Effect of reprocessing on the fatigue strength of a fibreglass reinforced polyamide

The mechanical recycling of short fibre reinforced thermoplastics by granulation and subsequent injection moulding allows for recovery of both post consumer waste and in-plant recycled material in many industrial sectors. Parts made of these materials are often subjected to cyclic loads and therefore need to be designed against fatigue. The fatigue behaviour of reprocessed glass fibre reinforced polyamide 6,6 has been studied, using standard injection moulded specimens containing different percentages of recycled material. The effect of reprocessing of clean materials is mainly represented by fibre shortening in the injection moulding process and consequent degradation of the load bearing capacity of material. The relationship between the fatigue strength and the fibre length distribution has been discussed.