Composite materials laminating

O Brien, T.K., Characterization of Delamination Onset and Growth in a Composite Laminate in Damage in Composite Materials, ASTM STP 775, p. 140-167,1982 Poursartip, A. Ashby, M. F., Beaumont P.W.R., The Fatigue Damage Mechanics of Fibrous Laminates in Proceedings of the European Workshop on Nondestructive Evaluation of Polymers and Polymer Matrix Composites, Polymer NDE (edited by Khg. Ashbee), Technomic Publishing, p. 250-260, 1984... 

Laminates aie materials made up of plies or laminae stacked up like a deck of cards and bonded together. Plywood is a common example of a laminate. It is made up of thin pHes of wood veneer bonded together with various glues. Laminates ate a form of composite material, ie, they ate constmcted from a continuous matrix and a reinforcing material (1) (see also Reinforced plastics). 

High performance composites may be laminates wherein veils of carbon fiber ate treated with an epoxy resin, stacked up to the desired final product thickness, and then laminated together under heat and pressure (see Composite materials Carbon and graphite fibers). Simply mixing together carbon or glass fibers and polymeric resins to form a reinforced plastic leads to a composite material, but this is not a laminate if not constmcted from discrete phes. 

Laminates ate a special form of composite material or reinforced plastic because the continuous reinforcing ply of fibrous material imparts significant strength in the x—j plane. The strength along the axis results from interlaminar bonding of resins. Very few fibers ate oriented in the direction, so it tends to be the weak link in this type of composite. 

The reinforcing ply acts as the carrier for the plastic resin during intermediate processing steps known as saturation and B-staging. It is this ply that together with the resin makes a laminate a composite material, and the layering of these pHes that makes the final product a laminate. 

Powell, P.C. Engineering with Fibre-Polymer Laminates, Chapman and Hall, London (1994). Daniel, I.M. and Ishai, O. Engineering Mechanics of Composite Materials, Oxford University Press (1994). 

Laminated composite materials that consist of layers of various materials... 

Laminated composite materials consist of layers of at least two different materials that are bonded together. Lamination is used to combine the best aspects of the constituent layers and bonding material in order to achieve a more useful material. The properties that can be emphasized by lamination are strength, stiffness, low weight, corrosion resistance, wear resistance, beauty or attractiveness, thermal insulation, acoustical insulation, etc. Such claims are best represented by the examples in the following paragraphs in which bimetals, clad metals, laminated glass, plastic-based laminates, and laminated fibrous composite materials are described. 

Numerous multiphase composite materials exhibit more than one characteristic of the various classes, fibrous, laminated, or particulate composite materials, just discussed. For example, reinforced concrete is both particulate (because the concrete is composed of gravel in a cement-paste binder) and fibrous (because of the steel reinforcement). 

Also, laminated fiber-reinforced composite materials are obviously both laminated and fibrous composite materials. Thus, any classification system is arbitrary and imperfect. Nevertheless, the system should serve to acquaint the reader with the broad possibilities of composite materials. 

For the remainder of this book, fiber-reinforced composite laminates will be emphasized. The fibers are long and continuous as opposed to whiskers. The concepts developed herein are applicable mainly to fiber-reinforced composite laminates, but are also valid for other laminates and whisker composites with some fairly obvious modifications. That is, fiber-reinforced composite laminates are used as a uniform example throughout this book, but concepts used to analyze their behavior are often applicable to other forms of composite materials. In many Instances, the applicability will be made clear as an example complementary to the principal example of fiber-reinforced composite laminates. 

Unlike most conventional materials, there is a very close relation between the manufacture of a composite material and its end use. The manufacture of the material is often actually part of the fabrication process for the structural element or even the complete structure. Thus, a complete description of the manufacturing process is not possible nor is it even desirable. The discussion of manufacturing of laminated fiber-reinforced composite materials is restricted in this section to how the fibers and matrix materials are assembled to make a lamina and how, subsequently, laminae are assembled and cured to make a laminate. 

Three principal layup processes for laminated fiber-reinforced composite materials are winding, laying, and molding. The choice of a layup process (as well as a curing process) depends on many factors part size and shape, cost, schedule, familiarity with particular techniques, etc. 

Find another example or type of laminated composite material than those mentioned in Chapter 1 and describe it. 

The topic of materials with different strengths and stiffnesses in tension than in compression will not be covered further in much depth (except to report different strengths) because research on such materials is still in its infancy. However, the topic is very important for the general class of composite materials, if not fiber-reinforced laminated composites. Ambartsumyan and his associates first reported research on this topic in 1965 [2-9]. A few Americans have also investigated some aspects of the mechanics of these materials (see Jones [2-10], Bert [2-11], and Bert and Reddy [2-12]). 

Actually, because of the stress and deformation hypotheses that are an inseparable part of classical lamination theory, a more correct name would be classical thin lamination theory, or even classical laminated plate theory. We wiiruS ffi bmmon term classical lamination theory, but recognize that it is a convenient oversimplification of the rigorous nomenclature. In the composite materials literature, classical laminationtheoryls en abbreviated as CLT. 

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