Micromechanical Modeling of Effective Orthotropic Elastic and Viscoelastic Properties of Parallel Strand Lumber Using the Morphological Approach

2019 ◽  
Vol 145 (9) ◽  
pp. 04019066 ◽  
Author(s):  
Sardar Malek ◽  
Carole Nadot-Martin ◽  
Benjamin Tressou ◽  
Chunping Dai ◽  
Reza Vaziri
2001 ◽  
Vol 35 (10) ◽  
pp. 849-882 ◽  
Author(s):  
Modris Megnis ◽  
Janis Varna ◽  
David H. Allen ◽  
Anders Holmberg

Experimental studies have been performed to obtain creep compliance functions of polypropylene (PP) and Glass Mat reinforced Thermoplastics (GMT) with PP matrix. It was found that both GMT and PP in the considered loading region may be considered as linear viscoelastic materials. The obtained viscoelastic compliance functions were successfully used to describe material behavior in the stress relaxation test. A micromechanical model based on the correspondence principle in the Laplace domain was developed to describe the viscoelastic behavior of GMT. This model considers the GMT composite with a given fiber orientation distribution function as consisting of an infinite number of unidirectional layers with orientations corresponding to this distribution function. The viscoelastic properties of the unidirectional layer are calculated using Hashin's concentric cylinder model that uses the experimentally determined viscoelastic properties of PP matrix. The predictions for GMT have been compared with experimental data. The model predicts rather good initial properties of GMT but it gives slightly less time dependence than compared to experimental data for both relaxation functions and compliance. The cause of the difference (debonding) between matrix and fiber, nonuniform fiber spatial distribution, stress concentrations etc.) is discussed.


1993 ◽  
Vol 3 (5) ◽  
pp. 597-602 ◽  
Author(s):  
Gregory A. DiLisi ◽  
E. M. Terentjev ◽  
Anselm C. Griffin ◽  
Charles Rosenblatt

Author(s):  
E. M. Timanin ◽  
N. S. Sydneva ◽  
A. A. Zakharova

Introduction. To date there is a lack of studies dedicated to the objectification of the palpation data obtained by a specialist during the osteopathic examination. The issue of the evidence of the results of osteopathic correction still remains important. Search for instrumental methods allowing to register and to measure various palpation phenomena and manifestations of somatic dysfunctions is very relevant for the development of osteopathy as a science. It is also very important to find objective characteristics of these methods.Goal of research — to study viscoelastic characteristics of the soft tissues of the lower legs by palpation and instrumental methods before and after osteopathic correction.Materials and methods. 22 volunteers (12 women and 10 men) aged 18–23 years without complaints of the musculoskeletal system were examined. Osteopathic diagnostics and measurement of the viscoelastic properties of muscles were carried out by the method of vibration viscoelastometry before and after osteopathic correction.Results. Correlation analysis by Spearman showed that the subjective assessment of an osteopath positively correlated with both elasticity (r=0,43, p<0,05) and viscosity of soft issues (r=0,29, p<0,05). For the gastrocnemius muscle, this pattern was even more pronounced — for elasticity r=0,51, p<0,05, for viscosity =0,34, p<0,05. After osteopathic correction no changes in the elasticity of the soft tissues were observed. The viscosity of the tissues reduced, but in the projection of the gastrocnemius muscle, these changes were not statistically significant (p=0,12), whereas in the projection of the soleus muscle statistically significant changes (p=0,034) were observed.Conclusion. Changes in the viscoelastic properties of tissues demonstrated that the effects of osteopathic correction with the use of myofascial mobilization techniques, articulation mobilization techniques, and lymphatic drainage techniques were not obvious. The elasticity of soft tissues of the lower legs did not change, while the viscosity decreased, especially in the projection of the soleus muscles. This effect of the osteopathic correction can be associated with the effect of thixotropy — the transformation of gel-like intercellular substance into sol. Thus, the research showed that vibration viscoelastometry can be used for the objectifi cation of the condition of soft tissues and of the effects of osteopathic correction.


2010 ◽  
Vol 1 (2) ◽  
pp. 56
Author(s):  
Arturo Rodriguez ◽  
Mohini M. Sain ◽  
Robert Jeng ◽  
Alexis Baltazar y Jimenez

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