scholarly journals Reduction of strength of GFRP sandwich panels in naval ships by face sheet holes, cracks and impact damage

2019 ◽  
Vol 21 (5) ◽  
pp. 1621-1653 ◽  
Author(s):  
Brian Hayman ◽  
Andreas T Echtermeyer
Keyword(s):  
Impact Damage ◽  
Compressive Loading ◽  
Finite Size ◽  
Sandwich Panels ◽  
Average Stress ◽  
Face Sheet ◽  
Reinforced Plastics ◽  
The Face ◽  
Circular Holes ◽  
Stress Models

Extensive studies have been previously carried out on the effects of various types of local damage on the performance of sandwich panels used in the hull structures of naval ships. More recently, the approach was adapted for application on board a specific ship series. Strength reduction data were obtained for a set of sandwich materials that were representative for the vessels in question. The face sheet materials were glass fibre-reinforced plastics with non-crimp fabrics and two different types of vinylester resin. The core materials were PVC foams. Tests were performed on laminate specimens with and without circular holes under tensile loading and on sandwich face sheets with holes, cracks and impact damage under compressive loading. The strength reductions caused by impacts with sharp and blunt objects were compared with those caused by machined cracks and circular holes, respectively, and with Whitney and Nuismer’s point stress and average stress models for infinitely large laminates with cracks and holes. It was found that strength reductions due to impact damage can be estimated using tests on specimens with machined cracks and holes, and also with the average stress models if appropriate values of characteristic length are assumed. Special attention is paid to the need to take account of the geometry and the finite size of tested specimens.

scholarly journals The Flexural Fatigue Behavior of Honeycomb Sandwich Composites Following Low Velocity Impacts

2020 ◽  
Vol 10 (20) ◽  
pp. 7262
Author(s):  
Murat Yavuz Solmaz ◽  
Tolga Topkaya
Keyword(s):  
Impact Damage ◽  
Damping Ratio ◽  
Sheet Material ◽  
Low Velocity Impact ◽  
Face Sheet ◽  
Low Velocity ◽  
Velocity Impact ◽  
Flexural Fatigue ◽  
Honeycomb Sandwich ◽  
The Face

This study experimentally investigated the flexural fatigue behaviors of honeycomb sandwich composites subjected to low velocity impact damage by considering the type and thickness of the face sheet material, the cell size and the core height parameters. Carbon-fiber reinforced composite and the aluminum alloy was used as the face sheet material. First, the static strength of undamaged and damaged specimens was determined by three-point bending loads. Secondly, the fatigue behaviors of the damaged and undamaged specimens were determined. Low velocity impact damage decreased the flexural strength and fatigue lives but increased the damping ratio for all specimens. Maximum damping ratio values were observed on specimens with a aluminum face sheet.

Wrinkling of Wide Sandwich Panels∕Beams With Orthotropic Phases by an Elasticity Approach

2004 ◽  
Vol 72 (6) ◽  
pp. 818-825 ◽  
Author(s):  
G. A. Kardomateas
Keyword(s):  
Compressive Loading ◽  
Sandwich Panels ◽  
Wave Mode ◽  
Buckling Load ◽  
Face Sheet ◽  
Beam Model ◽  
Elasticity Solution ◽  
Short Side ◽  
Euler Buckling ◽  
Sandwich Construction

There exist many formulas for the critical compression of sandwich plates, each based on a specific set of assumptions and a specific plate or beam model. It is not easy to determine the accuracy and range of validity of these rather simple formulas unless an elasticity solution exists. In this paper, we present an elasticity solution to the problem of buckling of sandwich beams or wide sandwich panels subjected to axially compressive loading (along the short side). The emphasis on this study is on the wrinkling (multi-wave) mode. The sandwich section is symmetric and all constituent phases, i.e., the facings and the core, are assumed to be orthotropic. First, the pre-buckling elasticity solution for the compressed sandwich structure is derived. Subsequently, the buckling problem is formulated as an eigen-boundary-value problem for differential equations, with the axial load being the eigenvalue. For a given configuration, two cases, namely symmetric and anti-symmetric buckling, are considered separately, and the one that dominates is accordingly determined. The complication in the sandwich construction arises due to the existence of additional “internal” conditions at the face sheet∕core interfaces. Results are produced first for isotropic phases (for which the simple formulas in the literature hold) and for different ratios of face-sheet vs core modulus and face-sheet vs core thickness. The results are compared with the different wrinkling formulas in the literature, as well as with the Euler buckling load and the Euler buckling load with transverse shear correction. Subsequently, results are produced for one or both phases being orthotropic, namely a typical sandwich made of glass∕polyester or graphite∕epoxy faces and polymeric foam or glass∕phenolic honeycomb core. The solution presented herein provides a means of accurately assessing the limitations of simplifying analyses in predicting wrinkling and global buckling in wide sandwich panels∕beams.

Optimum Stacking Sequence Design of Composite Sandwich Panel Using Genetic Algorithms

2012 ◽  
Vol 585 ◽  
pp. 29-33
Author(s):  
Amarpreet S. Bir ◽  
Hsin Piao Chen ◽  
Hsun Hu Chen
Keyword(s):  
Genetic Algorithms ◽  
Sandwich Panel ◽  
Compressive Loading ◽  
Face Sheet ◽  
Composite Sandwich ◽  
Minimization Problems ◽  
The Face ◽  
Coupling Terms ◽  
Laminate Thickness ◽  
Buckling Load Maximization

In the present study, both critical buckling load maximization and face-sheet laminate thickness minimization problems for the composite sandwich panel, subjected to bi-axial compressive loading under various imposed constraints have been investigated using genetic algorithms. In the previously published work, the optimization of simple composite laminate panels with only even number of laminae has been considered [1, 3]. The present work allows the optimization of a composite sandwich panel with both even and odd number of laminae in the face-sheet laminates. Also, the effects of the bending-twisting coupling terms (D16and D26) in bending stiffness matrix which were neglected in the previous studies [1, 2, 3], are considered in the present work for exact solutions. In addition effect of both balanced and unbalanced face-sheet laminates on the optimum solutions have also been investigated, whereas only balanced laminates were considered in the previous studies [1, 2, 3].

Specific bending stiffness of in-mould-assembled hybrid sandwich structures with carbon fibre reinforced polymer face sheets and aluminium foam cores manufactured by a polyurethane-spraying process

2017 ◽  
Vol 21 (8) ◽  
pp. 2779-2800 ◽  
Author(s):  
Peter Rupp ◽  
Peter Elsner ◽  
Kay A Weidenmann
Keyword(s):  
Carbon Fibre ◽  
Sandwich Panels ◽  
Aluminium Foam ◽  
Face Sheet ◽  
The Core ◽  
Four Point Bending ◽  
Reinforced Polymer ◽  
Carbon Fibre Reinforced Polymer ◽  
The Face ◽  
Fibre Reinforced Polymer

In this paper, the bending stiffness-to-weight-ratio of novel hybrid sandwich structures is investigated. The build-up of the sandwich panels consisted of face sheets made from carbon fibre reinforced polymer, aluminium foam cores and an interface of foamed polyurethane. The sandwich panels were produced in a single step, infiltrating the face sheet fibres and connecting the face sheets to the core simultaneously. By means of mechanical characterization, specimens with several variations of face sheet architecture and thickness, core structure and interface properties were examined. Quasi-static four-point bending and flatwise compression tests of the sandwich composites were conducted, as well as tensile tests of the face sheets. The results of the tensile and compressive tests were integrated in analytical models, describing the sandwich stiffness depending on the load case and the face sheet volume fraction. The effective Young’s modulus of the composite, measured in the four-point bending test, correlates well to the modelled effective bending modulus calculated from the single components face sheet and core. The model underestimates the effective density of the bending specimens. It could be shown that this underestimation results from the polyurethane foam connecting the face sheets to the core, as the mass of this polyurethane is not included in the model.

Sound transmission loss characteristics of four-side simply supported sandwich panels

2017 ◽  
Vol 21 (2) ◽  
pp. 707-726 ◽  
Author(s):  
Wei Li ◽  
Yansong He ◽  
Zhongming Xu ◽  
Zhifei Zhang
Keyword(s):  
Natural Frequencies ◽  
Transmission Loss ◽  
Flexural Rigidity ◽  
Sandwich Panels ◽  
Sound Transmission ◽  
High Accuracy ◽  
Face Sheet ◽  
Sound Transmission Loss ◽  
Simply Supported ◽  
The Face

In this study, a theoretical investigation on the sound transmission loss characteristics of four-side simply supported sandwich panels considering the flexural rigidity of the face sheet has been presented. With the flexural rigidity of the face sheet taken into account, the sound transmission problem of the sandwich panels is derived from the governing equation of bending vibration. The sound transmission loss expression is also derived. The validation of the theoretical prediction model is validated by comparing with the high-accuracy finite element and boundary element simulation. Numerical analysis shows that the flexural rigidity of face sheet influences the natural frequencies obviously, and the theoretical prediction model proposed has high accuracy on predicting the natural frequencies and sound transmission loss of four-side simply supported sandwich panels. The effects of the face sheet flexural rigidity, the thickness of face sheets and core layer, as well as the damping coefficient of the core on the sound transmission loss are systematically investigated.

scholarly journals The Low Velocity Impact Response of Foam Core Sandwich Panels with a Shape Memory Alloy Hybrid Face-Sheet

Materials ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2076 ◽  
Author(s):  
Hao Li ◽  
Zhenqing Wang ◽  
Zhengwei Yu ◽  
Min Sun ◽  
Yanfei Liu
Keyword(s):  
Impact Damage ◽  
Sandwich Panels ◽  
Low Velocity Impact ◽  
Face Sheet ◽  
Foam Core ◽  
Low Velocity ◽  
Damage Resistance ◽  
Velocity Impact ◽  
Bottom Face ◽  
The Impact

Most foam core sandwich panels are sensitive to the impact load because of the poor toughness of thin composite face-sheets and the low strength of foam core. Superelastic shape memory alloy (SMA) wires have been applied to enhance the impact damage resistance of composite laminates in recent decades. To improve the impact damage resistance of foam core sandwich panels and to protect the foam core, SMA wires were incorporated into the face-sheets of foam core sandwich panels in this work. Eight new types of SMA hybrid sandwich panels were designed, and low-velocity impact tests were carried out at an impact energy of 35 J. The damage morphology of the impacted sandwich panels was identified by visual inspection and scanning electron microscope technology. Results indicate that the impact damage resistance of the SMA hybrid sandwich panels is enhanced. The damage area in the hybrid sandwich panels is greatly reduced and a decrease of 85.63% can be reached in the bottom face-sheet. The maximum contact force has an improvement of 28.15% when the two layers of SMA wires are incorporated into the bottom face-sheet.

Response of aluminum corrugated sandwich panels under foam projectile impact – Experiment and numerical simulation

2016 ◽  
Vol 19 (5) ◽  
pp. 595-615 ◽  
Author(s):  
Xin Li ◽  
Shiqiang Li ◽  
Zhihua Wang ◽  
Jinglei Yang ◽  
Guiying Wu
Keyword(s):  
Impact Velocity ◽  
Aluminum Foam ◽  
Sandwich Panels ◽  
Face Sheet ◽  
Front Face ◽  
Comparable Amount ◽  
Projectile Impact ◽  
The Face ◽  
Core Height ◽  
The Impact

The paper studied the dynamic response of square aluminum corrugated sandwich panels under projectile impact. The aluminum foam projectile was utilized to apply the impulse on the sandwich panels. In order to increase the applied impulse under controlled impact velocity ( V < 200 m/s), a cylindrical Nylon mass was adhered to the back of foam projectile. Corrugated sandwich panels with two different configurations were tested and their typical deformation modes were obtained in the experiment. Based on the experiment, corresponding numerical simulations were presented. The energy absorption and deformation mechanism of corrugated sandwich panels were studied through the simulation. The influence of impact velocity, thickness of face sheet and wall thickness of corrugated core were discussed. The results indicated that the corrugated sandwich panels with smaller core height produce larger deformation than the panels with larger core height. The face sheets of corrugated sandwich panel absorbed comparable amount of energy with the corrugated core. The velocity histories show that under the combined action of aluminum foam projectile and nylon back mass, a second peak velocity of front face sheet can be produced during the impact process, which is defined as “accelerating impact stage” in current study. The influence of “accelerating impact stage” to the response of structures is sensitive to the impact velocity.

High-order crack propagation in compressed sandwich panels

2019 ◽  
Vol 21 (5) ◽  
pp. 1726-1750 ◽  
Author(s):  
Itay Odessa ◽  
Oded Rabinovitch ◽  
Yeoshua Frostig
Keyword(s):  
Geometrical Nonlinearity ◽  
Sandwich Panels ◽  
Interfacial Crack ◽  
Interfacial Debonding ◽  
High Order ◽  
Experimental Results ◽  
Face Sheet ◽  
Interfacial Instabilities ◽  
The Core ◽  
The Face

The response and the debonding mechanisms in axially compressed sandwich panels with an interfacial delamination are investigated using a nonlinear model. The mathematical model combines the extended high-order sandwich panel theory with a cohesive interface modeling. It includes the first-order shear deformation kinematic assumptions for the face sheets and high-order small deformations kinematic assumptions that account for out-of-plane compressibility for the core. The interfaces bond the face sheets and the core by means of traction–displacement gap laws. These interfacial laws can describe a diversity of physical conditions. In particular, interfacial debonding nucleation and propagation are described using cohesive laws that introduce the interfacial nonlinearity into the model. Geometrical nonlinearity of the face sheets is introduced in order to capture the instability associated with the buckling of the delaminated face sheet. The cohesive interfaces and others parameters are calibrated to match experimental results taken from the literature for a sandwich specimen subjected to an end-shortening compression. The instabilities due to the in-plane compression, together with the existence of delaminated regions and their tendency to grow, prompt buckling of the delaminated face sheet as well as nucleation and propagation of the interfacial debonding. The theoretical quantification of this complex mechanism compares well with the experimental results in terms of the physical response, the nucleation and propagation of the interfacial crack, and the evolution of local/global geometrical instabilities. In addition, the analysis explores debonding mechanisms that are beyond the capabilities of the experimental technique. Finally, the sensitivity of the response and the associated geometrical and interfacial instabilities to the boundary conditions are investigated.

scholarly journals Bending Response of 3D-Printed Titanium Alloy Sandwich Panels with Corrugated Channel Cores

Materials ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 556
Author(s):  
Zhenyu Zhao ◽  
Jianwei Ren ◽  
Shaofeng Du ◽  
Xin Wang ◽  
Zihan Wei ◽  
...  
Keyword(s):  
Titanium Alloy ◽  
Heat Dissipation ◽  
Sandwich Panels ◽  
Face Sheet ◽  
Collapse Mechanism ◽  
Corrugated Channel ◽  
Four Point Bending ◽  
Numerical Predictions ◽  
Load Carrying ◽  
3D Printed

Ultralight sandwich constructions with corrugated channel cores (i.e., periodic fluid-through wavy passages) are envisioned to possess multifunctional attributes: simultaneous load-carrying and heat dissipation via active cooling. Titanium alloy (Ti-6Al-4V) corrugated-channel-cored sandwich panels (3CSPs) with thin face sheets and core webs were fabricated via the technique of selective laser melting (SLM) for enhanced shear resistance relative to other fabrication processes such as vacuum brazing. Four-point bending responses of as-fabricated 3CSP specimens, including bending resistance and initial collapse modes, were experimentally measured. The bending characteristics of the 3CSP structure were further explored using a combined approach of analytical modeling and numerical simulation based on the method of finite elements (FE). Both the analytical and numerical predictions were validated against experimental measurements. Collapse mechanism maps of the 3CSP structure were subsequently constructed using the analytical model, with four collapse modes considered (face-sheet yielding, face-sheet buckling, core yielding, and core buckling), which were used to evaluate how its structural geometry affects its collapse initiation mode.

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