E2 Reinforcement Architecture

Topic

The reinforcement within this composite can be arranged geometrically in various ways; it is this type of reinforcement architecture—whether continuous, short-fiber, or laminated—that determines the orientation efficiency factor (as described by Krenchel's factor) in this model. Whether reinforcement fibers are arranged continuously and aligned, rather than being short and dispersed or stacked in layers with varying orientations, dictates—from the outset—the efficiency with which the reinforcement transmits its stiffness in a specific loading direction.

This orientation efficiency factor quantifies the fraction of stiffness that an individual fiber would contribute if perfectly aligned with the loading direction—and how much of that potential stiffness is actually utilized based on the fiber's specific orientation within the reinforcement architecture. Exact alignment of the fibers with the loading direction maximizes this orientation efficiency factor, whereas random orientation or orientation at an angle to the loading direction results in a lower factor.

This same orientation efficiency factor determines the effective fiber fraction in the loading direction: the portion of fiber that actually contributes to reinforcing the composite in that direction, after accounting for the inefficiency introduced by the reinforcement architecture. A higher orientation efficiency factor brings the effective fiber fraction closer to the composite's nominal fiber fraction, while a lower factor results in an effective fiber fraction well below that nominal value.

Ultimately, this effective fiber fraction in the loading direction determines the modulus of the quasi-isotropic laminate—a laminate stacked with enough varying orientations that its in-plane properties approximate those of an isotropic material, even though each individual layer remains anisotropic. A higher effective fiber fraction results in a higher modulus for that quasi-isotropic laminate, whereas a lower effective fiber fraction results in a lower modulus.

For this reason, the present model—based on the specific reinforcement architecture—modulates the property transfer utilized by another model in this set, the one describing the composite's effective elastic properties. Since the intrinsic properties of the matrix and reinforcement (established in a separate model within the set) do not transfer directly to those effective elastic properties, they must first be adjusted by the orientation efficiency factor and the effective fiber fraction, both of which this model determines based on the reinforcement architecture.

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