| 1. |
- Koissin, Vitali, et al.
(författare)
-
The elastic response of sandwich structures to local loading
- 2004
-
Ingår i: Composite structures. - 0263-8223 .- 1879-1085. ; 63:3-4, s. 375-385
-
Tidskriftsartikel (refereegranskat)abstract
- The paper addresses the elastic response of sandwich panels to local static and dynamic loading. The bottom face is assumed to be clamped, so that the overall bending is eliminated. The governing equations are derived using the static Lame equations for the core and the thin plate Kirchoff-Love dynamic theory for the faces. The plane and axisymmetric formulations are considered. The closed-form solutions are obtained using Fourier-Laplace (Hankel-Laplace) integral transformations for the cases of forced excitation and impact by a rigid body. The solutions allow to predict the stress-strain state of the structure. The analytical solutions demonstrate a good agreement with experimental data and finite element analysis.
|
|
| 2. |
- Koissin, Vitali, et al.
(författare)
-
The inelastic quasi-static response of sandwich structures to local loading
- 2004
-
Ingår i: Composite structures. - 0263-8223 .- 1879-1085. ; 64:2, s. 129-138
-
Tidskriftsartikel (refereegranskat)abstract
- The paper addresses the inelastic quasi-static response of sandwich beams and panels with foam core to localized loads. The plane and axisymmetric formulations for local indentation or local low-velocity impact by a rigid body are considered; no overall bending is assumed. The governing equations for the face are derived using the Kirchhoff-Love static theory under the assumption that the core crushing follows elastic-ideally-plastic behavior. Analytical solutions are constructed on the basis of the principle of minimum work. The solutions allow predicting the face deflection, size of crushed core area and contact force. In general, the solutions are in good agreement with experimental data and finite element analysis.
|
|
| 3. |
- Zetterberg, T., et al.
(författare)
-
On design of joints between composite profiles for bridge deck applications
- 2001
-
Ingår i: Composite structures. - 0263-8223 .- 1879-1085. ; 51:1, s. 83-91
-
Tidskriftsartikel (refereegranskat)abstract
- Techniques for joining of pultruded composite profiles for bridge-deck applications are designed and analyzed. It is shown that both adhesively bonded and bolted joints can be designed to fulfill stringent requirements, but it is clear that the former is the preferred alternative. The methodology used to analyze a large composite structure composed of modular construction elements and to determine the load transfer between composite profiles is described.
|
|
| 4. |
- Akbarpour, Sahar, et al.
(författare)
-
Enhancing the performance of bolted joints in composites by use of patched steel or titanium inserts
- 2021
-
Ingår i: Composite structures. - : Elsevier BV. - 0263-8223 .- 1879-1085. ; 275
-
Tidskriftsartikel (refereegranskat)abstract
- A new insert concept that interlaces metal inserts into composite laminates has earlier been shown to improve the relatively poor bearing strength of holes in fibre reinforced polymer composites, and it is here further and more thoroughly investigated. The concept was invented to increase the efficiency of joints with mechanical fasteners in composite materials and this work presents experiments on double-bolt joints with inserts made of either stainless steel or a titanium (Ti) alloy. In particular the work compares different implementations of the insert concept by reinforcing one or two holes in double bolt joints, and the effect of using different metals in the inserts. Some complementary tests on pin-loaded specimens and open hole tensile specimens are also performed and compared, partly with results that were reported previously. Considerable improvements of the bearing load capacity are attained, i.e. 50%-60% for steel and 35%-45% for Ti, compared to references. The open-hole tensile strength is also improved considerably (almost 30%) when the holes are reinforced with Ti inserts. The fact that the inserts can improve not only the bearing strength but also the performance in open-hole tension implies that the Ti inserts bring nothing but positive effects to the strength of the joints. The test results from single-shear double-bolt specimens with inserts at one hole showed improved strengths of 30% and 20% for specimens with steel and Ti inserts, respectively. Finally, an impressive strength improvement of 40-45% is achieved for single-shear double-bolt specimens having both holes reinforced with inserts of either steel or Ti.
|
|
| 5. |
- Akbarpour, Sahar, et al.
(författare)
-
Reinforcement around holes in composite materials by use of patched metal inserts
- 2019
-
Ingår i: Composite structures. - : Elsevier. - 0263-8223 .- 1879-1085. ; 225
-
Tidskriftsartikel (refereegranskat)abstract
- Metal inserts are sometimes used to improve the load carrying capacity of bolted joints in composite materials. In this paper a new concept is introduced where inserts are built during composite manufacturing by integrating stacked metal patches at locations where holes are to be made after consolidation. Initial tests and a parameter study enable more informed design, and specimens with improved stacked inserts are then produced and tested. The specimens with inserts show up to 60% strength improvement in pin-loaded tests. In addition to the experimental work, finite element analysis is performed to investigate the stress fields and the failure mechanisms. The model indicates that the singular stresses at the multi-material corner points are governing for the strength and give indications of the failure mechanisms. Some basic analytical estimates are also presented.
|
|
| 6. |
- Akbarpour, Sahar, et al.
(författare)
-
Strength improvement of bolted joints in composite materials by use of patched metal inserts
- 2020
-
Ingår i: Composite structures. - : Elsevier BV. - 0263-8223 .- 1879-1085. ; 52
-
Tidskriftsartikel (refereegranskat)abstract
- Metal inserts are occasionally used to improve bearing load capacity of bolted joints in laminated composite materials. This paper investigates a new reinforcement concept where inserts are built by locally replacing composite plies with metal patches of various diameters, surrounding the holes. The inserts are built during composite manufacturing by alternately placing the metal patches through the thickness of the laminate at locations where holes are to be drilled after consolidation. An extensive experimental study including pin‐ loaded, open–hole tensile, and single‐shear testing of bolted specimens is presented. Considerable improve- ment of the bearing strength – 50‐60% – is attained for pin‐loaded specimens with inserts, demonstrating the potential of the reinforcement concept. The open–hole tensile tests show that the by‐pass strength can be maintained or even improved with up to 20% if the inserts are properly designed. Finally, the results from the single‐shear tests of bolted joints show more than 25% improvement in strength for reinforced single‐ and double‐bolt specimens. It is possible that the inserts would maintain clamping pressure over time, which could then almost double the imrovement (47%) for bolted joints.
|
|
| 7. |
- Alcayde, B., et al.
(författare)
-
Fatigue behaviour of glass-fibre-reinforced polymers : Numerical and experimental characterisation
- 2024
-
Ingår i: Composite structures. - : Elsevier Ltd. - 0263-8223 .- 1879-1085. ; 337
-
Tidskriftsartikel (refereegranskat)abstract
- This work presents a novel numerical methodology to model the degradation and failure of composite materials like GFRP submitted to monotonic and high cycle fatigue loads. This is done by using the Serial–Parallel Rule of Mixtures homogenisation technique together with a proper mechanical characterisation of the constituent materials of the composite. This paper also proposes an efficient way of estimating the fatigue properties of each of the material constituents (fibre or matrix) to comply with the experimental results obtained at composite level; this enables to estimate the fatigue strength of any stacking/orientation of fibres with only one mechanical characterisation of the material properties. A comparison of the results obtained analytically and experimentally for GFRP is presented. The results show the applicability and accuracy of the proposed methodology in this field.
|
|
| 8. |
- Alfredsson, K. Svante, et al.
(författare)
-
Flexural analysis of discontinuous tile core sandwich structure
- 2012
-
Ingår i: Composite structures. - : Elsevier. - 0263-8223 .- 1879-1085. ; 94:5, s. 1524-1532
-
Tidskriftsartikel (refereegranskat)abstract
- Three-point flexure loading of sandwich beams with a core consisting of discrete ceramic tiles (DTSS) is considered. The tile gaps may be bonded or unbonded (open gaps). The analysis utilizes a layer-wise beam theory approach. The general formulation for the displacements and stresses in the face sheets, face/core adhesive layer, and core is derived. Solutions for stresses and displacements of the beam constituents are obtained from finite element formulation based on analytical solution of the face sheet/tile unit cell. The approach is verified by comparison to stress results obtained from ordinary finite element analysis where each layer is modeled discretely. Effects of load introduction and support conditions on the effective flexural stiffness are examined. It is demonstrated that the face sheets experience substantial stress concentrations at the tile joint locations, especially if the gaps are unfilled. Analysis of beam compliance reveals sensitivity to details of load introduction and support conditions, especially when the span length becomes comparable to the tile length.
|
|
| 9. |
- Alfredsson, K. Svante, et al.
(författare)
-
Stress analysis of axially and thermally loaded discontinuous tile core sandwich with and without adhesive filled core gaps
- 2011
-
Ingår i: Composite structures. - : Elsevier. - 0263-8223 .- 1879-1085. ; 93:7, s. 1621-1630
-
Tidskriftsartikel (refereegranskat)abstract
- An analytical study is performed to investigate the stress states in an axially and thermally loaded sandwich structure with a discontinuous ceramic tile core. General and simplified models are developed to determine stresses in the constituents of the sandwich structure with and without adhesive in the gaps between adjacent tiles. A general model that allows local bending of the face sheet and a simplified model which assumes uniform through-thickness stress distribution in the face sheets are developed. It is shown that the normal stress in the face sheet decreases when the gap is filled by adhesive, although the tile stress increases. The analytical model shows that normal and shear stresses at the face/core interface can be reduced by filling the gaps between tiles. Filled gaps also elevate the axial stiffness of the structure. Model results are verified by comparison to a previously developed analytical model and finite element analysis. (C) 2011 Elsevier Ltd. All rights reserved.
|
|
| 10. |
- Atashipour, Rasoul, 1983, et al.
(författare)
-
Exact Lévy-type solutions for bending of thick laminated orthotropic plates based on 3-D elasticity and shear deformation theories
- 2017
-
Ingår i: Composite Structures. - : Elsevier BV. - 0263-8223 .- 1879-1085. ; 163, s. 129-151
-
Tidskriftsartikel (refereegranskat)abstract
- Exact solutions for static bending of symmetric laminated orthotropic plates with different Lévy-type boundary conditions are developed. The shear deformation plate theories of Mindlin-Reissner and Reddy as well as the three-dimensional elasticity theory are employed. Using the minimum total potential energy principle, governing equilibrium equations of laminated orthotropic plates and pertaining boundary conditions are derived. Closed-form Lévy-type solutions are obtained for the governing equations of both theories using separation of variables method and different types of classical boundary conditions, namely simply-supported, clamped and free edge, are exactly satisfied. Thereafter, 3-D elasto-static equations for orthotropic materials are solved for bending analysis of laminated plates using two different approaches. First, the method of separation of variables is utilised and an exact closed-from solution is achieved for simply-supported laminated orthotropic plates. Next, a combined Fourier-Differential Quadrature (DQ) approach is employed to present a semi-numerical solution for bending of laminated orthotropic plates with Lévy-type boundary conditions based on the three-dimensional elasticity theory. High accuracy of the presented solutions are proven and comprehensive comparative numerical results are provided and discussed. Presented comparative numerical results can serve as benchmark for investigating the correctness of new solution methods which may be established in the future.
|
|
