Manufacture and testing of a functionally graded material

A novel technique is presented for the fabrication and fracture testing of large-scale polymeric based Functionally Graded Materials (FGMs). The techn ique generates a continuously inhomogeneous property variation by taking ad vantage of the susceptibility of a polyethylene carbon monoxide copolymer ( ECO) to ultraviolet irradiation. The resulting FGMs exhibit a varying Young 's modulus, usually in a linear fashion, from approximately 160 MPa to 250 MPa over 150 mm wide specimens. The fracture behavior of the FGM is experim entally investigated through the use of single edge notch fracture tests on both homogeneously irradiated and functionally graded ECO. Two approaches are used to evaluate fracture parameters: The first, a hybrid numerical-exp erimental method, is based on far field measurements only. The second uses digital image correlation to obtain near tip measurements. The energy relea se rates of uniformly irradiated ECO and of several FGMs are measured and c ompared. It was seen that the FGM showed a built-in fracture resistance beh avior implying that it requires increased driving force to sustain crack gr owth.