
• Specimen sampling: At least five specimens must be taken from stock. Specimens should be oriented so they shear in the direction representative of the most stressed brake shoe or pad under normal service.
• Specimen dimensions: Flat specimens with nominal dimensions:
  • Length: 20 ± 0.1 mm
  • Width: 20 ± 0.1 mm
  • Thickness: 5 ± 0.1 mm or 10 ± 0.1 mm
• Apparatus:
  • A tensile or compression testing machine equipped with a fixture that applies shear loading and records the peak shear load (examples: peak pointer, load-indicating spring or equivalent recording device).
  • A mounting assembly of two sliding blocks with minimal friction, maximum clearance 0.1 mm, and designed to receive the pad/lining so the specimen fills the space to prevent slipping.
  • Load application must be concentric (apply at the fixture center) and parallel to the sliding guide.
• Load application rate: Load should increase continuously at 4 500 ± 500 N/s. It is recommended that instantaneous rate control be within 4 500 ± 2 250 N/s when shear force exceeds 5 000 N. Load must not be applied by impacts.
• Reporting: Report the maximum applied load (mean of at least five tests) in newtons and the sheared area in mm².

Practical applications

• Validate the structural integrity of brake lining materials during material qualification and quality control.
• Compare shear performance of different friction formulations, backing adhesives, or bonded assemblies.
• Support safety and durability assessments for disc brake pads and drum brake linings used in passenger cars, commercial vehicles, and aftermarket components.

Who should use this standard

• Brake material manufacturers and compound formulators
• Automotive OEM and supplier test laboratories
• Quality engineers responsible for brake lining acceptance testing
• Regulatory and certification bodies assessing brake component performance

Related standards

• ISO 611 (referenced in ISO 6311) - vehicle braking terminology and related braking definitions.

Keywords: ISO 6311:1980, brake linings, internal shear strength, shear strength test, disc brake pads, drum brake linings, friction materials, test procedure, sampling, test rig.