Glass-fibre laminates

Table 29.4 Typical properties of glass-fibre laminates ...

Flexural strength of the polyester/glass fibre laminate... 

Fig. 2. Notched strengths of notched carbon and glass fibre laminates vs. laminate angle notch depth 5mm, except for glass for

Fig. 3. Strength vs. notch depth for [ 45]s carbon and glass fibre laminates.

Fig. 8. Apparent fracture toughnesses of glass fibre laminates, with laminate angles Indicated on the curves.

The glass fibre laminate results are less well characterized than the carbon. In the case of the lower angle results, Fig. 8, there seems to be a peak value between about 8 and 12mm notch depth. While the 15° angle ply laminates suffered much fibre breakage, the 30° laminates suffered relatively little, except at 15mm notch depth. Table 1. However, this was associated with a lower fracture toughness. Fig. 8. (The aberrant result at 3mm for

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Schulte [46,47] has demonstrated how different organic solvents, such as hydraulic fluid encountered in the aerospace stmctures, lead to a reduction in the secant modulus of 45° glass fibre laminate under flexural fatigue and the number of cycles to failure. The matrix in this case was a polyether imide (PEI) which is plasticised by ingress of the fluid. A reduction in the matrix modulus means that the shear strength of the matrix will also be reduced with the consequence that the failure mechanism in flexure will change from matrix-fracture to delamination. 

Fig. 3.74 Flexural strength of glass fibre laminates after half-hour exposure as a function of...

Figure 5.13 (a) shows the bolt load distribution for two equally thick (3.9 mm) glass fibre laminates joined together by 2, 3 and 4 tandem rows of fasteners. In the two-row joint (Wx=40 mm and 120 mm, respectively) the load is evenly distributed among the two rows. In the three row joint (Wx=40 mm and 60 mm, respectively) the fasteners at the end of the overlap transfer about 7% higher bolt load than that of an even distribution, whereas the bolt in the middle transfers a load 14% less than that of an even distribution. In the four-row configuration (Wx=40 mm) the bolts at the end of the overlap transfer about 20% higher load than that of an even distribution. Hence, the two bolts in the middle transfer about 20% less load than that of an even distribution. 

The incorporation of filler does reduce the expansion anisotropy in glass-fibre laminates. The latter use either continuous or very high-aspect-ratio fibre, 1/d > 1000 and the simple rule of mixtures for thermal expansion does not apply, as the expansion is governed principally by the fibre in the plane of the laminate (x-y direction). The consequence is that with an increase in temperature, the matrix, because it is coupled to the fibre, is constrained from expanding in the plane of the laminate and is thus put under compression. In this state, some stress relaxation by creep can occur. In the direction perpendicular to the plane (the z direction), the aspect ratio of the fibre is clearly one and the rule of mixtures can be applied. Thus, for a random chopped-strand laminate of fibre volume fraction 0.2, coefficient of thermal expansion in the plane of the laminate might be 25-35 ppm K, whereas in the perpendicular direction it would be 50-80 ppm K k Incorporation of 50 wt% filler in the matrix polymer could reduce this to 35-55 ppm K. ... 

This cycle is repeated until all the hydroperoxide has been decomposed. Cobalt naphthenate-methyl ethyl ketone peroxide or -cyclohexanone peroxide systems are very extensively used in the production of large glass-fibre laminates made by hand lay-up and cured at room temperature. 

The principal uses of silicone resins are in surface coatings and glass-fibre laminates. Thus it is appropriate to consider both film and bulk properties. 

Whilst the straight bisphenoi A-epichlorhydrin epoxies described above have found widespread use in such applications as adhesives, castings, encapsulations and glass-fibre laminates they are used to a relatively small extent in surface coatings. In this important field, mainly modified bisphenoi A-epichlorhydrin epoxies are used. Two principal types of modification are commercially practised, namely combination with other resins and esterification. 

Glass Fibre Laminates Ltd White Lund Morecambe Lancs Morecambe 4040... 

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