scholarly journals Damage Characterisation of Nanointerleaved Woven CFRP Under Fatigue Loading

2018 ◽  
Author(s):  
Sakineh Fotouhi ◽  
Mohamad Fotouhi ◽  
Hamed Saghafi ◽  
Giangiacomo Minak ◽  
Cristiano Fragassa
Keyword(s):  
Composite Laminates ◽  
Laminated Composites ◽  
Failure Mechanisms ◽  
Weight Ratio ◽  
High Strength ◽  
Fatigue Loading ◽  
Fatigue Tests ◽  
Limiting Factor ◽  
Marine Industry ◽  
Delamination Resistance

The use of high strength to weight ratio laminated composites is emerging in marine industry and applications as a very efficient solution for improving productivity. Nevertheless, delamination between the layers is a limiting factor for the wider application of laminated composites, as it reduces the stiffness and strengths of the structure. Interleaving nanofibrous mats between layers of composite laminates has been proved to be an effective method for improving composites delamination resistance. This paper aims to characterize the effect of interleaved nanofiber on mode I interlaminar properties and failure mechanisms when subjected to static and fatigue loadings. For this purpose, virgin and nanomodified woven laminates were subjected to Double Cantilever Beam (DCB) specimens. Static and fatigue tests were performed and the tests were monitored by acoustic emission technique. The mechanical results showed a 130% increase of delamination toughness for nanomodified specimens in the static loadings and more crack growth resistance in the fatigue loading. The AE results revealed that different type of failure mechanisms was the cause of these improvements for the modified specimens compared with the virgin ones.

scholarly journals Damage Characterisation of Nanointerleaved Woven CFRP Under Fatigue Loading

2018 ◽  
Author(s):  
Sakineh Fotouhi ◽  
Mohamad Fotouhi ◽  
Milad Saeedifar ◽  
Hamed Saghafi ◽  
Giangiacomo Minak ◽  
...  
Keyword(s):  
Composite Laminates ◽  
Laminated Composites ◽  
Failure Mechanisms ◽  
Weight Ratio ◽  
High Strength ◽  
Fatigue Loading ◽  
Fatigue Tests ◽  
Limiting Factor ◽  
Marine Industry ◽  
Delamination Resistance

The use of high strength to weight ratio laminated composites is emerging in marine industry and applications as a very efficient solution for improving productivity. Nevertheless, delamination between the layers is a limiting factor for the wider application of laminated composites, as it reduces the stiffness and strengths of the structure. Interleaving nanofibrous mats between layers of composite laminates has been proved to be an effective method for improving composites delamination resistance. This paper aims to characterize the effect of interleaved nanofiber on mode I interlaminar properties and failure mechanisms when subjected to static and fatigue loadings. For this purpose, virgin and nanomodified woven laminates were subjected to Double Cantilever Beam (DCB) specimens. Static and fatigue tests were performed and the tests were monitored by acoustic emission technique. The mechanical results showed a 130% increase of delamination toughness for nanomodified specimens in the static loadings and more crack growth resistance in the fatigue loading. The AE results revealed that different type of failure mechanisms was the cause of these improvements for the modified specimens compared with the virgin ones.

scholarly journals Damage Characterization of Nano-Interleaved CFRP under Static and Fatigue Loading

Fibers ◽  
2019 ◽  
Vol 7 (2) ◽  
pp. 13 ◽  
Author(s):  
Mohamad Fotouhi ◽  
Cristiano Fragassa ◽  
Sakineh Fotouhi ◽  
Hamed Saghafi ◽  
Giangiacomo Minak
Keyword(s):  
Acoustic Emissions ◽  
Weight Ratio ◽  
Laminated Composite ◽  
High Strength ◽  
Fatigue Loading ◽  
Fatigue Tests ◽  
Limiting Factor ◽  
Delamination Toughness ◽  
Delamination Resistance ◽  
Laminated Composite Materials

The use of high strength-to-weight ratio-laminated fiber-reinforced composites is emerging in engineering sectors such as aerospace, marine and automotive to improve productivity. Nevertheless, delamination between the layers is a limiting factor for the wider application of laminated composites, as it reduces the stiffness and strengths of the structure. Previous studies have proven that ply interface nanofibrous fiber reinforcement has an effective influence on delamination resistance of laminated composite materials. This paper aims to investigate the effect of nanofiber ply interface reinforcement on mode I properties and failure responses when being subjected to static and fatigue loadings. For this purpose, virgin and nanomodified woven laminates were subjected to Double Cantilever Beam (DCB) experiments. Static and fatigue tests were performed in accordance with standards and the Acoustic Emissions (AE) were acquired during these tests. The results showed not only a 130% increase of delamination toughness for nanomodified specimens in the case of static loads, but also a relevant crack growth resistance in the case of fatigue loads. In addition, the AE permitted to relate these improvements to the different failure mechanisms occurring.

PROGRESSIVE DAMAGE FAILURE ANALYSIS OF POST-BUCKLED COMPOSITE SINGLE-STRINGER PANEL WITH TEFLON INSERTS

2021 ◽  
Author(s):  
VIJAY K. GOYAL ◽  
AUSTIN PENNINGTON ◽  
JASON ACTION
Keyword(s):  
Experimental Data ◽  
Composite Structures ◽  
Laminated Composites ◽  
Compressive Loading ◽  
Weight Ratio ◽  
High Strength ◽  
Material Model ◽  
Stiffened Panels ◽  
Damage Initiation ◽  
Critical Aspects

The high strength-to-weight and stiffness-to-weight ratio materials, such as laminated composites, are advantageous for modern aircraft. Laminated composites with initial flaws are susceptible to delamination under buckling loads. PDA tools help enhance the industry’s understanding of the mechanisms for damage initiation and growth in composite structures while assisting in the design, analysis, and sustainment methods of these composite structures. The global-local modeling approach for the single-stringer post-buckled panel was evaluated through this effort, using Teflon inserts to simulate the defect of damage during manufacturing. This understanding is essential for designing the post-buckled structure, reducing weight while predicting damage initiation location, and addressing a potential design review for future aircraft repairs. In this work, the initial damage was captured with Teflon inserts as the starting configuration; and any reference to the damage initiation refers to any damage beyond the “initial unbonded region.” The effort aims to develop, evaluate, and enhance methods to predict damage initiation and progression and the failure of post-buckled hat-stiffened panels using multiple Abaqus FEA Virtual Crack Closure Technique (VCCT) definitions. Validation of the PDA using the VCCT material model was performed on a large single-stringer panel subjected to compressive loading. The compressive loading of the panel caused the skin to buckle before any damage began to occur locally. In addition, comparisons are made for critical aspects of the damage morphology, such as a growth pattern that included delamination from the skin-stiffener interface to the skin and ply interfaces. When compared against the experimental data produced through the NASA Advanced Composites Project (ACP), the present model captured damage migration from one surface to another, and model validations were ~5% of the experimental data.

Effect of Impact-Fatigue on Damage in Adhesive Joints

2007 ◽  
Vol 347 ◽  
pp. 653-658 ◽  
Author(s):  
Juan Pablo Casas-Rodriguez ◽  
Ian A. Ashcroft ◽  
Vadim V. Silberschmidt
Keyword(s):  
Damage Evolution ◽  
Weight Ratio ◽  
High Strength ◽  
Fatigue Loading ◽  
Lap Joints ◽  
Adhesive Joints ◽  
Bonded Joints ◽  
Impact Fatigue ◽  
Adhesively Bonded ◽  
Low Velocity

In recent decades the use of structural adhesive joints in the aerospace industry has increased considerably thanks to their high strength-to-weight ratio, low stress concentration and capacity to join different adherends. There is increasing interest in damage due to low-velocity impacts produced in adhesively bonded components and structures by vibrating loads. This type of loading is known as impact fatigue. The main aim of this paper is to investigate damage evolution in adhesive joints subjected to impact-fatigue and to compare this with damage evolution in standard fatigue (i.e. non-impacting, constant amplitude, sinusoidal fatigue). In this work, adhesively bonded lap joints were subjected to multiple tensile impacts tensile and it was seen that this type of loading was extremely damaging compared to standard fatigue. A number of methods of studying damage evolution in bonded joints subjected to fatigue and impact fatigue loading have been investigated and various parameters have been used to characterise these processes. Two modifications of the accumulated time-stress model [1-4] are proposed and it is shown that both models provide a suitable characterization of impact-fatigue in bonded joints.

scholarly journals Comparison of High-Temperature Compression and Compression-Compression Fatigue Behavior of Magnesium Alloys DieMag422 and AE42

Materials ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 497 ◽  
Author(s):  
Mirko Teschke ◽  
Alexander Koch ◽  
Frank Walther
Keyword(s):  
Magnesium Alloys ◽  
Elevated Temperatures ◽  
Fatigue Behavior ◽  
Weight Ratio ◽  
High Strength ◽  
Fatigue Tests ◽  
Fracture Mechanisms ◽  
Compression Tests ◽  
Computed Tomographic ◽  
Tensile Fatigue

Due to their high strength-to-weight-ratio, magnesium alloys are very attractive for use in automotive engineering. For application at elevated temperatures, the alloys must be creep-resistant. Therefore, the influence of the operating temperature on the material properties under quasistatic and cyclic load has to be understood. A previous study investigated tensile-tensile fatigue behavior of the magnesium alloys DieMag422 and AE42 at room temperature (RT). The aim of this study was the comparison of both alloys regarding compression, tensile, and compression-compression fatigue behavior. The quasistatic behavior was determined by means of tensile and compression tests, and the tensile-compression asymmetry was analyzed. In temperature increase fatigue tests (TIFT) and constant amplitude tests (CAT), the temperature influence on the cyclic creeping (ratcheting) behavior was investigated, and mechanisms-relevant test temperatures were determined. Furthermore, characteristic fracture mechanisms were evaluated with investigations of the microstructure and the fracture surfaces. The initial material was analyzed in computed tomographic scans and energy dispersive X-ray (EDX) analyses.

Optimum Design of Composite Pressure Vessel Based on 3-Dimensional Failure Criteria

2019 ◽  
Author(s):  
J. Sakai ◽  
Y. H. Park
Keyword(s):  
Optimum Design ◽  
Pressure Vessel ◽  
Composite Laminates ◽  
Three Dimensional ◽  
Weight Ratio ◽  
High Strength ◽  
Failure Criteria ◽  
Pressure Vessels ◽  
Fiber Reinforced ◽  
3D Elasticity

Abstract Anisotropic composite cylinders and pressure vessels have been widely employed in automotive, aerospace, chemical and other engineering areas due to high strength/stiffness-to-weight ratio, exceptional corrosion resistance, and superb thermal performance. Pipes, fuel tanks, chemical containers, rocket motor cases and aircraft and ship elements are a few examples of structural application of fiber reinforced composites (FRCs) for pressure vessels/pipes. Since the performance of composite materials replies on the tensile and compressive strengths of the fiber directions, the optimum design of composite laminates with varying fiber orientations is desired to minimize the damage of the structure. In this study, a complete mathematical 3D elasticity solution was developed, which can accurately compute stresses of a thick multilayered anisotropic fiber reinforced pressure vessel under force and pressure loadings. A rotational variable is introduced in the formalism to treat torsional loading in addition to force and pressure loadings. Then, the three-dimensional Tsai-Wu criterion is used based on the analytical solution to predict the failure. Finally, a global optimization algorithm is used to find the optimum fiber orientation and their best combination through the thickness direction.

scholarly journals Implementation of the ultrasonic through-transmission technique for the elastic characterization of fiber-reinforced laminated composite

DYNA ◽  
2019 ◽  
Vol 86 (208) ◽  
pp. 153-161
Author(s):  
Carlos A. Meza ◽  
Ediguer E. Franco ◽  
Joao L. Ealo
Keyword(s):  
Laminated Composites ◽  
Weight Ratio ◽  
Laminated Composite ◽  
High Strength ◽  
Mechanical Tests ◽  
Fiber Reinforced ◽  
Transmission Technique ◽  
Laminated Materials

Laminated composites are widely used in applications when a high strength-to-weight ratio is required. Aeronautic, naval and automotive industries use these materials to reduce the weight of the vehicles and, consequently, fuel consumption. However, the fiber-reinforced laminated materials are anisotropic and the elastic properties can vary widely due to non-standardized manufacturing processes. The elastic characterization using mechanical tests is not easy, destructive and, in most cases, not all the elastic constants can be obtained. Therefore, alternative techniques are required to assure the quality of the mechanical parts and the evaluation of new materials. In this work, the implementation of the ultrasonic through-transmission technique and the characterization of some engineering materials is reported. Isotropic materials and laminated composites of carbon fiber and glass fiber in a polymer matrix were characterized by ultrasound and mechanical tests. An improved methodology for the transit time delay calculation is reported.

scholarly journals Experimental Study on Steel to FRP Bonded Lap Joints in Marine Applications

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
Çiçek Özes ◽  
Nurhan Neşer
Keyword(s):  
Surface Roughness ◽  
Adhesive Bonding ◽  
Weight Ratio ◽  
Steel Structures ◽  
High Strength ◽  
Lap Joints ◽  
Bonded Joints ◽  
Bonding Performance ◽  
Marine Industry ◽  
Marine Applications

Steel structures coated with fiber-reinforced polymer (FRP) composites have gained wide acceptance in marine industry due to their high strength-to-weight ratio, good protection from environmental degradation, and impact loads. In this study, adhesive bonding performance of single-lap bonded joints composed of steel coated with FRP has been investigated experimentally for three different surface roughness and two epoxy types. Single-lap bonded joints have been tested under tensile loading. The adhesive bonding performance has been evaluated by calculating the strain energy values. The results reveal that the surface roughness of steel has a significant effect on the bonding performance of steel to FRP combinations and the performance of the resin can be improved by using the primer in an economical way.

scholarly journals Fracture Areas Quantitative Investigating of Bending–Torsion Fatigued Low-Alloy High-Strength Steel

Metals ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1620
Author(s):  
Wojciech Macek
Keyword(s):  
Fatigue Life ◽  
Surface Topography ◽  
High Strength ◽  
Fatigue Loading ◽  
Fatigue Tests ◽  
Void Volume ◽  
Variation Method ◽  
Rupture Area ◽  
The Impact ◽  
Maximum Stresses

In this study, the impact of pseudo-random non-proportional bending-torsion fatigue loadings proportion on the fatigue life and the fracture surface topography was analyzed. Investigation was carried out for 24 specimens made of S355J2 steel with 11 different ratios of maximum stresses λ. For these cases, after the fatigue tests, the surface topography measurements were carried out using an optical profilometer, using the focus variation method. Three fracture zones were analyzed for each specimen: (1) total; (2) propagation; (3) rupture, taking into account the root average square height Sq and void volume Vv parameters. The results pointed that ratio of maximum stresses λ is the most influenced on volume surface parameters represented by void volume at a given height Vv, in the rupture area. A new fatigue loading parameter P was used, depending on fatigue life T and ratio of maximum stresses λ, which shows very good correlation in 4th degree type of fit, to void volume Vv parameter for the rupture area.

scholarly journals Mechanical Characterization of TiO2 nanoparticles based on Glass Fiber Reinforced Polymer Composite

2021 ◽  
Vol 1206 (1) ◽  
pp. 012006
Author(s):  
Abhishek Singh ◽  
S. C. Jayswal
Keyword(s):  
Glass Fiber ◽  
Polymer Composite ◽  
Composite Laminates ◽  
Weight Ratio ◽  
High Strength ◽  
Bending Stiffness ◽  
Flexural Properties ◽  
Nano Composite ◽  
Set Up ◽  
The Impact

Abstract Nanotechnology has become the best truly developing innovation in the field of engineering science. Numerous examinations have been completed by different exploration researchers in the prior many years. In my examination work research, the impact of cross breed E-glass built up fiber with epoxy Nano composite. The Nano composite covers overlays were set up by hand layup procedures by shifting layers of Titanium Dioxide (TiO2) nanoparticles of 0.6% individually. The nano added substances are utilized to improve the strength from destroy opposition, hardness of the polymer composite and high strength to weight ratio. The Nano composite laminates this prepared are characterized by the compression and flexural test. The flexural properties of the glass fiber built up plastic improved with expansion of nanoTiO2 filler particles. At 0.6 wt% of TiO2 and having 12 layers the force at yield is 327.99N and bending stiffness 63.11 N/mm and in 9 layers force at yield is 149.06 and bending stiffness 36.22 N/mm. True interfacial bonding b/w the fiber and epoxy turned into the primary motive for reaching higher flexural properties.

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