Eksperimentalna analiza vijačenih spojev iz armirane plastike : diplomska naloga

Ponjavič, Robi (author), Korelc, Jože (mentor), Antolinc, David (comentor)

V diplomski nalogi sem obravnaval obnašanje natezno obremenjenih mehansko vijačenih spojev kompozitnih FRP elementov z enim vijakom. Za tri različne oddaljenosti središča luknje vijaka od obremenjenega roba v priključnih kompozitnih elementih sem izvedlel eksperimentalno analizo z nateznim preizkusom spoja. S tem smo dobili primerjavo obnašanja različnih konfiguracij spoja, kjer spojni vijak pritiska na luknjo kompozitne plošče. Dodatno sem preverili tudi obstoječe enačbe za projektiranje obravnavanih spojev, katere so navedene v priročniku podjetja Fiberline. Na začetku diplome so najprej predstavljene z vlakni armirane plastike (FRP), njihova sestava, materialne lastnosti, proizvodni postopki za konstrukcijske namene, standardi in smernice za načrtovanje konstrukcijskih spojev ter vrste konstrukcijskih spojev. Temu sledi opis preizkušancev in zasnova nateznega preizkusa vijačenega spoja. Oddaljenost središča luknje vijaka s premerom d od obremenjenega roba priključnih kompozitnih elementov je za prvo serijo preizkušancev znašala 1,5*d, za drugo serijo 3,5*d in za tretjo serijo 7*d. V vsaki seriji sem obravnaval po 4 preizkušance. Med vsako preiskavo sem merili silo in relativni pomik spojnega vijaka glede na kompozitno ploščo v katero se je vijak vtiskal. Zaradi bočnega pritiska vijaka je prišlo do različnih tipov porušnih mehanizmov kompozitnih plošč v odvisnosti od oddaljenosti luknje od obremenjenega roba plošče. Izkaže se, da sem dobil najbolj neugodno obliko porušitve in pri najnižji doseženi sili dobili pri preizkušancu z najmanjšo oddaljenostjo luknje od obremenjenega roba. Po nastanku prve poškodbe spoj skoraj popolnoma izgubi nosilnost in ne izkazuje nobene dodatne rezerve, pride do krhke porušitve. Pri preostalih dveh preizkušancih z večjo razdaljo se spoja obnašata duktilno in z rezervo v nosilnosti po nastanku prvih poškodb. S tem izkažeta tudi primernost za uporabo v konstrukcijske namene, medtem ko spoj z najkrajšo razdaljo predstavlja preveliko tveganje za takšno uporabo. Dodatno, sem tudi potrdil odvisnost porušne oblike od razdalje središča luknje vijaka do obremenjenega roba kompozita, katera je navedena v priročniku podjetja Fiberline za projektiranje konstrukcije iz kompozitnih materialov.

• Language: Slovenian
• Keywords: gradbeništvo, diplomska naloga, VSŠ, armirana plastika, karbonska vlakna, kevlar vlakna, steklena vlakna, vijačeni spoji
• Work type: Undergraduate thesis
• Typology: 2.11 - Undergraduate Thesis
• Organization: FGG - Faculty of Civil and Geodetic Engineering
• Place of publishing: Ljubljana
• Publisher: [R. Ponjavić]
• Year: 2016
• Number of pages: XII, 65 str.
• PID: 20.500.12556/RUL-84870
• UDC: 624.04(043.2)
• COBISS.SI-ID: 7643745
• Publication date in RUL: 14.10.2016

Secondary language

• Language: English
• Title: Experimental analysis of bolted joints from FRP

Abstract

This thesis presents the behaviour of FRP composite bolted connections with one steel bolt exposed to tension load. The experimental analysis of three different configuration of bolted connection with one bolt has been conducted with the tension test. The distance between the center of the hole and the loaded edge of the composite plate is the only changing parameter, where the rest are all constant. Additionally, we checked the current equations, which are in use by the company Fiberline to design one bolt FRP connections. The introduction of the thesis discusses the basic of the FRP materials with their composition, mechanical characteristics, production methods together with standards and guidelines for design of structural elements and connections made of FRP materials. This is followed by the detailed description of the specimen and the test setup itself. The distance between the loaded FRP plate edge and the center of the bolt hole with the diameter of d is for the first series of specimens 1.5*d, for the second is 3.5*d and for the last one is 7*d. Each series contained 4 specimens. During the experiment conduction the force and the relative displacement of the steel bolt have been recorded. Due to the bearing stress of the bolt the specimens have experienced different failure mechanisms in relationship to the distance between the center of the bolt hole and the loaded edge of the composite plate. As expected, the worst behaviour of the tested connections has shown the connection with the shortest distance (1.5*d). This type of connections has no post fracture load bearing capacity after the first recorded damage and represents brittle failure. For the other two configurations of specimens with longer distance between center of the bolt hole and the loaded edge of the FRP plate we observed ductile behaviour and good post fracture behaviour. This shows that we must ensure the minimum adequate distance between center of the bolt hole and loaded FRP plate edge whenever we use this type of connections for structural purposes. We additionally confirmed the failure mechanisms in relationship to the distance between the center of the bolt hole and the loaded FRP plate edge which are stated in the internal design manual of the company Fiberline.

• Keywords: graduation thesis, FRP-Fiber Reinforced Polymers, carbon fibres, kevlar fibres, glass fibres, bolted joints