Abstract
The crack growth behavior on the cleavage adhesive joints with various adhesive thicknesses was investigated by the echo characteristic of surface wave emitted toward the adhesive layer under the tensile load. The cross section of adhesive layer was 25×25mm2. The echo height reflected from the edge of the adhesive layer and the round-trip propagation time from the surface wave probe to the adhesive layer were measured for evaluating the crack growth behavior. The crack was generated along the adhesive interface when the ratio of the round-trip propagation time suddenly increased. After that, the crack rapidly grew. In the case where the distance between the surface wave probe and the adhesive layer was10mm, the crack of the adhesive layer was detected when the crack length was more than 0.2mm or the ratio of the echo height reflected from the edge of adhesive layer became about 60%. Moreover, the crack growth behavior was evaluated for measuring the ratio of the round-trip propagation time or the ratio of the echo height. The load of crack generation detected by the change ratio of the round-trip propagation time agreed well with that of the echo height. The load of crack generation and breaking load on the adhesive layer decreased as the adhesive layer thickness was thicker.
