Towards rapid screening of new composite matrix resins

Abstract

A study to test the correlations among neat-resin and composite properties was performed, to identify possible ways of reducing the number of tests necessary to screen candidate resins for use in aerospace structures. Neat-resin and composite tests were conducted for four different resin matrices, whose neat properties varied over a wide range, allowing reasonably strong tests of correlations. Since different fiber architectures and fiber types are often of interest to a designer, tested correlations included those between composite coupons containing the same resin but with different fibers and lay-up. Composite structural properties were represented by unnotched tension, open-hole tension, unnotched compression, and open-hole compression. Correlations were sought between these and neat-resin properties, composite shear strength, and Mode I composite delamination toughness. Strong linear correlations, which are proposed to be the most useful because they discriminate best between different resin systems, were found in certain cases, but not others. Most significantly, an Iosipescu shear test for a [0°/90°] composite of one fiber type was shown to be a good predictor, for the tested resins, of open-hole compression and unnotched compression in composites with different fibers and architecture; and a fair predictor of open-hole tension. Open-hole tension strength was shown to correlate better with neat-resin fracture toughness, but neat-resin properties were otherwise inferior indicators of most composite properties. While data for further resins are needed to enrich the statistical base, some rationalizations can be found for the presence of the stronger correlations that were observed. The correlations described here suggest that reduced test matrices, containing tests for only Iosipescu composite shear and either neat-resin toughness or Mode I delamination toughness, may suffice to evaluate the likely structural performance of composites containing new candidate resins. The tests could be performed on a standard fiber type and architecture, yet be predictors for other fiber types and architecture.