Degree of intimate contact

The Li-Loos intimate contact model was verified for compression molded unidirectional graphite-polysulfone and graphite-PEEK (APC-2) laminae and graphite-PEEK (APC-2) cross-ply laminates. The degrees of intimate contact of the unidirectional and cross-ply specimens were measured by optical microscopy and scanning acoustic microscopy, respectively. The predicted degrees of intimate contact agreed well with the measured values for both the unidirectional and cross-ply specimens processed at different temperature and pressures. 

Lee and Springer [19] and modified by Li and Loos [22,23] to include unidirectional and cross-ply lay-ups will be used to demonstrate the effects of various geometric, material, and processing parameters on the degree of intimate contact. 

Equations 7.2 and 7.3 represent expressions for the degree of intimate contact of a single prepreg ply in contact with a smooth rigid surface (Fig. 7.5). 

Probably the two most commonly used techniques for measuring the overall quality of the composite consolidation are optical photomicrographs and through transmission C-scan. Both of these techniques can be readily adapted to measuring the degree of intimate contact at the ply interfaces. 

Figure 7.14 Degree of intimate contact (Die) versus time for single-ply APC-2 samples...

The data shown in Figure 7.15 were obtained from two-ply T300/P1700 unidirectional specimens that were compression molded in a 76.2 mm (3 in.) square steel mold. The cross-sections of the consolidated specimens were examined by optical microscopy and the degree of intimate contact was determined as the amount of the interply region that was in contact divided by the total area of the cross-section. Additional details of the experimental procedures are given in Reference 22. 

The unidirectional interply interface model (see Eq. 7.4) was used to calculate the degree of intimate contact versus time for unidirectional samples consolidated at different temperatures and pressures. The surface characterization parameters for T300/P1700 and... 

Considering the complexities involved in the formation of the cross-ply interface during consolidation, the cross-ply interply interface model predicted degrees of intimate contact... 

A theoretical model for intimate contact for in-situ consolidation has been developed in Reference 21. In this model, the irregular surface of the thermoplastic tow is modeled as a series of rectangular elements, oriented along the fiber axis, which are deformed as local pressure is applied (Fig. 13.11). The amount of flattening is quantified as the degree of intimate contact Dic (Eq. 13.14)... 

An expression for the degree of intimate contact can be found by applying conservation of mass and equilibrium of forces (Eq. 13.15)... 

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