Characterizing Mode I Fatigue Delamination of Composite Materialsby Roderick H. Martin, Analytical Services and Materials, Hampton, United States,
Abstract: Evaluation of two techniques to characterize fatigue delamination using the double cantilever beam (DCB) specimen are presented. The two techniques were the delamination growth onset (G-N) method and the delamination growth the arrest (da/dN-G) method. Two glass/epoxy systems, S2/SP250 and S2/CE9000, were tested at R=0.1 and R=0.5. The values of strain energy release rate threshold, ΔGIth for no onset of delamination growth until one million cycles were compared with the values of ΔGI at delamination arrest. The values of ΔGI at delamination arrest were consistently higher than the values of ΔGIth. The ΔGI results were normalized by the value of mode I Interlaminar fracture toughness at the corresponding Δa and gave values at delamination arrest closer to the ΔGIth/GIc values obtained from the G-N technique. However, this normalization does not represent a generic materials characterization technique and does not allow for delamination onset predictions at loads above the threshold.
Subject Headings: Delaminating | Composite materials | Materials characterization | Fatigue (material) | Cracking | Structural analysis | Cantilevers
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