Laminates properties

These are materials which when used in conjunction with an organic peroxide catalyst increase the rate at which that peroxide breaks down into free radicals. Some of the commercially available accelerators are  

The basis for engineering design of a such material is then the properties of a cured ply or lamina as it exists in a laminate. This ply is treated as a thin two-dimensional item and is mechanically characterized by its stress-strain response to (i) loading in the direction of the filaments, which exhibits a nearly linear response up to a large fracture stress (ii) loading 

By the contrast with isotropic metallic materials, an oriented ply, in the form of a thin sheet, is anisotropic and requires four elastic (plane stress) constants to specify its stiffness properties in its natural orientation 

however, the ply is rotated with respect to the applied stress or strain direction additional moduli appear, which results in the direction-indicated shear coupling rotation simple extension 

In addition, lamination can result in up to 18 elastic coefficients and increased deformational complexities, but the additional coefficients can all be derived from the four primary coefficients using the concept of rotation and ply-stacking sequence. These complications are the result of geometric variables. If the laminate is properly constructed, the in-plane stretching or stiffness properties can still be specified by four elastic coefficients. We shall consider laminates of this nature. 

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The laminate properties may then be obtained as above from inspection of the compliance matrix. 

Figure 1-23 Translation from Constituent Properties to Lamina to Laminate Properties...

In addition to the nature of resin and fibre, the laminate properties also depend on the degree of bonding between the two main components and the presence of other additives including air bubbles. Because of this some parts, fabricated by simple hand building techniques, may exhibit strengths no better or even worse than unreinforced materials. This problem is often worst with glass fibres which are therefore normally treated with special finishes to improve the resin-glass bond. 

Table V. - Thermid -600/Un1directional HT-S Graphite Fiber Laminate Properties...

A thin molding of an acetylene-terminated phenylquinoxaline, fabricated by compression molding at 316°C for 26 hr and at 371°C for 5 hr, gave tensile strength of 103 MPa (15,000 psi), tensile modulus of 2.62 GPa (380,000 psi) and elongation of 5% (46). Preliminary unidirectional graphite fiber laminate properties are reported in Table VI. 

Table VI - Unidirectional HT-S Graphite Fiber Laminate Properties of Acetylene-Terminated Phenylquinoxaline Resin1 2...

Baicol hardness GLASS REINFORCED LAMINATE PROPERTIES 35... 

The important features of Figure 4 are the dependence of both G/f" and Ga on peel angle. This suggests that these parameters cannot be objective material (or laminate) properties. However, Ga can be seen to be independent of peel angle and hence this quantity is considered to be an objective measurement of the adhesive fracture toughness. The Ga values for all five laboratories are shown in Figure 5. 

In Table 7, typical key laminate properties for thermoset and thermoplastic composites are given. It is immediately apparent that suitable toughening (discussed previously) can achieve superior compression after impact and comparable edge delamination... 

Table 7 Typical laminate properties on intermediate modulus carbon fiber at a fiber volume of ca. 60%...

Laminate Property Conditioning NEMA FR-4 Requirements Test Results ... 

Laminate properties of Kevlar fabric/epoxy were calculated by using laminate theory.(6) A lamina stacking sequence of 0° and 90° was adopted for the calculations. 

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. 

All furan laminates must be postured to drive out the reaction condensate to achieve optimum properties. Curing for a fresh laminate should start with an initial temperature of SOT (66°C) for 4 h, which is slowly raised to 180°F (82°C) for 8 h of curing. Too fast a cure can result in a blistered or cracked laminate. A final Barcol hardness of 40-45 is necessary to develop optimum laminate properties. The structural formula for the resin is ... 

It is used primarily in film where its good tear resistance and laminating properties are required. 

Many low-pressure laminates are reinforced with fibers woven into fabrics. A large variety of weaves are available, although only a few are widely used. The weave affects the laminate properties and must be specified, along with the fiber type, when reporting data or when purchasing a laminate. MIL-HDBK 17A (1971) [ ] provides a description of the weaves most commonly used. 

Figure 3.10 Effect of adventitious moisture on the generation of thermal strain in a polyester resin based cross-ply GRP, postcured at 130°C. The continuous line represents experimental data calculated from the continuous monitoring of the curvature of an unbalanced, as-manufactured beam. The predicted values are calculated from dry (O) and wet ( ) (0.15%) laminate properties using equation [3.12] [25]...

Chem. Descrip. Thermoplastic acrylic based on BA/MMA Uses Binder for decorative laminates Properties MFT 19 C Tg 21 C 50% solids AcryGen DV 571 [OMNOVA Sol ns,]... 

On the other hand, there are several standard testing methods to determine the lamina and laminate properties. The majority of tests conducted on polymer composite materials for structural engineering applications are conducted on coupons cut from as-fabricated FRP composite parts. These... 

Laminated composites will usually combine laminae with fibres at different orientations. To predict the laminate properties, the stress-strain relations are required for loading a lamina at an angle 0 to the fibre direction and for loading both in-plane and in bending. Composite mechanics for laminated composites is well developed and... 

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