scholarly journals Manufacturing and Characterization of Highly Environmentally Friendly Sandwich Composites from Polylactide Cores and Flax-Polylactide Faces

Polymers ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 342
Author(s):  
Diego Lascano ◽  
Rene Guillen-Pineda ◽  
Luis Quiles-Carrillo ◽  
Juan Ivorra-Martínez ◽  
Rafael Balart ◽  
...  
Keyword(s):  
Sandwich Structures ◽  
Great Influence ◽  
Weight Ratio ◽  
Environmentally Friendly ◽  
Compression Molding ◽  
Hot Compression ◽  
Honeycomb Core ◽  
The Core ◽  
Core Thickness

This work focuses on the manufacturing and characterization of highly environmentally friendly lightweight sandwich structures based on polylactide (PLA) honeycomb cores and PLA-flax fabric laminate skins or facings. PLA honeycombs were manufactured using PLA sheets with different thicknesses ranging from 50 to 500 μm. The PLA sheets were shaped into semi-hexagonal profiles by hot-compression molding. After this stage, the different semi-hexagonal sheets were bonded together to give hexagonal panels. The skins were manufactured by hot-compression molding by stacking two Biotex flax/PLA fabrics with 40 wt% PLA fibers. The combined use of temperature (200 °C), pressure, and time (2 min) allowed PLA fibers to melt, flow, and fully embed the flax fabrics, thus leading to thin composite laminates to be used as skins. Sandwich structures were finally obtained by bonding the PLA honeycomb core with the PLA-flax skins using an epoxy adhesive. A thin PLA nonwoven was previously attached to the external hexagonal PLA core, to promote mechanical interlock between the core and the skins. The influence of the honeycomb core thickness on the final flexural and compression properties was analyzed. The obtained results indicate that the core thickness has a great influence on the flexural properties, which increases with core thickness; nevertheless, as expected, the bonding between the PLA honeycomb core and the skins is critical. Excellent results have been obtained with 10 and 20 mm thickness honeycombs with a core shear of about 0.60 and facing bending stresses of 31–33 MPa, which can be considered as candidates for technical applications. The ultimate load to the sample weight ratio reached values of 141.5 N·g−1 for composites with 20 mm thick PLA honeycombs, which is comparable to other technical composite sandwich structures. The bonding between the core and the skins is critical as poor adhesion does not allow load transfer and, while the procedure showed in this research gives interesting results, new developments are necessary to obtain standard properties on sandwich structures.

scholarly journals Innovation in Aircraft Cabin Interior Panels Part I: Technical Assessment on Replacing the Honeycomb with Structural Foams and Evaluation of Optimal Curing of Prepreg Fiberglass

Polymers ◽  
2021 ◽  
Vol 13 (19) ◽  
pp. 3207 ◽  
Author(s):  
Edgar Adrián Franco-Urquiza ◽  
Annika Dollinger ◽  
Mauricio Torres-Arellano ◽  
Saúl Piedra ◽  
Perla Itzel Alcántara Llanas ◽  
...  
Keyword(s):  
Weight Ratio ◽  
Viscoelastic Behavior ◽  
Compression Molding ◽  
Polyurethane Foams ◽  
Future Research ◽  
Honeycomb Core ◽  
Molding Process ◽  
Aircraft Cabin ◽  
Structural Applications ◽  
Cabin Interior

Sandwich composites are widely used in the manufacture of aircraft cabin interior panels for commercial aircraft, mainly due to the light weight of the composites and their high strength-to-weight ratio. Panels are used for floors, ceilings, kitchen walls, cabinets, seats, and cabin dividers. The honeycomb core of the panels is a very light structure that provides high rigidity, which is considerably increased with fiberglass face sheets. The panels are manufactured using the compression molding process, where the honeycomb core is crushed up to the desired thickness. The crushed core breaks fiberglass face sheets and causes other damage, so the panel must be reworked. Some damage is associated with excessive build-up of resin in localized areas, incomplete curing of the pre-impregnated fiberglass during the manufacturing process, and excessive temperature or residence time during the compression molding. This work evaluates the feasibility of using rigid polyurethane foams as a substitute for the honeycomb core. The thermal and viscoelastic behavior of the cured prepreg fiberglass under different manufacturing conditions is studied. The first part of this work presents the influence of the manufacturing parameters and the feasibility of using rigid foams in manufacturing flat panels oriented to non-structural applications. The conclusion of the article describes the focus of future research.

Effect of Core Thickness and Intermediate Layers on Mechanical Properties of Polypropylene Honeycomb Multi-Layer Sandwich Structures

2014 ◽  
Vol 59 (1) ◽  
pp. 11-16 ◽  
Author(s):  
J. Arbaoui ◽  
Y. Schmitt ◽  
J.-L. Pierrot ◽  
F.-X. Royer
Keyword(s):  
Mechanical Properties ◽  
Sandwich Structures ◽  
Bending Test ◽  
Honeycomb Core ◽  
Lightweight Construction ◽  
Specific Strength ◽  
High Specific Strength ◽  
Intermediate Layers ◽  
Core Thickness ◽  
Strength And Stiffness

Abstract Sandwich structures are widely used in lightweight construction especially in aerospace industries because of their high specific strength and stiffness. This paper investigates the effect of core thickness and intermediate layers on the mechanical properties of a polypropylene honeycomb core/composite facing multilayer sandwich structure under three points bending. We developed a theoretical model which makes it possible to calculate the shear properties in multi-cores. The results obtained by this model are agreed with our experimental results, and the results obtained with bending test showed that the mechanical properties of the composite multilayer structures increase with core thickness and intermediate layers.

Finite Elements for Curved Sandwich Beams

1977 ◽  
Vol 28 (2) ◽  
pp. 123-141 ◽  
Author(s):  
P J Holt ◽  
J P H Webber
Keyword(s):  
Finite Elements ◽  
Stiffness Matrix ◽  
Test Cases ◽  
Sandwich Beams ◽  
Honeycomb Core ◽  
The Core ◽  
The Face ◽  
Core Thickness ◽  
Displacement Approach ◽  
Circular Sandwich Ring

SummaryThe formulation of curved finite elements to represent a two-dimensional circular sandwich ring with honeycomb core and laminated faces is investigated. Assumed stress hybrid and equilibrium methods are found to be easier to employ in this case than the displacement approach. Using these methods, an element stiffness matrix is developed. The approximations of membrane faces and an infinite core normal stiffness are then used to develop simpler elements. Test cases show that these assumptions may become invalid, but that they are adequate for most practical cases where the core thickness to radius ratio and the face thickness to core thickness ratio are both low.

Particulate Enhanced Damping in Sandwich Structures

1999 ◽  
Author(s):  
Scott Maley ◽  
C. T. Sun
Keyword(s):  
Sandwich Structures ◽  
Equations Of Motion ◽  
Viscous Damping ◽  
Honeycomb Core ◽  
Moderate Amount ◽  
Damping Effect ◽  
The Core ◽  
Plate Equations ◽  
Aluminum Honeycomb ◽  
Vibration Tests

Abstract This paper investigates the damping effect of loose particulate within the core of sandwich structures. Beam specimens fabricated from aluminum honeycomb core and IM7 carbon fiber face sheets with various amounts of loose particulate are experimentally examined. Both free vibration and forced vibration tests are performed. It is shown that a moderate amount of particulate can cause a large increase in damping. The effect of varying amounts of particulate is also investigated. Plate equations of motion with damping and inertia terms are derived to model the beam and compare with experimental results. Effective mass and effective viscous damping are generated by matching the theoretical model to the experimental data.

On the Crashworthiness of Shear-Rigid Sandwich Structures

2005 ◽  
Vol 73 (4) ◽  
pp. 633-641 ◽  
Author(s):  
Dirk Mohr ◽  
Tomasz Wierzbicki
Keyword(s):  
Energy Absorption ◽  
Sandwich Structures ◽  
Automotive Applications ◽  
Practical Applications ◽  
The Core ◽  
Crushing Force ◽  
Box Structures ◽  
Core Thickness ◽  
Box Columns ◽  
Sandwich Sheets

This paper deals with the evaluation of the crashworthiness of thin-walled sandwich box structures for automotive applications. Quasi-static crushing simulations are carried out to estimate the energy absorption of prismatic box columns made from sandwich sheets. The sandwich sheets have perforated cores of different densities with staggered holes perpendicular to the panel faces. It is found that the specific energy absorption of columns made of sandwich sheets is approximately the same as that of conventional columns composed of homogeneous sheets of the same total wall thickness. Furthermore, theoretical analysis indicates that by increasing the core thickness, sandwich structures could be up to 50% lighter while providing the same mean crushing force. However, these gains may not be achieved in practical applications since increasing the core thickness also increases the likelihood of premature face sheet fracture during crushing.

scholarly journals Effect of the core thickness on the flexural behaviour of polymer foam sandwich structures

IOP SciNotes ◽  
2020 ◽  
Vol 1 (2) ◽  
pp. 024404
Author(s):  
Yash Gupta ◽  
Varghese Paul V ◽  
Ashish Jacob ◽  
Akash Mohanty
Keyword(s):  
Sandwich Structures ◽  
Flexural Behaviour ◽  
Polymer Foam ◽  
The Core ◽  
Core Thickness

scholarly journals Thermal characterization of honeycomb core sandwich structures

1997 ◽  
Author(s):  
David Copenhaver ◽  
Elaine Scott ◽  
Alexander Hanuska ◽  
David Copenhaver ◽  
Elaine Scott ◽  
...  
Keyword(s):  
Sandwich Structures ◽  
Thermal Characterization ◽  
Honeycomb Core

scholarly journals Thermal Characterization of Honeycomb Core Sandwich Structures

1998 ◽  
Vol 35 (4) ◽  
pp. 539-545 ◽  
Author(s):  
David C. Copenhaver ◽  
Elaine P. Scott ◽  
Alexander Hanuska
Keyword(s):  
Sandwich Structures ◽  
Thermal Characterization ◽  
Honeycomb Core

Use of Guided Waves for Inspection of Composite Skin-Honeycomb Core

2010 ◽  
Vol 636-637 ◽  
pp. 1533-1540
Author(s):  
A. Satour ◽  
F. Boubenider ◽  
Ali Badidi Bouda ◽  
Rachid Halimi
Keyword(s):  
Guided Waves ◽  
Sandwich Structures ◽  
Ultrasonic Guided Waves ◽  
Sandwich Plates ◽  
Aircraft Industry ◽  
Honeycomb Core ◽  
The Core ◽  
Honeycomb Sandwich

Sandwich plates, made of two aluminum layers and a metal honey comb core are used in the aircraft industry. The purpose of this study is to show the ultrasonic guided waves sensibility to discover delamination in skin-honeycomb sandwich structures used in aeronautics. Separation between the skin and the core can appear during the manufacture or after use. In this work, Lamb's waves are used to control this kind of plane structure. Indeed, these waves have the advantage to put in vibration the totality of the plate that we want to control and they propagate on long distances without too much attenuation. The revealing, by the guided waves, of the unsticking which can meet on such sandwiches, between the plate and the honeycomb core is studied and commented.

Precipitate coarsening during hot-compression testing of NiAl + 2 at.% Nb

1986 ◽  
Vol 44 ◽  
pp. 598-599
Author(s):  
W. M. Sherman ◽  
K. M. Vedula
Keyword(s):  
High Temperature ◽  
Flow Stress ◽  
Weight Ratio ◽  
Constant Strain Rate ◽  
Hot Compression ◽  
Compression Testing ◽  
Second Phase ◽  
Precipitate Coarsening ◽  
High Temperature Mechanical Properties ◽  
Ordered Intermetallic

The strength to weight ratio and oxidation resistance of NiAl make this ordered intermetallic, with some modifications, an attractive candidate to compete with many superalloys for high temperature applications. Recent studies have shown that the inherent brittleness of many polycrystalline intermetallics can be overcome by micro and macroalloying. It has also been found that the high temperature mechanical properties of NiAl can be enhanced through the addition of Nb by powder metallurgical techniques forming a dispersed second phase through interdiffusion in a polycrystalline matrix. A drop in the flow stress is observed however in a NiAl-2 at.% Nb alloy after 0.2 % strain during constant strain rate hot compression testing at 1025°C. The object of this investigation was to identify the second phase and to determine the cause of the flow stress drop.

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