The characteristics of flexibility and flex fatigue resistance frequently represent the key reasons that polymers are selected to comprise certain products. Cut-growth resistance represents an added dimension to flex fatigue and is frequently investigated under bending strain or high extension strain circumstances.
 
The experts at Smithers can work with your development team to understand the material requirements and develop a testing program that will meet your needs.  Several common test methods that are utilized include:
  • Tensile fatigue testing
    • Tensile fatigue can be carried out to internal procedures using dumbbell specimens which can be moulded or machined. Testing is carried out by applying a cyclic stress between zero and the target stress; typical conditions are a square wave at 1Hz.
  • Flexural fatigue testing
    • Flexural fatigue can be carried out to internal procedures using rectangular section specimens. These can be moulded or machined using our in-house equipment. Testing is carried out by applying a cyclic stress in four point bend between zero and the target stress; typical conditions are a square wave at 1Hz. A range of target stresses are used to generate failure times from 100s to 106s. This generates a plot of fatigue stress versus log failure time. A minimum of 20 data points are required to produce a fatigue plot. 
  • Fatigue to failure: Monsanto FTF
  • Mandrel fatigue: Ross Tester
  • High deflection fatigue: DeMattia Tester
  • Cut growth resistance testing
  • Compression fatigue: BF Goodrich tester
    • Permanent set resistance
    • Heat build-up
    • Dynamic properties
    • Blow-out time

About our Labs

Equipment

De Mattia Flexer

This machine measures the resistance to cracks or crack growth to BS ISO 132. Test pieces are clamped with one end in a stationary grip and the other end in a reciprocating grip. The degree of bending and the speed can be adjusted to the material requirements. Frequent inspections are made until the first small sign of cracking is detected on each test piece. For determination of crack growth, an artificial cut is made in the test piece to initiate cut growth.

MRPRA Flexer

This machine measures the fatigue resistance of rubber. Rubber rings are mounted vertically on pulleys which are free to rotate. Each specimen is expanded repeatedly at various strains at 300 cycles per minute to failure.

Our extensive sample preparation facilities can test a huge variety of materials and product forms and are equipped with a CNC machine, on-site moulding, and slitting and buffing equipment to reduce rubber thickness.