Laminate testing

Figure 5.123 Schematic tensile stress-strain diagram for a symmetric (0, 90°) cross-plied laminate tested at 2 = 0°. Reprinted, by permission, from P. K. Mallick, Fiber-Reinforced Composites, p. 187. Copyright 1988 by Marcel Dekker, Inc.

Figure 8. Photographs of 0 bare (water-sized) E-glass fiber laminates tested in flexure showing the tensile side of the specimen. The tensile side fibers failed first, then propagated delaminations along the tensile surface of the specimen.

FSI. All of the FSI values were within the standard deviation of the test. It should also be noted that the different types of glass and the various glass contents did not affect the FSI as shown in Figure 23.2. The first set of laminates tested had an FSI value between 15 and 25. 

Filler at 100 pph Phenolic laminate tested at Aluminum block tested at ... 

Subsequent work was, therefore, directed to substitution of resorcinol, a much more expensive phenol, in cold-setting, waterproof adhesives (38). Formulations based on 30 to 60% of extract mixed with a resorcinol-formaldehyde condensate and additional formaldehyde met pot-life and assembly time requirements for timber lamination. Test bonds passed requirements of the major performance standards in the United States, but competition from lower cost, phenol-modified resorcinol resins and the lack of longterm commercial perfor-... 

Accelerated aging testing and dynamic mechanical analysis were used to evaluate the stability of coated laminates. Testing results are provided in Table 2. 

Stress relaxation between manufacture and testing. Between manufacturing and testing, relaxation of the residual stress will occur as a result of the viscoelastic properties of the matrix, which controls the behaviour of the 90° layer. Measurements to determine the relaxation of the ply-to-ply residual stress of the carbon-polyetherimide lay-up, with the highest level of residual stresses of the laminates tested ([904c/04c]s), have been presented previously [5]. It shows that the level of residual stress follows a power law with time. For the purpose of this study, it was chosen to perform the bending experiments 240 hours after fabrication, as the level of residual stress remains more or less constant. The level of residual stress as calculated in (1) is then altered by a reduction factor,/,. The relaxed residual stress. 

The mechanical results of interlaminar shear strength for the two kinds of laminates prepared using hyperbranches impregnated in the reinforced fibers are presented in Table 15.8. The two laminates tested included Kevlar fabric primed with 1.5 wt.% HMW PAMAM (AD-102) and bonded with FM-73, and Zylon fabric primed with 1.5 wt.% HMW PAMAM (AD-102) and bonded with AF-191. 

For laminated test pieces, tests may be performed both flatwise and edgewise, and for each of these there exists the possibility of having the laminations parallel or normal to the direction of blow. All these are permitted, and a suitable coding scheme is defined to enable the options chosen in a given test to be defined very succinctly. 

Lead (0.0015 in.) 9 Some wrinkles in lead foil—possible cracks in foil Bond loosened between foil and laminate— wrinkles and cracks in foil Bond loosened between foil and laminate—wrinkles and cracks in foil but not as bad as above Foil badly cracked and bond broken between foil and laminate Testing stopped... 

Soutis C. Modelhng the open hole compressive strength of composite laminates tested in hot-wet conditions. Plastics Rubber Compos 2009 38(2/3/4) 55—60. 

K Rohwer, Stresses and Deformations in Laminated Test Specimens of Carbon Fibre Reinforced Composites, Braunschweig, DFVLR-FB 82-15,1982. 

Table 7.3 Laminates tested by Bradley and Grant [68] with failure locations for selected materials...

These polymers were combined with unsized carbon fiber, into 15° laminated, test specimens approximately 2.5 cmx7.5 cmxO.3 cm. Testing was performed in three point bending giving the results in Table 2.55. 

Where particular circumstances are to be tested, such as stressed laminates in an aggressive environment, standard tests are unlikely to exist. Suitable methods must be agreed by all concerned with the testing. This particularly applies when laminate testing is carried out as part of the testing of a complete structure see 7.3.5. 

Figure 22.4 Interlaminar shear stress as a function of ply angle for Type I high modulus carbon fiber epoxy resin laminate tested in uniaxial tension in x-direction. The maximum interlaminar shear strength occurs at 0 = 35° and the stresses are zero at 0, 60 and 90°. Source Reprinted with permission from Pipes RB, Pagano NJ, Interlaminar shear stress in composite laminates under axial tension, J Composite Mater Sci, 13, 2131-2136, 1978. Copyright 1978, Sage Publications.

Metal-to-metal laminate test for large bonded areas but may also be used with plastic subsfiates Specifically for adhesives used in plywood laminate constructions Specifically for wooden (two-ply) laminate substrates... 

Table 9.4 shows the effect of fiber orientation on the properties. The large differences in tensile strength and modulus of unidirectional laminates tested at 0 and 90° should be noted. 

Unidirectional laminate tested along the fibers (0°) and across the fibers (90°). Isotropic laminate tested in two directions perpendicular to each other... 

This document is the most comprehensive and most widely used compilation of copper-clad laminate test methods. It is administered by IPC (Association Cormecting Electronic Industries) and available in print or online. ... 

The second set of tests is an expanded set of qualification tests that focuses on all key properties that are commonly evaluated for laminates. However, the final decision about a quaUfi-cation test plan for a new laminate should always be driven by product-level requirements, which means that additional laminate tests as well as board-level tests may need to be added to the set of tests described in the following section. 

Table 27.1 lists some laminate tests covered in IPC-TM-650. 

Metal-to-metal laminate test for large bonded areas but may also be used with plastic substrates... 

Rohwers K., Stresses and deformations in laminated test specimens of carbon fiber reinforced composites, DFVLR - FB 82-15, Institut fiir Strukturmechanik, Braunschweig, FR Germany, 1982. 

In this paper, the failure criterion developed in [1] was employed to study failure in a number of matrix-dominated laminates, such as [ 0]2s [i0/9O]s and some fiber-dominated 7t/4 laminates. For some 7t/4 laminates, test results showed that open-mode delamination could occur along interfaces adjacent to the 90° layer. Such failure of delamination depends on the stacking sequence of the laminate. Results indicated that the present method can also be used to predict the onset of open-mode delamination. 

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