Development and characterization of a HDPE-sand natural fiber composite

A composite material consisting of HDPE, sand and short henequen fibers has been developed and characterized. It is shown that it is possible to incorporate as high as 50% w/w filler contents to the thermoplastic resin. A central composite design (Box-Hunter) was utilized to optimize the mechanical properties of the composite materials. The independent variables under study were: (i) sand content; (ii) henequen content and (iii) processing temperature. The selected response variables were the tensile and flexural properties of the composite. The tensile strength of the HDPE-sand composite does not seem to be affected by the processing temperature, for any filler content, but the tensile modulus shows similar behavior for filler contents greater than 15% w/w. The flexural strength shows a maximum at filler content of 30% w/w while the flexural modulus increase linearly. The flexural properties are not affected appreciably by the processing temperature. For the HDPE-henequen composite, the processing temperature does seem to adversely effect the tensile strength but not The tensile modulus. The flexural properties are slightly increased by the processing temperature. It is shown that fiber-matrix adhesion does play an important role in the final properties of the composite. The HDPE-sand-henequen composite shows a more complicated behavior. An increase in filler content decreases the tensile strength. Similar behavior was found with an increase in the processing temperature. The processing temperature seems to have a more pronounced effect on the tensile modulus. At low temperatures the modulus behavior is governed by the sand content, while at higher temperatures, such behavior is governed by the fiber content. The flexural properties are also affected by the processing temperature. At low temperatures and sand contents below 30% w/w, the flexural strength increases with fiber content and at higher sand contents an opposite behavior is observed. At higher processing temperatures the behavior is the same as for lower temperatures, but the flexural properties are slightly decreased. It is also shown that adhesion between fiber and matrix plays an important role on the final mechanical properties. (C) 1997 Elsevier Science Ltd.