Date of Graduation

2000

Document Type

Thesis

Degree Type

MS

Committee Chair

Hota V. S. GangaRao

Abstract

Use of FRP composites in construction industry has been growing rapidly. However, currently all composite products are manufactured with one and/or two dimensional fibers and fabrics (1-D or 2-D). A shortcoming thick composite (> 0.75 in.) made of 1-D or 2-D fabrics is its dramatic reduction in strength, i.e., up to 50% of thin (<0.5 in.) composites. This can be attributed to shear lag leading to ply-by-ply failure; in addition, premature failure of matrix and fibers or the interface failure is very common in thick composites. Therefore, the motivation of the present work is to fabricate and test composites with 3-D stitched fabrics, which overcome the limitations in composites made of 1-D or 2-D fabrics.

In this study, composites were fabricated using 3-D stitched fabrics with different: (1) fiber architecture; (2) stitch density; (3) stitch material; and (4) manufacturing process. Strength and stiffness of composites with 3-D stitched fabrics (at coupon level) under tension, bending and shear loads were experimentally established and theoretically evaluated. Structural properties of composites made of 3-D stitched fabrics were compared with the structural properties of composites made of unidirectional fibers and 2-D stitched fabrics. Composites made of 3-D stitched fabrics were found to have enhanced strength and stiffness (about 30%).

The existing FRP bridge deck component (first generation) was modified with respect to weight, fiber architecture and manufacturing process leading to the development of the second generation FRP bridge deck component. In the second generation FRP bridge deck component, the self-weight was reduced by about 11% without sacrificing strength and stiffness. The global stiffness of second generation FRP bridge deck component was evaluated experimentally (3 point bending test) and theoretically by Approximate Classical Lamination Theory. The ultimate stress of second generation FRP bridge deck component (30.8 ksi) was three times more than that of first generation FRP bridge deck component (10.3 ksi). The stiffness of second generation FRP bridge deck component was found to be 8.28E+08 lbs-in2/foot width while the stiffness of first generation FRP bridge deck component was found to be 8.44E+08 lbs- in2/foot. Trail second generation FRP bridge deck module has to be tested under fatigue loads.

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