Detection of Undercure in Carbon-Fibre/Epoxy Composites by Dynamic Mechanical Thermal Analysis *

Abstract

Desirable properties in thermosetting polymer matrix composites can only be realised after a sufficient degree of matrix curing. It is, thus, important that the state of cure should be clearly identified. Carbon-fibre/epoxy laminates of varying degrees of matrix cure were prepared, and evaluated using static mechanical tests, impact tests and dynamic mechanical thermal analysis. Interlaminar shear and compression tests, although widely used in quality control, were not sufficiently sensitive to distinguish between the cured and significantly undercured laminates. Furthermore, considerable scatter was experienced in the interlaminar shear strength measurements. In contrast, the data obtained from dynamic mechanical analysis were reproducible and indicated more accurately the condition of the materials. Instrumented impact testing also produced relevant information.

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