Combined Effects of Stress Concentration and Fatigue on the Reliability of Notched Laminates

2006 ◽  
Author(s):  
R. Ganesan ◽  
A. K. Arumugam
Keyword(s):  
Stress Concentration ◽  
Composite Laminates ◽  
Composite Laminate ◽  
Fatigue Loading ◽  
Stochastic Approach ◽  
Strength Properties ◽  
Combined Effect ◽  
Practical Reasons ◽  
Aerospace Applications ◽  
Structural Applications

Composite laminates are used in structural applications such as aircraft wings and tail structures. Drilling holes and making cutouts in these laminates are unavoidable for practical reasons. As a result, stress concentration is introduced near the hole or cutout, and the load-bearing capacity of the structure is reduced. In addition, composite laminates used in aerospace applications are subjected to considerable fatigue loading due to service conditions. In composite laminates, fatigue causes reduction in stiffness and strength. The objective of the present work is to study the combined effect of stress concentration and fatigue on the composite laminate. Since composite laminate displays significant variation in material and strength properties, the stress distribution in the laminate is stochastic in nature. It is more appropriate to analyze the notched composite laminates using a stochastic approach and to design the laminate based on a reliability-based design approach. In the present work, such an approach is developed and the combined effect of stress concentration and fatigue on the reliability of the laminate is investigated.

Effect of Notch Location on the Stress Concentration and Reliability of Notched Composite Laminates Based on a Probabilistic Approach

2007 ◽  
Author(s):  
R. Ganesan ◽  
A. K. Arumugam
Keyword(s):  
Stress Concentration ◽  
Stress Distribution ◽  
Composite Laminates ◽  
Probabilistic Approach ◽  
Stochastic Approach ◽  
Strength Properties ◽  
Practical Reasons ◽  
Commercial Aircraft ◽  
Reinforced Plastics ◽  
Reliability Based Design

Composite materials and laminates are being widely used in aerospace and automotive industries due to their less weight to stiffness ratio. Especially the use of composite laminates, made up of Carbon or Graphite Fiber Reinforced Plastics (CFRP/GFRP), in military and commercial aircraft structures has progressed steadily over the past few decades. Drilling holes and making cutouts in these laminates are unavoidable for practical reasons. These holes (or) cutouts introduces stress concentration near the hole (or) cutout edge and reduces the load-bearing capacity of the structure. Cutouts are made at the edges of composite laminates for practical purposes, which is capable of reducing the delamination effect in notched laminates. The stress distribution in notched composite laminates can vary according to the location of the notch in the laminate, which leads to the variation in strength and reliability values of notched laminates. The objective of the present work is to study the effect of notch location on the stress concentration and reliability of notched composite laminates. Composite laminate displays significant variation in material and strength properties and the stress distribution in the laminate becomes stochastic in nature. Thus the notched laminates were analyzed using a stochastic approach and designed based on a reliability-based design approach.

Influence of fibre alignments on the mechanical properties of novel Spirograph based non-woven mat composites

2021 ◽  
pp. 073168442110584
Author(s):  
Madavan Prabakaran ◽  
Siddharthan Arjunan
Keyword(s):  
Mechanical Properties ◽  
Glass Fibre ◽  
Composite Laminates ◽  
Composite Laminate ◽  
Laminate Composite ◽  
Fibre Orientation ◽  
Shear Resistance ◽  
Continuous Glass ◽  
Reinforced Polymer ◽  
Structural Applications

Fibre architecture of glass fibre (GF) reinforced polymer composites has a major impact on the mechanical properties for structural applications. In this study, a novel continuous glass fibre non-woven GF mat based on Spirograph art pattern is laid using a customized mechanical system. Spirograph-based continuous glass fibre non-woven (SNW) mat of different patterns was prepared and GF laminate epoxy composites were fabricated with the aim of achieving quasi-isotropic mechanical properties. The samples were cut to dimensions of test specimens from various identical locations symmetrically from a circular-shaped SNW composite laminates which were subjected to flexural, impact, shear and modified compression with anti-buckling tests. One particular SNW pattern composite laminate exhibited 40.82% better impact and 49.01% better shear resistance than commercial 0°/90° woven roving mat composite. The developed SNW laminate composite had quasi-isotropic fibre orientation and better mechanical properties without any stitching and interlacing as in case of woven fibre laminate composite.

Mechanical Properties of a Centrally Notched APC-2 Composite Laminate Due to Fatigue Loading at Elevated Temperature (II)

2009 ◽  
Vol 25 (3) ◽  
pp. 251-259
Author(s):  
M.-H. R. Jen ◽  
Y.-C. Tseng
Keyword(s):  
Mechanical Properties ◽  
Elevated Temperature ◽  
Cyclic Loading ◽  
Composite Laminates ◽  
Composite Laminate ◽  
Stress Amplitude ◽  
Fatigue Loading ◽  
The Cross ◽  
Applied Stresses ◽  
Strain Model

AbstractThe temperature versus life (T-N) curves of both centrally notched and unnotched AS-4/PEEK (APC-2) composite laminates due to constant stress amplitude tension-tension (T-T) fatigue loading were investigated systematically. The cross-ply laminate possesses the higher mechanical properties than those of the quasi-isotropic laminate at elevated temperature, and also the mechanical properties of both lay-ups are degraded significantly as the temperature increasing. Combining both effects of notch and temperature at various normalized stresses it is found the cross-ply laminate possesses more resistance to cyclic loading than that of the quasi-isotropic laminate. Additionally, the predictive strain model is in a practical and simple form. Alternatively, the T-N curves, instead of conventionally S-N curves, at variously applied stresses are accomplished for preliminary designs and applications.

scholarly journals Behaviour of Hybrid Titanium Composite Laminate (HTCL) under In-Plane Loading

2004 ◽  
Vol 13 (1) ◽  
pp. 096369350401300 ◽  
Author(s):  
G. Allegri ◽  
S. Corradi ◽  
M. Marchetti ◽  
L. Suanno
Keyword(s):  
Hybrid Composite ◽  
Composite Laminates ◽  
Composite Laminate ◽  
Damage Mechanics ◽  
Fatigue Loading ◽  
Harsh Environments ◽  
Fatigue Properties ◽  
Mechanical Degradation ◽  
Titanium Grade ◽  
Good Agreement

The Hybrid Titanium Composite Laminate (HTCL) incorporates the mechanical advantages of existing hybrid composite laminates such as ARALL and GLARE while extending their applications to harsh environments. Hybrid composite laminates, consisting of layers of Titanium Grade 2 foils bonded together with fibre-reinforced prepreg plies, have been tested under fatigue loading. HTCL has proven to possess exceptional strength and fatigue resistance. Degraded stiffness and ultimate resistances are provided through experimental stress-strain response of HTCL laminates, which are compared with predicted results by a laminate analysis code. The roles of mechanical degradation, the static and dynamic behaviour and fatigue properties of HTCL are addressed. The development of damage in HTCL specimens during fatigue is shown including titanium ply cracking, interfacial debonding, and layer failure. These tests provided several parameters in order to calibrate a numerical Lamaitre's Continuous Damage Mechanics (CDM) fatigue model, which resulted in good agreement with experimental data. The influence of the fatigue properties of titanium layers on the fatigue of HTCL is discussed. The performance of HTCL laminates in fatigue is shown superior to that of the monolithic titanium alloy for room-temperature conditions.

scholarly journals Mechanical Properties of E-Glass Fiber - Basalt Fiber Reinforced Polymer Matrix Composite

2020 ◽  
Vol 9 (2) ◽  
pp. 1019-1022
Keyword(s):  
Mechanical Properties ◽  
Composite Materials ◽  
Glass Fiber ◽  
Composite Laminates ◽  
Basalt Fiber ◽  
Strength Properties ◽  
Fiber Reinforced ◽  
Specific Strength ◽  
Aerospace Applications ◽  
Constituent Elements

Composite materials have significant role in automobile and aerospace applications because of their attractive mechanical properties compared. This fascinating properties attracted several industries especially automotive sectors. In contrast to metallic alloys, composite materials composed of individual constituent elements with distinguishable interfaces and chemical identities, however, when combined e-glass and basalt fiber, they will produce superior properties. The fundamental advantage of composite materials is their high specific strength and specific stiffness, which emphasis on its weight saving potential in the finished part. Two principal constituent elements of composites are matrix and reinforcement materials. In the present work, an attempt has been made to understand the advancements achieved in the combination of e-glass fiber and basalt fiber composites. Based on the comprehensive literature review, it is observed that broad work was done on the manufacturing techniques and characterization of the composites, however, limited works were carried out in analyzing the tensile, flexural and shear strength properties of differently oriented fibers in the laminated composites. In this paper, focus was given in fabricating and characterizing the glass fiber reinforced epoxy composite laminates with different fiber orientations, thereby, examining the mechanical properties of prepared laminates for tensile and bending strengths.

scholarly journals Soil microbiomes mediate degradation of vinyl ester-based polymer composites

2020 ◽  
Vol 1 (1) ◽  
Author(s):  
Adam M. Breister ◽  
Muhammad A. Imam ◽  
Zhichao Zhou ◽  
Md Ariful Ahsan ◽  
Juan C. Noveron ◽  
...  
Keyword(s):  
Polymer Composites ◽  
Polymer Composite ◽  
Structural Integrity ◽  
Abiotic Factors ◽  
High Strength ◽  
Strength Properties ◽  
Naturally Occurring ◽  
Structural Applications ◽  
Acrylate Esters ◽  
Bacterial Groups

AbstractPolymer composites are attractive for structural applications in the built environment due to their lightweight and high strength properties but suffer from degradation due to environmental factors. While abiotic factors like temperature, moisture, and ultraviolet light are well studied, little is known about the impacts of naturally occurring microbial communities on their structural integrity. Here we apply complementary time-series multi-omics of biofilms growing on polymer composites and materials characterization to elucidate the processes driving their degradation. We measured a reduction in mechanical properties due to biologically driven molecular chain breakage of esters and reconstructed 121 microbial genomes to describe microbial diversity and pathways associated with polymer composite degradation. The polymer composite microbiome is dominated by four bacterial groups including the Candidate Phyla Radiation that possess pathways for breakdown of acrylate, esters, and bisphenol, abundant in composites. We provide a foundation for understanding interactions of next-generation structural materials with their natural environment that can predict their durability and drive future designs.

SELF-HEALING OF WOVEN COMPOSITE LAMINATES VIA IN SITU THERMAL REMENDING

2021 ◽  
Author(s):  
ALEXANDER D. SNYDER ◽  
ZACHARY J. PHILLIPS ◽  
JASON F. PATRICK
Keyword(s):  
Composite Laminates ◽  
Composite Laminate ◽  
Laminated Composites ◽  
Reaction Times ◽  
Carbon Fiber Composites ◽  
Self Healing ◽  
Damage Mode ◽  
Woven Composite ◽  
Internal Damage

Fiber-reinforced polymer composites are attractive structural materials due to their high specific strength/stiffness and excellent corrosion resistance. However, the lack of through-thickness reinforcement in laminated composites creates inherent susceptibility to fiber-matrix debonding, i.e., interlaminar delamination. This internal damage mode has proven difficult to detect and nearly impossible to repair via conventional methods, and therefore, remains a significant factor limiting the reliability of composite laminates in lightweight structures. Thus, novel approaches for mitigation (e.g., self-healing) of this incessant damage mode are of tremendous interest. Self-healing strategies involving sequestration of reactive liquids, i.e. microcapsule and microvascular systems, show promise for the extending service- life of laminated composites. However, limited heal cycles, long reaction times (hours/days), and variable stability of chemical agents under changing environmental conditions remain formidable research challenges. Intrinsic self- healing approaches that utilize reversible bonds in the host material circumvent many of these limitations and offer the potential for unlimited heal cycles. Here we detail the development of an intrinsic self-healing woven composite laminate based on thermally-induced dynamic bond re-association of 3D-printed polymer interlayers. In contrast to prior work, self-repair of the laminate occurs in situ and below the glass-transition temperature of the epoxy matrix, and maintains >85% of the elastic modulus during healing. This new platform has been deployed in both glass and carbon-fiber composites, demonstrating application versatility. Remarkably, up to 20 rapid (minute-scale) self-healing cycles have been achieved with healing efficiencies hovering 100% of the interlayer toughened (4-5x) composite laminate. This latest self-healing advancement exhibits unprecedented potential for perpetual in-service repair along with material multi-functionality (e.g., deicing ability) to meet modern application demands.

Damage Control in Composite Laminates

2001 ◽  
Author(s):  
Alexander P. Suvorov ◽  
George J. Dvorak
Keyword(s):  
Composite Laminates ◽  
Composite Laminate ◽  
Damage Control ◽  
Thermomechanical Loading ◽  
Interlaminar Stresses ◽  
Damage Resistance ◽  
Viscoelastic Composite ◽  
Mechanical Loads ◽  
Composite Damage ◽  
The Matrix

Abstract Several effects that fiber prestress may have on stress redistribution in the plies of composite laminates and in the phases of individual plies are illustrated. These include improvement of composite damage resistance under tensile mechanical loads, reduction/cancelation of interlaminar stresses at free edges of composite laminate subjected to thermomechanical loading, and stress relaxation in the matrix phase of viscoelastic composite laminates. Specific results are found for quasi-isotropic and cross-ply symmetric S-glass/epoxy and carbon/epoxy AS4/EPON 828 laminates.

THE EFFECT OF LAMINATION SCHEME AND ANGLE VARIATIONS TO THE DISPLACEMENTS AND FAILURE BEHAVIOUR OF COMPOSITE LAMINATE

2015 ◽  
Vol 76 (11) ◽  
Author(s):  
Azizul Hakim Samsudin ◽  
Jamaluddin Mahmud
Keyword(s):  
Fiber Orientation ◽  
Composite Laminates ◽  
Finite Element Modelling ◽  
Composite Laminate ◽  
Maximum Stress ◽  
Failure Load ◽  
Failure Criteria ◽  
Stress Theory ◽  
Failure Behaviour ◽  
Failure Index

This paper aims to investigate the effect of lamination scheme and angle variations to the displacements and failure behaviour of composite laminate. Finite element modelling and analysis of symmetric, anti-symmetric and angle-ply Graphite/ Epoxy laminate with various angles of fiber orientation subjected to uniaxial tension are performed. Maximum Stress Theory and Tsai-Wu Failure Criteria are employed to determine the failure load (failure index = 1). Prior to that, convergence analysis and numerical validation are carried out. Displacements and failure behaviour of the composite laminates (symmetric, anti-symmetric and angle ply) are analysed. The failure curves (FPF and LPF) for both theories (Maximum Stress Theory and Tsai-Wu) are plotted and found to be very close to each other. Therefore, it can be concluded that the current study is useful and significant to the displacements and failure behaviour of composite laminate.

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