Substructure Assembly of Composite Structures
Translated title
Underkonstruktion af komposit strukturer
Author
Gonzalez Madruga, Efren
Term
4. term
Education
Publication year
2018
Submitted on
2018-08-16
Pages
120
Abstract
Dette speciale undersøger, hvordan et kulfiberchassis kan opdeles i fremstillingsvenlige understrukturer og samles ved hjælp af strukturelle limsamlinger. Arbejdet er udført i samarbejde med Agile Automotive omkring det nye køretøj Agile SC122 og kombinerer geometriudvikling, materialeafprøvning og samlingsdesign. Chassiset designes og optimeres for lav masse og høj stivhed gennem topologi- og FEM-baserede iterationer, mens materialevalget afklares ved at sammenligne en ny termoplastisk resin med en traditionel termosetharpiks ud fra procesforsøg og mekaniske målinger af bl.a. interlaminær forskydningsstyrke. Termoset vælges, da den testede termoplast viste lavere interlaminær forskydningsstyrke. Det valgte kompositmateriale karakteriseres analytisk ved mikromekanik, og den kritiske samling identificeres og submodelleres. En forenklet enkelt overlapssamling modelleres i FEM og valideres analytisk (Goland & Reissner), suppleret af et MATLAB-program til at undersøge spændingsfordeling. Joint-geometrien udformes til at arbejde overvejende i forskydning for at reducere peel- og tværspændinger, og effekten af limens stivhed/tykkelse samt laminatets oplægsrækkefølge vurderes. Eksperimenter og fysiske tests gennemføres hos Agile Automotive. Resultatet er et valideret konstruktionsgrundlag og en endelig limsamling med væsentligt forbedret styrke sammenlignet med en konventionel overlapssamling, samt konkrete designanbefalinger til limede samlinger i et kompositchassis.
This thesis examines how a carbon-fiber chassis can be divided into manufacturable substructures and assembled using structural adhesive joints. Conducted in collaboration with Agile Automotive for the Agile SC122, the work combines chassis geometry development, materials testing, and joint design. The chassis is designed and iteratively optimized for low mass and high stiffness using topology and finite element analyses, while material selection is resolved by comparing a new thermoplastic resin with a conventional thermoset through processing trials and mechanical measurements, notably interlaminar shear strength. The thermoset is selected because the tested thermoplastic showed lower interlaminar shear strength. The chosen composite is characterized analytically via micromechanics, and the structure’s critical joint is identified and submodeled. A simplified single-lap joint is modeled in FEM and validated analytically (Goland & Reissner), supported by a MATLAB tool to study stress distributions. The joint geometry is tailored to promote shear-dominated loading and reduce peel and transverse stresses, and the effects of adhesive stiffness/thickness and laminate lay-up sequence are assessed. Experiments and physical tests are performed at Agile Automotive. The outcome is a validated design basis and a final bonded joint with a significant strength improvement over a conventional lap joint, along with practical design recommendations for adhesive joints in a composite chassis.
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