scholarly journals Damaged Response In Natural Fibre Reinforced Composites: Characterisation and Modelling Under Quasi-Static and Fatigue Conditions

2021 ◽  
Author(s):  
Ziauddin Mahboob
Keyword(s):  
Strain Rate ◽  
Strain Amplitude ◽  
Mechanical Behaviour ◽  
Material Properties ◽  
Inelastic Strain ◽  
Natural Fibre ◽  
Fatigue Tests ◽  
Stiffness Degradation ◽  
Progressive Damage ◽  
Damage Mechanisms

‘Natural’ fibrous material are subjects of accelerated research on account of the non-renewability and environmental costs of traditional ‘synthetic’ engineering fibres like Carbon and Glass. Of all candidates, Flax plant fibres have been found to offer composite reinforcement similar, or even superior, to Glass fibres in specific mechanical properties. Despite repeated evidence of its potential from independent studies, industry adoption of natural fibre reinforcement for load-bearing applications is still negligible, owing to their relatively immature body of research that discourages confidence in their long-term strength, durability, and predictability. This work contributes original findings on the complex damaged-condition response of natural fibre composites (NFC), and proposes modelling approaches to simulate the same. Material properties and mechanical behaviour of several Flax-epoxy composites are determined under tensile and compressive static loading, and correlated to internal damage mechanisms observed by micrography. Stiffness degradation and accumulated permanent strain are quantified along principal in-plane orthrotropic directions, which are used to develop a Continuum Damage Mechanics-based mesoscale model wherein constitutive laws are specifically formulated to reproduce NFC quasi-static response, including their highly nonlinear fibre-direction stiffness loss and inelasticity progression. Current progress of fatigue research is critically and extensively reviewed. Reported fatigue endurance and progressive damage behaviour of several NFC laminates are analysed. Existing knowledge on NFC fatigue damage is found to be insufficient and ambiguous, therefore inadequate for engineering design consideration. The unique fatigue-stiffening phenomenon reported for Flax-epoxy specimens is argued to be a misleading consequence of increasing strain-rate under constant stress-amplitude cycling. To minimise the influence of a varying strain-rate, original constant strain-amplitude fatigue tests are conducted on Flax-epoxy laminates, where no evidence of stiffening is observed. Considering this sensitivity to strain-rate, strain-amplitude controlled fatigue tests may be better suited for NFC investigation. Strain-controlled fatigue lives of Flax-epoxy can be modelled by a linearised strain/log-life relationship. Evolution of several material properties and dissipation phenomena (inelastic strain, peak stress, stiffness, hysteresis energy, superficial temperature) are measured, and correlated with SEM-observed damage mechanisms in the microstructure. An evolution/growth model is proposed to simulate laminate-scale stiffness degradation and cumulative inelastic strain as a function of applied peak strain and fatigue cycles, and is found to well-capture experimental trends for Flax-epoxy. The combined contribution of this work provides much-needed original data on the damaged-condition mechanical behaviour of Flax-epoxy and other NFCs under a variety of loading conditions, clarifies contradictory aspects of critical NFC behaviour, and proposes numerical methods to replicate observed progressive damage and failure in NFCs.

Damaged Response In Natural Fibre Reinforced Composites: Characterisation and Modelling Under Quasi-Static and Fatigue Conditions

2021 ◽  
Author(s):  
Ziauddin Mahboob
Keyword(s):  
Strain Rate ◽  
Strain Amplitude ◽  
Mechanical Behaviour ◽  
Material Properties ◽  
Inelastic Strain ◽  
Natural Fibre ◽  
Fatigue Tests ◽  
Stiffness Degradation ◽  
Progressive Damage ◽  
Damage Mechanisms

‘Natural’ fibrous material are subjects of accelerated research on account of the non-renewability and environmental costs of traditional ‘synthetic’ engineering fibres like Carbon and Glass. Of all candidates, Flax plant fibres have been found to offer composite reinforcement similar, or even superior, to Glass fibres in specific mechanical properties. Despite repeated evidence of its potential from independent studies, industry adoption of natural fibre reinforcement for load-bearing applications is still negligible, owing to their relatively immature body of research that discourages confidence in their long-term strength, durability, and predictability. This work contributes original findings on the complex damaged-condition response of natural fibre composites (NFC), and proposes modelling approaches to simulate the same. Material properties and mechanical behaviour of several Flax-epoxy composites are determined under tensile and compressive static loading, and correlated to internal damage mechanisms observed by micrography. Stiffness degradation and accumulated permanent strain are quantified along principal in-plane orthrotropic directions, which are used to develop a Continuum Damage Mechanics-based mesoscale model wherein constitutive laws are specifically formulated to reproduce NFC quasi-static response, including their highly nonlinear fibre-direction stiffness loss and inelasticity progression. Current progress of fatigue research is critically and extensively reviewed. Reported fatigue endurance and progressive damage behaviour of several NFC laminates are analysed. Existing knowledge on NFC fatigue damage is found to be insufficient and ambiguous, therefore inadequate for engineering design consideration. The unique fatigue-stiffening phenomenon reported for Flax-epoxy specimens is argued to be a misleading consequence of increasing strain-rate under constant stress-amplitude cycling. To minimise the influence of a varying strain-rate, original constant strain-amplitude fatigue tests are conducted on Flax-epoxy laminates, where no evidence of stiffening is observed. Considering this sensitivity to strain-rate, strain-amplitude controlled fatigue tests may be better suited for NFC investigation. Strain-controlled fatigue lives of Flax-epoxy can be modelled by a linearised strain/log-life relationship. Evolution of several material properties and dissipation phenomena (inelastic strain, peak stress, stiffness, hysteresis energy, superficial temperature) are measured, and correlated with SEM-observed damage mechanisms in the microstructure. An evolution/growth model is proposed to simulate laminate-scale stiffness degradation and cumulative inelastic strain as a function of applied peak strain and fatigue cycles, and is found to well-capture experimental trends for Flax-epoxy. The combined contribution of this work provides much-needed original data on the damaged-condition mechanical behaviour of Flax-epoxy and other NFCs under a variety of loading conditions, clarifies contradictory aspects of critical NFC behaviour, and proposes numerical methods to replicate observed progressive damage and failure in NFCs.

scholarly journals Fatigue Damage of Al/SiC Composites - Macroscopic and Microscopic Analysis

2015 ◽  
Vol 60 (1) ◽  
pp. 101-105 ◽  
Author(s):  
A. Rutecka ◽  
Z.L. Kowalewski ◽  
K. Makowska ◽  
K. Pietrzak ◽  
L. Dietrich
Keyword(s):  
Fatigue Damage ◽  
Microscopic Analysis ◽  
Inelastic Strain ◽  
Damage Parameter ◽  
Fatigue Tests ◽  
Cyclic Plasticity ◽  
Damage Mechanisms ◽  
Before And After ◽  
Fatigue Damage Parameter ◽  
Sic Composites

Abstract The results of comparative examinations of mechanical behaviour during fatigue loads and microstructure assessment before and after fatigue tests were presented. Composites of aluminium matrix and SiC reinforcement manufactured using the KoBo method were investigated. The combinations of two kinds of fatigue damage mechanisms were observed. The first one governed by cyclic plasticity and related to inelastic strain amplitude changes and the second one expressed in a form of ratcheting based on changes in mean inelastic strain. The higher SiC content the less influence of the fatigue damage mechanisms on material behaviour was observed. Attempts have been made to evaluate an appropriate fatigue damage parameter. However, it still needs further improvements.

Predicting Fatigue Initiation Life of Sn/3.8Ag/0.7Cu Solder using Endochronic Cyclic Damage-Coupled Viscoplastic Theory

2008 ◽  
Vol 24 (4) ◽  
pp. 369-377 ◽  
Author(s):  
C. F. Lee ◽  
Z. H. Lee
Keyword(s):  
Strain Amplitude ◽  
Hysteresis Loops ◽  
Inelastic Strain ◽  
Cyclic Stress ◽  
Fatigue Tests ◽  
Cyclic Behavior ◽  
Dendritic Microstructure ◽  
Fatigue Initiation ◽  
Cyclic Damage ◽  
Good Agreement

AbstractThis paper studied cyclic behavior Sn/3.8Ag/0.7Cu solder with dendritic microstructure. A cyclic damage factor D under constant strain amplitude fatigue tests, was defined by using the reducing rate of maximum cyclic tensile stress σa. The critical cyclic damage DC and it's fatigue initiation life NI were determined very consistently by using separately the experimental σavs. N curves and the percolation theory. The endochronic cyclic damage-coupled viscoplastic theory proposed by the 1st author was used to simulate cyclic stress-strain hysteresis loops with damage under strain amplitude (εa) 0.8% at 298K. The results were in very good agreement with data. Combining the evolution equation of intrinsic damage and the computed cyclic stress-inelastic strain relation, a modified Coffin-Manson relationship was derived. By setting DC = 0.3, it predicted very effectively the NI data under σa from 0.2% to 1.0%.

Uncertainties and Margins in Environmental Fatigue Analysis Rules

2014 ◽  
Author(s):  
C. Faidy
Keyword(s):  
Strain Amplitude ◽  
Material Properties ◽  
Cyclic Strain ◽  
Fatigue Curve ◽  
Fatigue Analysis ◽  
Fatigue Tests ◽  
Pressure Vessels ◽  
Life Assessment ◽  
Combination Rules ◽  
Reduction Factors

During the past 30 years the main rules for fatigue analysis of pressure vessels were based on elastic approaches in order to evaluate cyclic strain amplitude and compare with an S-N fatigue curve for the corresponding material. After review of some rules in different Nuclear and Non-Nuclear Codes, like ASME Boiler & Pressure Vessel Code Section III, French RCC-M and RCC-MRx, European Standards EN 13445, the major conservatisms and uncertainties of different rules are discussed. All these Codes propose simple rules to evaluate the strain amplitude based on elastic approaches and simplified correction factors (Ke and Kν), transient combination rules and damage cumulating procedure. In the other hand, the material properties are based on standard fatigue tests done on the material associated to reduction factors to consider some particular effects like scatter, scale, surface roughness, mean stress or environmental effects to transfer them from small specimen to real structures. Concerned components in this paper are mainly piping systems. No existing Code covers all the aspects of fatigue with similar conservatisms that can affect the in-service inspection programs and the remaining life assessment of the corresponding components. After the review of different rules, key factors that affect the results and predictions will be identified. Some proposals will be issued to progress in the near future. Finally, a first set of recommendation on fatigue analysis will be presented to improve existing codes on harmonized way, associated to material properties needed, as fatigue curves associated to reduction factors.

Models for Estimating the Durability of Repeated Impacts

2007 ◽  
Vol 348-349 ◽  
pp. 205-208 ◽  
Author(s):  
Ion Dumitru ◽  
Liviu Marsavina ◽  
Nicolae Faur ◽  
I. Hajdu
Keyword(s):  
Strain Rate ◽  
19Th Century ◽  
Material Properties ◽  
Cyclic Load ◽  
Impact Test ◽  
Fatigue Tests ◽  
Impact Fatigue ◽  
Repeated Impact ◽  
Repeated Impacts

Many components from industry are subjected to repeated impacts, or in some cases these impacts can appear as additional loads. Repeated impacts define a fatigue phenomenon known under the name of Impact Fatigue. Because the strain rate changes the material characteristics it is to expect that the material properties at impact fatigue to be different in regard to those obtained at non-impact fatigue. First studies at repeated impacts were made at the middle of 19th Century, but the progress in this field is not as fast as non-impact fatigue, due to experimental difficulties and the lake of standards for impact fatigue tests. This paper presents a classification of repeated impact tests, and starting from this a series of parameters used for durability estimation will be analyzed. The high number of parameters used by different authors creates difficulties in comparison the different laboratories results. The importance of the shape and dimensions of specimens, and the stiffness of bearing are highlighted. In order to avoid these influences the authors proposed an experimental technique, based on testing of Charpy specimens, in similar conditions as single impact test. The paper presents a series of results obtained for additional impacts overlapped to a cyclic load.

Strain-rate dependent material properties of selective laser melted AlSi10Mg and AlSi3.5Mg2.5

2020 ◽  
Vol 62 (6) ◽  
pp. 573-583
Author(s):  
Andreas Lutz ◽  
Lukas Huber ◽  
Claus Emmelmann
Keyword(s):  
Strain Rate ◽  
Material Properties ◽  
Rate Dependent

scholarly journals A Review on Mechanical Properties of Natural Fibre Reinforced Polymer Composites under Various Strain Rates

2021 ◽  
Vol 5 (5) ◽  
pp. 130
Author(s):  
Tan Ke Khieng ◽  
Sujan Debnath ◽  
Ernest Ting Chaw Liang ◽  
Mahmood Anwar ◽  
Alokesh Pramanik ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
Polymer Composites ◽  
Stress Transfer ◽  
Natural Fibre ◽  
Transfer Efficiency ◽  
Strain Rates ◽  
Reinforced Polymer ◽  
Fibre Reinforced Polymer ◽  
Fibre Matrix

With the lightning speed of technological evolution, the demand for high performance yet sustainable natural fibres reinforced polymer composites (NFPCs) are rising. Especially a mechanically competent NFPCs under various loading conditions are growing day by day. However, the polymers mechanical properties are strain-rate dependent due to their viscoelastic nature. Especially for natural fibre reinforced polymer composites (NFPCs) which the involvement of filler has caused rather complex failure mechanisms under different strain rates. Moreover, some uneven micro-sized natural fibres such as bagasse, coir and wood were found often resulting in micro-cracks and voids formation in composites. This paper provides an overview of recent research on the mechanical properties of NFPCs under various loading conditions-different form (tensile, compression, bending) and different strain rates. The literature on characterisation techniques toward different strain rates, composite failure behaviours and current challenges are summarised which have led to the notion of future study trend. The strength of NFPCs is generally found grow proportionally with the strain rate up to a certain degree depending on the fibre-matrix stress-transfer efficiency. The failure modes such as embrittlement and fibre-matrix debonding were often encountered at higher strain rates. The natural filler properties, amount, sizes and polymer matrix types are found to be few key factors affecting the performances of composites under various strain rates whereby optimally adjust these factors could maximise the fibre-matrix stress-transfer efficiency and led to performance increases under various loading strain rates.

Bending fatigue of single-wall and double-wall corrugated paperboards under sinusoidal and random loads

2021 ◽  
pp. 109963622110204
Author(s):  
Zhi-Wei Wang ◽  
Yang-Zhou Lai ◽  
Li-Jun Wang
Keyword(s):  
Energy Dissipation ◽  
Fatigue Failure ◽  
Fatigue Tests ◽  
Stiffness Degradation ◽  
Random Load ◽  
Bending Fatigue ◽  
Random Loads ◽  
Vibration Fatigue ◽  
Sinusoidal Load ◽  
Double Wall

The bending fatigue tests of single-wall and double-wall corrugated paperboards were conducted to obtain the εrms– N curves under sinusoidal and random loads in this paper. The εrms– N equation of corrugated paperboard can be described by modified Coffin–Manson model considering the effect of mean stress. Four independent fatigue parameters are obtained for single-wall and double-wall corrugated paperboards. The εrms– N curve under random load moves left and rotates clockwise compared with that under sinusoidal load. The fatigue life under random load is much less than that under sinusoidal load, and the fatigue design of corrugated box should be based on the fatigue result under random load. The stiffness degradation and energy dissipation of double-wall corrugated paperboard before approaching fatigue failure are very different from that of single-wall one. For double-wall corrugated paperboard, two turning points occur in the stiffness degradation, and fluctuation occurs in the energy dissipation. Different from metal materials, the bending fatigue failure of corrugated paperboard is a process of wrinkle forming, spreading, and folding. The results obtained have practical values for the design of vibration fatigue of corrugated box.

Sign in / Sign up

Export Citation Format

Share Document