CORRELATION BETWEEN THE STRENGTH OF FIBER REINFORCED PLASTICS AND THE ADHESIVE STRENGTH OF FIBER/MATRIX JOINTS

摘要

The relationship between the strength (#sigma#_c) of unidirectional fiber-reinforced plastics in different stressed states and the interfacial strength of their components is investigated. The adhesive shear strength (#tau#_0) of fiber-matrix joints determined by the pull-out technique is used as a measure of the interfacial strength. To obtain the correlation curves between #sigma#_c and #tau#_0, we use the experimental results where both the plastic and adhesive strength changes under the influence of a single factor. In this case, such factors are the fiber surface treatment, nature and composition of polymer matrices, and test temperature. It is shown that the strength of the glass, carbon, and boron plastics increases practically linearly with increased interfacial strength. Such a behavior is observed in any loading conditions (tension, shear, bending, and compression). Sometimes, a small (10-20 percent) increase in the adhesive strength induces a significant (50-70 percent) growth of the material strength. Therefore, the interface is the "weakest link" in these composites. The shape of #sigma#_c-#tau#_0 curves for the composites based on the high-strength and high-modulus aramide fibers and different thermoreactive matrices depends ort the nature of the fiber and the type of the stressed state. In many cases, the composite strength does not depend on the interfacial strength. Then, the fiber itself is a "weak link" in these composites.