New acoustic emission analysis for characterization of fiber/matrix interfacial strength of woven fabric laminates
Uenoya Toshiyuki; Oguri Taizo
Abstract:Laboratory tests have some limitation and problems in estimation of the fiber/matrix interface strength of commercial composites. It is strongly required to clarify the detailed fracture process in composites and to evaluate the properties of interphase in commercial composite materials. New tests based on non-destructive testing (NDT) have been attempted for this purpose, but not enough data have been generated so far by the new methods. So, an experimental assessment was proposed for the failure progression and the strength of the interface in structural composite materials by using acoustic emission (AE) technique in this paper. Samples used are two types, fabricated with fibers differing only in their surface treatment. The mechanical and AE behaviors of E-glass fiber fabric/epoxy laminates were investigated in combination with transmitted light microscopy observation. Failure progress, consisting of several micro-failure mechanisms, contributed to the characteristic AE behavior. They can be discriminated through frequency spectrum analysis of AE signals detected from the laminates. The estimated results were demonstrated as 'damage progress curve' to applied loads, being in good agreement with that optically observed through a microscope. The fiber/matrix debonding strength was examined based on a certain AE event rate in the damage progress curve originated by debonding for the two laminate samples. Key Words:surface treatment, failure progress, interfacial strength, fiber/matrix debonding, acoustic emission, glass fiber fabric/epoxy laminates