Composite consolidation

All VGCF was graphitized prior to composite consolidation. Composites were molded in steel molds lined with fiberglass reinforced, non-porous Teflon release sheets. The finished composite panels were trimmed of resin flash and weighed to determine the fiber fraction. Thermal conductivity and thermal expansion measurements of the various polymer matrix composites are given in Table 6. Table 7 gives results from mechanical property measurements. 

It is clear from the description of the commonly used fabrication techniques that thermoplastic composite consolidation is a nonisothermal manufacturing process that involves continuous heating, compacting, and solidification. The major mechanisms,... 

The final step of thermoplastic composite consolidation is to cool and solidify the consolidated parts. It is well known that the physical and mechanical properties of composites are determined by the microstructure of the matrix in addition to the reinforcement, whereas the morphology of the thermoplastics is determined by its thermal history [14-17]. 

The mechanism by which a thermoplastic matrix composite consolidates to form a laminate was attributed to autohesive bond formation between plies [13,18]. Autohesion, however, can... 

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. 

The process by which a thermoplastic matrix composite consolidates to form a laminated structure has been attributed to autohesive bond formation at the ply interfaces. Autohesive bond formation is controlled by two mechanisms (1) intimate contact at the ply interfaces, and (2) diffusion of the polymer chains across the interface (healing). The rate of autohesive bond formation and hence the speed of the composite consolidation process is directly related to the temperature-pressure-time processing cycle. 

In general, composite consolidation degrades fiber properties and it becomes necessary to devise procedures that allow determination of Sc and m to be evaluated relevant to the fibers within the composite. This is a challenging problem. In some cases, it is possible to dissolve the matrix without further degrading the fibers and then measure the bundle strength.77 This is not feasible with most CMCs of interest. The following two alternatives exist. 

M.N. Bureau, J. Denault, Fatigue resistance of continuous glass fiber/polypropylene composites consolidation dependence, Composites Science and Technology 64 (2004), pp. 1785-1794. 

A high temperature class composition, consolidated by pressing. 

Fig. 1 Process feasibility window for the thermal processing of a self-reinfOTced composite from the fibre and matrix precursor into a composite structure. The process-feasible window is dictated by four boundaries of temperature and pressure (based rui [22, 23]). (a) When excessive temperature is applied, molecular relaxatimi of the fibrous reinfOTcement can occur, resulting in a loss in mechanical properties and, at the miset of fibre melting, a loss of reinforcemcmt volume fraction. (b) In a similar way to excessive temperature, an excess in applied pressure can encourage flow, disrupting molecular alignment and resulting in a loss in mechanical properties. Conversely, the lower temperature and pressure houndaries of the process-feasible windows (c) and (d), respectively, are dictated by the need to apply a minimum temperature and pressure to achieve adequate composite consolidation...

Ref. Lead Polymer fibre Composite Consolidation technique Eibre Longitudinal Longitudinal Transverse Transverse... 

Ref. Lead author, year Polymer Composite Consolidation Longitudinal Longitudinal... 

Composition Consolidation pressure (MPa) Density Crush force (kN)... 

R Monteverde, C. Melandri, and S. Guicciardi, Microstructure and mechanical properties of an HfBj + 30 vol% SiC composite consolidated by spark plasma sintering. Mater. Chem. Phys., 100 513-519,2006. 

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