Nr

a Strongwell (2002).

b Creative Pultrusions (2000).

d Estimated.

e NR, not reported by manufacturers.

plays a significant role in the analysis of thin-walled pultruded shapes. The effects of shear deformation should be accounted for in deflection calculations as well as in stability calculations wherever possible.

The properties of pultruded shapes are affected by the environment in which they are used and the conditions under which they are used. These ''environmental-use'' effects can include time, temperature, radiation, solvents, fire, impact, abrasion, and fatigue. The way in which these effects are accounted for in design is not yet clear. In some cases (e.g., temperature, creep) some guidance is available. The safety factors recommended by pultrusion companies for use in design are intended to account for some of these effects.

In the case of elevated temperature service, pultrusion companies specifically recommend reductions in strength and stiffness properties as a function of temperature for different resin systems (usually isophthalic polyester or vinylester). At 65° C (150° F) the strength of isophthalic polyester resin pul-trusions is 50% of the room temperature strength and the modulus is 85% of the room temperature modulus. For vinylester resin pultrusions at 65° C (150° F) the strength and modulus are 80 and 90% of their room temperatrue values, respectively. At temperatures higher than 65° C (150° F) the use of isophthalic polyester resin pultrusions is not recommended and vinylester resin pultrusions are recommended to a maximum use temperature of 93° C (200° F) with further strength and stiffness reductions (strength = 50%, moduli = 85%).

Stiffness and strength properties used in design are typically obtained from short-term testing. Long-term changes in stiffness and strength can be accounted for using different models. For creep deflections the models proposed by the SPDM (1984) developed by Findley can be used to determine effective viscoelastic moduli for use in predicting long-term deflections of pultruded structures.

Long-term degradation due to corrosive environments is typically determined by use of corrosion resistance guides that provide recommendations on the use of different pultruded materials in a variety of different chemical environments and temperatures. These guides are based on coupon test data. Fundamental studies to develop models to predict the long-term degradation of FRP composites in different service environments are ongoing but cannot yet be used for reliable lifetime prediction.

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