Mechanical and acoustical properties of polylactic acid based multilayer-structured foam biocomposites

Polylactic acid (PLA) based multilayer-structured foam biocomposites were prepared in a three-step process. In step 1, PLA plastic particles mixed with hollow glass beads (HGB) and other additives were blended, pelletized, and foamed and turned into plies using compression moldings. During step 2, the plies were stacked alternately and glued together with glass-fiber cloth reinforced PLA interlayers. The result is a multilayer-structured ply. In step 3, environmental sound-absorbing cotton was spliced on both sides of the ply to obtain the desired foam biocomposites. Then, foam morphology, and both mechanical and acoustical properties of the plies were investigated using a scanning electron microscope, a universal testing machine and a multianalyzer system. Our experimental results indicate that the compressive strength and acoustical properties of the plies made during the first step perform best when the mass fraction of HGB is 15%. We then compared a ply made in the first step with the multilayer-structured ply made in the second step. We found that the mechanical and sound insulation properties became more uniform after the addition of a PLA layer. We also found that the sound-absorbing cotton improved sound insulation by about 30%. The biocomposites achieved the best mechanical and acoustical properties after careful consideration of several factors.