Effects of the Temperature–Time Regime of Curing of Composite Patch on Repair Process Efficiency

polyme s A icle E ec s o he Tempe a u e–Time Regime o Cu ing o Composi e Pa ch on Repai P ocess E iciency And ii Kond a ie 1, Václa Píš ˇek 2, Lina Smo ziuk 3, Ma yna She so a 4, Anna Fomina 5, Pa el Kuˇce a 2 and Aleš P okop 2,*   Ci a ion: Kond a ie , A.; Píš ˇek, V.; Smo ziuk, L.; She so a, M.; Fomina, A.; Kuˇce a, P.; P okop, A. E ec s o he Tempe a u e–Time Regime o Cu ing o Composi e Pa ch on Repai P ocess E iciency. Polyme s 2021,13, 4342. h ps://doi.o g/10.3390/ polym13244342 Academic Edi o : An onio Pizzi Recei ed: 13 No embe 2021 Accep ed: 9 Decembe 2021 Published: 11 Decembe 2021 Publishe ’s No e: MDPI s ays neu al wi h ega d o ju isdic ional claims in published maps and ins i u ional a il- ia ions. Copy igh : © 2021 by he au ho s. Licensee MDPI, Basel, Swi ze land. This a icle is an open access a icle dis ibu ed unde he e ms and condi ions o he C ea i e Commons A ibu ion (CC BY) license (h ps:// c ea i ecommons.o g/licenses/by/ 4.0/). 1 Depa men o Building Technology and Cons uc ion Ma e ials, O.M. Beke o Na ional Uni e si y o U ban Economy in Kha ki , Ma shal Bazhano S . 17, 61002 Kha ki , Uk aine; [email p o ec ed] 2Ins i u e o Au omo i e Enginee ing, B no Uni e si y o Technology, Technická2896/2, 616 69 B no, Czech Republic; [email p o ec ed].cz (V.P.); [email p o ec ed].cz (P.K.) 3 Depa men o In e na ional P ojec s and P og ams, Na ional Ae ospace Uni e si y “Kha ki A ia ion Ins i u e”, Chkalo a S . 17, 61070 Kha ki , Uk aine; [email p o ec ed] 4Depa men o Composi e S uc u es and A ia ion Ma e ials, Na ional Ae ospace Uni e si y “Kha ki A ia ion Ins i u e”, Chkalo a S . 17, 61070 Kha ki , Uk aine; [email p o ec ed] 5 Depa men o Railway, Au omobile T anspo and Handling Machines, Ins i u e o T anspo and Logis ics, Volodymy Dahl Eas Uk ainian Na ional Uni e si y, Cen al A enue 59a, 93400 Sewe odone sk, Uk aine; [email p o ec ed] *Co espondence: ales.p okop@ u b .cz; Tel.: +420-541-142-261 Abs ac : Repai p ocedu es wi h he use o composi e pa ches a e conside ed o be he mos e ec i e among he cu en echnologies o epai o he s uc u es o a ious applica ions. In he p ocess o moulding-on o a pa ch made o polyme ic composi e ma e ial by means o cu ing, echnological s esses a ise in he pa ch. De e mina ion o esidual echnological s esses is a p io i y ask o he modelling o he epai p ocess. Reduc ion o esidual s esses can be achie ed by op imiza ion o he mode o epai pa ch cu ing. Fo mee ing his objec i e, he me hod o de e mina ion o echnological s esses, which a ise in he s uc u e unde epai in he p ocess o cu ing o a composi e pa ch, has been de eloped. The me hod akes in o accoun he sh inkage, change in physico-mechanical cha ac e is ics, heological p ocesses occu ing in he binde du ing moulding p ocess, and de e mina ion o s esses in he s uc u e unde epai a any ime. The e o e, p ema u e ailu e o he epai join a he s age o epai can be a oided. I is shown ha he me hod adequa ely desc ibes he le el o de o ma ions and s esses in he s uc u e being epai ed a he s age o hea ing and holding o he composi e pa ch. Inc ease in he moulding empe a u e leads o a educ ion in esidual s esses in he s uc u e unde epai . Howe e , cu en s esses a he s ages o hea ing and empe a u e holding a e inc eased signi ican ly. Reliabili y o assump ions and de eloped me hod is con i med by he compa ison wi h he expe imen al da a. The ob ained expe imen al g aph o o al de o ma ion o he composi e pa ch allowed us o clea ly de e mine he momen o esidual s ess occu ence in he s uc u e unde epai . This momen ma ches qui e exac ly (wi h he disc epancy no exceeding 5 min) he gel poin de e mined analy ically based on dependence o he deg ee o cu ing on he moulding mode. Consequen ly, he esea ch oge he wi h he esul s p e iously ob ained allows making an in eg a ed choice o geome ic pa ame e s o he epai composi e pa ch and empe a u e– ime egime o i s cu ing in o de o ensu e he speci ied le el o s eng h and s i ness o he s uc u e unde epai . Keywo ds: empe a u e– ime egime; binde sh inkage; gela ion 1. In oduc ion In he p ocess o ope a ion o a ious s uc u es, de ec s may a ise in a numbe o si ua ions, and de elopmen o such de ec s leads o damage ha p e en s u he use o he s uc u e [ 1 , 2 ]. E ec i e epai o any de ec ed de ec s, including he epai in he ield Polyme s 2021,13, 4342. h ps://doi.o g/10.3390/polym13244342 h ps://www.mdpi.com/jou nal/polyme s Polyme s 2021,13, 4342 2 o 20 condi ions, allows o he p o ec ion o he damaged elemen s [3,4] and o he a oidance o leng hy and cos ly capi al epai s [5,6]. Acco ding o esea ch [ 7 , 8 ], ins alla ion o epai pa ches is conside ed an e ec i e me hod o he epai o de ec s such as den s, ailu es o bea ing skins and delamina ions in he me al and composi e panel s uc u es. High physico-mechanical cha ac e is ics o he mode n polyme ic composi e ma e ials (PCM) [ 9 – 11 ] de e mine success ul use o he composi e pa ches o he epai o bo h polyme ic and me al s uc u es [ 12 , 13 ]. The composi e pa ch can also ha e po en ial applica ions in cons uc ing elec omagne ic nanocomposi es o in elligen ma e ials, as he e is ca bon ma e ials in he composi e [ 14 , 15 ]. Howe e , s esses occu ing in he p ocess o cu ing he epai pa ch u he a ec he bea ing capaci y o epai ed p oduc [ 16 ]. P esence o un eco ded ini ial s esses in he epai ed s uc u e causes he appea ance o de ec s such as delamina ions, buckling and mic oc acks in he binde [ 17 , 18 ], which in u n has a signi ican e ec on he s a ic and a igue s eng h o he p oduc made wi h such s uc u es [19,20]. Reduc ion o esidual s esses can be achie ed by op imiza ion o he mode o epai pa ch cu ing. Technological s esses a e caused by sh inkage o he polyme ic binde , as well as he di e ence in he linea he mal expansion coe icien s o ma e ials o be joined [ 21 ]. Cu ing o he mo- eac i e polyme ic binde as he mos commonly used binde in he epai pa ches o a ious applica ions [ 22 ] is, in ac , he combina ion o a numbe o physico-chemical p ocesses. Thei mu ual in luence de e mines he beha iou o he binde and he na u e o changes in i s main cha ac e is ics. Assessmen o he in luence o pa ame e s o he cu ing mode on he s ess–s ain beha iou o he s uc u e unde epai and choice o hei a ional alues can be pe o med only wi h a se o in e ela ed ma hema ical models o de e mine he cu en alues o iscosi y, sh inkage, deg ee o cu ing and mechanical cha ac e is ics o he PCM a any ime. A signi ican pa o pape s such as [ 23 , 24 ] is ocused on he s udy o kine ics o he mo- eac i e binde cu ing and analy ical modelling o he change in he cu ing deg ee depending on he empe a u e– ime pa ame e s o he p ocess. This ocus is d i en by he ac ha achie emen o high cu ing a es is a p e equisi e o he manu ac u ing o high-s eng h composi e s uc u es [ 25 ]. The a ie y o phenomenological models o cu ing kine ics ound in he li e a u e is explained by signi ican di e ences in he beha iou o a ious binde s [26,27]. The simpli ied model o he binde in he p ocess o cu ing, aking in o accoun s ess elaxa ion, is p oposed in [ 28 ]. This model p o ides he balance o he modelling accu acy and e iciency, which is ex emely necessa y in p ac ice. Modelling and analysis o he he mo- eac i e binde cu ing aking in o accoun g adual changes in he he mal and mechanical p ope ies is p esen ed in [ 29 ]. I is shown ha empo al and spa ial changes in he physical p ope ies o epoxy esin in he cou se o cu ing a ec he elas ic modulus o he cu ed PCM specimens. The pape [ 30 ] p esen s a iscoelas ic model o epoxy esin, depending on empe a u e and deg ee o cu ing. The esul s we e ob ained based on he hypo hesis o ime and empe a u e o e lap. The e ec o he deg ee o cu ing was aken in o accoun h ough glass ansi ion empe a u e, dependen on he cu ing, used as a e e ence empe a u e o he shea coe icien s. The pa e n o modelling o esidual s esses and echnological de o ma ions in he PCM is p oposed in [ 31 ]. Expe imen al compa ison o he modelling esul s o all mechanical cha ac e is ics a all s ages o he phase ans o ma ion o he ma e ial is gi en. Un o una ely, he equa ions ob ained o modelling o all key p ocesses associa ed wi h he empe a u e cycle o ha dening o he he moplas ic ma ix a e p esen ed oge he wi h he co esponding ma e ial cons an s using he example o polye he e he ke one (PEEK) only. The me hod o p edic ing he dis ibu ion o esidual s esses in PCM caused by he echnological p ocess in he cou se o binde cu ing is p oposed in [ 32 ]. Dis ibu ions o he empe a u e and deg ee o cu ing we e ob ained. The elas ic modulus o he binde was de e mined using a model o ins an aneous linea elas ici y a cu ing. Polyme s 2021,13, 4342 3 o 20 The analy ical model o eco ding o he mo iscoelas ic e ec s on he esidual s esses o composi e pa s du ing he cu ing p ocess is de eloped in [ 33 ]. Viscoelas ic e ec s on he esidual s esses and elas ici y due o angen ial and adial he mochemical expansion a e conside ed sepa a ely in o de o help unde s and hei indi idual in luence. The pape s [ 34 , 35 ] deal wi h he change in dis ibu ion o he ield o esidual s esses in he specimen o ma e ial AS4/8552-1 wi h he lay-up o (0 ◦ /90 ◦ ) in he p ocess o cu ing. To simula e he cu ing, he coupled he mal and s eng h p oblem is sol ed unde plane de o ma ion condi ions. A common disad an age o he pape s conside ed is ha hey ocus only on he me hod o s ess de e mina ion, wi hou paying due a en ion o he cu ing p ocess i sel . As a esul , hey do no ake in o accoun he change in he PhMC o he composi e ma e ial du ing he cu ing p ocess, and conside he esidual s esses caused by he empe a u e componen , only wi hou aking in o accoun he sh inkage. In many pape s, only he cooling s age is conside ed, i.e., s esses a ising du ing he hea ing p ocess a e un easonably neglec ed. An excep ion is [ 36 ], whe e he s ess–s ain beha iou is de e mined, aking in o accoun he p e iously de eloped kine ic model o he binde pe o mance in he cu ing p ocess, as well as [ 34 , 35 ], p o iding he model o beha iou o iscoelas ic ma e ial o desc ibe he PCM ope a ion in he manu ac u ing p ocess, including he p ocesses o o ma ion, polyme iza ion, and de elopmen o esidual de o ma ions and s esses. The esul s o a numbe o expe imen al s udies a e o g ea impo ance o unde - s anding he mechanisms o occu ence o empe a u e s esses in he p ocess o cu ing o he epai pa ch and possible ways o educe hem [ 37 , 38 ]. S udy o he empe a u e de o ma ions occu ing in he s uc u e unde a ious empe a u e and ime condi ions o polyme iza ion a e deal wi h in [ 39 , 40 ]. Howe e , he expe imen al measu emen o esidual s esses a cu ing is o en an expensi e and di icul p ocess [ 41 ]. The e o e, esul s o expe imen al s udies in a numbe o wo ks a e supplemen ed wi h he da a ob ained using he ini e elemen modelling [ 42 , 43 ]. I allowed he au ho s o gi e some ecom- menda ions ega ding he choice o op imal pa ame e s o he epai p ocess [ 44 ]. The pape [ 45 ] p oposes a mul iscale model o p edic ion o esidual s esses o composi es in he p ocess o cu ing. Howe e , he main disad an age o he nume ical app oach is ha he ini e elemen model is c ea ed o a s ic ly de ined s uc u e and canno be a bi a ily ex ended o simila elemen s and manu ac u ing p ocesses [46]. Thus, i can be said ha , e en as he p oblem o de e mining he esidual echno- logical s esses in panels epai ed by a composi e pa ch is discussed in mode n li e a u e om a ious posi ions, he s udies conside ed do no ake in o accoun a numbe o signi ican ac o s. The objec i e o he wo k is o de elop a me hod o de e mining he echnological s esses a ising in he s uc u e unde epai in he p ocess o cu ing o he composi e pa ch, which would ake in o accoun he sh inkage, changes in physico-mechanical cha ac e is ics and heological p ocesses occu ing in he binde du ing he moulding p ocess. Figu e 1 shows he esea ch low cha . Polyme s 2021,13, 4342 4 o 20 Polyme s 2021, 13, x FOR PEER REVIEW 4 o 22 Figu e 1. The esea ch low cha . 2. Ma e ials and Me hods To de e mine he s ess–s ain beha iou o he s uc u e in he p ocess o cu ing o he composi e pa ch, ad anced ma hema ical model o a panel o s ep- a iable hickness was used [47]. The ma hema ical model o he change in he PCM physical and mechanical cha ac e is ics in he p ocess o cu ing o he composi e pa ch was de eloped o aking in o accoun he echnological s esses a ising in he p ocess o he composi e pa ch moulding-on. In he amewo k o his model, o he de e mina ion o kine ics o cu ing, iscosi y and sh inkage o he binde , empi ical dependences o hese pa ame e s on he empe a u e and ime o cu ing ob ained in [48,49] on he esul s o iso he mal and dynamic calo ime ic es s o he epoxy binde Hysol EA9396 (Henkel, Bay Poin , CA, USA) we e used. In he p ocess o cons uc ion o he ma hema ical model, aking in o accoun a sha p change in he binde iscosi y du ing ansi ion om he liquid o he elas ic s a e, i was assumed ha echnological s esses would a ise in he s uc u e a e gela ion o he binde only. The linea dependence o he elas ic modulus on he deg ee o cu ing was aken. Addi ionally, i was assumed ha Poisson’s a io and coe icien o linea he mal expansion o he binde we e no dependen on he deg ee o cu ing, wi h he linea he mal expansion coe icien being he known unc ion o empe a u e. Dependences o he cu en elas ic cha ac e is ics o he monolaye a a pa icula momen o cu ing on he cha ac e is ics o he ib e and ma ix we e de e mined om he known dependences o he ein o ced media mechanics [50,51]. Wo en ein o cing ma e ial was conside ed as a package, consis ing o wo iden ical monolaye s wi h laying angles o [0°, 90°]. Technological s esses in he s uc u e unde epai we e de e mined as a sum o s esses a ising in sepa a e ime in e als, wi hin which he empe a u e and sh inkage Figu e 1. The esea ch low cha . 2. Ma e ials and Me hods To de e mine he s ess–s ain beha iou o he s uc u e in he p ocess o cu ing o he composi e pa ch, ad anced ma hema ical model o a panel o s ep- a iable hick- ness was used [ 47 ]. The ma hema ical model o he change in he PCM physical and mechanical cha ac e is ics in he p ocess o cu ing o he composi e pa ch was de eloped o aking in o accoun he echnological s esses a ising in he p ocess o he composi e pa ch moulding-on. In he amewo k o his model, o he de e mina ion o kine ics o cu ing, iscosi y and sh inkage o he binde , empi ical dependences o hese pa ame e s on he empe a u e and ime o cu ing ob ained in [ 48 , 49 ] on he esul s o iso he mal and dynamic calo ime ic es s o he epoxy binde Hysol EA9396 (Henkel, Bay Poin , CA, USA) we e used. In he p ocess o cons uc ion o he ma hema ical model, aking in o accoun a sha p change in he binde iscosi y du ing ansi ion om he liquid o he elas ic s a e, i was assumed ha echnological s esses would a ise in he s uc u e a e gela ion o he binde only. The linea dependence o he elas ic modulus on he deg ee o cu ing was aken. Addi ionally, i was assumed ha Poisson’s a io and coe icien o linea he mal expansion o he binde we e no dependen on he deg ee o cu ing, wi h he linea he mal expansion coe icien being he known unc ion o empe a u e. Dependences o he cu en elas ic cha ac e is ics o he monolaye a a pa icula momen o cu ing on he cha ac e is ics o he ib e and ma ix we e de e mined om he known dependences o he ein o ced media mechanics [ 50 , 51 ]. Wo en ein o cing ma e ial was conside ed as a package, consis ing o wo iden ical monolaye s wi h laying angles o [ 0◦, 90◦ ]. Technological s esses in he s uc u e unde epai we e de e mined as a sum o s esses a ising in sepa a e ime in e als, wi hin which he empe a u e and sh inkage Polyme s 2021,13, 4342 5 o 20 s esses we e caused by co esponding changes in empe a u e and sh inkage; he elas ic modulus and he coe icien o linea he mal expansion o he binde we e cons an . The numbe o a eas o di ision was de e mined by he equi ed compu a ional accu acy. Reliabili y o he cons uc ed ma hema ical model is con i med by compa ison wi h he esul s o expe imen al s udies o de o ma ions a ising in he aluminium panel and ca bon ib e composi e pa ch in he moulding-on p ocess. To do his, a ca bon ib e composi e pa ch (EA9396/Ca bon 3K-70-P, Henkel, Bay Poin , CA, USA) wi h a lay-up pa e n o (0 ◦ ; 90 ◦ ) was laid on p e ab ica ed specimen o he aluminium alloy 2024T3 (TW Me als Co po a e Headqua e s, Ex on, PA, USA) by we me hod. Thickness o he pa ch a e cu ing was 2.2 ± 0.07 mm. De o ma ions a ising in he es ed s uc u e in he p ocess o cu ing o he composi e pa ch we e measu ed using KF5P1-20-400 (VEDA G oup o Companies, Kyi , Uk aine) s ain gauges. To implemen he selec ed cu ing modes o he epai pa ch, he he mal o en p o iding he uni o m hea ing o e he en i e a ea o he specimen was used. Fo mo e accu a e empe a u e con ol, an addi ional he mocouple was ins alled di ec ly on he es specimen. Due o small hickness o he specimen and wo- way hea ing p o ided in he u nace, une en empe a u e dis ibu ion o e he hickness was no aken in o accoun . To p e en he impac o he in e nal empe a u e de o ma ions o he s ain gauge on he esul s o he expe imen , s ain gauges we e connec ed o he measu ing sys em aking in o accoun he he mal compensa ion 3. Theo e ical Backg ound As s a ed abo e, i is no possible o cons uc he gene al cu ing model sui able o any he mo- eac i e binde [ 23 , 24 ]. This is due o signi ican di e ence in he beha iou o a ious ypes o polyme s [22]. Epoxy binde Hysol EA9396 (Henkel), widely used o epai s in he o eign a ia ion indus y, was chosen o he esea ch. To de e mine he kine ics o cu ing, iscosi y and sh inkage o he binde EA 9396, empi ical dependences cons uc ed in [ 48 , 49 ] unde he in e na ional p ojec SENARIO (AST5-CT-2006-030982) wi h he inancial suppo o he Eu opean Commission we e used, based on he esul s o iso he mal and dynamic calo ime ic es s and expe imen al s udy o sh inkage. Figu e 2shows he g aphs o changes in he abo emen ioned cha ac e is ics a he cu ing mode ecommended by he binde manu ac u e . Polyme s 2021, 13, x FOR PEER REVIEW 5 o 22 s esses we e caused by co esponding changes in empe a u e and sh inkage; he elas ic modulus and he coe icien o linea he mal expansion o he binde we e cons an . The numbe o a eas o di ision was de e mined by he equi ed compu a ional accu acy. Reliabili y o he cons uc ed ma hema ical model is con i med by compa ison wi h he esul s o expe imen al s udies o de o ma ions a ising in he aluminium panel and ca bon ib e composi e pa ch in he moulding-on p ocess. To do his, a ca bon ib e composi e pa ch (EA9396/Ca bon 3K-70-P, Henkel, Bay Poin , CA, USA) wi h a lay-up pa e n o (0°; 90°) was laid on p e ab ica ed specimen o he aluminium alloy 2024T3 (TW Me als Co po a e Headqua e s, Ex on, PA, USA) by we me hod. Thickness o he pa ch a e cu ing was 2.2 ± 0.07 mm. De o ma ions a ising in he es ed s uc u e in he p ocess o cu ing o he composi e pa ch we e measu ed using KF5P1-20-400 (VEDA G oup o Companies, Kyi , Uk aine) s ain gauges. To implemen he selec ed cu ing modes o he epai pa ch, he he mal o en p o iding he uni o m hea ing o e he en i e a ea o he specimen was used. Fo mo e accu a e empe a u e con ol, an addi ional he mocouple was ins alled di ec ly on he es specimen. Due o small hickness o he specimen and wo-way hea ing p o ided in he u nace, une en empe a u e dis ibu ion o e he hickness was no aken in o accoun . To p e en he impac o he in e nal empe a u e de o ma ions o he s ain gauge on he esul s o he expe imen , s ain gauges we e connec ed o he measu ing sys em aking in o accoun he he mal compensa ion 3. Theo e ical Backg ound As s a ed abo e, i is no possible o cons uc he gene al cu ing model sui able o any he mo- eac i e binde [23,24]. This is due o signi ican di e ence in he beha iou o a ious ypes o polyme s [22]. Epoxy binde Hysol EA9396 (Henkel), widely used o epai s in he o eign a ia ion indus y, was chosen o he esea ch. To de e mine he kine ics o cu ing, iscosi y and sh inkage o he binde EA 9396, empi ical dependences cons uc ed in [48,49] unde he in e na ional p ojec SENARIO (AST5-CT-2006-030982) wi h he inancial suppo o he Eu opean Commission we e used, based on he esul s o iso he mal and dynamic calo ime ic es s and expe imen al s udy o sh inkage. Figu e 2 shows he g aphs o changes in he abo emen ioned cha ac e is ics a he cu ing mode ecommended by he binde manu ac u e . Wi h he use o hese models and based on he ac ha a sha p change in he binde iscosi y co esponds o i s ansi ion om he liquid o elas ic s a e [25], calcula ions showed ha , a he ime o gela ion, he deg ee o he binde cu ing was equal o 52%. Wi h he inc ease in he deg ee o he binde cu ing, he change in i s elas ic cha ac e is ics occu s [26,27,29]. Figu e 2. Change in iscosi y (η), sh inkage (ξ) and deg ee o cu ing (θ) o he binde EA 9396 a he cu ing mode ecommended by he manu ac u e [48,49]. Figu e 2. Change in iscosi y ( η ), sh inkage ( ξ ) and deg ee o cu ing ( θ ) o he binde EA 9396 a he cu ing mode ecommended by he manu ac u e [48,49]. Wi h he use o hese models and based on he ac ha a sha p change in he binde iscosi y co esponds o i s ansi ion om he liquid o elas ic s a e [ 25 ], calcula ions showed ha , a he ime o gela ion, he deg ee o he binde cu ing was equal o 52%. Wi h he inc ease in he deg ee o he binde cu ing, he change in i s elas ic cha ac e - is ics occu s [26,27,29]. Assuming he linea dependence o he elas ic modulus on he deg ee o cu ing and aking in o accoun he sha p change in he elas ic modulus du ing passing h ough he gel Polyme s 2021,13, 4342 6 o 20 poin expe imen ally p o en in [ 50 ], we use he unc ion below o se ing o he binde elas ic modulus Eb( ) = (0, < g Eθ=100% bθ, ≥ g , (1) whe e θ —cu en alue o he deg ee o cu ing; g —gela ion ime; Eθ=100% b —binde elas ic modulus a 100% deg ee o cu ing. Assuming ha a e gela ion he Poisson’s a io and he binde linea he mal expan- sion coe icien change insigni ican ly, we conside hem independen o he deg ee o cu ing. Howe e , we ake in o accoun a signi ican change in he binde linea he mal expansion coe icien on he empe a u e T. Dependence o he elas ic cha ac e is ics o ini ial PCM componen s ( ib e and ma ix) on he empe a u e will be neglec ed because o a sligh change in hese p ope ies a low cu ing empe a u es [ 22 ]. Dependences o he cu en elas ic cha ac e is ics o he monolaye a a pa icula momen o cu ing on he cha ac e is ics o he ib e and ma ix we e de e mined using he known dependen- cies [51,52]: E1( ) = E Θ+Eb( )(1−Θ),E2( ) = E Eb( ) Eb( )Θ+E (1−Θ), G12( ) = G Gb( ) Gb( )Θ+G (1−Θ),µ12(T) = µ Θ+µb(1−Θ), α1( ) = E α Θ+Eb( )αb(T)(1−Θ) E Θ+Eb( )(1−Θ), α2( ) = (α Θ+αb(T)(1−Θ))(E Θ+Eb( )(1−Θ)) E Θ+Eb( )(1−Θ)+ Θ(1−Θ)(αb(T)−α )(E µb−Eb( )µ ) E Θ+Eb( )(1−Θ), ξ1( ) = Ebξb(1−Θ) E Θ+Eb( )(1−Θ), ξ2( ) = E Θ+Eb( )(1−Θ)+Θ(E µb−Eb( )µ ) E Θ+Eb( )(1−Θ)(1−Θ)ξb,                                            (2) whe e E ,E b ,G ,G b , µ , µb , ξ , ξb —elas ic modulus, shea modulus, Poisson’s a ios, ib e and binde sh inkage, acco dingly; Θ— ela i e olume ic con en o ib es. Wo en ein o cing ma e ial is conside ed as a package consis ing o wo iden ical monolaye s wi h laying angles o [0◦, 90◦], o which [34,46]: Ex=Ey=E1 2+E2 2−2E2 1µ2 21 E1+E2;Gxy =G12, αx=αy=(α1E1 2+α2E2 2+α1+α2 2E1µ21)( E1 2+E2 2−E1µ21) (E1 2+E2 2)2−E2 1µ2 21 , ξx=ξy=(ξ1E1 2+ξ2E2 2+ξ1+ξ2 2E1µ21)( E1 2+E2 2−E1µ21) (E1 2+E2 2)2−E2 1µ2 21 ,                    (3) whe e E1=E1 1−µ12µ21 ,E2=E2 1−µ12µ21 . In o de o de e mine he s ess–s ain beha iou o he s uc u e unde epai , we apply he analy ical model o a panel o s ep- a iable hickness [ 19 ]. Now we shall analyse he ex e nal and in e nal o ce ac o s leading o he appea ance o s esses in he s uc u e unde epai , using he example o ypical empe a u e– ime dependence o he polyme ic binde cu ing mode (Figu e 3) [19,22]. Polyme s 2021,13, 4342 7 o 20 Polyme s 2021, 13, x FOR PEER REVIEW 7 o 22 he ex e nal and in e nal o ce ac o s leading o he appea ance o s esses in he s uc u e unde epai , using he example o ypical empe a u e– ime dependence o he polyme ic binde cu ing mode (Figu e 3) [19,22]. Figu e 3. Typical empe a u e– ime dependence o he polyme ic binde cu ing mode Taking in o accoun ha echnological s esses occu in he s uc u e only a e gela ion (poin O) [25,29,31], he ypical cu ing p ocess can be oughly di ided in o ou s ages, as shown in Figu e 3. A he i s s age, occu ence and g ow h o s esses is de e mined by hea ing and a ailable sh inkage de o ma ions. When me al s uc u es a e epai ed using he composi e pa ch, he mal and sh inkage s esses can ha e he same sign a he de ini e a io o he linea he mal expansion coe icien and s i nesses [19]. In his case, empe a u e s esses supplemen ed wi h sh inkage ones may lead o occu ence o de ec s al eady in he hea ing p ocess, since physico-mechanical cha ac e is ics o he pa ch ma e ial a he i s s age a e conside ably lowe han he inal alues. I de e mines he need o con ol he s esses a poin A. Du ing he iso he mal holding (AC), s esses esul om he con inuing sh inkage (II) and elaxa ion p ocesses (III) [28,32,33]. A he ou h s age, he occu ing s esses a e de e mined by cooling o he s uc u e being epai ed and he ongoing elaxa ion p ocesses. The inal echnological s esses a poin D summa ize he s esses a all p e ious s ages and a e subjec o con ol [22]. Unde ce ain condi ions, a each s age he e ec i e ol ages can exceed he cu en pe missible alues. I de e mines he need o con ol bo h he esidual s esses (poin D), and he cu en s esses a design poin s A, B and C [47]. In o de o de e mine he s ess–s ain beha iou o he s uc u e wi h he cha ac e is ics changing in he cu ing p ocess, a ising s esses a e de e mined as a sum o s esses on he ce ain a eas, wi hin which [19]: • The mal and sh inkage s esses a e caused by co esponding inc ease in he empe a u e and sh inkage ∆=−; ∆=−; (4) • Elas ic modulus o he binde is aken o be cons an and equal o = 󰇛󰇜  ; (5) • The binde linea he mal expansion coe icien is aken o be cons an and equal o  = 󰇛󰇜  . (6) The numbe o a eas o di ision is de e mined by he equi ed compu a ional accu acy. Figu e 3. Typical empe a u e– ime dependence o he polyme ic binde cu ing mode. Taking in o accoun ha echnological s esses occu in he s uc u e only a e gela ion (poin O) [ 25 , 29 , 31 ], he ypical cu ing p ocess can be oughly di ided in o ou s ages, as shown in Figu e 3. A he i s s age, occu ence and g ow h o s esses is de e mined by hea ing and a ailable sh inkage de o ma ions. When me al s uc u es a e epai ed using he composi e pa ch, he mal and sh inkage s esses can ha e he same sign a he de ini e a io o he linea he mal expansion coe icien and s i nesses [ 19 ]. In his case, empe a u e s esses supplemen ed wi h sh inkage ones may lead o occu ence o de ec s al eady in he hea ing p ocess, since physico-mechanical cha ac e is ics o he pa ch ma e ial a he i s s age a e conside ably lowe han he inal alues. I de e mines he need o con ol he s esses a poin A. Du ing he iso he mal holding (AC), s esses esul om he con inuing sh inkage (II) and elaxa ion p ocesses (III) [28,32,33]. A he ou h s age, he occu ing s esses a e de e mined by cooling o he s uc u e being epai ed and he ongoing elaxa ion p ocesses. The inal echnological s esses a poin D summa ize he s esses a all p e ious s ages and a e subjec o con ol [22]. Unde ce ain condi ions, a each s age he e ec i e ol ages can exceed he cu en pe missible alues. I de e mines he need o con ol bo h he esidual s esses (poin D), and he cu en s esses a design poin s A, B and C [47]. In o de o de e mine he s ess–s ain beha iou o he s uc u e wi h he cha ac e is- ics changing in he cu ing p ocess, a ising s esses a e de e mined as a sum o s esses on he ce ain a eas, wi hin which [19]: • The mal and sh inkage s esses a e caused by co esponding inc ease in he empe a- u e and sh inkage ∆Ti=Ti+1−Ti;∆ξi=ξi+1−ξi; (4) •Elas ic modulus o he binde is aken o be cons an and equal o Ei b=1 i+1− iZ i+1 i E( )d ; (5) •The binde linea he mal expansion coe icien is aken o be cons an and equal o αi b=1 Ti+1−TiZTi+1 Ti α(T)dT. (6) The numbe o a eas o di ision is de e mined by he equi ed compu a ional accu acy. The basis o op imiza ion o he s uc u e epai using PCM is he analysis o he in luence o indi idual pa ame e s o he epai pa ch cu ing p ocess. They can be oughly di ided in o wo g oups: •Cu ing p ocess pa ame e s; Polyme s 2021,13, 4342 8 o 20 •Repai p ocess pa ame e s. Among he pa ame e s o he moulding mode, signi ican e ec on he s ess–s ain beha iou is exe ed, i s o all, by cu ing empe a u e ( Tc ), hea ing a e ( V1 ) and cooling a e ( V2 ) o he s uc u e unde epai . Holding ime a Tc de e mines he deg ee o cu ing o he epai pa ch and a ec s no so much he s ess–s ain beha iou , bu physico-mechanical cha ac e is ics o he PCM. The second g oup o pa ame e s should include he condi ions o he s uc u e ixa ion du ing he epai p ocess, me hod o implemen ing he empe a u e– ime egime, and p esence o addi ional ex e nal loads. Le ’s in es iga e he s ess–s ain beha iou o he la ec angula panel (Figu e 4) made o he aluminium alloy 2024T3, o he pa ame e s below: •Cu ing empe a u e Tc; •Hea ing a e V1; •Condi ions o he s uc u e ixa ion in he epai p ocess; •Hea ing me hod. Polyme s 2021, 13, x FOR PEER REVIEW 8 o 22 The basis o op imiza ion o he s uc u e epai using PCM is he analysis o he in luence o indi idual pa ame e s o he epai pa ch cu ing p ocess. They can be oughly di ided in o wo g oups: • Cu ing p ocess pa ame e s; • Repai p ocess pa ame e s. Among he pa ame e s o he moulding mode, signi ican e ec on he s ess–s ain beha iou is exe ed, i s o all, by cu ing empe a u e (), hea ing a e () and cooling a e () o he s uc u e unde epai . Holding ime a  de e mines he deg ee o cu ing o he epai pa ch and a ec s no so much he s ess–s ain beha iou , bu physico- mechanical cha ac e is ics o he PCM. The second g oup o pa ame e s should include he condi ions o he s uc u e ixa ion du ing he epai p ocess, me hod o implemen ing he empe a u e– ime egime, and p esence o addi ional ex e nal loads. Le ’s in es iga e he s ess–s ain beha iou o he la ec angula panel (Figu e 4) made o he aluminium alloy 2024T3, o he pa ame e s below: • Cu ing empe a u e ; • Hea ing a e ; • Condi ions o he s uc u e ixa ion in he epai p ocess; • Hea ing me hod. Figu e 4. Geome ic pa ame e s o he in es iga ed s uc u e unde epai Repai o he s uc u e unde s udy is ca ied ou by ins alling a ec angula ca bon ib e composi e pla e. Physico-mechanical cha ac e is ics o he ini ial PCM componen s a e gi en in Table 1 [49]. Table 1. Physico-mechanical cha ac e is ics o ini ial PCM componen s Ini ial Componen s Binde EA9396 Ca bon Fib e Cha ac e is ics Elas ic modulus, MPa 2750 290,000 Poisson’s a io 0.35 0.07 Linea he mal expansion coe icien α·10−6, 1/C 85 a T ≤ 65 °C$$75 a 65 °C < T ≤ 95 °C$$70 a 95 °C < T ≤ 105 °C$$65 a 105 °C < T ≤ 125 °C$$50 a T > 125 °C −0.64 Volume ic con en in PCM 0.45 0.55 Fo he modes p esen ed in Table 2, s ess–s ain beha iou occu ing du ing epai o he analysed s uc u e in a ee s a e has been de e mined. In his case, he bounda y condi ions co esponded o he hinge moun o he panel a he cen al poin , ensu ing i s un es ic ed de o ma ion in he moulding p ocess. The uni o m empe a u e se ing o e he en i e s uc u e a ea modelled he pa ch cu ing in he o en. Non-uni o mi y o Figu e 4. Geome ic pa ame e s o he in es iga ed s uc u e unde epai . Repai o he s uc u e unde s udy is ca ied ou by ins alling a ec angula ca bon ib e composi e pla e. Physico-mechanical cha ac e is ics o he ini ial PCM componen s a e gi en in Table 1[49]. Table 1. Physico-mechanical cha ac e is ics o ini ial PCM componen s. Cha ac e is ics Ini ial Componen s Binde EA9396 Ca bon Fib e Elas ic modulus, MPa 2750 290,000 Poisson’s a io 0.35 0.07 Linea he mal expansion coe icien α·10−6, 1/C 85 a T≤65 ◦C 75 a 65 ◦C < T≤95 ◦C 70 a 95 ◦C < T≤105 ◦C 65 a 105 ◦ C < T ≤ 125 ◦ C 50 a T> 125 ◦C −0.64 Volume ic con en in PCM 0.45 0.55 Fo he modes p esen ed in Table 2, s ess–s ain beha iou occu ing du ing epai o he analysed s uc u e in a ee s a e has been de e mined. In his case, he bounda y condi ions co esponded o he hinge moun o he panel a he cen al poin , ensu ing i s un es ic ed de o ma ion in he moulding p ocess. The uni o m empe a u e se ing o e he en i e s uc u e a ea modelled he pa ch cu ing in he o en. Non-uni o mi y o empe a u e o e he hickness was no aken in o accoun because o he small hickness o pa s and he p esence o a wo-way hea supply. Polyme s 2021,13, 4342 9 o 20 Table 2. Pa ame e s o analysed cu ing modes. Numbe o Regime Hea ing Ra e V,◦C/min Cu ing Tempe a u e Tc,◦C Cu ing Time c,◦min No e 1 – 25 7200 S anda d mode ecommended by he manu ac u e [49] 2 1 90 60 Mode No.1 + addi ional hea ea men 3 1 66 60 Accele a ed mode, ecommended by he manu ac u e 4 1 70 60 – 5 1 90 60 – 6 1 120 60 – 7 1 150 – – 8 0.5 90 60 – 9 3 90 60 – 10 5 90 60 – Da a ob ained as a esul o calcula ions a e p esen ed in he o m o : • Pic u es o s ess dis ibu ion in he panel and pa ch a he s age o empe a u e holding and a e cooling o he s uc u e (Figu e 5); • Diag ams o maximum s esses in he s uc u e du ing moulding a di e en empe a- u es (Figu e 6); • Diag ams o maximum s esses in he s uc u e du ing moulding a di e en hea ing a es (Figu e 7). Polyme s 2021, 13, x FOR PEER REVIEW 9 o 22 empe a u e o e he hickness was no aken in o accoun because o he small hickness o pa s and he p esence o a wo-way hea supply. Table 2. Pa ame e s o analysed cu ing modes. Numbe o Regime Hea ing Ra e $$V, °C/min Cu ing $$Tempe a u e Tc, °C Cu ing $$Time c, °min No e 1 – 25 7200 S anda d mode ecommended $$by he manu ac u e [49] 2 1 90 60 Mode No.1 + addi ional$$hea ea men 3 1 66 60 Accele a ed mode, ecommended by he manu ac u e 4 1 70 60 – 5 1 90 60 – 6 1 120 60 – 7 1 150 – – 8 0.5 90 60 – 9 3 90 60 – 10 5 90 60 – Da a ob ained as a esul o calcula ions a e p esen ed in he o m o : • Pic u es o s ess dis ibu ion in he panel and pa ch a he s age o empe a u e holding and a e cooling o he s uc u e (Figu e 5); • Diag ams o maximum s esses in he s uc u e du ing moulding a di e en empe a u es (Figu e 6); • Diag ams o maximum s esses in he s uc u e du ing moulding a di e en hea ing a es (Figu e 7). Figu e 5. Dis ibu ion o no mal s esses σx in he aluminium panel (a,b) and epai pa ch (c,d) on comple ion o he empe a u e holding a Tc and cooling. Figu e 5. Dis ibu ion o no mal s esses σx in he aluminium panel ( a , b ) and epai pa ch ( c , d ) on comple ion o he empe a u e holding a Tcand cooling. Polyme s 2021, 13, x FOR PEER REVIEW 10 o 22 Figu e 6. Maximum no mal s esses occu ing in he aluminium panel (a) and composi e pa ch (b) a di e en cu ing empe a u es. Figu e 7. Maximum no mal s esses occu ing in he aluminium panel (a) and composi e pa ch (b) a di e en hea ing a es (V1). Fo he mode No.5 (see Table 2) he s ess–s ain beha iou occu ing in he p ocess o epai o he s uc u e unde s udy wi hou p elimina y disman ling wi h he use o ine- ib e esis i e s uc u e in he hea ed ool was also calcula ed [19]. In his case, bounda y condi ions co esponded o he hinge moun o he s uc u e along he con ou . Se ing o he empe a u e on he su ace a ea being 15 mm la ge han he pa ch on each side modelled he local hea ing using he he mal blanke [19]. Figu e 8 shows he quali y pic u e o he dis ibu ion o no mal s esses in he aluminium panel unde epai and pa ch a he s age o hea ing and a e cooling o he s uc u e. Figu e 9 shows he maximum alues o no mal s esses a ising in he s uc u e unde a ious epai condi ions. Figu e 6. Maximum no mal s esses occu ing in he aluminium panel ( a ) and composi e pa ch ( b ) a di e en cu ing empe a u es. Polyme s 2021,13, 4342 16 o 20 Polyme s 2021, 13, x FOR PEER REVIEW 16 o 22 Figu e 15. Change in he empe a u e, deg ee o cu ing (a) and de o ma ions occu ing (b) in he aluminium panel unde epai and composi e pa ch in he p ocess o cu ing acco ding o he mode 3 (Table 3). (a) (b) Figu e 16. Change in he empe a u e, deg ee o cu ing (a) and de o ma ions occu ing (b) in he aluminium panel unde epai and composi e pa ch in he p ocess o cu ing acco ding o he mode 4 (Table 3). Nume ical alues o de o ma ions a con ol poin s C (holding comple ion o he cooling a =) and D (comple ion o cooling s age) o all in es iga ed modes a e summa ized and analysed in Table 4. Table 4. Compa ison o esul s o heo e ical calcula ions and expe imen al s udies. Poin De o ma ions in Ca bon Fib e Composi e Pa ch De o ma ions in Aluminium Panel Shea De o ma io n Exp. Analy ical E o , % Exp. Analy ical E o , % Analy ical Cu ing mode 1 C −1.69 × 10−4 −1.60 × 10−4 5.79% 3.59 × 10−4 3.43 × 10−4 4.70% 5.31 × 10−5 D 5.05 × 10−5 1.89 × 10−4 — −7.55 × 10−4 −8.53 × 10−4 12.29% −6.21 × 10−5 Cu ing mode 2 C −3.06 × 10−4 −2.85 × 10−4 7.07% 8.11 × 10−4 7.78 × 10−4 4.12% 1.10 × 10−4 D 2.63 × 10−5 1.61 × 10−4 — −7.19 × 10−4 −8.21 × 10−4 13.35% −5.47 × 10−5 Figu e 16. Change in he empe a u e, deg ee o cu ing ( a ) and de o ma ions occu ing ( b ) in he aluminium panel unde epai and composi e pa ch in he p ocess o cu ing acco ding o he mode 4 (Table 3). Inc ease in he di e ence be ween he expe imen al and heo e ical alues a he cooling s age is explained by he p esence o elaxa ion p ocesses, which we e no aken in o accoun in he heo e ical calcula ions because o lack o heological cha ac e is ics o he ma e ials used. Taking hese p ocesses in o accoun will imp o e he calcula ion accu acy, as well as p o ide an addi ional oppo uni y o op imize he cooling mode (selec ion o empe a u e holdings) and o u he educe he le el o esidual s esses. The pe missible le el o esidual s esses in he epai ed s uc u e is no a gua an ee o high-quali y epai , since he cu en s esses can signi ican ly exceed he esidual s esses and lead o appea ance o hidden de ec s (c acks, delamina ion) o e en he ailu e o he epai join al eady in he cu ing p ocess (as in expe imen No. 2 Figu e 14). 5. Discussion The e o e, he new me hod o de e mina ion o echnological s esses occu ing in he s uc u e unde epai in he p ocess o he composi e pa ch cu ing has been de eloped. This me hod is based on he analy ical model p e iously de eloped in [ 47 ] o de e mine he s ess–s ain beha iou o he panel o s ep- a iable hickness. The esea ch demons a ed he signi ican in luence o he empe a u e– ime egime o cu ing and me hods o i s implemen a ion on he bea ing capaci y o he s uc u e unde epai . Resul s o he esea ch allowed o he conside able imp o emen o he model o he mo- eac i e binde Polyme s 2021,13, 4342 17 o 20 cu ing ob ained ea lie in [ 23 , 25 , 26 ]. Consequen ly, i is now possible o ob ain a mo e comple e pic u e o he changes conce ned and o de e mine he cu en and esidual s ess–s ain beha iou o he s uc u e unde epai . Ou s udies, which con i m he indings o [ 24 – 27 ], p o e ha a , he ime o gela ion, he deg ee o binde cu ing is a cons an cha ac e is ic o he polyme no depending on he cu ing mode. Fo he epoxy binde Hysol EA9396 (Henkel) [ 48 ] unde s udy, he deg ee o i s cu ing is 52%. When analysing he esul s, i is necessa y o no e he signi ica e ise in s esses and mo e une en s ess dis ibu ion in he p ocess o epai o he panel wi hou p elimina y disman ling, as p oposed in [ 19 ]. The e o e, owing o he high equi emen s o he bea ing capaci y o he s uc u e being epai ed, he pe o mance o epai s ha wo k in his way equi es mo e ca e ul choice o he cu ing mode pa ame e s; in ex eme cases, i may no be accep able a all. The ob ained expe imen al g aph o o al de o ma ion o he composi e pa ch allowed he esea che s o clea ly de e mine he momen o s ess occu ence in he s uc u e unde epai . This momen ma ches qui e exac ly (wi h he disc epancy no exceeding 5 min) he gel poin de e mined analy ically based on dependence o he deg ee o cu ing on he moulding mode. I con i ms he alidi y o he hypo hesis accep ed based on [ 26 , 27 , 29 , 49 ] on he occu ence o echnological s esses in he s uc u e a e gela ion only. The de eloped me hod allows o inc easing he epai e iciency [ 7 , 12 , 47 ] by aking in o accoun he empe a u e– ime egime o cu ing and me hods o i s implemen a ion. The ad anced comp ehensi e algo i hm o choosing he e ec i e pa ame e s o he dam- aged panel epai p ocess can be ep esen ed as ollows. 1. In o de o ensu e he minimum down ime o he s uc u e, and aking in o accoun high complexi y o disman ling ope a ions, a he i s s age he epai wi hou p e- limina y disman ling is chosen. 2. Taking in o accoun he limi a ions ela ed o he quali y o su ace being epai ed, he me hod o he epai pa ch ins alla ion is chosen. 3. The choice o ma e ials o be used o epai s should, i s o all, be guided by hei physico-mechanical cha ac e is ics, a ailabili y and abundance. Much a en ion is also paid o he op imal combina ion o he mechanical and s eng h cha ac e is ics o he s uc u e being epai ed, he pa ch and adhesi e used. 4. Wi h he use o he cu en me hods, geome ic pa ame e s o he epai pa ch, which ensu e he es o a ion o ini ial bea ing capaci y o he s uc u e, a e de e mined. 5. Fo he esul ing epai pa ch geome y, pa ame e s o he cu ing mode gi ing ise o occu ence o he minimum esidual echnological s esses a e de ined wi h he use o he de eloped model. A his ime, con ol o he cu en s esses in he s uc u e unde epai o p e en he ailu e o adhesi e join a he s age o epai is manda o y. 6. The impac o esidual echnological s esses on he bea ing capaci y o he epai ed s uc u e unde he ac ion o ope a ional loads is assessed. I he o al alue o ope a ional and echnological s esses exceeds he pe missible le el, he ollowing s eps o adjus he epai pa ch geome ic pa ame e s a e aken: • I he p esence o he esidual echnological s esses leads o he ailu e o adhe- si e laye , plan dimensions o he pa ch should be inc eased and/o be elling o edges is used o educe he ope a ional shea s esses; • When he bea ing capaci y o he s uc u e unde epai dec eases in gene al, hickness o he epai pa ch should be inc eased. I con ibu es o he edis ibu- ion o s esses and he educ ion o he load pe cei ed by he panel. In his case, i can also be necessa y o inc ease plan dimensions o he pa ch o sa is y he condi ions o adhesi e laye s eng h; • Simila ac ions a e o be aken in case o he iola ion o he condi ions o epai pa ch s eng h as well. • As e idenced in p ac ice, he e is no need o epea edly op imize he cu ing mode in case o sligh adjus men o he epai pa ch dimensions. The e o e, esidual Polyme s 2021,13, 4342 18 o 20 echnological s esses occu ing in he s uc u e wi h he adjus ed geome y du ing moulding a e de e mined in acco dance wi h pa ame e s o p. 5, and hei accep abili y is assessed. • The sequence o ac ions desc ibed in p. 4–7 should be ollowed un il he se o pa ame e s o he epai p ocess is de e mined ( epai pa ch geome y + cu ing mode), which allows o sa is ying a condi ion o es o a ion o he s uc u e bea - ing capaci y. I no such pa ame e s a e ound du ing he sea ch, i is necessa y o : • Re u n o p. 3 and choose he ma e ials (adhesi e and/o PCM) wi h he highe s eng h cha ac e is ics, and hen con inue o sea ch o pa ame e s acco ding o he desc ibed algo i hm; • When he o he ma e ials a e no a ailable, o he condi ion o es o a ion o he bea ing capaci y s ill canno be sa is ied wi h he use o such ma e ials, i is possible o choose he epai o disman led panel, i.e., o e u n o p. 1. Howe e , i is impo an o no e ha i is he leas e ec i e me hod in e ms o labou cos s and ime equi ed; • I in he cou se o epai o he disman led panel he bea ing capaci y ails o each he speci ied alue, he epai is conside ed inexpedien , and he damaged s uc u e is eplaced by a new one. Thus, he esea ch, oge he wi h he esul s p e iously ob ained [ 19 , 47 ], allows e- sea che s o make an in eg a ed choice o geome ic pa ame e s o he epai composi e pa ch and empe a u e– ime egime o i s cu ing in o de o ensu e he speci ied le el o s eng h and s i ness o he s uc u e unde epai . 6. Conclusions and Fu he Resea ch The me hod o de e mina ion o echnological s esses, which a ise in he s uc u e unde epai in he p ocess o cu ing o he composi e pa ch, has been de eloped. This me hod allows one o: • Take in o accoun he sh inkage, change in physico-mechanical cha ac e is ics and heological p ocesses occu ing in he binde du ing he moulding p ocess; • De e mine he s esses in he s uc u e being epai ed a any ime, which allows a oiding p ema u e ailu e o he adhesi e join a he epai s age; •Take in o conside a ion he impac o he condi ions o epai wo ks. Reliabili y o assump ions and de eloped me hod is con i med by compa ison wi h he expe imen al da a. Ou s udies demons a ed a signi ican e ec o he empe a u e– ime egime o cu ing and he me hods o i s implemen a ion on he bea ing capaci y o he s uc u e being epai ed. Ne e heless, in o de o inc ease he economic e iciency o he ope a ion o he epai ed s uc u es o a ious applica ions, i is necessa y when choosing hese pa ame e s o addi ionally ake in o accoun he ac o s o he cos o ma e ials and epai wo ks, inc ease in ope a ing expenses as a esul o highe mass o he s uc u e and down ime. Au ho Con ibu ions: Concep ualiza ion, A.K. and V.P.; me hodology, M.S. and L.S.; alida ion, A.F., P.K and A.P.; o mal analysis, V.P. and P.K.; in es iga ion, L.S. and M.S.; esou ces, A.F. and L.S.; da a cu a ion V.P., M.S. and A.K.; w i ing—o iginal d a p epa a ion, L.S., A.F. and M.S.; w i ing— e iew and edi ing V.P. and A.K.; isualiza ion, L.S. and A.F.; supe ision, M.S.; p ojec adminis a ion, A.K. All au ho s ha e ead and ag eed o he published e sion o he manusc ip . Funding: The au ho s g a e ully acknowledge unding om he Speci ic esea ch on BUT FSI-S-20-6267. Ins i u ional Re iew Boa d S a emen : No applicable. In o med Consen S a emen : No applicable. Da a A ailabili y S a emen : No applicable. Acknowledgmen s: The au ho s hank B no Uni e si y o Technology o suppo . Con lic s o In e es : The au ho s decla e no con lic o in e es . Polyme s 2021,13, 4342 19 o 20 Re e ences 1. Balak ishnan, V.S.; Seidli z, H. Po en ial epai echniques o au omo i e composi es: A e iew. Compos. 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