October 7-10, 2008    Evanston, IL, USA


Plenary 2 - Wednesday Oct. 8th

The estimation theory of creep behavior on Fiber Reinforced Thermoplastics

Satoshi Somiya, Ph.D.

Visiting Lecturer
Keio University
Tokyo, Japan


Structure and parts in some machines which was made with some engineering polymers usually shows creep deformation. In the case of delicate machine, the deformation according to time and temperature became a problem. Composition of reinforcements in resin is well known to decrease the creep progress but it was very difficult to estimate them with the theoretical analysis and calculation by FEM method recently. One of the reasons is this phenomenon sometimes shows non-linearity. Now some influences factors such as physical aging, crystallinity, polymerization, moisture, water absorption and filer composition on viscoelastic behavior have been found, but their effect on creep deformation have not obtained quantitatively.
            The effect of filer composition on creep behavior was researched quantitatively at first. For GFRP of polycarbonate with perfectly physical aging treatment, creep compliance Dc(t) under some temperature conditions were measured and it was confirmed that all creep behavior were presented by  master curves Dc(t’) on specimens of each fiber volume fraction and also one grand master curve Dc(t’’) on all master curves of several FRPS was obtained by some shift factors such as temperature shift factors and modulus shift factor. Because it was found “Time-Temperature superposition principle” was adaptive, creep strain curve to real time of several FRP is able to be calculated with the grand master curve and some shift factors, using linear visco-elastic theory as follows;


  The effect of physical aging on creep deformation was researched on FRP of PC. From these results, it was found that the effect of these factors is able to present by shift factor as same as the effect of fiber contents. In addition we can estimate the creep process of FRPs, which are several fiber contents under some kinds of physical aging conditions on arbitrary temperature.

Bio: Dr. Somiya received his PhD degree of Engineering from the graduate school of Keio university.  He served as Assistant of Keio University in 1973. He then became Associate Professor, Assistant Professor and Professor and retired from Keio University at 2008. He is now a visiting lecturer of Keio University at 66 years old.  He was a chair of the division of Material and Processing on Japan Society of Mechanical Engineers from 1994 to 1995.
Dr. Somiya’s research fields; Fracture strength, Fracture mechanism and viscoelastic deformation of polymers and polymer matrix composite and the development of recycle method for fiber reinforced Plastics.

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