Bimodular Behavior and Crack Closure in Compression in a Brittle Material,
AEROSPACE CORP EL SEGUNDO CA MATERIALS SCIENCES LAB
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A vibrating beam method was used to determine the elastic modulus of graphite rods. The frequency and apparent modulus were determined as a function of compressive end loading. Following fracture of the rod, the frequency and apparent modulus were decreased. At a compressive and loading of about 0.83 MPa 120 psi, crack closure was sufficient for the fractured rod to behave similarly in vibration to the unfractured rod. Thus, the fractured material behaves in a bimodular fashion and crack closure can be achieved to enable unimpeded stress transfer across the fracture surface during vibration. Keywords Bimodular behavior, Elastic modulus measurements, Graphite, Microcracking and modulus.