Indentation of functionally graded polyester composites

In order to evaluate the performances of functional graded materials (FGMs), local mechanical tests are needed. This study discusses the use of an instrumented macro-indentation test to measure the effect of the local filler content. Glass and silica filled functional graded materials were produced by the sedimentation casting method. An unsaturated polyester resin was used as matrix, and filled and unfilled polyester samples were cut to have 5 mm thick slices. Flat punch indentation tests were performed on the composite slices to evaluate the effect of the graded filler content. Indentation slope and load were extracted from the experimental curves, and correlated one to the other. A finite element (FE) model was built to simulate the sample behavior under indentation, and was used to extract material properties from the experimental curves in terms of elastic modulus and maximum compressive stress during the test. Thanks to the indentation test, a steep gradient of the mechanical properties was found for the glass-filled FGM whereas the silica filled FGM had a less pronounced variation of properties.