Failure Mechanisms Due to Debonding

Since the mechanical features of the adhesive resin are considerably higher than those of concrete, if the composite is properly laid up, debonding only takes place within the couCTete with the removal of a layer of material. 

These are four possible failure modes due to debonding of the composite material (Fig. 5.1)  

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In addition, as a typical failure mechanism, fiber/matrix debonding occurs due to the shear and tension type loading. If fiber/matrix debonding has taken place, the local separation initiates additional fiber cracking, wear debris formation, and a more intensive wear process. In the steady state wear process, a so-called compacted wear debris layer (CWDL) covers the surface it is composed of pulverized wear debris and matrix material. During the wear process, this layer is continuously formed and removed by the surfaces sliding over each other. 

Figure 3.497. Schematic of possible failure mechanisms near L - oriented fibers (1) tendency to form a straight crack profile (2) coalescence of crazes or cracks between ends of fiber or fiber bundles (3) void formation around fibers and rupture of the polymeric interphase (4) craze initiation at fiber ends (5) debonding along misoriented fibers and eventually fiber fracture due to bending. [1267],...

While unique properties, such as dimensional stability or increased hardness and modulus, are the usual motivation for exploiting particulate filled composites, special attention must be paid to other mechanical properties, such as yield and ultimate strength and fracture toughness [1 ]. Due to the low adhesion between non-polar hydrophobic polymer matrix and hydrophilic filler surface, the interfacial debonding is very frequently the first step of failure in these materials [2]. Mainly for this reason the effective application of particulate composites is first of all determined by the interfacial interaction between polymer and filler. 

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