Reinforced plastics impact behavior

Plastics that are brittle frequently have lower impact strength and higher stiffness properties. A major exception is reinforced plastics. The tensile S-S curves of brittle materials often show relatively little deviation from the initial linearity, relatively low strain at failure, and no point of zero slope. Different materials may exhibit significantly different tensile S-S behavior when exposed to different factors such as the same temperature and strain rate or at different temperatures. 

Reinforced Plastics Congress, British Plastics Federation, London, Paper No. 19, pp 145-151 Russell AJ, Street KN (1985) Moisture and temperature effects on the mixed-mode delamination fracture of unidirectional graphite/epoxy. Delamination and debonding of materials, ASTM 537 STP 876, American Society for Testing and Materials, Philadelphia, pp 349-370 Saito H, Kimpara I (2007) Effect of water absorption on compressive strength after impact and post impact fatigue behavior of woven and knitted CFRP laminates. Key Eng Matra-334-335 517-520... 

Reinforced plastics form an important area of structural application of plastics since the modulus and strength of plastics can be increased significantly through reinforcement. In reinforced plastics, the polymer (popularly called the resin) forms the matrix and a filler (mostly used in the form of fibers, hut particles, for example glass spheres, are also used) provides the reinforcing effect. In view of then-distinctive nature and extensive use as materials of construction in load-hearing applications, a special focus has been on analysis of properties of reinforced plastics, especially those reinforced by continuous or discontinuous fibers, as well as their deformation, fi-acture, fatigue, and impact behaviors. 

Transition from liquid behavior to solid behavior has been reported with fine particle suspensions with increased filler content in both Newtonian and non-Newtonian liquids. Industrially important classes are rubber-modified polymer melts (small rubber particles embedded in a polymer melt), e.g. ABS (acrylo-nitrile-butadiene-styrene) or HIPS (high-impact polystyrene) and fiber-reinforced polymers. Another interesting suspension is present in plasticized polyvinylchloride (PVC) at low temperatures, when suspended PVC particles are formed in the melt [96], The transition becomes evident in the following... 

The dynamic mechanical behavior of most homogeneous and heterogeneous solid and molten polymeric systems or composite formulations can be determined by DMA. These polymeric systems may contain chemical additives, including fillers, reinforcements, stabilizers, plasticizers, flame retardants, impact modifiers, processing aids, and other chemical additives, which are added to the polymeric system to impart specific functional properties and which could affect the process-ability and performance. 

The major problem in the reprocessing of commingled plastics, and therefore of utmost importance for PAB s, is the immiscibility of most polymers so that poor mechanical properties develop when they are blended together. Ways to enhance the mechanical behavior of these mixtures include adding a compatibilizer, adding a mbbery phase to impact modify the blend, or adding a reinforcement to restore mechanical properties. 

With both the PEA/P(S-co-MMA) and PB/PS IPN s, an important variable is the ratio of elastomer to plastic in the final material. When the plastic component predominates, a type of impact-resistant plastic results. In this manner the PB/PS IPN s are analogous to the impact-resistant graft copolymers. When the elastomer component predominates, a self-reinforced elastomer results, the behavior resembling that of the ABA-type block copolymers (thermoplastic elastomers) described in Section 4.4. When the overall compositions of both the PB/PS and the PEA/P(S-co-MMA) series are close to 50/50, the materials behave like leathers. 

When the elastic phase predominates the IPN s behave as reinforced elastomers. As the glassy component is increased the material becomes an impact resistant plastic. At midrange compositions between the two glass transition temperatures materials exhibiting leathery behavior are obtained. 

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