Y Gong, Z-G. Yang/Composites: Part B 53(2013)103-1 Table 2 EDS results of the glass fiber and the foreign fibers(wt%). 31.08 15.59 6.92 73.61 1.6 146 Fig. 11. Microscopic morphologies of the fracture surfaces of the unused sample (a evenly distributed glass fibers, and (b)agglomerated glass fibers and foreign fiber. Fig. 12. SEM micrographs of the stress concentration corner(with counterpart) of the unused sample (a)total, and(b)magnification. be regarded universal, even normal for the pedal arm products of seemed to be coincidences, i.e. the defects happened to exist on the this manufacturer. However, why did several fracture failure inci- weakest stress concentration corners. In other words, if those inev- lents including the one in this paper occurred after all? According itable defects did not occur on these areas, the pedal arms could to the fracture surfaces, it is easy to find out the critical point was still exhibit qualified strength, like most of the other products that the joint between the pedal and the e, the destined frac- But anyway the defects did exist, and moreover, even if just one ure position under loads, was coincidentally encountered with pedal arm fractured during actual service, severe traffic accidents Ich defects on its stress concentration corner. Consequently, would be engendered. Consequently, solutions to relieve ever merely under loads far lower than the qualified value 1100 N, eliminate them still need to be proposed. Since the processing of cracks could be initiated from the sites without glass fibers on this the pedal arms was injection molding, three countermeasures corner, and then quickly propagated. ardingly suggested. (1)improving the pellets quality Till oot causes se fracture failures had been identi- the introduction of defective pellets (too short, not fied. Nevertheless, from the probability point of view, such causes plump, bare glass fibers, etc )and organic(probably the recycledbe regarded universal, even normal for the pedal arm products of this manufacturer. However, why did several fracture failure inci￾dents including the one in this paper occurred after all? According to the fracture surfaces, it is easy to find out the critical point was that the joint between the pedal and the frame, the destined frac￾ture position under loads, was coincidentally encountered with such defects on its stress concentration corner. Consequently, merely under loads far lower than the qualified value 1100 N, cracks could be initiated from the sites without glass fibers on this corner, and then quickly propagated. Till now, root causes of those fracture failures had been identi- fied. Nevertheless, from the probability point of view, such causes seemed to be coincidences, i.e. the defects happened to exist on the weakest stress concentration corners. In other words, if those inev￾itable defects did not occur on these areas, the pedal arms could still exhibit qualified strength, like most of the other products. But anyway, the defects did exist, and moreover, even if just one pedal arm fractured during actual service, severe traffic accidents would be engendered. Consequently, solutions to relieve even eliminate them still need to be proposed. Since the processing of the pedal arms was injection molding, three countermeasures were accordingly suggested, (1) improving the pellets quality, i.e. ensuring the introduction of defective pellets (too short, not plump, bare glass fibers, etc.) and organic (probably the recycled Table 2 EDS results of the glass fiber and the foreign fibers (wt%). Element C O Na Mg Al Si Ca Cl K Site A 31.08 15.59 0.45 1.97 7.65 23.19 20.06 / 2.068 Site B 61.33 16.63 6.75 0.35 0.50 1.11 2.05 6.92 4.36 Site C 73.61 17.71 1.63 0.35 0.64 1.73 1.79 1.46 1.08 Fig. 11. Microscopic morphologies of the fracture surfaces of the unused sample (a) evenly distributed glass fibers, and (b) agglomerated glass fibers and foreign fiber. Fig. 12. SEM micrographs of the stress concentration corner (with counterpart) of the unused sample (a) total, and (b) magnification. 110 Y. Gong, Z.-G. Yang / Composites: Part B 53 (2013) 103–111