Prediction of fiber/matrix debonding kinetics in glass fibre reinforced polyoximethylene under creep
(2011)
A method for independent prediction of creep damage accumulation on the basis of damage at short term loading and long-term strength is verified for the case of fiber/matrix debonding of injection moulded short glass fibre reinforced polyoximethylene. Small angle Scattering X-ray refractometry is applied for damage registration. The method is applicable to materials which display delocalised damage prior to fracture. The predicted damage is compared with the experimental data for damage accumulation in creep.
The effect of X-ray refraction employs an unconventional small angle X-ray scattering (SAXS) technique which has been developed and applied to meet actual problems for improved non-destructive characterisation of advanced materials. The X-ray refraction technique makes use of X-ray optical effects at micro interfaces of composite materials. This method reveals the inner surface and interface concentrations in nanometer dimensions due to the short X-ray wavelength near 10-4 µm. Sub-micron crack and pore sizes are easily determined by X-ray refractometry without destroying the structure by cutting or polishing for microscopic techniques. The non-destructive characterisation of microfailure e.g. voids, fibre debonding, fibre cracks and microcracks of a short glass fibre reinforced polyoximethylene (POM-GF) after mechanical loading and accelerated ageing is investigated. X-ray refraction topographs are illustrated, showing the damage accumulation of POM-GF specimens after the fatigue test.
Micro damage structures of fiber reinforced polymers (FRP) can be characterized nondestructively by X-ray refraction topography, which images inner surfaces. The damage accumulation after fatigue treatment of short glass fiber reinforced polybutylene terephthalate (PBT-GF) is correlated to the applied load and the number of cycles. Micro cracks and fiber/matrix debonding during fatigue can be detected separately due to their different direction of X-ray small angle scattering. The residual strength over the crack surface decreases by a linear decay as 30 %, 60 % and 90 % of the materials lifetime is passed.