Damage detection device and method

A method of determining an impact width from a test tap, comprising:

• (a) receiving an impact signal from an acceleration sensor;
• (b) passing the signal to a timing circuit in the event that the impact signal reaches in amplitude a timing threshold;
• (c) starting a clock upon passing the signal to the timing circuit and timing the duration of the amplitude of the impact signal above the timing threshold;
• (d) stopping the clock once the impact signal falls in amplitude below the timing threshold;
• (e) detecting with circuitry associated with the accelerometer whether the impact signal reached a predetermined, high amplitude threshold above the timing threshold to determine that the impact signal was created by an impact adequate for making reliable measurements of the integrity of the composite;
• (f) displaying an “insufficient impact” signal on an alphanumeric display associated with the accelerometer, if the high amplitude threshold has not been reached;
• and
• (g) displaying as a number on the display representative of the time measured by the timing circuit, if the high amplitude threshold has been reached.

A method of detecting defects in composite structures, comprising the steps of:

• (a) manually striking a hand-held tool including an accelerometer against a composite structure to produce an impact;
• (b) determining whether the impact was adequate to allow a reliable measurement of integrity of the composite structure by determining with a comparator connected to the accelerometer whether the impact produces a signal in the accelerometer that has an amplitude above a predetermined threshold;
• (c) if the impact was above the threshold, then measuring the length of time in seconds that the signal remains above a measurement amplitude threshold by triggering a clock upon the rise and fall of the test signal;
• (d) displaying the time as a value on an alphanumeric readout;
• and
• (e) reading the time value displayed on an alphanumeric output display.

A method of detecting defects in composite structure, comprising the steps of:

• (a) manually striking an accelerometer by hand against a composite structure to produce an output signal;
• (b) amplifying the output signal;
• (c) determining whether the output signal exceeds a timing threshold value;
• (d) if the output signal exceeds the timing threshold value, then measuring and recording a time during which the output signal exceeds the timing threshold value with a clock;
• and
• (e) then, displaying the numerical value of the time measured by the clock on an alphanumeric display of the tool.

A method for detecting defects in a composite structure, comprising the steps of:

• (a) manually striking a hammer by hand against a composite structure to define an impact signal in seconds from a tap at a first location which is known to be good, the hammer having an accelerometer attached to a display and a memory;
• (b) recording a good numerical value for the tap in the memory, the good value being the length of time that the amplitude of the impact signal exceeds a predetermined timing threshold as measured by a clock associated with the accelerometer;
• (c) manually striking the hammer a second time by hand against the composite structure defining a test signal for a test tap at a suspect location on the composite structure;
• (d) recording a second numerical value in seconds in the memory being the length of time that the amplitude of the test signal of the test tap is over the timing threshold;
• (e) comparing in a comparator associated with the memory the second numerical value with the good numerical value to determine whether the second value is within an acceptable range;
• and
• (f) generating a signal based upon the comparison indicative of whether the value is in the acceptable range.