Active control of crack-tip stress intensity by contraction of shape memory TiNi fibers embedded in epoxy matrix composite: dependency of stress intensity factor on crack-tip domain size

摘要

Shape memory TiNi fiber reinforced/epoxy matrix composite is fabricated to demonstrate the suppression effect of crack-tip stress concentration and the increase of fracture toughness (K value) of the composite. The increase of fracture toughness is attributed to the compressive stress field in the matrix which is induced when the prestrained TiNi fibers contract to the initial length upon heating above austenitic finish temperature of TiNi fiber (T>Af). The dependence of K value on the prestrain value of TiNi fibers as well as the compressive stress domain size between a crack-tip and fiber are discussed based on the analytical equivalent inclusion model for a composite. The experimental data agreed well to theoretical predictions.