Effect of atomic oxygen exposure on polybenzoxazine/POSS nanocomposites for space applications

A new thermoset resin system, based on a polybenzoxazine blend, has been subjected to high ATOX fluence (2.69 x 1021 atom/cm2), equating to a period of 300 days in low Earth orbit. Several baseline tests were carried out on the resin and the addition of POSS decreased ATOX erosion yield by 69 % compared with unmodified resin system. SEM and FTIR results confirm that the protection mechanism involves the formation of a silicon -rich surface layer in response to ATOX exposure, shielding the resin below from further erosion and principal components analysis was used to elucidate the degradation mechanism. Carbon fibre reinforced polymer (CFRP) laminates based on the new resin systems were tested for their mechanical properties. The addition of 6 wt% POSS leads to a 50 % increase in the energy required to initiate fracture and 41 % increase in the energy required to propagate a crack. Mode II fracture toughness is also improved by the addition of POSS (61.5 % increase in energy required to initiate a crack and 35.7 % increase in energy required to propagate it).