scholarly journals Non Destructive Testings on Damaged Multi-Cores Materials Sandwich Structures

Proceedings ◽  
2020 ◽  
Vol 39 (1) ◽  
pp. 13
Author(s):  
Mezeix ◽  
Wongtimnoi
Keyword(s):  
Sandwich Structures ◽  
Landing Gear ◽  
Core Material ◽  
Phase Array ◽  
The Core ◽  
Porosity Defects ◽  
Sandwich Specimen ◽  
Impact Protection ◽  
Non Destructive ◽  
Composite Skins

Sandwich structures are widely used in aeronautics both for primary and secondary structures such as landing gear doors, flaps or floors. Multi-cores materials sandwich structures presents many advantages. By adding layers with another materials that the core one, extra properties can be obtained as heat or impact protection. Manufacturing quality must be controlled and therefore bonding needs to be inspected. In this paper bonding defects between multi-layers of sandwich specimen are inspected through Non Destructive Tests. Due to its large use in industry, ultrasonic phase array is used to detect manufacturing bonding defects. Three different type of multi-cores materials specimen are investigated. Results show that due to the high PVC foam porosity, defects cannot be detected both between composite skins and foam and between foam and core material.

Experimental investigations on the sandwich composite beams and panels with elastomeric foam core

2017 ◽  
Vol 21 (3) ◽  
pp. 865-894 ◽  
Author(s):  
AR Nazari ◽  
H Hosseini-Toudeshky ◽  
MZ Kabir
Keyword(s):  
Carrying Capacity ◽  
Sandwich Structures ◽  
Failure Mechanisms ◽  
Composite Beams ◽  
Core Material ◽  
Foam Core ◽  
Sandwich Beams ◽  
Load Carrying Capacity ◽  
The Core ◽  
Load Carrying

In this paper, the load-carrying capacity and failure mechanisms of sandwich beams and panels with elastomeric foam core and composite laminate face sheets are investigated. For this purpose, the flexural behavior of laminated composite beams and panels (applied as face sheets) is firstly investigated under three-point bending and central concentrated loads, respectively. Then, the same examination is conducted for the sandwich beams and panels, in which the proposed elastomeric foam is utilized as the core material. It is shown that the failure mechanisms which are associated to the core in the sandwich structures with crushable foams are not considered in the examined sandwich structures. The collapse of the sandwich specimens, examined here, is observed due to the failure of the skins in some steps. By multi-step collapse of these specimens via separately failure of the top and bottom skins, a considerable amount of energy is absorbed between these steps. Due to non-brittle behavior of the core material under loading, a large compression resistance is observed after failure of the top skin which led to the recovery of the load-carrying capacity in the sandwich beams. A similar behavior for the sandwich panels led to the increase of the ultimate strength after appearance of the failure lines on the top skin. The general outcomes of this investigation promise a good influence for the application of elastomeric foam as core material for sandwich structures.

The influence of different types of core materials on the impact behaviour of sandwich composites

2018 ◽  
pp. 78-83
Author(s):  
Cihan Kaboglu
Keyword(s):  
Sandwich Structures ◽  
Core Material ◽  
Sandwich Composite ◽  
Balsa Wood ◽  
Impact Behaviour ◽  
The Core ◽  
Glass Fibre Reinforced Polymer ◽  
Glass Fibre Reinforced ◽  
The Impact ◽  
Core Materials

Sandwich structures are popular in applications in which the weight of the component affects the efficiency, especially in the aviation and aerospace industries. This study aims to understand the impact behaviour of sandwich structures with different core materials. Sandwich structures are manufactured with glass fibre reinforced polymer skins and balsa wood, polyethylene terephthalate (PET) and polyvinyl chloride (PVC) core through resin infusion under flexible tools. Three different core materials were tested and compared using the damaged area of the back face of the sample. The effect of the core materials on the mechanical behaviour of the structures is crucial. The results showed that the microstructure of the core materials plays an important role, because althoughthe density of balsa wood is greater than the density of PET and PVC, the structures having PVC and PET as core materials undergo less damage than those having balsa wood as a core material. Keywords: Sandwich composite, impact behaviour, core materials.

scholarly journals Delamination Testing of Additive Manufactured Sandwich Structures with Lattice Truss Core

2021 ◽  
Author(s):  
Miguel Nuño ◽  
Jannik Bühring ◽  
Narasimha Rao Mekala ◽  
Kai-Uwe Schröder
Keyword(s):  
Adhesive Bonding ◽  
Sandwich Structures ◽  
Sheet Thickness ◽  
Tensile Tests ◽  
Design Guidelines ◽  
Core Material ◽  
The Core ◽  
Truss Core ◽  
Out Of Plane ◽  
Peel Tests

Abstract Sandwich structures possess a high bending stiffness compared to monolithic structures with a similar weight. This makes them very suitable for lightweight applications where high stiffness to weight ratios are needed. Most common manufacturing methods of sandwich structures involve adhesive bonding of the core material with the sheets. However, adhesive bonding is prone to delamination, a failure mode which is often difficult to detect. In this paper, the results of delamination testing of fully additive manufactured (AM) AlSi10Mg sandwich structures with pyramidal lattice truss core are presented. To characterise the bonding strength, climbing drum peel tests and out-of-plane tensile tests are done. The thickness of the faces and the diameter of the struts is 0.5 mm, while the core is 2 mm thick. The inclination of the struts is 45°. To predict the expected failure loads and modes, analytical formulas are derived. The analytics and tests are supported by finite element (FE) calculations. From the analytic approaches, design guidelines to avoid delamination in AM sandwich structures can be followed. The study shows, that critical ratios for face sheet thickness to strut diameter can be determined, to define if the structure tends to delaminate under certain loads. Those ratios are mainly influenced by the strut inclination. The peel tests resulted in face yielding, which can also be followed from the analytics and numerics. The out-of-plane tensile tests didn't damage the structure.

scholarly journals Analysis Of Potentiometric Methods Used For Crack Detection In Forging Tools

2015 ◽  
Vol 12 (1) ◽  
pp. 27-30
Author(s):  
Jozef Pilc ◽  
Mário Drbúl ◽  
Dana Stančeková ◽  
Daniel Varga ◽  
Juraj Martinček ◽  
...  
Keyword(s):  
Crack Detection ◽  
High Hardness ◽  
Core Material ◽  
Tool Steels ◽  
Working Process ◽  
The Core ◽  
Heat Treated ◽  
The Right ◽  
The Cost ◽  
Non Destructive

Abstract Increased use of forging tools in mass production causes their increased wear and creates pressure to design more efficient renovation process. Renovation is complicated because of the identification of cracks expanding from the surface to the core material. Given that the production of forging tools is expensive, caused by the cost of tool steels and the thermo-chemical treatment, it is important to design forging tool with its easy renovation in mind. It is important to choose the right renovation technology, which will be able to restore the instrument to its original state while maintaining financial rentability. Choosing the right technology is difficult because of nitrided and heat-treated surface for high hardness and wear resistance. Article discusses the use of non-destructive method of detecting cracks taking into account the size of the cracks formed during working process.

ANALISIS PENGARUH VARIASI MATERIAL CORE TERHADAP KUALITAS NIPPLE

2020 ◽  
Vol 8 (2) ◽  
pp. 82-88
Author(s):  
Moh Rofi Julian ◽  
Yopi Handoyo
Keyword(s):  
Surface Defects ◽  
Core Material ◽  
Smelting Process ◽  
Air Voids ◽  
The Core ◽  
Iron Castings ◽  
Large Numbers ◽  
Porosity Defects ◽  
Coarse Surface ◽  
The Cost

This study aims to determine the effect of variations in core material made of iron and resin sand on the Nepel Brass smelter on hardness, surface results of castings, shrinkage, density apparent, time, and cost. To find out which core material is more efficient for use in large quantities. The product material used is Brass in the form of Hose Nipple with a size of 1/5 x 5/8 inch. The average specimen weight in this study was 8.33 gr. From the research conducted, the differences were found, namely the hardness of the smelting process with the core material of iron castings and resin sand is 37.14 BH 5 / 250-25 and 30.94 BH 5/250-25. Material defects found are in iron castings specimens, namely rough surface defects, pinhole, scrabs, gas holes and air voids with 19 points of defect points and an area of ​​78 mm or 10.57% of the inside area of ​​the specimen. Likewise with resin sand-coated specimens experiencing defects of Coarse Surface, Needle Hole, Scrabs, Gas Hole, Air Cavity and sand inclusion / erosion hardness, with large numbers almost covering all parts of the specimen or 95.1%. For shrinkage, cast specimens with iron castings are smaller at 0.35% and resin-coated specimens of 0.40%. For porosity defects, iron castings in the specimens were 8.33 and 8.40 in the core of the resin sand castings. The higher the true density, the more dense the material is. The production time is 555 seconds (9 minutes 15 seconds) from the smelting process of specimens with the core of resin sand castings which is for 829 seconds (13 minutes 49 seconds). Whereas for the process of releasing specimens from molds, products with resin sand castings are faster at 14 seconds, while for specimens with iron castings core is 28 seconds. The cost required to make specimens with iron cast core is Rp. 4,718,500, the cost is cheaper than the manufacture of specimens with core resin sand castings that require capital of Rp. 4,999,000.

A New Approach to Manufacturing Biocomposite Sandwich Structures: Mycelium-Based Cores

2016 ◽  
Author(s):  
Lai Jiang ◽  
Daniel Walczyk ◽  
Gavin McIntyre ◽  
Ronald Bucinell
Keyword(s):  
Sandwich Structures ◽  
Agricultural Waste ◽  
Core Material ◽  
Processing Conditions ◽  
New Approach ◽  
Three Point Bending ◽  
The Core ◽  
Materials Used ◽  
Optimal Material ◽  
Core Mixture

A new approach to manufacturing biocomposite sandwich structures is introduced. Materials used in the biocomposite are natural textile reinforcement, mycelium-bound agricultural waste as core, and bioresin. This paper focuses on three specific steps of the seven-step manufacturing process: filling pre-stamped textile shells with core mixture; allowing the core material to grow thereby binding reinforcement particles and textile skins into a unitized preform; and oven drying said preform to drive off moisture and inactivate the mycelium. Specific process details highlighted include design and thermoforming of growth trays, tray sterilization, filling trays with mycelium-inoculated substrates filling and allowing growth to occur, and finally conduction and convection drying/inactivation of the grown parts. To study the new material’s stiffness using different materials and under different processing conditions, specimen dimensions were based on ASTM D7250 and C393 standards. All dried samples were tested in flexure by three-point bending method to determine the stiffness and strength of the resin-less preforms and to identify optimal material combinations.

Vibration-Based Non-Destructive Evaluation of Internal Damage in Foam Cored Sandwich Structures Using Wavelet Analysis

2019 ◽  
Vol 24 (No 1) ◽  
Author(s):  
Andrzej Katunin
Keyword(s):  
Wavelet Analysis ◽  
Modal Analysis ◽  
Sandwich Structures ◽  
Destructive Testing ◽  
Internal Damage ◽  
The Core ◽  
Environmental Interactions ◽  
Stiffness Properties ◽  
Low Mass ◽  
Non Destructive

Modern mechanical and civil structures are increasingly designed using polymeric composites that ensure great strength-to-mass ratio and are resistant to various environmental interactions, like corrosion. The application of sandwich structures in the design of mechanical and civil constructions is determined by their good stiffness properties and very low mass, which is a very attractive combination. Due to their wide applicability, these structures should be properly maintained and diagnosed, and thus, appropriate non-destructive testing (NDT) methods should be developed in order to detect and identify various types of damage. Special attention should be paid to internal damage (damage to the core of a sandwich structure), which cannot be detected during a visual inspection. In the paper, an NDT method based on modal analysis and further processing of modal shapes using a wavelet transform is proposed. Three sandwich structures with damage to the core of various types were experimentally tested using modal analysis, the damage positions were detected and identified using wavelet analysis, and verified by comparing the results of previously performed thermographic tests. The obtained results show a high effectiveness of the proposed approach, which could find an application in the industrial inspection of sandwich structures in a non-destructive and non-contact manner.

Specific Properties of Novel Two-Dimensional Square Honeycomb Composite Structures

2014 ◽  
Vol 695 ◽  
pp. 694-698 ◽  
Author(s):  
Mohd Ruzaimi Mat Rejab ◽  
W.A.W. Hassan ◽  
Januar Parlaungan Siregar ◽  
Dandi Bachtiar
Keyword(s):  
Energy Absorption ◽  
Composite Structures ◽  
Sandwich Structures ◽  
Core Material ◽  
Foam Core ◽  
Specific Strength ◽  
The Core ◽  
Reinforced Plastic ◽  
Honeycomb Cores ◽  
Lightweight Core

Hexagonal honeycomb cores have found extensive applications particularly in the aerospace and naval industries. In view of the recent interest in novel strong and lightweight core architectures, square honeycomb cores were manufactured and tested under uniform lateral compression. A slotting technique has been used to manufacture the square honeycomb cores based on three different materials; glass fibre-reinforced plastic (GFRP), carbon fibre-reinforced plastic (CFRP) and self-reinforced polypropylene (SRPP). As semi-rigid polyvinyl chloride (PVC) foam was placed in each of unit cells to further stiffen the core structure. The core then was bonded to two skins to form a sandwich structure. The compressive responses of the sandwich structures were measured as a function of relative density. In this paper, particular focus is placed on examining the compression strength and energy absorption characteristics of the square honeycombs with and without the additional foam core. Comparisons in terms of specific strength and specific energy absorption have shown that the CFRP core offers excellent properties. The presence of the foam core significantly increases the energy absorption capability of overall structure and the SRPP core could potentially be used as an alternative lightweight core material in recyclable sandwich structures.

Homogenization of selective laser melting cellular material for impact performance simulation

2015 ◽  
Vol 6 (4) ◽  
pp. 439-450 ◽  
Author(s):  
G. Labeas ◽  
Evangelos Ptochos
Keyword(s):  
Selective Laser Melting ◽  
Failure Modes ◽  
Sandwich Structures ◽  
Sandwich Panels ◽  
Core Material ◽  
Laser Melting ◽  
Stress Strain ◽  
Content Type ◽  
The Core ◽  
Modelling Approaches

Purpose – The purpose of this paper is to present, the global behaviour of sandwich structures comprising cellular cores is predicted by finite element (FE) analysis. Two modelling approaches are investigated, providing different levels of accuracy; in both approaches, the sandwich structure is idealised as a layered stack with the skin modelled using shell elements; while the core is either modelled with fine detail using beam micro-elements representing the cell struts, or is modelled by three-dimensional solid elements after an appropriate core homogenisation. Design/methodology/approach – The applied homogenisation methodology, as well as the all important modelling issues are presented in detail. Experimental tests performed using a mass-drop testing machine are used for the successful validation of the simulation models. Findings – It was concluded that the core microscale models having detailed FE modelling of the core unit cells geometry with fine scale beam elements are suitable for the analysis of the core failure modes and the prediction of the basic core stiffness and strength properties. It was demonstrated that the homogenised core model provides significant advantages with respect to computing time and cost, although they require additional calculations in order to define the homogenised stress-strain curves. Research limitations/implications – Special microscale material tests are required for the determination of appropriate materials parameters of the core models, as steel selective laser melting (SLM) microstrut properties differ from the constitutive steel material ones, due to the core manufacturing SLM technique. Stress interactions were not taken into account in the homogenisation, as the applied core material model supports the introduction of independent stress-strain curves; however, the predicted load deflection results appeared to be very close to those obtained from the detailed core micromodels. Originality/value – The paper is original. The dynamic behaviour of conventional sandwich structures comprising conventional honeycomb type cores has been extensively studied, using simple mass-spring models, energy based models, as well as FE models. However, the response of sandwich panels with innovative SLM cellular cores has been limited. In the present paper, novel modelling approaches for the simulation of the structural response of sandwich panels having innovative open lattice cellular cores produced by SLM are investigated.

scholarly journals Acoustic Panels Made of Paper Sludge and Clay Composites

2021 ◽  
Vol 13 (2) ◽  
pp. 637
Author(s):  
Tomas Astrauskas ◽  
Tomas Januševičius ◽  
Raimondas Grubliauskas
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Composite Panel ◽  
Sound Absorption Coefficient ◽  
Core Material ◽  
Paper Sludge ◽  
Frequency Range ◽  
Absorption Properties ◽  
Air Gaps ◽  
The Core

Studies on recycled materials emerged during recent years. This paper investigates samples’ sound absorption properties for panels fabricated of a mixture of paper sludge (PS) and clay mixture. PS was the core material. The sound absorption was measured. We also consider the influence of an air gap between panels and rigid backing. Different air gaps (50, 100, 150, 200 mm) simulate existing acoustic panel systems. Finally, the PS and clay composite panel sound absorption coefficients are compared to those for a typical commercial absorptive ceiling panel. The average sound absorption coefficient of PS-clay composite panels (αavg. in the frequency range from 250 to 1600 Hz) was up to 0.55. The resulting average sound absorption coefficient of panels made of recycled (but unfinished) materials is even somewhat higher than for the finished commercial (finished) acoustic panel (αavg. = 0.51).

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