L6: Abrasion

Abrasion

contact between 2 solids resulting in a loss of matter/physical integrity of the weaker surface

Abrasion Hazards

accidental contact with rough surfaces, normal wear; affected by surface roughness, hardness, and presence of a 3rd medium

Wear

material is lost/displaced from a solid to an atomic level

Polymer Abrasion

displacement of surface materials in relative motion

Microploughing

ridge formed as material moves along a surface; material displacement

Microcutting/Microshearing

material chipped away as a channel is produced; material loss

• 2 body abrasive wear

• 3 body abrasive wear

Abrasion of Elastomers

mechanical abrasion caused by mechanical failure from local stress concentrations; basic wear - characteristic wave pattern

Abrasion of Yarns/Fibres

Abrasive surface adheres to the fibre, junction is formed, surfaces slide, junctions shear, one surface left attached to the other

Abrasion of Fabrics

fibre breakage and entanglement, strong effect of weave pattern, surface flattens and may become fuzzy

Martindale abrasion tester

38 mm specimen in circular holder: measure number of cycles before endpoint

Wyzenbeek tester

cylinder moves back and forth over fabric, tested in warp and weft direction: endpoint is when 2 broken yarns or noticeable wear

Taber abrader

2 wide discs of abrasive material: measure number of cycles to end point

Impact Abrasion

• Used for motorcycle protective(EN 13595-2, 13594, 13634)

• Specimen secured to a sensor and dropped onto a 30 km/h abrasive belt

• Measure time to complete abrasion

Challenges with abrasion testing

• lack or correlation between test methods

• degradation proceeds differently according to test method

• sensitivity to other factors

• lack of precise endpoint evaluation

• not correlated with real use conditions

Hard surface coatings

• Plastic: Superfabric

• Ceramic: Schoeller ceramic coated textiles

Elastomers

• Polyurethane

• Nitrile rubber

• Natural rubber

Leather

• Excellent abrasion resistance compared to textiles

• Depends on tanning process to improve strength and wear resistance

• Full grain leather has the best resistance

• Preferred in impact resistance applications