An Analysis of the Nonlinear Behavior of Lignin-Based Flax Composites

Pupure, Liva; Vārna, Jānis; Joffe, Roberts; Pupurs, Andrejs

doi:10.1007/s11029-013-9330-x

Cited by 22 publications

(20 citation statements)

References 23 publications

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“…One of them is a "single specimen" methodology approved for different types of materials. 28,29,36,[38][39][40][41][42] Stress-and time-dependent parameters of the strain components (elastic, viscoelastic, and viscoplastic) are determined for a single specimen from repeated creeprecovery tests with an increasing load and creep time in each cycle. These parameters are then intended to be averaged for replicate samples, although no comments on the related data scatter are found in the referred above studies.…”

Section: Tensile Propertiesmentioning

confidence: 99%

“…9,10 Some similarities in discussions on smoothing of data scatter are found in a study of Pupure et al for natural fiber composites. 39 Authors introduced a damage function in the form of strain-dependent (instead of common stress-dependent) stiffness degradation, although mentioning coupled effects of damage and viscoplasticity.…”

Section: Relationship Between the Residual And Total Creep Strainmentioning

confidence: 99%

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Relationship between the residual and total strain from creep‐recovery tests of polypropylene/multiwall carbon nanotube composites

Starkova

Анискевич

Sevcenko

et al. 2020

J of Applied Polymer Sci

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An assessment of accumulated irreversible strains in polymer composites is a crucial element for controlling dimensional stability of structural components and their remnant life. The residual strains as functions of total creep strains are analyzed by example of creep-recovery data of polypropylene (PP)/multiwall carbon nanotube (MWCNT) composites. To cover wide range of strains, creep test regimes with different stresses, loading time, and number of cycles were applied. Totally, data of 62 single creep-recovery tests for 7 material compositions were used for analysis. A general empirical relationship between the residual and total creep strain is established and finely described by a power law. The residual strain increases with increasing stress and time of loading and decreases with growing amount of MWCNT. The total creep strain, which is implicitly related to stress, time, and sample specificity, determines the contribution of irreversible deformation. This fact overcomes data variability within one series of samples. Similar empirical relationships are obtained for 25 polymer composites from literature reinforced with different types and amount of fillers and tested under different temperatures. The empirical relationship can be used for an express assessment of residual strains accumulated in a long term by performing just a few short-term control tests.

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Section: Tensile Propertiesmentioning

confidence: 99%

Section: Relationship Between the Residual And Total Creep Strainmentioning

confidence: 99%

Relationship between the residual and total strain from creep‐recovery tests of polypropylene/multiwall carbon nanotube composites

Starkova

Анискевич

Sevcenko

et al. 2020

J of Applied Polymer Sci

View full text Add to dashboard Cite

show abstract

“…The behavior for all composites is rather linear until 0.6% strain. The source of the inelastic behavior at higher strains was not investigated: it could be a combination of viscoplasticity and viscoelasticity typical for natural fiber composites (Marklund et al 2006, Varna et al 2012, Pupure et al 2013. Average values from tensile tests and standard deviations are presented in Table 4.…”

Section: Tensile Test Resultsmentioning

confidence: 99%

Mechanical properties of natural fiber composites produced using dynamic sheet former

Pupure

Vārna

Joffe

et al. 2018

Wood Material Science & Engineering

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Composites formed from wood fibers and man-made cellulosic fibers in PLA (polylactic acid) matrix, manufactured using sheet forming technique and hot pressing, are studied. The composites have very low density (due to high porosity) and rather good elastic modulus and tensile strength. As expected, these properties for the four types of wood fiber composites studied here improve with increasing weight fraction of fibers, even if porosity is also increasing. On the contrary, for man-made cellulosic fiber composites with circular fiber cross-section, the increasing fiber weight fraction (accompanied by increasing void content) has detrimental effect on stiffness and strength. The differences in behavior are discussed attributing them to fiber/ fiber interaction in wood fiber composites which does not happen in man-made fiber composites, and by rather weak fiber/ matrix interface for man-made fibers leading to macro-crack formation in large porosity regions.

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“…The used VP model was suggested by Zapas and Crissman 20 and it has been successfully used to describe VP strain development in several materials. 10,21–26 In this model the VP strain is written in form of stress dependent integral, with parameters determined in creep and strain recovery tests (the applicability of this model is also verified in the suggested testing methodology). Tests are performed on [+45 °/−45 °] s specimens subjected to axial loading and measuring axial strain and transverse contraction strain; method which allows analysing irreversible shear strains in layers which is the irreversible strain component that in relatively short tests at 35 MPa even at room temperature can reach value of 0.3% 9,10 and, hence, may in many cases give the largest contribution to stress relaxation.…”

Section: Introductionmentioning

confidence: 99%

Effect of degree of cure on viscoplastic shear strain development in layers of [45/−45]s glass fibre/ epoxy resin composites

Pupure

Saseendran

Vārna

et al. 2018

Journal of Composite Materials

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Effect of degree of cure on irreversible (viscoplastic) shear strain development in layers of glass fibre/ epoxy resin (LY5052 epoxy resin) [+45 °/−45 °]s laminate is studied performing a sequence of constant stress creep and viscoelastic strain recovery tests. For fixed values of degree of cure in range from 79.7% to 100%, the viscoplastic strains were measured as dependent on time and stress and Zapa's integral representation was used to characterize the observed behaviour. It is shown that at all degrees of cure the viscoplastic behaviour can be described by Zapa's model with parameters dependent on degree of cure. It is shown that for degree of cure lower than 80% the viscoplastic strains grow much faster and are much more sensitive to the increase of the applied shear stress. These irreversible strains developing in the final phase of the curing can significantly alter the residual stress state in the composite structure.

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An Analysis of the Nonlinear Behavior of Lignin-Based Flax Composites

Cited by 22 publications

References 23 publications

Relationship between the residual and total strain from creep‐recovery tests of polypropylene/multiwall carbon nanotube composites

Relationship between the residual and total strain from creep‐recovery tests of polypropylene/multiwall carbon nanotube composites

Mechanical properties of natural fiber composites produced using dynamic sheet former

Effect of degree of cure on viscoplastic shear strain development in layers of [45/−45]s glass fibre/ epoxy resin composites

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