A dynamic mechanical analyzer was modified to perform pull-put tests to measure theinterfacial shear strength of a series of glass fibers having different surface treatments embeddedin an epoxy. Single glass filaments were processed in a thin epoxy disk of nominal 1 mm or lessand inserted in a tensile fixture on a TA Instruments 2980 DMA. The DMA was operated inforce control, using a load application rate of 0.1 N/minute. The DMA was successful inquantifying the interfacial shear strength of the samples tested in this study. An additionalbenefit of this approach is the entire pull-out event was captured during the application of load,enabling the stress to be plotted as a function of strain. The DMA offers the ability to conductpull-out tests over a wide range of temperatures. This paper reports the initial findings of using aDMA to evaluate interfacial properties of glass fiber reinforced epoxy.In addition to pull-put tests, a new test geometry was developed that enables the glasstransition of the polymer at the interphase to be measured directly using dynamic mechanicalanalysis. The new geometry consists of a single reinforcing fiber embedded between two tabs ofpolymer. The specimen is inserted in the tensile fixture of the DMA leaving a gage area of freefiber of nominal 1/4 to 1/2 inch connecting the two tabs. The DMA is then used to put anoscillatory tensile stress on the specimen while conducting a temperature sweep. In this way thefiber serves as a probe of the matrix, and the glass transition of the interphase was successfullymonitored. An additional benefit of this test is that the fiber tensile strength can be measuredusing the DMA force ramp function at the conclusion of the temperature sweep. Examples ofcarbon fibers embedded in thermoplastic and thermosetting polymers are given.
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