Damage development in pultruded composites for optical telecommunications cables under tensile and flexural fatigue

This paper investigates the long-term behaviour of pultruded glass-fibre composites, which are used as load-bearing components in optical telecommunications cables. Both flexural and tensile fatigue tests were conducted using the materials in their commercial product forms. Fatigue damage progression was monitored on-line by the acoustic emission technique. Damage accumulation was quantified by the stiffness loss evaluated from the change of resonance frequency in a free vibration test. The resonance measurement is able to determine modulus degradation to an accuracy of 0.01%. A definition of fatigue failure under tensile and flexural fatigue is proposed. Fatigue damage development is discussed and is found to be dependent on stress level and stress history.