Mechanics of Polymers

Fiber reinforced polymers are widely used in highly stressed, safety sensitive structures, e. g. in aircraft, automotive and wind energy applications. The division is working in the characterisation of the mechanical properties of polymers and composites. The spectrum of investigation ranges from static strength over fatigue behaviour to the determination of fracture mechanical and viscoelastic properties of polymers and fiber reinforced materials. The length scale spans from microscale, for example the determination of the adhesion between fibers and polymer matrix up to lifetime tests on components for wind energy rotor blades. Besides conventional destructive test methods also nondestructive testing procedures and numerical simulation are adopted.

The uniaxial and multiaxial failure of fiber reinforced polymers is investigated experimentally using standard test methods or specific techniques, e. g. to analyse the delamination, as well as by finite element simulations. Specific test techniques such as acoustic emission analysis and X-ray refraction topography are used in order to characterise the damage evolution for example in carbon fiber reinforced coverings of pressure vessels or lightweight airplanes made of glass-fiber reinforced epoxy resin. The local properties of polymers are determined by nanoindentation. The influence of chemicals on the strength of polymers is investigated with regard to applications as materials for containments in dangerous goods transportation.

Goal

Safety and reliability of structural parts made of polymers and composites under extreme loading

Areas of competence

• Micromechanics
• Fatigue testing, failure analysis, damage mechanics
• Mechanics of materials and acoustic emission testing
• Multiaxial failure criteria for composites
• Degradation of polymers by chemicals

Working areas

• Characterisation of the mechanical properties of polymers and composites under static and dynamical load as well as under long-term and cycling temperature load
• Structural parts and components testing for aircraft, automotive and wind energy industry
• Characterisation of the damage behaviour with acoustic emission and X-ray refraction topography
• Influence of chemicals on the strength and fracture behaviour of polymers
• Fracture mechanical tests of the delamination behaviour of fiber reinforced polymers - Double-cantilever-beam Test (DCB), End-notched-flexure Test (ENF), Mixed-mode-bending Test (MMB)Dynamical-Mechanical-Thermal-Analysis of polymers (DMTA)
• Materials characterisation on microscale (foils, films, fibers, surfaces, adhesion, particle filled polymers)
• Long term behaviour of polymers and composites
• Development and validation of acoustic emission procedures
• Special test procedures – shear frame test, inter fiber failure evaluated by NDT, biaxial testing of tubes in tension/compression-torsion, cylindrical structures under compresssion
• Experimental investigations and finite-element simulation of multiaxial failure of composites
• Common damage analysis of polymer products, failure expertises
• Mechanical testing according to standards (DIN/EN/ISO, ASTM)
• Research and development projects in the field of technical safety and reliability of polymers and composites
• Development of test methods on customer request
• Standardisation (DIN/EN/ISO) and regulation (DGZfP, AFF, ANF DVM, VAMAS)
• Consulting and information for government and industry
• Supervision of trainees, bachelor- master- and PhD students, post docs

Technical equipment

• Servo-hydraulic computer controlled tensile testing machines with load range 10 kN to 500 kN
• Biaxial servo-hydraulic testing machine (+/- 250 kN / 2.000 Nm with climate chamber - 60 °C to + 180 °C / 10 % to 90 % rel. humidity)
• Electro-mechanical testing machines with load range 10 kN to 100 kN
• Microtensile/compression tester 10 mN to 5 N
• Multichannel measurement systems for acoustic emission testing
• X-ray generators for nondestructive testing of composites
• Cyclic loading climate chamber - 60 °C to + 180 °C / 10 % to 90 % rel. humidity, 15 K/min
• CAD and FEM
• Hardness and microhardness tester, 0,01 mN to 10 mN
• Dynamical-mechanical-thermal tester (DMTA)
• Scanning probe microscope
• Scanning electron microscope (SEM)
• Light microscopes (stereo microscope, polarisation)
• Instrumented Charpy testing system with temperature chamber (4 J to15 J, - 70 °C to +300 °C)
• Long term test device with temparature chamber (- 30 °C to + 130 °C)
• Full notch creep test (FNCT) under chemical enviroment (+ 20 °C to + 95 °C)
• Flow testing device MFR und MVR (Tmax 400 °C)
• Hydraulic moulding press (Tmax 400 °C, Pmax 15 MPa)
• Cryo-microtome, grinding and polishing devices

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