000202944 001__ 202944 000202944 005__ 20181203023643.0 000202944 0247_ $$2doi$$a10.1016/0022-5096(93)90007-3 000202944 022__ $$a0022-5096 000202944 037__ $$aARTICLE 000202944 245__ $$aTHE TOUGH TO BRITTLE TRANSITION IN BRITTLE MATRIX COMPOSITES 000202944 260__ $$c1993 000202944 269__ $$a1993 000202944 336__ $$aJournal Articles 000202944 520__ $$aA THEoRY is presented to predict the ultimate tensile strength of brittle matrix composites as a function of underlying material parameters, and specifically to investigate the origin of the tough to brittle transition often observed in these materials as the fiber-matrix interfacial sliding resistance tau is increased. The theory relaxes the usual assumption of global load sharing of the load transfer from broken to unbroken fibers in the composite [CURTIN, W. A., J. Am. Ceram. Soc. 74, 2837 (1991)] by taking the load to be equally distributed among only N(f) fibers around a broken fiber (local load sharing). The composite is then modeled as a collection of independent fiber bundles with Nf fibers per bundle, and composite failure occurs when the weakest bundle fails. Composite strength is thus controlled by the strength distribution of size-N(f) bundles, which is calculated here by analytical and simulation techniques. As N(f) --textgreater infinity the global load sharing results for composite strengths are regained, but significant composite strength degradation is predicted for bundle sizes N(f) less-than-or-equal-to 100. An ansatz relating N(f) to material parameters is then proposed and calculations of the strengths of C-Nicalon composites agree well with experiment. Model calculations on a Nicalon-LAS glass composite show that local load sharing effects lead to a tough to brittle transition between 100 and 200 MPa, much lower than predicted by the global load sharing theory although still larger than found experimentally. 000202944 6531_ $$aceramics 000202944 6531_ $$acrack 000202944 6531_ $$afiber 000202944 6531_ $$afracture 000202944 6531_ $$ainterface 000202944 6531_ $$amechanical-properties 000202944 6531_ $$astrength 000202944 700__ $$0246474$$g211624$$aCurtin, W. A. 000202944 773__ $$j41$$tJournal Of The Mechanics And Physics Of Solids$$q217-245 000202944 909C0 $$xU12614$$0252513$$pLAMMM 000202944 909CO $$pSTI$$particle$$ooai:infoscience.tind.io:202944 000202944 937__ $$aEPFL-ARTICLE-202944 000202944 970__ $$acurtin_tough_1993/LAMMM 000202944 973__ $$rREVIEWED$$sPUBLISHED$$aOTHER 000202944 980__ $$aARTICLE