3

Alternatively, the plate flexural properties (the Ds above) may be obtained from the in-plane flexural properties, however, this is seldom done in practice for commercially produced pultruded materials consisting of layers of unidirectional roving and continuous filament mats. In this case, for example, the longitudinal flexural stiffness, DL, is written as (Barbero 1998)

Ebtp

The in-plane strength properties may be obtained from theoretical calculations or from testing of coupons taken from the laminate. Where theoretical predictions are used, the first-ply-failure (FPF) is assumed to represent the strength of the laminate. Coupon testing is highly recommended for obtaining the strength properties.

Property data provided in pultrusion company manuals and design guides are obtained from tests on coupons of pultruded materials taken from sections. Data reported are typically applicable to a broad range of section sizes and types. The specific fiber architectures (volume fractions of roving, mats, and fabrics) in the different section sizes and types varies. Fiber architecture may also vary within the section (e.g., web reinforcement architecture may be different from flange reinforcement architecture). The properties given by manufacturers can be assumed to be lower bounds for the sections indicated in the manuals. No data are provided to determine the statistics of these properties for use in probabilistic-based design. In addition, the property data are not related to the capacity of members subjected to specific loading conditions (e.g., axial load, flexure) and are based on coupon testing. Representative mechanical property data for pultruded materials used in commercially available pultruded shapes, flat sheets, and rods are shown in Table 16.2. Properties of pultruded carbon-reinforced epoxy strips for structural strengthening of concrete are shown for comparison purposes. Selected physical and electrical property data reported by manufacturers are shown in Table 16.3.

It is assumed that the pultruded material behaves in a linear elastic manner in tension, compression, and shear in both the longitudinal and the transverse directions and that failure is brittle. This assumption is reasonable in the service range (~20% ultimate) but is not reasonable, especially in the shear and transverse directions, at higher loads where the stress-strain behavior is highly nonlinear.

All orthotropic plates of pultruded material in pultruded shapes are assumed to be thin (i.e., the out-of-plane thickness is an order of magnitude less than the in-plane length and breadth of the plate).

Standard pultruded structural shapes are often assumed to be homogenous on the section level (i.e., the shape consists of plates all having the same properties). However, it should be noted that some manufacturers (e.g., Creative Pultrusions) have optimized their shapes and provide properties separately for the webs and the flanges of many of their shapes.

It is assumed that the properties of the junctions between the plates (e.g., the web-flange junctions in an I beam) are the same as those of the plates themselves.

The ratio of the longitudinal modulus to the shear modulus, EL/GLT, for pultruded orthotropic material plates can be much larger than that for isotropic material plates. As a result of this, shear deformation

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