Improving the weld lines mechanical properties by combining alternate dynamic packing and rapid heat cycle moulding

This is the first study that investigates the combined effect of alternate dynamic packing and rapid heat cycle moulding (RHCM) on the weld line mechanical properties of glass fibre reinforced thermoplastics. In conventional injection moulding, the outer layers rapidly solidify leaving a superficial weld line that do not recover when applying the dynamic packing. The results show that the thermal effect of RHCM reduces the thickness of the solidified skin layer and allow the alternate dynamic packing to reorient the fibres along the flow direction even in the outer layers. With reference to conventionally moulded tensile specimens made of 35% glass fibre reinforced polypropylene and having a front weld line, the proposed technological combination increased specimens’ strength and stiffness by 201% and 46%, respectively.