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.

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.

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 Geometrical behavior of laminated graphite/epoxy composite using hypermesh

2018 ◽  
Vol 7 (2.20) ◽  
pp. 214
Author(s):  
Ch Siva RamaKrishna ◽  
KV Subba Rao ◽  
Saineelkamal Arji
Keyword(s):  
Residual Stresses ◽  
Epoxy Composite ◽  
Weight Ratio ◽  
Laminated Composite ◽  
High Strength ◽  
Element Analysis ◽  
Aspect Ratios ◽  
Military Applications ◽  
Inherent Strength

The laminated composite material is  made of ply which are specically used in automotive, aerospace and military applications due to less in weight and high strength to weight ratio. The role of structural strength is very important in composites, as the material is weak in inherent strength leads to damage of equipment made with the laminated composite. Hence, an accurate understanding of their structural geometrical behavior for residual stresses is required, such as residual stresses with different aspect ratios. In present work, various aspect ratios of laminated composite and its residual stresses are investigated using finite element analysis. The numerical results showed, on the residual stresses, that the effects the change the residual stresses due change of aspect ratio of laminated Graphite/epoxy composite. 

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.

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.

Tensile Properties of Angle Cured Laminated Composites Structures under Gravity Effects

2013 ◽  
Vol 465-466 ◽  
pp. 101-105
Author(s):  
Mohd Yuhazri bin Yaakob ◽  
T.T.T. Jennise ◽  
H. Sihombing ◽  
Md Radzai bin Said ◽  
U. Nirmal ◽  
...  
Keyword(s):  
Tensile Properties ◽  
Composite Structures ◽  
Weight Ratio ◽  
Laminated Composite ◽  
High Strength ◽  
Maximum Force ◽  
Composites Materials ◽  
Laminated Composite Structures ◽  
Gravity Effects ◽  
Optimum Productivity

As the usage of composites materials are significant in the industries of automobiles, shipping and constructions due to their non-corrosive and high strength to weight ratio. Anyway, the production of composites needed to be increased to meet the demand. At this stage, problem faced by Small and Medium Industries / Entrepreneurs (SMI/E) is the confined and limited space available that restricts the optimum productivity. They commonly cure the composites horizontally that requires ample space and unable to afford for high-end equipment such as mechanical oven and autoclave in the production as a result of high capital cost.This research is carried out to study the feasibility of the gravity effects on curing position of the laminated composite structures to enhance the curing space needed. The aim of the research was to investigate the tensile properties of the thermosetting laminated composite by curing the laminate at different angle using vacuum bagging technique. From the testing, SN 5 which denominated to be 60 ̊ found to have the best tensile properties in term of maximum force exerted and Youngs modulus.

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.

The Effect of Inclusions on Mechanical Behaviour in Ultra-High Strength Alloy Steels

2010 ◽  
Vol 654-656 ◽  
pp. 51-56 ◽  
Author(s):  
Xi Shan Xie ◽  
Yan Ping Zeng
Keyword(s):  
Harmful Effect ◽  
High Strength ◽  
Fatigue Loading ◽  
Fatigue Tests ◽  
Small Particles ◽  
Early Failure ◽  
The Matrix ◽  
Alloy Steels ◽  
Strength Alloy

Inclusions are un-avoidable even in super-clean engineering alloy steels because of the necessary melting process. These inclusions (such as TiN, AlN etc) are considered as harmful phases especially for ultra-high strength alloy steels. The unique experiments (in-situ tension and in-situ fatigue tests) have been conducted in a loading chamber of scanning electron microscope. TiN often characterizes with large blocky cubic morphology. Cracks easily initiate at the sharp corners of TiN cubic particles or sometimes directly initiate in TiN particles because of its brittleness. These cracks propagate to the matrix and to introduce early failure. AlN small particles (in several microns) often distribute as inclusion chains in steels. At tensile and fatigue tests cracks very often initiate at the inclusion chains among AlN small particles and line up to develop voids, which rapidly propagate to the matrix till early failure. These important results reveal the harmful effect of inclusions in micro-scale and can be connected with tensile and fatigue loading processes for understanding the early failure mechanisms.

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