Mechanical Properties and Void Formation within Injection Molded Thermoplastic Composites

DOI: 10.14416/


  • Chantiya Kringkasemsri Department of Material Engineering, Faculty of Engineering, Kasetsart University
  • Somjate Patcharaphun Department of Material Engineering, Faculty of Engineering, Kasetsart University


Polypropylene composites, Injection molding, Mechanical properties, Fiber reinforcement, Formation of voids


The influences of glass-fiber length and concentration on the mechanical properties and formation of micro-voids within injection molded polypropylene composites were investigated in this work. The primary results obtained from the mechanical testing showed that the tensile and impact strength of PP composites increased with increasing fiber length and concentration. The analytical results indicated that the short-glass-fiber content of 20 wt% did not have a significant influence on the formation of voids. However, the size and content of voids within the core layer were considerably increased with the increase of fiber concentration, especially for PP filled with 30 and 40 %wt short-glass-fibers. This was due to the increase of cooling rate at the solidified skin layer by increasing glass-fiber contents. Considering the effect of fiber length on the formation of voids, it can be seen that the void contents tended to decrease whereas the size of micro-voids tended to increase with the increase of fiber length. This was due to the reduction of heat transfer efficiency caused by the decrease of contact area between the fiber surface and the polymer matrix.


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บทความวิจัย (Research article)