Preparation of hybrid poly(lactic acid)/flax composites by the insert overmolding process: Evaluation of mechanical performance and thermomechanical properties

This article presents research into the development of a new type of composite materials prepared with the use of the overmolding method. The overmolded insert for the tested samples was in the form of composite prepreg. Poly(lactic acid) (PLA)/flax laminate was prepared by the compression molding technique from the commingled fabric. Two types of materials were used during the injection molding stage: pure PLA and PLA/harl composite prepared with 20 wt% of the flax harl particles. Harl straw is a waste byproduct of the flax fiber manufacturing process. All samples were subjected to a detailed analysis of their mechanical properties, dynamic thermomechanical analysis (DMTA), and structure observations. The reinforcing efficiency of the used prepreg overmolding procedure was found to be very high. In addition to the significant increase in sample modulus, the most favorable improvement relates to impact test results. Most of the conducted studies confirm that high adhesion occurs between the composite insert and the injection-molded material, which confirms the effectiveness of the used methodology.