Honeycomb Sandwich Structures Research Articles

Flexural creep response of honeycomb sandwich pultruded GFRP composite cross-arm: Obtaining full-scale viscoelastic moduli and creep coefficients

The application of pultruded glass fibre-reinforced polymer composites (PGFRPC) as a replacement material for conventional wooden cross-arm in high transmission towers is relatively new. Although there are several studies on enhancement of the cross-arm structure, there is still a lack of study on the elastic properties of a full-scale PGFRPC cross-arm enhanced with honeycomb sandwich structure. To full-fill the gap, this paper describes an experimental methodology used to obtain the elastic properties of the cross-arm using a three-point bending (3-PB) flexural test by following ASTM D790 standard for deflection behaviour and flexural creep response. The investigation involved several cross-arm members subjected to loading across different span lengths by propose two methods in order to measure the effective cross-arm member section flexural modulus (Ec) and shear modulus (Gc). The creep behaviour of the panels was successfully modeled using Findley's power law, confirming the ability of this empirical approach to simulate the viscoelastic response of the cross-arm. Next predictions were made for up to 50 years of service and the results shows the elastic modulus reduction for the enhanced cross-arm with the honeycomb sandwich structure was approximately reduce to 70 % compare with existing cross-arm which reduce almost 75 % at 50 years of application. The enhanced cross-arm exhibited lower deflection and better creep resistance and increased the bending strength of the cross-arm as well as extended its potential lifespan. Predictions indicated that the enhanced cross-arm maintained better mechanical properties over time compared to the existing one.

Experimental and numerical investigation of impact behavior in honeycomb sandwich composites

This paper presents an experimental and numerical study on the low-energy impact fatigue and bending behavior of sandwich panels reinforced with composite laminate glass and carbon fabric facesheets, supported by a honeycomb core made of Nomex. The crushing behavior of honeycomb sandwich specimens subjected to the impact test was compared and discussed. Our results indicate that the carbon composite facesheets have a significant effect on the impact, resulting in an increase in impact resistance and a 157.14% increase in crack depth in the elastic region compared to glass facesheets reinforcement. This increase serves as an indicator of the laminate's ability to resist damage initiation and impact fracture mechanisms. Also, an increasing in flexural strength about 45.72% was observed in carbon facesheets honeycomb specimens compared to glass facesheets reinforcement. Microscopic illustration of the damaged honeycomb sandwich specimens was conducted to evaluate the interfacial characteristics and describe the damage mechanics of the composite facesheets and core adhesion under the impact test. The numerical approach proves to be efficient in terms of accuracy and simplicity compared to existing methods for predicting the damage mechanisms of honeycomb sandwich structures. It was noted that results of numerical study show best agreements with experiment results and the model can be used to predict the low-energy impact fatigue.

Design of Honeycomb Sandwich Structures with Curved Edge Cores for Optimal Thermal Buckling Strength

Design of Honeycomb Sandwich Structures with Curved Edge Cores for Optimal Thermal Buckling Strength

Infrared thermal imaging detection and defect classification of honeycomb sandwich structure defects

Infrared thermal imaging detection and defect classification of honeycomb sandwich structure defects

Study on Impact Resistance of Connection Joints for Honeycomb Sandwich Structures

Study on Impact Resistance of Connection Joints for Honeycomb Sandwich Structures

A Bandpass Frequency-Selective Surface Based on an Aramid-Paper Honeycomb Sandwich Structure

A Bandpass Frequency-Selective Surface Based on an Aramid-Paper Honeycomb Sandwich Structure

Mechanics Model of Face-Core and Inner Core Debonding of Composite Honeycomb Sandwich Structures

Mechanics Model of Face-Core and Inner Core Debonding of Composite Honeycomb Sandwich Structures

Study on Shear Fatigue Performance of Scarf Repaired Honeycomb Sandwich Structure

The shear static and shear fatigue tests of the honeycomb sandwich composite were carried out to study the effects of three different repair methods on shear fatigue performance: the unilateral panel scarf repair, the unilateral panel and core scarf repair, and the bilateral panel and core scarf repair. The stress ratio R=0.1 was selected. The results show that the failure mode of the honeycomb sandwich structure is the destruction of the honeycomb core. The structure is torn into two halves from the core, and the core tends to squeeze to one side. There is no debonding between the panel and the core, and no delamination in the panel. The static strength, fatigue limit, fatigue life and residual strength of the specimens are significantly decreased by the scarf repair. The rank of reduction from most to least is: the unilateral panel scarf repair, the bilateral panel and core scarf repair, and the unilateral panel and core scarf repair.And the latter two are remarkably similar.

Research on pulse infrared thermal wave detection technology for honeycomb sandwich structure defects

Through the method of numerical simulation, the detection rules of different defect characteristics and the detection effect of detection process parameters on different defects were explored. The optimal detection process parameters for GFRP/NOMEX honeycomb sandwich structure specimens with delaminating, debonding, water accumulation, and glue plugging defects were obtained. Experimental research was carried out to verify its detection effect for actual tests. The result is that the technology under this parameter can get better defect detection effect.

The 3D Printing of Novel Honeycomb-Hollow Pyramid Sandwich Structures for Microwave and Mechanical Energy Absorption.

Honeycomb sandwich (HS) structures are important lightweight and load-bearing materials used in the aerospace industry. In this study, novel honeycomb-hollow pyramid sandwich (HPS) structures were manufactured with the help of fused deposition modeling techniques using PLA and PLA/CNT filaments. The microwave and mechanical energy absorption properties of the HPS structures with different geometry parameters were studied. Compared with the HS structure, the HPS structure enhanced both microwave absorption and mechanical properties. The HPS structures possessed both broadband and wide-angle microwave absorption characteristics. Their reflection loss at 8-18 GHz for incident angles of up to 45° was less than -10 dB. As the thickness of the hollow pyramid increased from 1.00 mm to 5.00 mm, the compressive strength of the HPS structure increased from 4.8 MPa to 12.5 MPa, while mechanical energy absorption per volume increased from 2639 KJ/m3 to 5598 KJ/m3. The microwave absorption and compressive behaviors of the HPS structures were studied.

Fabrication of a novel continuous fiber 3D printed thermoset all-composite honeycomb sandwich structure with polymethacrylimide foam reinforcement

Continuous fiber-reinforced composite (CFRC) 3D printing provides attractive solutions for integrated fabrication of all-composite honeycomb sandwich structures. However, weak matrix strength and insufficient interlayer bonding degrade the performance of 3D-printed thermoplastic honeycomb sandwich structures. The curing-mold-dependent thermoset honeycomb sandwich structures are challenging to fabricate integrally by 3D printing. This study addressed these issues by filling the honeycomb cells with lightweight polymethacrylimide (PMI) foam during 3D printing, achieving co-curing support and enhanced performance of the integrally 3D-printed honeycomb sandwich structures. The novel foam-reinforced structure was studied using three-point bending tests and compared to the foam-free bonding-based structure. With a minor weight gain (9.48 %), the PMI foam reinforcement increased the peak load capacity of the honeycomb sandwich structure by 198.31 % (4.32 kN). The specific bending stiffness and the specific core shear strength were increased by 49.32 % and 165.69 %, respectively. Finally, the failure flow maps and stress state were analyzed to reveal structural failure modes and PMI foam reinforcing mechanisms.

A bone structure-inspired design of bionic wing rib

This paper presents a method to generative design bionic bone structures wing ribs by simulating the formation process of soap bubble boundary. In this method, the position of the central control point is optimized by the genetic algorithm to simulate the moving process of the bubble, and the control point is simplified by the K-means classification method to improve the computational efficiency. The boundary formed by the extrusion of bubbles is filled with a bone-like grid structure to realize the optimal design of a bone-like rib structure. Compared with the traditional honeycomb sandwich structure, the bone-like rib structure can distribute the stress evenly throughout the structure, thus reducing the stress concentration and improving the bearing capacity of the structure. The method proposed in this paper provides a new idea for a multilevel structure design.

Reliability Optimization of the Honeycomb Sandwich Structure Based on A Neural Network Surrogate Model

Composite radomes are usually located in the nose of aircraft and are important structural components that protect radar antenna. The finite element model of a radome structure is developed and analyzed in this article. Single-objective deterministic and reliability optimization models based on the minimum total mass of the radome structure were established, and the layer thickness of each part of the honeycomb sandwich radome structure was considered a design variable. A multi-objective deterministic and reliability optimization model for a radome structure with a minimum total mass and maximum buckling critical load was established, and a particle swarm optimization algorithm was used to solve the problem. Our optimized results satisfied the constraints and utilization rate of materials, and structural safety was improved.

On Impact Damage and Repair of Composite Honeycomb Sandwich Structures

This study is conducted on glass fiber-reinforced composite honeycomb sandwich structures by introducing delamination damage through low-velocity impact tests, establishing a three-dimensional progressive damage analysis model, and evaluating the delamination damage characteristics and laws of honeycomb sandwich structures under different impact energies through experiments. Repair techniques and process parameters for delamination damage are explored. It is found that as the impact energy increases, the damage area of honeycomb sandwich panels also increases, and the delamination damage extends from the impact center to the surrounding areas, accompanied by damage such as fiber fracture and matrix cracking. The strength recovery rates of sandwich panels at impact energies of 5 J, 15 J, and 25 J after repair are 71.90%, 65.89%, and 67.10%, respectively, which has a considerable repair effect. In addition, a progressive damage model for low-velocity impact on the composite honeycomb sandwich structure is established, and its accuracy and reliability are verified.

Experimental study of 3D printed carbon fibre sandwich structures for lightweight applications

Honeycomb sandwich structures are widely used in lightweight applications. Usually, these structures are subjected to extreme loading conditions, leading to potential failures due to delamination and debonding between the face sheet and the honeycomb core. Therefore, the present study is focused on the mechanical characterisation of honeycomb sandwich structures fabricated using advanced 3D printing technology. The continuous carbon fibres and ONYX-FR matrix materials have been used as raw materials for 3D printing of the specimens needed for various mechanical characterization testing; ONYX-FR is a commercial trade name for flame retardant short carbon fibre filled nylon filaments, used as a reinforcing material in Morkforged 3D printer. Edgewise and flatwise compression tests have been conducted for different configurations of honeycomb sandwich structures, fabricated by varying the face sheet thickness and core cell size, while keeping the core cell thickness and core height constant. Based on these tests, the proposed structure with face sheet thickness of 3.2 mm and a core cell size of 12.7 mm exhibited the highest energy absorption and prevented delamination and debonding failures. Therefore, 3D printing technology can also be considered as an alternative method for sandwich structure fabrication. However, detailed parametric studies still need to be conducted to meet various other structural integrity criteria related to the lightweight applications.

Quantitative structural uncertainty analysis of composite honeycomb sandwich using a feedback neural network

The quantification of margins and uncertainty (QMU) method was applied using a neural network to inversely determine the strength boundary of a composite honeycomb sandwich structure considering the random uncertainty of its elastic modulus, shear modulus, tensile strength, compressive strength, and shear strength in the warp and fill directions, and panel thickness. An application framework for the deterministic quantitative analysis of strength was proposed based on margin design theory, combining the strength problem with the quantitative analysis of uncertainty. First, the failure criterion of the structure was modeled based on the progressive damage principle using ABAQUS. Next, Latin hypercube sampling was applied to simulate the stochastic uncertainty of the structural parameters, and the resulting sample sets were input into ABAQUS to calculate the corresponding structure lateral bearing capacities. These results were considered to collectively represent the actual strength boundary of the composite structure. A feedback neural network was subsequently trained on these ABAQUS data to obtain the functional mapping relationship between the parameters and capacity. The capacity obtained using this relationship was multiplied by an empirical safety factor to serve as the theoretical strength boundary. Finally, the QMU method was applied using cumulative distribution functions of the theoretical and actual strength boundaries to calculate the confidence factor and thereby evaluate the reliability of the composite honeycomb sandwich structure.

Investigating the Excellence of Different Thermography Approaches to Subsurface Dis-bonds Detection in Aluminum Honeycomb Sandwich Structures

Investigating the Excellence of Different Thermography Approaches to Subsurface Dis-bonds Detection in Aluminum Honeycomb Sandwich Structures

Preparation of microscale multi-layered viscoelastic polymers and analysis of their noise control effects on composite structures

Multi-layered design is an effective method to improve the damping performance of structures. The existing research focuses more on the multi-layered design of the structure from the macro-perspective, but lacks attention to the material itself from the micro-perspective. Thus, whether microscale multi-layered (MML) viscoelastic polymers have advantages in damping performance is not clear. Moreover, damping materials preparation and structural noise control is an interdisciplinary study. The noise and vibration control effect of MML viscoelastic polymers in actual composite structures needs to be further investigated. This paper conducts such a study on these issues. First, two different types of MML viscoelastic polymers, i.e., free damping (FD) and micro-constrained damping (MCD) composites, were prepared, and their material properties were characterized. Second, the frequency-dependent damping loss factors and elastic modulus of the different damping composites were identified. The influences of damping composite types and MML designs on material damping loss factor and elastic modulus were compared. Third, a prediction model of vibroacoustic behaviours of the honeycomb sandwich structure was established and validated to investigate the noise and vibration control effects of the MML damping composites on composite structures. The influences of the types, numbers of layers and application positions of the MML damping composites on the honeycomb sandwich structure were studied. The results indicated that MML design is helpful to improve the damping performance of viscoelastic polymers, but its influence on different damping composites is quite different. For noise control, MML-FD is more suitable for controlling airborne sound propagation, while MML-MCD is more suitable for controlling structural sound propagation.

Mechanical properties of 3D-printed Al2O3 honeycomb sandwich structures prepared using the SLA method with different core geometries

In this study, Al2O3 honeycomb sandwich structures with different core geometries (square, triangular, circular) have been fabricated through an additive manufacturing system based on the stereolithography (SLA) method. The debinding procedure was performed under both nitrogen and air atmospheres. The impacts of the debinding atmosphere and core geometry on the densification and mechanical properties were investigated. The stiffness and flexural strength of the ceramics were examined experimentally using an impulse excitation of vibration technique and a three-point bending test, respectively. The specific stiffness and specific strength of the ceramics were also evaluated, with the core geometries taken into consideration. The outcomes showed that higher densification was achieved when the ceramics were exposed to debinding in nitrogen. The stiffness values were found to be similar for the same debinding condition within the honeycomb sandwich structures, irrespective of the core geometry. Notably, the highest specific stiffness (98 MNm/kg) was achieved for the samples subjected to debinding in nitrogen with a square core geometry. Furthermore, ceramics with square cores for debinding in a nitrogen atmosphere also demonstrated the highest performance in terms of specific strength (110 kNm/kg) within the honeycomb structures. This study demonstrated that Al2O3 honeycomb sandwich structures with square cores may be suitable candidates for lightweight-structure demanding applications.

Water ingress detection in an aluminum honeycomb sandwich structure using laser ultrasonics based on mode conversion behaviors

This paper investigates the method for water ingress detection in an aluminum honeycomb sandwich structure by laser ultrasonics. To clarify the propagation of Scholte waves generated at the solid-liquid interface, the theoretical dispersion curves in the water-aluminum layered structure are calculated by the global matrix method. Using a laser ultrasonic visualizing inspector, the guided wave propagation in the wavefields has been visualized, which shows the mode conversion behaviors occurring in the water ingress area. The clarification of mode conversion is then investigated by the finite element method. The Scholte modes at the solid-fluid interface and the Lamb modes in the face sheet are interconverted because of the change in the waveguide structure. Wavenumber filter reconstruction and the resulting energy maps are applied to illustrate the mode conversion in the wavefields and to detect the water ingress area. Results show that the appearance of the water layer contributes to the mode conversion behaviors during the guided wave propagation in the honeycomb sandwich structure, which offers the potential for water ingress detection based on the mode conversion behaviors.