Laminated composite 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. 

Consider the two cases of (1) two unbonded metal strips of different coefficients of thermal expansion placed side by side but not bonded and (2) the same two strips bonded together. For case (1), at room temperature, the two strips are the same length. When they are heated, both strips elongate (their primary observable change, but they do also get wider and thicker). For case (2) at room temperature, the strips are also of the same length but bonded together. When the bonded bimetallic 

Strip is heated, strip B wants to expand more than strip A, but they are bonded, so strip B causes the bimetallic strip to bendl This bending under a loading that would othenwise seem to cause only extension is our first (qualitative) example of the structural phenomenon of coupling between bending and extension that we will study in more detail in Chapter 4. 

The concept of protection of one layer of material by another as described in the previous category. Clad Metals, has been extended in a rather unique way to automotive safety glass. Ordinary window glass 

---

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

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

The existence of interlaminar stresses means that laminated composite materials can delaminate near free edges whether they be at the edge of a plate, around a hole, or at the ends of a tubular configuration used to obtain material properties. In all cases, delamination could cause premature failure so must be considered in specimen design because othen/vise the specimen does not represent the true physical situation. 

In heat transfer analysis, a material is normally assumed to be isotropic that is, to have unifonn properties in ail directions. This assumption is realistic for most materials, except those that exhibit different structural characteristics in different directions, such as laminated composite materials and wood. The thennal conductivity of wood across the grain, for example, is different than that parallel to the grain. 

These remarks evaluate the effect of filler-related phenomena on failure of plastic materials. Several reasons for the failure ofplastics are filler related. They include delamination of laminated composite materials, debonding in particulate filled materials, stress cracking of filler particles, yielding, cavitation, and corrosion. 

Fracture toughness tests for isotropic materials normally use edge-notched flexure beams and compact tension specimens. These methods are. as for the impact tests, only suitable for the injected or compression molded materials, which do not have a strongly laminated structure. Laminated composite materials have their primary failure path between the layers, and a new set of test geometries has been developed. 

Susceptibility to interlaminar failure is a major weakness of advanced laminated composite materials. It can occur by in-plane shearing (i.e., sliding) (mode II). and out-of-plane shearing (i.e.. tearing) (mode III) as well as by tensile (mode I) deformation. Mode II loading is of particular interest, as values have been shown to correlate with compression after impact data [142.143]. which is required for such purposes as civil aircraft certification. 

Nuistner RJ. Continuum modeling of damage accumulation and ultimate failure in fiber reinforced laminated composite materials. In Research workshop, mechanics of composite materials. Durham (NC) Duke University 1978. p. 55—77. 

Abrate S. Impact on laminated composite materials. Appl Mech Rev 1991 44(4) 155-90. 

Porras, A. and Maranon, A. (2012) Development and characterization of a laminate composite material from polylactic acid (PLA) and woven bamboo fabric. Composites Part B, 43 (7), 2782-2788. 

With the extensive use of laminated composite materials in almost all engineering fields, the optimal design of laminated composites has been an extensive subject of research in recent years. The dimensions of the composite leaf spring are taken as that of the conventional steel leaf spring. Each leaf of the composite leaf spaing consists of 20 plies of thickness 0.275 mm each. The number of leaves is also the same for composite leaf spring. The design parameters selected are listed in Table 4... 

Gurdal, Z., Haftka, R. T., Hajek, P. (1999) Design and Optimization of Laminated Composite Materials. New York Wiley-lnterscience. 

Abot, J., et al. Novel carbon nanotube array-reinforced laminated composite materials with higher interlaminar elastic properties.Compos.5ci.7ec/z o/.2008, 65(13), 2755-2760. 

Expoxy laminates Composite materials Processing and quality control... 

---