Prepreg Testing

It also indicates that it should be possible to process the resin after a 60 day aging period by shortening the hold period to around 20 minutes. But note what happens when a similar study is made on the prepreg (upper three curves). The data clearly indicates that the hold period for the 21 day old sample should be shortened to around 30 minutes and that the 60 day old prepreg may not be processible at all This is a clear indication of the importance of proper material selection and testing when doing process studies. 

The ratio of the toughness for ALF/epoxy to that for CF/epoxy was about two, and this ratio remained constant without respect to the fracture mode and test environment. This ratio was correlated to geometrical factors such as the thickness of the resin rich region at the prepreg interface. 

The work reported here was part funded by EPSRC (UK) (GR/ R 90369). The supply of prepreg by Cytec for this work and for TC4 round robin activities is gratefully acknowledged. The technical assistance of Mr M. Heusser (EMPA) for part of the tests is gratefully acknowledged. 

Test panels 10x10 in. were fabricated from 10 layers of syntactic foam prepreg (7804 iaminated IZ-ply). 

Laminates constructed from 12 plies of Style 7628, 1-399 finish glass cloth prepreg press cured one hour at 350°F. and 150 psi were tested versus NEMA FR-4 specification limits. Results are listed... 

The machines necessary to accomplish the above prepregging procedures are many and varied. There are three distinct aspect to quality control raw material screening, on-line control, and batch testing. All three are obviously important, but the first two are more critical. 

Fibers and base resins are supplied against certificates of conformance and often property test certificates. On-line control during the manufacture of prepreg revolves around the correct ratio of fiber to resin. This is done by a traversing Beta-gauge, which scans the dry fiber (either unidirectional of fabric) and then the impregnated fiber and provides a continuous real-time plot of the ratio across the width of the material. This can be linked back to the resin system application point for continuous adjustment. 

Batch testing is carried out to verify prepreg properties, such as resin content, volatile level, and flow. The resin advancement (chemical reaction) is monitored via a Differential Scanning Calorimeter (DSC) and the formulation consistency by testing the Tg via DSC or Dynamic Mechanical Analyzer (DMA). The laminate properties are also determined. All are documented and quoted on a Release Certificate. 

This decay rate is nearly equivalent to that exhibited by one g of radium in equilibrium with its disintegration products. A miUicurie (mCi) is 0.001 curie, curie point See magnetized curie point, curing See autoclave nitrogen atmosphere cure extruder wire and cable process, dry cure inhibitor prepreg volatile content reinforced plastic resin transfer molding test, Barcol hardness test, scorch Mooney thermoset plastic vulcanization welding, induction. 

Iwasaki and Todoroki [92] use a response surface technique to process the electrical resistance measurements. A large number of cross-ply and quasi-isotropic specimens were tested such that statistical data processing could be applied. Copper-foil electrodes mounted on one side of the CFRP specimens during prepreg layup were co-cured with the specimen (Figure 16.39). Impact-induced matrix cracking and delaminations were detected. Probability of location estimation and error bands were computed [92]. The extension of this method to woven CFRP composites is described in Hirano and Todoroki [93]. 

As described in chapter 3.1 1ST and ITA already tested alternative ways to bring the B-staged prepreg inside of the concrete into the C-stage (Fig. 7). Thus, there is no further need to use a mould or autoclave process at all. This saves expenses. UV-, microwave or heat-curing systems are not favored by ISF and ITA, because cost intensive equipment would be needed as well as workers who have to deal with it on the construction side. 

Immersion in water does not always have adverse effects. Sometimes the properties improve, or some properties may improve and others deteriorate. Kosuri and Weitsman [79] and Smith and Weitsman [80] conducted fatigue tests (5Hz at 74-89% ultimate tensile strength) on cross-plied AS4/ 3501-6 prepreg carbon/epoxy laminates in three conditions ... 

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