| Popis: |
This attempt aims at assessing heat generation in thermal conductive polymer (TCP) composites widely used in aerospace sectors. Temperature histories were investigated in both nonreinforced and glass-fiber-reinforced TCPs during abrasive milling. Glass/epoxy and glass/polyester composites with 30% unidirectional glass fiber content were prepared according to appropriate curing cycles. Type K thermocouples connected to a data acquisition system ensured the recording of temperature history along the trim plan during milling. Unexpectedly, when milling TCP composites parallel to fibers, peak temperature was found to be slightly lower than that recorded in nonreinforced polymers. The lateral surface of fibers acts to favor sliding friction, which limits heat generation at interfaces, while relatively low specific heat capacity and thermal conductivity of glass fiber disadvantage heat transfer. However, when milling perpendicular to fibers, the contact area between the tool and the transverse failure area of fibers increases drastically, hence involving severe friction at interfaces. This yields peak temperatures sensitively higher than those obtained in nonreinforced polymers. SEM inspections highlighted the failure modes dominating the material removal process in both nonreinforced and glass-fiber-reinforced polymers. The microcracks and debris observed at the trim plan explain, in part, the heat generation detected on temperature rate plots. Thus, heat conduction between phases governs sensitive surface finish integrity and tool lifetime and, hence, has great economic impact on the manufacturing steps. |
