Infrared welding of continuous fibre-reinforced thermoplastics Investigations on overlapping joints

Transcription

1 Chemnitz University of Technology Department of Mechanical Engineering Professorship of Plastics Engineering - Prof. Dr.-Ing. Michael Gehde Infrared welding of continuous fibre-reinforced thermoplastics Investigations on overlapping joints Speaker: Authors: M.Sc. Marios Constantinou M.Sc. Marios Constantinou, Prof. Dr.-Ing. Michael Gehde

2 Contents 1. Introduction 2. Component manufacturing technologies 3. Problem statement 4. Research objective 5. Experimental approach 6. Results 7. Summary and outlook 2

3 Introduction Semi-finished products made of continous fibre-reinforced thermoplastics Thermoplastic prepregs / Organic sheets Glass- or carbonfibres Thermoplastic matrix Schematic cross section of an organic sheet Commercially available organic sheets Advantages of organic sheets: Short component manufacturing cycles Thermoformability Weldability 3

4 Component manufacturing technologies Semi-finished organic sheets Source: BASF SE Half shells Hollow body structures Source: Institute of polymer technology, FAU Erlangen Nürnberg Source: BASF SE, Adam Opel AG 4

5 Problem statement Cap profile shaped joints in current parts F F F F Deflection of fibres in the joint plane Fibre reinforcement cannot be used across the weld seam 5

6 Research objective Overlapping welding of organic sheets F F F F Manufacturing of hollow body parts by welding whilst using the fibres in the weld 6

7 Experimental approach Investigations on specimens Overlapping infrared welding trials with organic sheets Determination of influences on the mechanical, thermal and structural properties of overlapping weld seams Development of welding criteria Matrix, fibre type, fibre content and fibre alignment need to be considered Development of a welding process for the manufacturing of hollow body parts 7

8 Experimental approach Materials Abbreviation Matrix Fibres Weave pattern Fibre alignment Fibre content PP1 Woven fabric (twill weave) 0 /90 (50%/50%) 47 vol.% PP2 Polypropylene Glass Woven fabric (plain weave) 0 /90 (80%/20%) PP3 Non-crimp fabric (unidirectional) 0 35 vol.% 8

9 Experimental approach Infrared welding trials 9

10 Experimental approach Mechanical tests on unwelded materials Tensile tests Determination of interlaminar shear strength (ILSS) 500 µm Test setup for determination of interlaminar shear strength (left, middle) and shear fracture of a specimen (right) Mechanical tests on weld seams Tensile tests on cap profile shaped welds Determination of tensile lap-shear strengths 10

11 Experimental approach Thermal analyses Differential scanning calorimetry (DSC) and Thermogravimetric analysis (TGA) Top view on overlapping joint Specimen A Specimen B Microscopic analyses 11

12 Tensile lap-shear strength [N/mm²] Results Influence of welding pressure on weld seam strengths ILSS PP2 ILSS PP3 ILSS PP Welding pressure p w [N/mm²] PP1 PP2 PP 3 12

13 PP3 (non crimp fabric) PP1 (woven fabric) Results Weld seam cross sections depending on the weave pattern Specimen A Specimen A Viewing direction Weld Specimen B Specimen B 500 µm Specimen A Specimen A Viewing direction Weld Specimen B Specimen B 500 µm 13

14 Tensile lap-shear strength [N/mm²] Results Influence of additional polymer matrix Welding pressure 25 ILSS PP Welding pressure p w [N/mm²] PP2 with polymermatrix coating PP2 14

15 Lap tensile-shear stress [N/mm²] Results Influence of additional polymer matrix Behaviour under tensile-shear stress 25 ILS PP2 PP2 PP2 with polymer matrix coating Shear fracture in entire weld Fibre pull-out from joining partner surfaces Strain [%] 15

16 Tensile lap-shear strength [N/mm²] Avg. fvc = 34 % Avg. fvc = 46 % Avg. fvc = 46 % Avg. fvc = 46 % Results Development of welding criteria Fibre volume contents (fvc) in weld seams ILS PP2 PP2, p w = 1 N/mm² p w = 4 N/mm² Welding pressure [N/mm²] PP2 with polymer matrix coating PP2 High fibre volume contents in welds do not lead to a weakening in every case Maintaining of fibre alignment in the weld is essential for weld strengths near ILSS 16

17 Summary and outlook Summary Overlapping joining by infrared welding leads to weld strengths close to the ILSS of the unwelded organic sheets The required welding pressures depend on type of weave pattern Matrix depletion and fibre deflection in the joint lead to decreasing strengths Additional polymer matrix results in: a wide range of usable welding pressures and a more ductile fracture behaviour. Outlook Definition of general criteria for the overlapping welding of organic sheets Thermoforming of organic sheets and manufacturing of hollow body structures by infrared welding 17

18 Thank you for your attention Chemnitz University of Technology Professorship of Plastics Engineering Prof. Dr.-Ing. Michael Gehde Contact: Marios Constantinou Tel.: +49 (0)