Description:Field of Invention
The goal is to enhance specific energy absorption (SEA) while reducing the initial peak crushing force.
Background of the invention
Sandwich panels are becoming more and more popular in the construction, automotive, aerospace, and marine industries because they provide a number of benefits over traditional monolithic materials. It has been demonstrated that sandwich panels, which contain a cellular core and fiber-reinforced plastic skins, provide better specific stiffness and strength qualities in flexure than their monolithic counterparts. Many foams honeycomb cores origami-type cores and truss cores have all been the basis for new core designs with enhanced quasi-static and dynamic features that have been put out in recent years.
Typically, sandwich panels are made up of a core and two facing sheets. When the core experiences shear loads, these two face sheets often withstand bending loads. The materials used for the skin and core can differ greatly; the core kinds include corrugated, solid, and honeycomb. The core performs a number of essential tasks. Simple parallel strip arrangement, tubular core, double truss core, and pulp-board are a few examples of corrugate variations.
Foam is the most often utilized core material. Foam cores are the most recommended option whenever cores with sound, heat, and waterproof properties are needed. The modest increase in buckling stress and negligible flaw sensitivity of sandwich panels filled with foam are encouraged by filling. The face sheets are stabilized and kept apart by the corrugated core, which prevents vertical deformations. Additionally, it provides greater strength and allows the entire structure to be seen as a single panel due to its shearing strength. Polyurethane foam significantly increased the panel's fatigue life and supported energy absorption. Sandwich panels without foam absorbed half as much energy as samples filled with foam for all core types.
Web cores filled with foam improve absorption of energy during suddenly applied loading conditions. As the foam contracts, energy is transferred and less impact effect is applied to the face-sheets. This quality is useful for protective fatigue fractures.
Corrugated core resists bending and twisting in response to vertical shear, in contrast to soft honeycomb core. Corrugated core sandwich panels are typically utilized in aerospace, automotive, marine, civil engineering, and other fields where weight is a major design consideration because of its high ratio of flexural stiffness to weight. Multiple core materials have been tried in an effort to combine the beneficial properties of foams. PU-foam had a relatively superior bending performance in comparison to other core kinds. Sandwich panels with a PU-foam core were recognized for their economical and good strength to weight ratios. This study focused primarily on the effectiveness of sandwich panels with different cores in flexural tests.
Sandwich panels with corrugations and different cores were made and put through flexural bending tests. In order to provide a comparison, various core materials were tested with empty corrugate. Peak load, initial failure load, and bending strength data were anticipated.
Preparation of corrugated sandwich panels are known in the prior art. For instance,CN212636772U discusses the preparation of multilayered corrugated composite sandwich structure. The utility model discloses a sandwich structure of multilayer corrugated composite material, which comprises a corrugated sandwich, wherein the corrugated sandwich comprises at least one layer of sandwich. The sandwich plate is used as an impact-resistant material for shock absorption and energy absorption, and it absorbs more energy than a single-layer corrugated sandwich plate on the theory of guaranteeing a particular amount of compression resistance. However, the thickness of the multilayer increases the overall weight of the structure which affects thrust to weight ratio in aero industries.
Preparation of sandwich mechanism of sandwich panels are known in the prior art. For instance, CN219060595U discusses the preparation of a sandwich panel which is essentially composed of two panels: a first panel and a second panel. The utility model provides a sandwich mechanism for a sandwich panel. Sandwiched between the two panels lies the mechanism. This sandwich mechanism layer is structurally designed to increase the sandwich plate's supporting force. However, the simply supported points produce reaction forces only in vertical direction which gives support for compressive strength but it would not support for flexural strength.
Summary of the invention
The flexural test performed on the specimens in UTM provided the sandwich panel's flexural qualities. We came to the conclusion that the model's maximum load, or the numerical test result, falls within the range of the experimental results.
Theoretical study predicted the sandwich structure's bending stiffness, initial failure load, and peak load. In comparison to empty and wood-filled corrugated cores, the PU foam provided the highest deflection in flexural tests, and the analytical predictions accorded well with the experimentally measured results. These testing led us to the conclusion that sandwich panels with foam-filled cores have the highest strengths.
Brief Description of Drawings
The invention will be described in detail with reference to the exemplary embodiment's shown in the figures wherein:
Figure 1 Corrugated Sandwich Panel
Detailed description of the invention
Foam-filled corrugated cores are a good choice for sophisticated sandwich structures because of their increased stiffness and peak load capacity, which can help with lightweight design without sacrificing structural integrity. By efficiently increasing the load distribution and delaying the start of local buckling, the foam addition to the corrugated core improves mechanical performance under both compressive and flexural loads. In applications like crashworthiness and impact-resistant structures, the foam's ability to sustain the corrugated structure during deformation results in more stable failure modes and increased energy absorption.
Foam is the most commonly utilized core material. Sandwich panels are composed of two face sheets that have been strengthened and separated by a core material that weighs less than traditional materials. Lightweight sandwich panels are frequently utilized in aircraft components like wings, control surfaces, etc. because mass reduction is a crucial factor for the aviation sector. Sandwich panels that are flat and curved are commonly used for aviation components like wings and control surfaces. While core offers bending stiffness by putting face sheets away from the neutral axis, thin face sheets give the structures rigidity. Corrugated core resists twisting and bending in response to vertical shear, in contrast to soft honeycomb core.
The process of making sandwich panels with different types of corrugated panels packed with different types of cores and without cores. Al6061 grade aluminum was used to create the face-sheets and core web (density =2700 kg/m3). Wood fillings and commercial closed-cell polyurethane foam with a density of =30 kg/m3 were used as the filler materials. Polyurethane foams have superior insulating qualities, commendable compressive strength characteristics, and tolerance to temperature changes. Aluminum strips were cut in accordance with ASTM standard C393M-11. The strips were then bent, and foam cubes were placed using epoxy adhesives into the intersections of the corrugated core.
A computer-controlled mechanical tester was used to conduct the three-point bending tests in accordance with ASTM D-790M standard test procedure. Three-point bending involves placing the material in the form of a Simply Supported Beam (SSB) and applying a transverse load to the specimen at the specimen's centre of span length.
A three-point flexural test was performed on the materials with a set loading rate in compliance with ASTM D-790M and ASTM C393M-11 standards. The sandwich panels measured 265 mm in total length and 170 mm in span L between supports. The force and displacement of the specimens were measured, and their bending strength was ascertained by unloading them.
A three-point bending test was conducted for the core-filled corrugated sandwich panels, which have three different types of cores: empty, wood-filled, and polyurethane. The results indicate that, when compared to other panels, the foam-filled corrugated sandwich panels yield greater strength. Several failure mechanisms, including face yielding, face wrinkling, and indentation core shear, were taken into consideration when core-filled corrugated sandwich panels were exposed to three-point bending. when the corrugated sandwich panels with a filled core began to disintegrate. The sandwich construction continued to bear the strain until the core gave way because the core insertions remained elastic.
The ultimate tensile load is approximately 3000 kN for an empty panel, 3300 kN for a wood panel, and 3500 kN for a foam panel. When compared to empty and wood corrugated panels, the foam-filled corrugated panel was able to bear a larger compressive load.
As the load is passed to the face sheets, the core stiffness softens. As the core becomes softer, the sandwich panel tends to be an isotope plate—that is, the face sheets will yield before the core material. An improvement in the load applied to the face sheets occurs due to the softer center rigidity. For every given value, five tests were performed, and the standard deviation was either less than or equal to the value. Face sheets typically withstand bending stresses while the core experiences shear loads. When it comes to peak load resistance, corrugated panels that are empty can withstand a lower peak load than those that are filled with PU foam.
Using UTM, compressive strength tests were performed on sandwich panels made of foam, wood, and empty material. Plotting of load vs displacement curves was done in each picture, and the outcomes were evaluated against one another. According to the graphs, a wood panel's ultimate tensile load is approximately 2800 kN, while an empty panel's is around 3200 kN for foam panels and 3000 kN for other materials. Consequently, the Compared to empty and wood corrugated panels, foam-filled corrugated panels may sustain a higher compressive force.
The foam sandwich panels' peak load and bending stiffness were determined through theoretical analysis and contrasted with those of other sandwich panels. The foam sandwich panel that provided the greatest deflection in comparison to empty and wood-filled corrugated cores was the subject of a flexural test and measurement by experimental analysis.
These enhancements make sandwich panels with foam-filled corrugated cores attractive options for lightweight, high-strength applications in civil engineering, automotive, and aerospace. To further assess and improve these structures for real-world settings, future research may incorporate impact testing and numerical modelling. , Claims:The scope of the invention is defined by the following claims:

Claim:
1. The fabrication of corrugated sandwich panel comprising:
a) The face-sheets and core web were made using aluminium 6061 grade and commercial closed-cell polyurethane foam. The density of face-sheet and core web are taken as 2700 kg/m3 and 30 kg/m3.
b) The aluminum sheets were taken in strips in accordance with ASTM C393M-11, and the sheet was bent. Using epoxy adhesives, the measured number of wood samples and the cubic pieces of polyurethane foam were evenly put into the corrugated core's intersections.
c) The face-sheets is acting as mold is prepared with aluminium 6061 grade in order to create a layer of core web between face-sheets. The layer of core web is filled with foam and wood material as filling material.
2. As mentioned in claim 1, according to ASTM C393M-11 and ASTM D-790M, a sandwich panel specimen measuring 265 mm in total length and 170 mm in span L between the supports is taken into consideration for a flexural test with a set loading rate. The specimen is positioned atop a Simply Supported Beam (SSB), with the center of the specimen's span length experiencing transverse load application.
3. According to claim 1, the three-point bending tests were performed following the ASTM D-790M standard test method using a computer-controlled mechanical tester. when the corrugated sandwich panels with a filled core began to disintegrate. The sandwich construction continued to bear the strain until the core gave way because the core insertions remained elastic.