Fiber-reinforced polymer (FRP) laminates are being used as external reinforcement for strengthening concrete members. The performance of unidirectional FRP laminates is highly dependent on fiber orientation with respect to applied load direction. In the case of fabrication by manual layup, it is possible to have fiber plies installed with improper orientation. In this project, the degradation of strength and modulus of carbon FRP laminates from fiber misalignment was investigated experimentally using tensile coupons. The specimens consisted of one and two plies of unidirectional carbon FRP impregnated with a two-component epoxy. The misalignment angles varied from 0 to 40° for the one-ply samples, and from 0 to 90° for one ply of the two-ply samples. The size effect on the strength and modulus was investigated for one-ply specimens with misalignments of 5 and 10°. For these specimens, the ply width was maintained constant, and the length was varied so that the aspect ratio ranged between 2 and 8. It was concluded that misalignment affects strength more than elastic modulus. However, provided that mechanical parameters are related to the cross-sectional area of laminate with fibers continuous from end to end of the coupon, the degradation of strength can be accounted with a knock-down factor that is independent of misalignment angle.


Civil, Architectural and Environmental Engineering

Second Department

Mechanical and Aerospace Engineering

Keywords and Phrases

Degradation; Fiber-reinforced materials; Laminates; Polymers; Size-effect; Stiffness; Strength

International Standard Serial Number (ISSN)


Document Type

Article - Journal

Document Version


File Type





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Publication Date

01 Jul 2002