Effect of cooling rate on interlaminar fracture energy and shear strength of APC-2 laminates

van der Hoeven, W.

Effect of cooling rate on interlaminar fracture energy and shear strength of APC-2 laminates

Title

Effect of cooling rate on interlaminar fracture energy and shear strength of APC-2 laminates

Author

van der Hoeven, W.

Institution

National Aerospace Laboratory NLR

Date

1993-05-31

Abstract

The effect of cooling rate on some mechanical properties of APC-2/AS4 composite was investigated over the range between 1 and 70° C/min. Preconsolidated unidirectional laminates were reprocessed in a hot platen press at controlled cooling rates. Double Cantilever Beam specimens and End Notch Flexure specimens were used to determine the mode I and mode II fracture energies, respectively. The interlaminar shear properties were measured using the losupescu shear test method. The results indicated that the shear modulus and the shear strenght tended to decrease slightly with increasing cooling rate. The mode I fracture energy was observed to increase with cooling rate by about 8 per cent within the range investigated. The type of precrack was found to have a significant effect on the mode II fracture energy calculated from the test results. Specimens with mechanically induced precracks yielded fracture energies that were significantly lower than those for specimens with moulded-in precracks. For specimens with mechanically induced precracks the mode II fracture energy was found to increase with cooling rate by about 19 per cent within the range investigated. It is concluded that decreasing the cooling rate below the minimum value specified by the material supplier (10° C/min) will most probably not lead to an abrupt or substantial degradation of the mechanical performance of APC-2.

Subject

carbon fibre reinforced plastics
peek
thermoplastic resins
fracture strength
temperature effects
strain energy release rate
polymer matrix composites
laminates
crack opening displacement
cooling
auto claving