Composites samples containing 80% and 85% organic filler in a polymer-plastizer binder were produced by mixing, extruding, cutting, drying and pressing. Before pressing the extruded material was in some cases coated with a thin layer of graphite (= one micron) for ease in pressing. As part of a general study of these composites the compressive strength, σm, was determined as a function of temperature, strain rate and the thickness of the graphite coating. Without graphite σm increases with decreasing temperature and increasing strain rate. With graphite σm has the same behavior above approximately −10 C, but is independent of both temperature and strain rate below −10 C for a strain rate of 1.0/Sec. In addition, the low temperature value of σm decreases with increasing graphite thickness. The cracking and fracture patterns are temperature and strain rate dependent and are different with and without graphite. These results indicate that the bond produced by pressing the graphite containing material is stronger than the composite above −10 C and weaker below −10 C so that failure initiates in the composite above −10 C and in the bond below −10 C. With decreasing strain rate this transition temperature decreases. The bonding is discussed.
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The author wishes to thank Carl Hu for assistance with data taking, and E. Baker, M. Mezgar and J. Pinto for helpful discussions. The author also thanks E. Baker, D. Geiss, M. Mezgar, B. Strauss and J. Pinto for making materials available, and M. Joyce and associates for pressing some of the composites.
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Wiegand, D.A. Bond Strength of Pressed Composites. MRS Online Proceedings Library 318, 387–392 (1993). https://doi.org/10.1557/PROC-318-387