Effects of Gamma Irradiation on the Morphological, Physical, and Thermal Properties of B₄C/CF/PI/AA6061 Hybrid Composite Laminates

B₄C/CF/PI/AA6061 hybrid composite laminates (BCPAs) with different configurations were fabricated using a hot molding process and then were irradiated by a ⁶⁰Co gamma ray with various doses (250, 500, 750, and 1000 kGy) under ambient conditions. The effects of gamma irradiation on the morphological, physical, and thermal properties of the BCPAs were evaluated correspondingly. It was shown that the specimens maintained good interfacial adhesion even after gamma irradiation up to 1000 kGy and that no obvious delamination, swelling, and surface irradiation damage could be observed. Fourier transform infrared spectroscopy of the BCPAs after gamma irradiation indicated no obvious discrepancy when compared with that of nonirradiated specimens. The specimens still maintained good thermal stability with the experimental temperature up to 400°C. When the specimens were gamma irradiated with the dose of 750 kGy, the thermal stability of the BCPAs was optimal. Polyimide resin under gamma irradiation was inclined to form free radicals close to each other and underwent radiation decomposition, a chain scission and cross-linking reaction, and a secondary cross-linking reaction. By analyzing the C-C bond, C-O bond, and C = O bond in the C1s spectrum, the relative intensity of the C = O bond decreased with the irradiation dose; moreover, gamma irradiation caused the decomposition of a certain amount of the oxygen functional group C = O.