Investigation of the shape-memory capabilities of stretched thermoplastic polymers for mandrel production

Kurzfassung

Context: The choice of material, manufacturing process, and tooling significantly effects the quality, environmental impact, and cost efficiency of composite components. Producing one- piece hollow profiles with smooth inner surfaces and undercuts presents major challenges for conventional mold concepts. A promising solution are shape memory polymer mandrels. Objectives: This study targets on orientation of thermoplastic polymer chains. Stretched polymers resume a stored shape by thermal activation which allows for the demolding of one- piece mandrels with undercuts. Methods: For a defined manufacturing process two polyamides (PA6, PA66) and polyethylene terephthalate (PET) are selected from differential scanning calorimetry and dynamic mechanical analysis measurements. Coupons are stretched by a tensile test machine. A parameter study is carried out aiming for the influences on the shape-memory properties of stretched thermoplastics. Results: A correlation between temperature and degree of stretching with the shape-memory capabilities of the investigated materials is shown. PET exhibits the best shape-memory properties allowing for 15% (1D) / 38% (3D) shape recovery. Conclusion: PA6 and PET are suitable for the defined process by means of temperature allowance and shape memory properties. Follow up research will aim on transferring the one- dimensional results into 3D test specimen.