CPA Help Pages
Help for Microstructure
Continuous Fiber Laminae:

The thermoelastic properties of a transversely isotropic lamina consisting of collimated continuous fibers may be obtained by assigning the effective aspect ratio, ae, a value approaching infinity (e.g., 10,000). The assignment fa = -0.5, fp = 1.0 identifies the "1" axis as the unique longitudinal axis with the 2, 3 plane serving as the plane of transverse isotropy.
The output from this program can be used as input to Laminate Property Analysis (LPA) to predict the properties of a laminated composite with various stacking sequences and orientation of lamina.


Sheet Molding Materials:

This class of composite materials is fabricated under conditions to promote the formation of 2-dimensional orientation distributions. The thermoelastic properties for this class of materials may be generated by assigning the effective aspect ratio, ae, an observed (or test) value greater than unity. The assignment fa = -0.5 assures that the fibers are confined to the 1, 2 plane. Various values of fp may be specified or scanned. A value of fp = 0.0 yields a quasi-isotropic material within the 1, 2 plane. In this case the unique axis is the "3" or through-the-thickness-direction. A value of fp = 1.0 generates a collimated system of short fibers aligned along the "1" direction. Intermediate values of fp generate various states of planar orientation. The influence of "out-of-plane" tilting of the fibers may be investigated by small increases in fa from the planar condition given by fa = -0.5.

Extruded Short Fiber Materials:

The properties of extruded rods of short fiber materials can be predicted under the assumption that the fibers are axially symmetric around the extrusion direction. This condition can be obtained by assigning the orientation parameter fp = 0.0. Various stages of axial orientation are generated for values of fa in the range –0.5< fa < 1.0. In this case, the unique axis is the "3" axis with the 1, 2 plane exhibiting transverse isotropy.

For this assignment
A value of fa = -0.5 corresponds to fibers oriented parallel to the 1, 2 plane and random within this plane; a value of fa = 0.0 (with fp = 0.0) corresponds to a "true" 3-dimensional random distribution; a value of fa = 1.0 corresponds to a fiber alignment along the "3" axis. If the individual filaments are fully dispersed, the effective aspec ratio, ae, may be taken as the observed filament aspect ratio.
Particulate Systems:

Resin/Filler systems may be obtained by setting ae = 1. The presumption of spherical particles obtained with ae = 1 precludes a dependency on orientation. Accordingly, any value of fa and fp can be used as input since the orientation averaging procedures will be bypassed. The resulting material will be isotropic.


Platelet Reinforced Systems:

The thermoelastic properties of composite materials containing essentially circular platelets may be predicted by assigning the effective aspect ratio, ae, an observed (or test) value less then unity. A specification of fa = -0.5 and fp = 1.0 identifies the "1" axis as the unique axis (perpendicular to the "thin" dimension of the platelet). Transverse isotropy is exhibited in the 2, 3 plane. Out-of-plane tilting of the platelets can be simulated by varying fa.


Three Dimensional:

This is the most general microstructure for which the user may specify the orientation parameters fp and fa and the aspect ratio.
The three dimensional core can be used to predict properties for injection and transfer molded materials. However, a "skin-core" microstructure can develop. The "skin" tends to consist of fibers aligned in the flow direction; the "core" region approaches three-dimensional random orientation. The relative thickness of the skin to core regions is dependent upon molding conditions.
This program can be used to analyze this situation by first assigning the skin region an orientation of fa = -0.5 and fp = 1 (or appropriate observed values). The second computation for the core region is obtained by setting fa = fp = 0. The results from these computations can be used as input to (LPA) to generate the properties for this layered structure.

Random Fiber Reinforcement:

This is a special microstructure in which the fibers are in a three dimensional random state of orientation with fp = fa= 0. The user can specify the aspect ratio.