Sökning: "Janis Varna"

Visar resultat 1 - 5 av 20 avhandlingar innehållade orden Janis Varna.

  1. 1. Analysis of transverse composite cross-ply laminates

    Författare :Janis Varna; Luleå tekniska universitet; []
    Nyckelord :ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Polymera konstruktionsmaterial; Polymeric Composite Materials;

    Sammanfattning : Advanced polymer composites are commonly based on thin prepreg plies stacked at different angles to form a laminate. When the laminate is loaded, intralaminar transverse cracking in off-axis plies is one of the first damage modes. In the presented thesis, cross-ply laminates are used to study the transverse cracking phenomenon. LÄS MER

  2. 2. Microcracking in fiber composites and degradation of thermo-elastic properties of laminates

    Författare :Mohamed Sahbi Loukil; Janis Varna; Zoubir Ayadi; Mohamed Loukil; Sweden Luleå Luleå University of Technology Sciences and Mathematics Department of Engineering Division of Materials Science; []
    Nyckelord :ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Polymeric Composite Materials; Polymera konstruktionsmaterial;

    Sammanfattning : The macroscopic failure of composite laminates subjected to tensile increasing load is preceded by initiation and evolution of several microdamage modes. The most common damage mode and the one examined in this thesis is intralaminar cracking in layers. LÄS MER

  3. 3. Experimental and numerical studies of intralaminar cracking in high performance composites

    Författare :Mohamed Sahbi Loukil; Janis Varna; Zoubir Ayadi; Constantinos Soutis; Luleå tekniska universitet; []
    Nyckelord :ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Polymeric Composite Materials; Polymera konstruktionsmaterial;

    Sammanfattning : The macroscopic failure of composite laminates subjected to tensile increasing load is preceded by initiation and evolution of several microdamage modes. The most common damage mode and the one examined in this thesis is intralaminar cracking in layers. LÄS MER

  4. 4. Comprehensive numerical analysis of stress state in adhesive layer of joint including thermal residual stress and material non-linearity

    Författare :Nawres Al-Ramahi; Roberts Joffe; Janis Varna; Lars Mikkelsen; Luleå tekniska universitet; []
    Nyckelord :ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; TEKNIK OCH TEKNOLOGIER; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; ENGINEERING AND TECHNOLOGY; Single-lap adhesive joint; Double-lap adhesive joint; Unbalanced bi-material DCB; Residual thermal stresses; Finite element method; Crack path; Crack closure; Polymeric Composite Materials; Polymera kompositmaterial;

    Sammanfattning : The main objective of this work is to improve understanding of the stress state in the adhesive layer of bonded joints and identify key parameters which govern performance of adhesive joints. This information is crucial for the prediction of the failure initiation and propagation with the further estimation of the durability and strength of adhesively bonded structures. LÄS MER

  5. 5. Numerical stress analysis in hybrid adhesive joint with non-linear materials

    Författare :Nawres Al-Ramahi; Roberts Joffe; Janis Varna; Rickard Östlund; Luleå tekniska universitet; []
    Nyckelord :ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Polymeric Composite Materials; Polymera kompositmaterial;

    Sammanfattning : This thesis presents systematic numerical study of stresses in the adhesive of a single-lap joint subjected to various loading scenarios (mechanical and thermal loading). The main objective of this work is to improve understanding of the main material and geometrical parameters determining performance of adhesive joint for the future analysis of failure initiation and development in these structures. LÄS MER