Method and apparatus for evaluating multilayer objects for imperfections

A method of evaluating a multilayer object for imperfections of voids, delaminations and microcracks, the multilayer object comprising multiple layers arranged in a stacking direction, the evaluation method comprising the steps of:

• transmitting a pulsed acoustic wave into the multilayer object in the stacking direction;
• receiving the transmitted acoustic wave, in the stacking direction, after the transmitted acoustic wave has propagated laterally through the multilayer object;
• and
• correlating the received acoustic wave with the presence or absence of imperfections in the multilayer object;
• the correlating step further comprising:
• generating pulse echo signals indicative of the received acoustic wave over a period of time;
• and
• determining a respective time interval between successive pulse echo signals, wherein nonuniform time intervals indicate an unacceptable presence of imperfections in the multilayer object.

An apparatus for evaluating a multilayer object for imperfections of voids, delaminations and microcracks, the multilayer object comprising multiple layers arranged in a stacking direction, the apparatus comprising:

• means for transmitting an acoustic wave into the object in the stacking direction, such that the acoustic wave propagates laterally through the multilayer object;
• means for receiving the transmitted acoustic wave after the transmitted acoustic wave has propagated laterally through the multilayer object;
• and
• means for correlating the received acoustic wave with the presence or absence or imperfections in the multilayer object;
• the correlating means further comprising means for generating pulse echo signals indicative of the received acoustic wave and means for determining a respective time interval between successive pulse echo signals, wherein uniform time intervals indicate the absence of imperfections in the multilayer object.

An apparatus for evaluating a multilayer object for imperfections of voids, delaminations and microcracks, the multilayer object comprising multiple layers arranged in a stacking direction, the apparatus comprising:

• means for transmitting an acoustic wave into the object in the stacking direction, such that the acoustic wave propagates laterally through the multilayer object;
• means for receiving the transmitted acoustic wave after the transmitted acoustic wave has propagated laterally through the multilayer object;
• and
• means for correlating the received acoustic wave with the presence or absence or imperfections in the multilayer object;
• the correlating means further comprising means for generating pulse echo signals indicative of the received acoustic wave and means for determining a respective time interval between successive pulse echo signals, wherein nonuniform time intervals indicate an unacceptable presence of imperfections in the multilayer object.