INSPECTION OF COMPOSITE COMPONENTS

Abstract

A method and apparatus for scanning a workpiece (100) comprises providing an insert (120) insertable within a countersunk bore (106), the insert (120) being acoustically mounted to the workpiece (100) in order to scan regions below the countersunk area.

Description

A method and apparatus in accordance with the present invention will now be described with reference to the accompanying figures in which:

FIG. 1 is a side section view of a composite component;

FIG. 2 is a side section view of the component of FIG. 1 being scanned from a first direction in accordance with a first prior art method;

FIG. 3 is side section view of the component of FIG. 1 being scanned from a second direction in accordance with a second prior art method;

FIG. 4 is a side section view of the component of FIG. 1 being scanned in accordance with a first embodiment of the present invention; and

FIG. 5 is a side section view of the component of FIG. 1 being scanned in accordance with a second embodiment of the present invention.

The prior art methods of FIGS. 2 and 3 have been described above. Turning to FIG. 4, the composite component 100 is shown provided with an insert 120. The insert 120 comprises a male frustro-conical formation 122 and a relatively short projecting cylindrical portion 124. The insert 120 is shaped to fit into the bore 106 with the male frustro-conical portion 122 fitting into the female frustro-conical portion 110 of the bore 106. The male cylindrical portion 124 fits into the female cylindrical portion 108 of the bore 106. A continuous mating contact is therefore defined between the component bore 106 and the insert 120 shown as boundary surface 126. Preferably, there are no air gaps along the boundary 126. The insert 120 is a press-fit into the bore 106. In order to ensure adequate sonic coupling, the workpiece 100 and insert 120 may be immersed in a couplant liquid (e.g. water) whilst scanning takes place.

The insert 120 is constructed from material which is acoustically matched to the workpiece 100. For example, for a CFRP (carbon fibre reinforced polymer) workpiece 100, the material of the insert 100 may be formed from a plastic with a similar density to CFRP with a speed of sound within 4% of that of CFRP. The material may be constructed from epoxy or polyester, both of which have a speed of sound similar to that of CFRP.

As shown in FIG. 4, as the scanning vector V passes the boundary surface 126, it is refracted slightly towards the normal N by an angle of a few (typically 2) degrees due to the slight difference in the speed of sound of the insert 120 and the workpiece 100. Because the materials are acoustically matched, this angle is not significant and, as such, the resulting adjusted vector V′ is close to the angle of the scanning vector V. As such the region 112 can be scanned successfully. The reflected sound waves are measured by the probe 114 to detect any faults in the first region 112 of the workpiece 100.

Turning to FIG. 5, an alternative set-up is shown in which the ultrasonic probe 114 is moulded into, or insertable into a cavity in an insert 128.

The insert 128 is constructed from material with a significantly different speed of sound to the CFRP workpiece 100 (in this case the speed of sound of the insert 128 is somewhat lower than the workpiece 100), for example it may be constructed from rubber.

The ultrasonic probe 114 is mounted within the insert 128 at an angle to accommodate for the fact that the scanning vector V is refracted away from the normal vector N to provide an adjusted scanning vector V″ which is directed normal to the interior surface 104 of the workpiece 100. As such, the region 112 can be scanned.

The insert 128 is axisymmetric, and as such it can be rotated to scan the circumference of the bore 106.

It will be noted that although the technique of FIG. 5 produces a useful scan, the advantage of the insert of FIG. 4 is that the probe 114 can be swept along the surface of the workpiece 100 without interruption.

Variations fall within the scope of the present invention. For example, the insert may be formed to suit any required shape of female formation within the workpiece 100. The “countersnk” formation need not be frustro-conical in nature, and may be, for example, a cylindrical formation of larger diameter than the main bore, having an annular shoulder between the two, such a formation being suitable to receive an alien-key type fastener.

Other materials may be used to form the insert as long as the ultrasonic probe is adjusted in orientation to ensure that the adjusted scanning vector is approximately perpendicular to the plies of the component.

Claims

1. A method of inspecting a component comprising the steps of: providing an ultrasonic transducer,providing a component to be inspected defining a countersunk bore, which countersunk bore defines a countersunk formation open to a first surface of the component, the component having a first region to be inspected on an opposite side of the countersunk formation to the first surface in a direction perpendicular to the first surface,providing an insert defining a male feature corresponding to the countersunk formation,engaging the male feature in the countersunk formation to define a boundary between the component and the insert,directing ultrasonic energy from the transducer, through the insert, across the boundary and into the first region of the component,inspecting the first region of the component by detecting the ultrasonic energy.

2. A method according to claim 1 in which the component is constructed from a laminar composite material, and the countersunk bore is oriented perpendicular to layers of the laminar composite.

3. A method according to claim 1 in which the insert defines a scanning surface which is parallel to the first surface of the component in use.

4. A method according to claim 3 in which the scanning surface is flush with the first surface of the component.

5. A method according to claim 1 in which the insert is constructed from a material having a speed of sound similar to that of the component.

6. A method according to claim 5 in which the speed of sound of the insert is within 10% of the speed of sound of the component.

7. An apparatus for inspecting a composite component comprising: an insert having a male formation corresponding to a countersunk formation for engaging a corresponding countersunk formation of a composite workpiece bore, the insert having a scanning surface for contact with an ultrasonic probe.

8. An apparatus according to claim 7 in which the male formation comprises a cylindrical portion for engaging in the composite workpiece bore.

9. An apparatus according to claim 7 in which the male formation defines an axis, and the scanning surface is perpendicular to the axis.

10. An apparatus according to claim 9 in which the insert is shaped such that, in use, the scanning surface is flush with a surface of a workpiece in which the bore is defined.

11. An apparatus according to claim 7 in which the insert is primarily constructed from a material having a speed of sound similar to that of CFRP.

12. An apparatus according to claim 11 in which the insert is primarily constructed from epoxy resin or polyester.

13. An apparatus according to claim 7 in which the insert defines a probe receiving formation for receiving a probe in a predetermined position relative to the male formation.

14. An apparatus according to claim 7 in which the insert is axisymmetric.

15. (canceled)

16. (canceled)