Examining composite combinations

Olympus has a heritage of producing testing equipment used in a range of industries. With the growth of composite materials, the company has had to develop solutions suited to these diverse materials which have very different characteristics compared to their metallic counterparts.

“A surface crack on high-performance aluminium is a very different phenomenon compared to delamination defects in an aircraft fuselage structure made with composite materials, for example, so there’s a great diversity of flaws that can occur and that leads to a diversity of products that we offer,” begins Olympus Europa’s senior vertical market specialist, Markus Fabich.

Olympus says when it comes to composites there are three main areas where its technology is used: delamination identification of final parts, carried out by its ultrasonic testers (UT) and other technologies such as its Bondmaster 600; wear and stress resistance confirmation of a process or part, often inspected by microscopy; porosity; and meeting dimensional specifications and gauging thicknesses, again using methods such as UT.

Ultrasonic testing and its further development Phased Array (PA) ultrasound is a form of NDT well established by Olympus for applications such as those found in the aerospace sector. It uses very short pulses of sound waves transmitted into materials to detect internal flaws or to define materials. A common application would be thickness measurement. In the past, it was mainly used for metallic applications, but improvements to the technology mean it can also be used in composites. Phased Array is particularly suited for inspecting materials, such as CFRP, honeycomb and other laminate composites.

With components like aircraft fuselages getting bigger, portability, automation along with operational safety are increasingly important. Olympus’ latest Epoch 6LT ultrasonic flaw detector is an example of a mobile device that can be used for testing composites. Its Focus PX acquisition unit is a phased array device that can be integrated into the manufacturing process to rapidly obtain test results.

Building bonds

Olympus has also developed systems that it says in some circumstances are better suited to testing composites parts.

“The benefits of phased array UT on most materials are clear, but there is a greater diversity of challenges with composites,” Fabich explains. “With these combinations of resins, fibres and other materials the impedance levels can vary substantially. You may have volumes or voids that are not actually a flaw but a feature of the material so interpreting the signal response is more challenging. We produce machines that are specifically designed for composites, such as the Bondmaster 600 designed to produce results when used on composites. The Bondmaster uses sound to find examples of flaws such as delamination, especially at the time of manufacturing.”

The Bondmaster can detect faults such as honeycomb composite skin to core separation; general detection of delamination and areas that have been repaired. It uses methods such as mechanical impedance (MIA) and pitch-catch ultrasonic testing.

Optical options

Microscopy is used to analyse composite samples in minute detail. Olympus microscopes combine high resolution optics with software to create sharp images and the capturing of useful information. In composite materials microscopy is used in cross sections samples to confirm lamination and direction of fibres right down to the submicron scale. Additionally, its 3D laser scanning digital microscopes can test surface roughness and quality. Much of this technology is used by customers at the R&D phase or during failure root case analysis.

Portability and flexibility are naturally important for tests on composites carried out in the field or when an aircraft is on the ground.

The Epoch 6LT can be easily used by operators on large structures consisting of composites such as wings on aircraft or while scaling a large wind turbine.

“It is capable of testing big structures, possibly by rope access and allows single hand use which is a huge benefit in these circumstances,” Fabich continues. “In aerospace, for example, the demands of inflight inspection or MRO are very different from those used during manufacturing. Inflight inspection is driven by the operator. An MRO company may use a handheld flaw detector, such as the Epoch 6LT to check the integrity of a composite fuselage before it can be passed for flight.”

Olympus has plenty of solutions for testing while composite components during the manufacturing process too.

“To produce composite parts the process is more complex than pressing aluminium for instance, so you need good in-process automated inspection to help throughput. The Focus PX is a phased array device which is remotely controllable and programmable. This makes it very useful for integrated, in-process inspection. When it comes to large structures, the same kinds of technology are used for flaw detection in the Focus PX as our portable devices but an OEM or tier 1 supplier may need a large inspection area where an automated probe will screen the whole part.”

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Accessing all areas

In safety-critical industries such as aerospace, inspection has to be carried out regularly to insure damage or wear and tear does not become dangerous. A revolution in inspection technology has taken place with the introduction of Remote Visual Inspection (RVI) through the use of videoscopes, rigid borescopes and flexible fiberscopes and Olympus has been a leading developer of this equipment.

These systems allow inspection of awkward to access areas without the need for disassembly. Large structures such as fuel tanks or wind turbines can be inspected internally using this technology.

“RVI extends the reach of the human eye into small, enclosed spaces that otherwise cannot be seen, using a combination of CCD, LED and video-capturing technologies,” Fabich comments. “A slim and highly flexible viewing device is inserted into the area of interest through a small opening and guided by the operator with a joystick, providing a bright, clear image for the operator to view. Software commonly provides magnification and dimensional measurement of the observed surface.”

One application of this technology is for the inspection of wind turbine blades. Operators using devices such as Olympus’ IPLEX NX can scale turbines and inspect the inside of the blade for problems such as failures in the bonds of fibre-resin parts, blocked drainage holes, condensation, water and ice build-up or to check the blade root close to the hub assembly of the turbine.

Olympus is continuously striving to make its equipment easier to use. This includes software that organizes inspection results for easier comparison. Other advances include new sensors, electronics, displays and interfaces and wi-fi and cloud connectivity ready for developments in Industry 4.0.

Fabich says: “We have different design intentions for a benchtop machine compared to a machine that is used in the hand. Some of our latest equipment for example has automatic recognition of the probe type and its parameters so you don’t have to set up everything from scratch when you attach a new probe. The journey is always ongoing but it is a clear that whatever innovation we have in the future it is the duty of our design team to implement it to contribute to our customers’ workflow in the best possible way.”

www.olympus-ims.com/en/composite-inspection-solutions