LAUSR

Abstract In this paper, glass fiber-reinforced polypropylene (GF50-PP) composite composed of long fibers was prepared by the thermo-compression process for the very first time. This composite presents high mechanical strength and is used in infrastructures, which demand resistance against severe conditions. Mechanical strength and multi-scale damage analysis of GF50-PP composite at ambient and cryogenic temperatures have been investigated in this study using a special sampling procedure according to the microscopy observation, X-ray microtomography, ultrasonic measurement, and pyrolysis . The results demonstrated the exceptional behavior of the GF50-PP at the cryogenic temperature of −70 °C mainly due to the employment of a novel processing method (thermo-compression) for composites with long fibers, which have been previously prepared by traditional injection molding process . Tensile results presented no difference in failure strain at 20 °C and −70 °C and the fatigue lifetime for different fiber orientations was similar in 3-points bending fatigue tests for different orientations of fibers or in samples taken from different regions of the composite plate , indicating the efficinecy of this processing method. Moreover, the results of damage analysis through monotonic loading presented that by decreasing the temperature from 20 °C to −70 °C, the plasticity threshold didn’t change notably. Overall, the proposed preparation method provided outstanding uniformity and excellent mechanical properties in GF50-PP composite even at temperatures as low as −70 °C, which has not been investigated at this cryogenic temperature before.