Sandwich Composite Laminates Research Articles

Forming behavior during drawing of aluminum sandwich composite laminate – a comprehensive experimental analysis

Forming behavior during drawing of aluminum sandwich composite laminate – a comprehensive experimental analysis

Influence of Aspect Ratio on the Flexural and Buckling Behavior of an Aluminium Sandwich Composite: A Numerical and Experimental Approach.

In the field of engineering materials, lightweight and ultra-lightweight composites are used in real time to a greater extent, with high-performance targeting for tailor-made systems in aerospace, automotive, and biomedical applications. Sandwich composites are among the most popular lightweight materials used in structural and vehicle-building applications. In the present investigation, one such sandwich composite laminate composed of aluminum face sheets and a high-density polyethylene core was considered to analyze sandwich composites' flexural and buckling behavior experimentally and numerically. The influence of aspect ratios, such as length to thickness and width to thickness, on the flexural and buckling performance of sandwich composite laminates was explored in the study. Laminates with different widths, namely, 10, 12, and 15 mm, and a uniform thickness and length of 3 mm and 150 mm, respectively, were used for flexural analysis, whereas laminates with widths of 10, 12, and 15 mm and a uniform thickness and length of 3 mm and 350 mm, respectively, were used for buckling analysis. The geometrical influence of the laminates on mechanical performance was studied through performance measures such as critical bending load, flexural stiffness, inter-laminar shear stress, and critical buckling load. A significant influence of aspect ratio on the mechanical behavior of the laminates was observed using both experimental and numerical approaches. Flexural behavior was observed to be better at greater widths, namely, 15 mm, and with a minimum support span of 90 mm due to reduced spring back effects and increased bending resistance. A maximum width of 15 mm allowed for a higher buckling load capacity similar to that of bending resistance. A critical buckling load of 655.8 N seemed to be the maximum and was obtained for the highest aspect ratio, b/t = 5. The soft core and ductile metal face sheets offered combined resistance to both bending and buckling. A lower aspect ratio (span to thickness) rendered these sandwich laminates better in terms of both bending and buckling.

Flame retardant and mechanical properties of carbon fiber/novel phenolic resin sandwich composite laminates

This study investigated a novel phenolic resin that possesses the advantages of both epoxy and phenolic resins and significantly improves their disadvantages. This novel phenolic resin was impregnated into the carbon fiber woven to prepare a sandwich composite. Composites with sandwich structures were analyzed for their flame retardant and mechanical properties. The flame retardancy of the novel phenolic resin composite was similar to that of a pure phenolic resin composite without the processing disadvantages of pure phenolic resin, and these two composites were better than epoxy sandwich composites. The mechanical properties, such as facesheet, and core shear test results of the sandwich composite revealed that both epoxy and novel phenolic composites with a flame retardant added had poor interfacial bonding, resulting in lower strength than that of the neat sandwich composite.

Sandwich composite laminate with intraply hybrid woven CFRP/dyneema core for enhanced impact damage resistance and tolerance

The present paper investigates the response a sandwich composite laminate that involves intraply hybrid carbon fiber reinforced polymer (CFRP)/Dyneema core under impact and post-impact tests. This intraply hybrid core was designed to gain the high elasticity and high stiffness/weight ratio of Dyneema fibers while maintaining the structural integrity of CFRP at the laminate core. Low-velocity impact and compression after impact tests were employed to evaluate the damage resistance and tolerance of the laminates. Micro-computed tomography was deployed to inspect the different modes of damage and their propagation during low-velocity impact. The results showed that the damage started in the sandwich composite as localized matrix cracks and delaminations at CFRP impacted face. However, it was distributed through the whole laminate thickness in the monolithic CFRP composites. The fiber cut initiated at 70 J impact energy for the sandwich composite at the impacted CFRP face plies as fiber kinking due to compressive stresses. However, it was initiated at the lower plies of the CFRP composite at 30 J due to high bending and normal strains. This delayed fiber breakage revealed the better residual compression after impact (CAI) strength of the sandwich composite, where it showed 33.5% improved specific CAI strength compared to the monolithic CFRP composite.

Investigation on preparation and mechanical properties of carbon fiber fabric/hollow glass beads/epoxy resin sandwich composite laminates

AbstractTo expand the application of light‐weight and high‐strength polymer matrix composites in the fields of aerospace, shipbuilding and transportation, it has designed and fabricated a new‐type carbon fiber fabric/hollow glass beads/epoxy resin (CFF/HGB/EP) composite with a three‐layer sandwich structure, consisting of an upper composite layer (CFF/EP), core layer (HGB/EP) and lower composite layer (CFF/EP). The effects of the CFF/EP layer and the HGB content on the sandwich composites were explored through a systematic investigation of the mechanical properties and microstructure. The results indicate that the density of the sandwich composite can be reduced to 0.83 g cm−3, while the flexural, impact, and tensile strength of the sandwich composite can be increased by 227%, 156%, and 118% compared with pure epoxy resin, respectively. The great improvement of mechanical properties of the sandwich composite makes its application in various industries more promising.

Experimental Study on The Effect of Aspect Ratio on Flexural Behavior of Aluminum Sandwich Composite

Sandwich composites are one such kind of light-weight composites developed for structural and vehicle body buildings etc. Due to their remarkable features such as high specific strength, high toughness and resistance to inter laminar shear strength. In this study, commercially available aluminium sandwich composite (ASC) laminate was considered for investigating its flexural behavior and buckling behavior as it was mostly used for various structural applications. Flexural analysis was done for different aspect ratios in order to analyze the influence of cross section of the specimen and support span on the flexural capability of the sandwich beam. The composite specimens prepared for flexural test consist of length 150 mm and widths 15, 12 and 10 mm. The flexural test was done for support span of 90, 110 and 130 mm respectively. The performance measures of flexural test are maximum bending load, deflection, flexural stiffness and inter-laminar shear stress. The flexural analysis revealed the fact that the aspect ratio appreciably affected the flexural capacity of the sandwich composite laminates. Maximum flexural capacity with bending load around 3.5 to 4 kN and flexural stiffness around 2.5 to 4.7 kN/mm respectively was observed for the sandwich specuimen for the aspect ratios L/t = 30 and b/t = 5. Being a anisotropic structure, the flexural behavior of this sandwich composite exposed as a combination of bending and shear failure. The soft core material and ductile skin face sheets resulted in a combined failure against flexural load in static condition.

On the impact damage resistance and tolerance improvement of hybrid CFRP/Kevlar sandwich composites

This work presents an experimental demonstration of the significant improvement in the damage resistance of carbon fiber reinforced polymer (CFRP) Kevlar sandwich composite laminates under impact and compression after impact loads. A core of Kevlar plies was sandwiched between two face sheets of CFRP, representing two-third the global laminate thickness. Hand lay-up and vacuum bagging were used to manufacture the sandwich composite structure. Tests of low velocity impact and compression after impact (CAI) were performed to characterize the damage resistance. The different damage modes and their sequence during low velocity impact were visualized using microcomputed tomography. The results showed different damage levels in CFRP/Kevlar core laminates at low and high impact energies. At low impact energy, 10 J, few matrix cracks and delaminations were the main damage modes inside CFRP/Kevlar core laminate, however, extensive delamination, matrix cracks and fiber cut at the lower part of the laminate were appeared inside the fully CFRP laminate. At high impact energy, 70 J, fiber cut was observed inside the whole CFPR laminate, however, for CFRP/Kevlar core laminate, the lower CFRP face sheets did not suffer from any kind of damage. This allowed CFRP/Kevlar core laminate to sustain large load after the load drop occurred when the maximum load capacity of the laminate is reached. Moreover, it allowed CFRP/Kevlar core laminate to sustain larger compressive load during CAI tests resulting in improved residual CAI strength. Owing to the low density of Kevlar fibers and lower damage level during impact (better damage resistance), CFRP/Kevlar core laminate showed up to 51% larger specific CAI strength than CFRP laminate (better damage tolerance).

Comparative Analysis of Delamination Factor in CNC Drilling of Novel Kenaf Fiber Reinforced Aluminum Wire Mesh Sandwich Composite and Kenaf Fiber Laminate with 45o /0o /45o Ply Orientation Angle

Comparative Analysis of Delamination Factor in CNC Drilling of Novel Kenaf Fiber Reinforced Aluminum Wire Mesh Sandwich Composite and Kenaf Fiber Laminate with 45o /0o /45o Ply Orientation Angle

Comparative Analysis of Hole Surface Quality in CNC Drilling of Novel Sisal Fibre Reinforced Aluminium Wire Mesh Sandwich Composite and Sisal Fiber Laminate With 90°/0°/90° Ply Orientation Angle

Comparative Analysis of Hole Surface Quality in CNC Drilling of Novel Sisal Fibre Reinforced Aluminium Wire Mesh Sandwich Composite and Sisal Fiber Laminate With 90°/0°/90° Ply Orientation Angle

Comparative Analysis of hole surface quality in CNC Drilling of Novel Sisal Fibre Reinforced Aluminium Wire Mesh Sandwich Composite and Sisal Fiber Laminate with 45°/0°/45° Ply Orientation Angle

Comparative Analysis of hole surface quality in CNC Drilling of Novel Sisal Fibre Reinforced Aluminium Wire Mesh Sandwich Composite and Sisal Fiber Laminate with 45°/0°/45° Ply Orientation Angle

Synthesis and characterization of fabricated fiber metal laminates for aerospace applications

The necessity for high-performance, lightweight materials in the aerospace sector has sparked a significant trend toward the formulation of sophisticated models for fiber-metal laminates during the last few decades. The fiber metal laminates are hybrid composite materials consisting of layers of thin metals and fibers in different orientation sequences. Generally, the composites are placed on top or sometimes both on top and bottom of the metal alloys (especially Al or Ti alloys). In the present study, Carbon fiber reinforced Aluminium sandwich composite laminates are fabricated in a traditional way i.e., compression molding method. The fabricated laminates are examined for assessment of the properties such as tensile, flexural, and impact strength for more usage in engineering applications. The assessments are accomplished under the ASTM standards. Scanning Electron Microscope (SEM) analysis is used to analyze the failure of the fabricated sandwich laminates. The microstructures of tested specimens evidently specify the fractured surface.

Investigation on low velocity impact behavior of sandwich composite and monolithic laminate plates using FEM analysis

Because the fiber composite approach can provide significant improvement in specific strength and stiffness over conventional metal alloys, the consuming demand is getting more increase. Moreover, the composite material structures are more effective in economic point of view due to great reduction of number of parts and manufacturing processes relatively to the conventional metal structure. However the composite structures has an disadvantage for instance, very weak for impact damage due to foreign object damage such as, sand, rock, birds, tool, etc. Especially the damage due to low velocity impact rather than that by high velocity impact cannot be visually found. Such the low velocity damage can be divided into some types such as matrix cracking, fiber fracture, delamination, etc. In this study low velocity impact behaviors of monolithic laminate plate were investigated and sandwich composite plate compared using a commercial FEM Code.

Low-Velocity Impact Behavior of Interlayer/Intralayer Hybrid Composites Based on Carbon and Glass Non-Crimp Fabric.

Composites have gained wide use in structural applications; however, they are sensitive to impact damage. The use of hybrid composites is an effective way to overcome this deficiency. The effects of various hybrid structures of interlayer and intralayer warp-knitted fabrics with carbon and glass fibers on the low-velocity impact behavior of composite laminates were studied. Drop-weight impact tests were conducted on two types of interlayer, sandwich and intralayer hybrid composite laminates, which were compared with homogenous composite laminates. During low-velocity impact tests, the time histories of impact forces and absorbed energy by laminate were recorded. The failure modes were analyzed using the micro-CT (computed tomography) and C-scan techniques. The results revealed that the hybrid structure played an important role in peak force and the absorbed energy, and that the hybrid interface had an influence on damage modes, whereas the intralayer hybrid composite laminate damage was affected by the impact location. The intralayer hybrid laminate with C:G = 1:1 exhibited better impact resistance compared to the other hybrid structures.

Edge effects in elastic and piezoelectric laminated panels under thermal loading

An analytical solution for accurately predicting the edge effects in elastic and hybrid multilayered panels integrated with piezoelectric actuator and sensor layers under thermal gradient loading is presented. The associated thermal problem is solved independently by performing a heat transfer analysis. The extended Reissner-type mixed variational principle is employed to develop the governing equations of the three dimensional (3D) piezothermoelasticity problem. Their solution is obtained using the mixed-field multiterm extended Kantorovich method, developed recently by the author group. The mixed field solution exactly satisfies all the mechanical and electric boundary conditions pointwise, leading to an accurate solution. The formulation is general, and is applicable for composite, sandwich and hybrid panels with arbitrary lay-up and boundary conditions. The solution is validated against the exact 3D solution available for simply supported panels. The free edge stress field in sandwich and hybrid composite laminates is investigated under uniform as well as gradient thermal loading. The solution successfully captures the singularity in free edge interlaminar stresses. The significance of pyroelectric coupling on the free edge thermal stress field is investigated, and the feasibility of its control through electric field actuation is examined.

Flexural properties of sandwich composite laminates reinforced with glass and carbon Z-pins

This study aims to enhance the flexural properties of sandwich composites made from glass or carbon face and glass and carbon fibre Z-pin inserted extruted-polystyrene (XPS) foam cores. Carbon and glass pins were placed through XPS foams with two different column and row densities (15 and 30 mm). Results indicated that flexural loads, strength and modulus of glass/XPS and carbon/XPS sandwich composites significantly increased after inserting of glass and carbon rods. Core shear strengths and facing stresses of glass/XPS and carbon/XPS increased by increasing of carbon or glass rod densities. The rod type, rod density and face type of the sandwich composites are considered as significant parameters which affect the flexural behaviour of sandwich composites while using carbon rods enhanced flexural properties more than that of using glass rods due to better interfacial bonding.

An advanced high rigidity thin sandwich composite laminate with COREMAT and dissimilar skins

Within this paper, the most important mechanical properties determined in simple tensile tests of a thin sandwich composite laminate with nonwoven polyester mat used as core and dissimilar skins are presented. This nonwoven polyester mat known as COREMAT increases the overall stiffness of a composite laminate by the increase of the entire thickness of the laminate avoiding stacking a specific number of layers. The skins are dissimilar, the upper one has a polyester reinforced RT glass fabric and the lower one is a gelcoat layer. Following main mechanical properties have been determined: stiffness, Young’s modulus, load/stress/strain at maximum load, load/stress/strain at maximum extension, load/stress/strain at minimum load, load/stress/strain at minimum extension, tensile strength, work to maximum load/extension, work to minimum load/extension and load/stress at break.

Evaluating the heat resistance of thermal insulated sandwich composites subjected to a turbulent fire

SummaryThe fire structural response of sandwich composite laminates incorporating bio‐derived constituents subjected to a turbulent flaming fire was investigated. Fire structural tests were conducted on thermal insulated sandwich composites incorporating a thin surface‐bonded non‐woven glass fibre tissue impregnated with char‐forming fire retardant, ammonium polyphosphate. The sandwich composite laminates were loaded in compression at 10%, 15% or 20% of the ultimate compressive strength while simultaneously subjected to turbulent flames imposing an incident heat flux of 35 kW/m2. Generally, the failure time increased with the reduced applied compressive load. The thermal insulated sandwich composite laminates had considerably improved fire resistance in comparison to their unmodified counterparts. The unmodified composites failed 96 s earlier than the thermal insulated specimens when the compression load was 10% of the ultimate compressive strength. The presence of ammonium polyphosphate at the heat‐exposed surface promoted the formation of a consolidated char layer, which slowed down heat conduction into composite laminate substrate. The fire reaction parameters measured via the cone calorimeter provided insights into the thermal response hence fire structural survivability of sandwich composite laminates. Copyright © 2015 John Wiley & Sons, Ltd.

Evaluation of the sensitivity and fatigue performance of embedded piezopolymer sensor systems in sandwich composite laminates

It has been claimed that embedding piezoceramic devices as structural diagnostic systems in advanced composite structures may introduce mechanical impedance mismatches that favor the formation of intralaminar defects. This and other factors, such as cost and their high strain sensitivity, have motivated the use of thin-film piezopolymer sensors. In this paper, we examine the performance of sandwich composite panels fitted with embedded piezopolymer sensors. Our experiments examine both how such thin-film sensors perform within a structure and how the inclusion of sensor films affects structural performance. Strain-controlled tests on sandwich panels subjected to three-point bending under wide-ranging static and dynamic strains lead us to conclude that embedding thin piezopolymer films has no marked reduction on the tensile strength for a wide range of strain loading paths and magnitudes, and that the resilience of the embedded sensor is itself satisfactory, even up to the point of structural failure. Comparing baseline data obtained from standard surface-mounted sensors and foil gauges, we note that whereas it is possible to match experimental and theoretical strain sensitivities, key properties—especially the pronounced orthotropic electromechanical factor of such films—must be duly considered before an effective calibration can take place.

RT500/RT800 Sandwich Composite Laminate with COREMAT Subjected to Bending Tests

Abstract In this paper, the most important mechanical features determined in three-point bend tests of a sandwich composite laminate with glass-fibre reinforced dissimilar skins and embedded nonwoven polyester mat as core are presented. The nonwoven polyester mat known as COREMAT increases the overall stiffness of a composite laminate by the increase of the entire thickness of the laminate. The skins are dissimilar, the upper one has a polyester reinforced RT500 and RT800 glass roving fabric and the lower one is a gelcoat layer reinforced with a chopped strand mat CSM450. Following main mechanical properties have been determined: stiffness, Young's modulus of bending, flexural rigidity, load/stress/strain at maximum load, load/stress/strain at maximum extension, load/stress/strain at minimum load, load/stress/strain at minimum extension, work to maximum load/extension, work to minimum load/extension and load/stress at break.

Tensile Property Evaluation of Carbon Fiber Reinforced Aluminium Sandwich Composites

Composite materials are finding new applications in many situations and are better than the conventional materials because of their excellent properties. In the present investigation, aluminium sandwich composite laminates are fabricated and their tensile property is evaluated. The structure of the composites and their fractured surface are studied by using Scanning Electron Microscope. The analysis of the experimental results indicated that the incorporation of aluminium stack as sandwich improves the properties and can be used as a structural material for construction.