Recyclable self-reinforced ductile fiber composite materials for structural applications

Sammanfattning: Lightweight structures in vehicles are a proven way to reduce fuel consumption and the environmental impact during the use. Lower structural weight can be achieved by using high performance materials such as composites or using the material efficiently as a sandwich structure. Traditional composite materials such as carbon or glass fiber reinforced polymers have high weight specific mechanical properties but are inherently brittle and expensive. They consist of at least two different materials making recycling a difficult endeavor.The best composite material would have good weight specific properties and is ductile, cheap and comprises of a reinforcement and matrix material based on the same recyclable material making recycling easy. In self-reinforced polymer (SrP) composite materials, reinforcing fibers and matrix material are based on the same recyclable thermoplastic polymer making recycling to a straightforward process. SrP composite materials are ductile, inexpensive and have a high energy absorption potential. The aim of this thesis is to investigate the potential of SrP composites in structural applications. Firstly, the quasi-static and dynamic tensile and compression properties of a self-reinforced poly(ethylene terephthalate) (SrPET) composite material are investigated confirming the high energy absorption potential. Sandwich structures out of only SrPET with a lattice core are manufactured and tested in quasi-static out-of-plane compression showing the potential of SrPET as core material. Corrugated sandwich structured out of only SrPET are manufactured and tested in out-of-plane compression over a strain rate range10−4 s−1 - 103 s−1. The corrugated SrPET core has similar quasi-static properties as commercial polymeric foams but superior dynamic compression properties. Corrugated sandwich beams out of only SrPET are manufactured and tested in quasi-static three-point bending confirming the high energy absorption potential of SrPET structures. When comparing the SrPET beams to aluminum beams with identical geometry and weight, the SrPET beams shows higher energy absorption and peak load. The experimental results show excellent agreement with finite element predictions. The impact behaviorof corrugated SrPET sandwich beams during three-point bending is investigated. When comparing SrPET sandwich beams to sandwich beams with carbon fiber face sheets and high performance thermoset polymeric foam with the same areal weight, for the same impact impulse per area, the SrPET shows less mid-span deflection.