2016 Volume 57 Issue 11 Pages 1915-1921
We propose a new method of applying homogeneous low potential electron beam irradiation (HLEBI) externally to both sides of glass fiber (GF) chopped strand mat (GF-CSM) reinforced thermoplastic polypropylene (PP) interlayered samples (CSM-GFRTP) after lamination assembly and hot press with layup of [PP]6[GF-CSM]5. The external process apparently improved the Charpy impact values (auc) over that of untreated. HLEBI dose from 0.22 to 0.43 MGy apparently enhanced the auc at low cumulative probability of fracture (Pf = 0.06) 40% over the untreated from 48 to 67 kJ/m2. Moreover, based on the 3-parameter Weibull equation, applying 0.30 MGy HLEBI increased the statistically lowest impact value, as at Pf = 0 significantly 120% over that of the untreated from 29 to 64 kJm−2. The improvements of weakest samples in the data set indicate increase in reliability and safety. The improvement in auc can be attributed to HLEBI generating dangling bonds in the PP polymer evidenced by an ESR peak with inflection point at B = ~322.5 mT. The HLEBI apparently acts to generate nano-compressive stresses from repulsive forces between the severed bond electrons in the PP and GFs hence strengthening the GF and PP as well as GF/PP interface causing rise in impact energy. Therefore, the external HLEBI application aims to be a viable method to increase Charpy impact value in articles of GF-CSM reinforced PP (CSM-GFRTP) for industry such as automotive, aerospace and construction.