NDT of Carbon-NOMEX (honeycomb core) composite: Dynamic loading on a large yacht hull

Mari­ne NDE (Spain) used the tech­ni­cal advan­ta­ges of our She­aro­gra­phy-Sys­tem espe­cial­ly in com­bi­na­ti­on with the dyna­mic exci­ta­ti­on for non-dest­ruc­ti­ve exami­na­ti­on (NDE) of lar­ge are­as such as com­ple­te yacht hul­ls (see image below). The hull with a lenghts of 30,5m was a car­bon-fir­ber-com­po­si­te and part of high per­for­mance sai­ling yacht in build. Becau­se of the full-field method (100% of the inspec­ted area is exami­ned), the tes­ting of the ent­i­re hull requi­red only 240 shots, in three workdays.

 

The yacht hull con­sists of a sand­wich con­struc­tion, whe­re are in par­ti­cu­lar used honey­comb cores (NOMEX).

Marine NDT1Marine NDT2

 

 

 

 

 

 

On the left — A she­aro­gram of a detec­ted bon­d­ing defect (in red oval). The yel­low X marks the loca­ti­on of the core sam­ple shown at the right. The dest­ruc­ti­ve test con­firms the shearogram’s indi­ca­ti­on that the­re is a signi­fi­cant never-bond bet­ween the honey­comb core mate­ri­al and the film adhe­si­ve in this area.

 

Dynamic loading on a wind turbine blade and resin bridges

Analysis of a wind turbine blade

The test panel was an ori­gi­nal sec­tion of a wind tur­bi­ne bla­de with a defect (a foam block with brid­ges). Pre­vious­ly the defect was loca­ted by infil­tra­ti­on of color through small dril­led holes. The sam­ple is exami­ned non-dest­ruc­tively by the SE-Sen­sor.

 

Section RotorBlade-a  Section RotorBlade2

left: Set-up

right: Time average result at fre­quen­cy of 2569Hz showing the debon­d­ing area.

 

 

 

 

Section RotorBlade3Section RotorBlade4left: Live view of sur­face inclu­ding shearing.

right: Time average mea­su­re­ment from the mar­ked area in the live image.

 

 

 

De-bonding of resin bridges

A GFRP sand­wich with foam blocks and resin brid­ges should be exami­ned. The detec­tion of the defect type und struc­tu­re is very quick and reli­able in this case, becau­se the defects are visi­ble, not only at their local natu­ral fre­quen­ci­es, but also due to their for­ced deflec­tion shapes over a wide fre­quen­cy bandwidth.

Section2 RotorBlade

 

The exci­ta­ti­on fre­quen­ci­es of the selec­ted mea­su­re­ments are 1398 Hz (1), 3133 Hz (2), 2442 Hz (3) and 4906 Hz (4) — num­be­ring in fol­lowing images:

Section2 RotorBlade2
 

Vakuum loading on battery packs

Air inclu­si­on or air pockets in modern Li-bat­te­ry packs is a serious and dan­ge­rous pro­blem. The isi-sys SE2 sen­sor is able to detect tiny and lar­ge defects such as air bub­bles, air pockets, cracks and other wit­hin a second. The defects can be far below or near to the sur­face. An examp­le of a bat­te­ry pack (test sam­ple from Uni­ver­si­ty of Munich, IWB) and the mea­su­re­ment result is shown below.

Test set­up:

The test has been done by SE2 sen­sor in com­bi­na­ti­on with a glass vacu­um cham­ber for a simp­le manu­al test. This is an eco­no­mic solu­ti­on for spot NDT by manu­al ser­vice. For auto­ma­ted seri­es test in pro­duc­tion dif­fe­rent set­ups are required.

Test poce­du­re:

The bat­te­ry packs are tes­ted by small pres­su­re dif­fe­ren­ces of some mbar, which can be app­lied in seconds or below in small cham­bers. The sen­sor is moni­to­ring the sur­face of the bat­te­ry pack while the pres­su­re is chan­ged, mea­su­ring the dif­fe­ren­ti­al defor­ma­ti­on of the sur­face. Due to the expan­si­on of the air bub­bles and air pockets, the air inclu­si­ons can be loca­ted such as shown in the fol­lowing images.

The first image shows the live view of the bat­te­ry pack from the sen­sor. The second shows the recont­ruc­ted pha­se, which is cor­re­spon­ding to the local defor­ma­ti­on gradient.

battery pack3

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

battery pack2

Gene­ral­ly the requi­red pres­su­re dif­fe­rence depends on the defect depth, defect size an the mecha­ni­cal stiff­ness of the tes­ted struc­tu­re, but in gene­ral the load is small due to the high sen­si­ti­vi­ty of the sen­sor detec­ting dif­fe­ren­ti­al defor­ma­ti­ons of the surface.

Dynamic excitation on a spacecraft

Historic measurement from 2000

This examp­le com­bi­nes the Vibro­gra­fie Sys­tem with a Pie­zos­ha­ker Modu­le for a non-dest­ruc­ti­ve inspec­tion. The heat shield with C‑Si‑C (car­bon fiber-sili­con com­po­si­te) of the pro­spec­ti­ve reco­very vehicle/ space­craft x38 was review­ed by She­aro­gra­phy.

Spacecraft6

For easier hand­ling, the Pie­zos­ha­ker modu­le is com­pres­sed on the sur­face of the object via a suc­tion base.
(a) Pie­zos­ha­ker modu­le, (b) the heat shield of the space­craft X38 © Flight of the space­craft X38.

x

spacecraft2

The pic­tu­re shows the deter­mi­na­ti­on of times of the heat shield with the natu­ral fre­quen­cy (1400 Hz).

 x

spacecraft3

Local vibra­ti­on forms of defects at 10kHz and 18 kHz of the nose hood in the mar­ked area of the image. During the inspec­tions, two defects have been detec­ted in the upper area of the dog.

NDT on Wind Rotor Blades

First test NDT Mea­su­re­ment by she­aro­gra­phy on a wind tur­bi­ne bla­de in 1996 by P. Mäckel, L. Yang, G. Kup­fer and A. Tie­mich at Kas­sel Uni­ver­si­ty. The object is a spe­cial wind rotor bla­de of a sin­gle wing wind tur­bi­ne ener­gy plant.

RotorBlade

App­lied loading method: Loading by inter­nal pres­su­re (the bla­de has been sea­led). A manu­al pump has been used to incre­a­se a pres­su­re dif­fe­rence against the sur­roun­ding. The frin­ge images show are­as at dif­fe­rent loca­ti­ons. The frin­ges are pro­por­tio­nal to the out of pla­ne defor­ma­ti­on gra­di­ents of the sur­face, which allows to iden­ti­fy inho­mo­ge­ne­ous stiff­ness of the struc­tu­re: left — Dela­mi­na­ti­on; right — Axi­al crack; cen­ter ‑Struc­tu­ral chan­ge over (dif­fe­rent num­ber of glas­fi­ber layers).

 

 

Dynamic loading on a yacht mast

The examp­le shows an app­li­ca­ti­on of NDT on a 30m CFK yacht mast (lower left). The time average result of the SE1 mea­su­re­ment and dyna­mic loading by our Pie­zos­ha­ker (lower right) is indi­ca­ting a lar­ger deli­mi­ta­ti­on below the sur­face star­ting from a small visi­ble crack. Usual­ly, small cracks are often seen on the sur­face, but not all are rela­ted to dela­mi­na­ti­on, which needs any repair.

NDT Yacht   NDT Yacht2


SE1 with Pie­zos­ha­ker for dyna­mic loading


Defect detec­ted by Vibro­gra­phy / dyna­mic loading


Dynamic loading on rudder blade

 

NDTRuder

Detec­tion and mea­su­re­ment of defects on a rud­der bla­de by the SE-Sen­sor and dyna­mic loading.

NDTRuder2

Set­up for mea­su­re­ment on a rud­der by dyna­mic loading.

The direct rigid moun­ting of the sen­sor on the rud­der by the suc­tion cups allows out­door mea­su­re­ment even at strong winds with high fle­xi­bi­li­ty. The high qua­li­ty inter­fe­rence fil­ters of the sen­sor per­mits mea­su­re­ment under day light conditions.

 

NDTRuder3   NDTRuder5  NDTRuder4

A: 9,3 kHz                                            B: 7,5 kHz                                           C: 5,5 kHz

Mea­su­re­ment results (time average) showing local vibra­ti­on modes of defects due to redu­ced or inho­mo­ge­ne­ous stiff­ness of the mate­ri­al. Even if a big field of view is selec­ted, it is pos­si­ble to detect small defects. Defect size and type as well as the depth of the defect (dela­mi­na­ti­on) deter­mi­ne the nor­mal modes (reso­nance fre­quen­cy) of the local defect area.