Polymers Performance Overview. Bruce Duncan. Wednesday 18 th April 2007

Transcription

1 Polymers Performance Overview Bruce Duncan Wednesday 18 th April 27

2 Measurements for Materials Performance Scope and Aims: The Performance of Materials programme will develop measurement methodologies and models for the assessment, prediction and ongoing evaluation of the properties of materials in a service environment critical to maintaining fitness for purpose. Knowledge and best practice will be promoted to users through new facilities, standardised test methods and access to experts.

3 E1: Non-destructive Adhesion Measurement of Coatings Project run by TWI and NPL Focussing on engineering coatings, e.g. thermal spraying plating physical/chemical vapour deposition polymer based Aim to develop NDE technique(s) to identify defective coatings Supplied with coatings by industry

4 E1: Non-destructive Adhesion Measurement of Coatings Assess/prioritise available NDE techniques Review report issued Report on most promising techniques Thermography static and flash (pulse) Acoustic microscopy Acoustic emission Terahertz imaging Surface acoustic waves Measurement protocols and case studies GPG to assist method selection

5 E1: Non-destructive Adhesion Measurement of Coatings static Thermography Improving adhesion Poor adhesion appears cold Yellow: Oxide interlayer Blue: Carbon interlayer Purple: Gold interlayer Red: Greasy substrate Green: Clean substrate Flash thermography Flash lamp Good adhesion appears hot IR radiation flash Thermal camera to PC Subsurface defect Heat conduction

6 E1: Non-destructive Adhesion Measurement of Coatings Ultrasonic technique that uses focused ultrasonic waves to image defects (15 or 75 MHz) Waves travel through specimen and portion reflected back by defects Scanning acoustic microscope (SAM)

7 E1: Non-destructive Adhesion Measurement of Coatings Terahertz imaging Limited to non-conducting materials Flat Painted Panels - Aged F1 Circled regions indicate defects F3 F5

8 E1: Non-destructive Adhesion Measurement of Coatings Scanning acoustic microscopy able to detected delamination of coatings but not poor adhesion interface. Heat transmission thermography able to detect delamination but not poor adhesion. Flash thermography able to identify poorly adhered coatings that have not delaminated. Laser surface acoustic wave also able to detect poorly adhered coatings Terahertz able to detect defects in organic coatings

9 F2: Sensing the Onset of Damage at Polymer Surfaces due to Environmental Exposure Weathering of Surfaces Case study on durability or recycled plastics Autocatalytic degradation of previously weathered materials Nano-indentation sensitive to surface embrittlement 'Weathering of Recycled Photo-Degraded Polyethylene', A. S. Maxwell, Feb 27 (Submitted to Polymer Science and Engineering 27) IR days UV exposure 4 days UV exposure 6 days UV exposure 1 days UV exposure.12.1 Nano-indentation Absorbance Hardness (GPa) HDPE-A HDPE-B Wavenumber (cm -1 ) days UV ageing 4 days UV ageing 6 days UV ageing 1 days UV ageing

10 F2: Sensing the Onset of Damage at Polymer Surfaces due to Environmental Exposure Environmental Stress Cracking 17 Development of accelerated techniques Strain hardening modulus correlates well with long-term ESC ranking Suite of ISO standards published ISO FDIS 2288 parts 1-6 'Prediction of Environmental Stress Cracking Resistance in Polyethylenes', A. A. S. Maxwell and G. Pilkington, (Draft paper 27) Stress (MPa) notch tests LLDPE 1 LLDPE 2 LLDPE 3 Strain hardening modulus (MPa) Strain hardening ExxonMobil LLDPE Flexirene ExxonMobil 3518PA 9 LLDPE Polymer Grades Time (hours)

11 F4 Accelerated Ageing Protocol For Service in Hostile Conditions 5 4 Four case studies completed Weathering Good correlation of gloss and hardness with residual strength Full immersion, no load Full immersion, continuous load (flexure) Residual strength falls with stress and temperature Intermittent exposure, no load Flexural Streng th (MPa) Flexural Strength (MPa) Barcol Hardness Gloss Retention (%)

12 F4 Accelerated Ageing Protocol For Service in Hostile Conditions Accelerated Weathering: Performance Testing of Polymer Matrix Composites, W R Broughton, G D Pilkington and D K Ratnakela, (NPL Measurement Note, DEPC-MN47, March 27) Measurement Good Practice Guide No. 13: Accelerated Environmental Ageing of Polymeric Materials, W R Broughton and A S Maxwell Review of accelerated ageing methods and lifetime prediction techniques for polymeric materials, A S Maxwell, W R Broughton, G Dean and G D Sims, DEPC-MPR 16, March 25

13 F7 Permeation, Absorption and Desorption of Liquids and Gases in Polymer and Multilayer Systems Influence of Temperature and Stress on moisture diffusion coefficient (D) Significant temperature dependence: can be the largest component of the uncertainty budget for D D increases with tensile stress: dramatically above yield stress Observations of the Influence of Temperature and Stress on Diffusion of Moisture in a Rubber-Toughened Epoxy Adhesive, Bruce Duncan and Gordon Pilkington, Draft paper 27 Measurement Good Practice Guide No. 12: Absorption and Diffusion of Moisture In Polymeric Materials, B C Duncan and W R Broughton, March 27 D depends on temperature

14 F7 Permeation, Absorption and Desorption of Liquids and Gases in Polymer and Multilayer Systems Investigation into the role of interfaces in diffusion 3-D finite difference model Dielectric sensors for assessing local moisture levels Uptake in different joint configurations faster than predicted in the initial stages Diffusion of Moisture in Adhesive Bonds, B C Duncan, G Pilkington, J S Nottay, C R G Allen, K Lawrence, J Urquhart and S J Roberts, DEPC-MPR 62, March Grit and Etched Milled & Etched 1-D Analytical Model Predictions Predicted using 3-D FV model Moisture Absorption (%) Square Root Time (h 1/2 )

15 F9 Prediction of the Lifetime of Adhesive Joints under Sustained Loading Develop methods for characterising non-linear creep behaviour in structural adhesive joints NPL Report DEPC-MPR 11 A Review of Creep Modelling for Toughened Adhesives and Thermoplastics Model developed for characterising non-linear creep behaviour in structural adhesives Modelling Non-Linear Creep Behaviour of an Epoxy Adhesive accepted for publication in International Journal of Adhesives and Adhesion Characterise creep behaviour in thermoplastics and welded thermoplastics polypropylene Model developed for characterising non-linear creep behaviour in amorphous polymers Paper A Model for Non-Linear Creep in Polypropylene to be submitted to Journal of Plastics, Rubber and Composites

16 Creep Modelling superposition experimental differential equation polypropylene Superposition for non-linear behaviour (2-step loading) strain MPa ε(t) = D σ t exp t 1 + t t t 1 1 n + D ( σ 1 σ t t )exp t MPa time (s).16 polypropylene.14 strain MPa 6.8 MPa.8.6 superposition differential equation experiment time (sec)

17 F9 Prediction of the Lifetime of Adhesive Joints under Sustained Loading Develop measurement techniques and predictive model for characterising cyclic fatigue behaviour of structural adhesives Measurement Good Practice Guide No. 14: Fatigue and Creep Testing of Adhesives and Thermoplastics Produce design protocols for above areas in electronic form accessible via the internet Module added to Adhesives Design Toolkit

18 F1 Adhesive Design Toolkit

19 F1 Adhesive Design Toolkit Adhesive selection - Want to find an adhesive for a particular application but don't know where to start? Try this module. Adhesive suppliers - Looking for who supplies what to where? Try this module. Case Histories - A searchable selection of case histories but we are always looking for more. Stress analysis - A powerful tool to enable stress analyses to be carried out on a variety of co-axial joints. Change joint geometries, features, adherends, cure conditions (hot or cold) and see what effect it has on the stress profile. Design guidance - It is easy to produce a poor adhesive joint and blame the adhesive. This module is designed to assist with the process and enable the user to avoid 'obvious' mistakes. Standards (NEW) - This module covers most, if not all, of the available standards (e.g. BSI, ISO, ASTM etc) that are relevant to adhesives and adhesive bonding. The information provided lists the standard reference number, the title and a short summary of each standard. Design, Preparation and Testing (NEW) - This module provides detailed information relating to the design, preparation and testing of adhesives and adhesively bonded structures. Forensic assessment (NEW) - Forensic analysis forms an important part both in the optimisation of bonding processes, understanding the factors that affect bond quality, and in the evaluation of bond failures.

20 F12 Development of test methods for determining the criticality of defects in composite materials systems under long-term loading Development of defect tolerance test methods for long-term loading Development of open hole tension and compression fatigue tests New method for assessing damage tolerance of carbon fibre panels (based on compression after impact test) Methods for monitoring defect growth, such as flash thermography Applying Impact Excitation Methods to assess damage from vibration modes

21 F12 Development of test methods for determining the criticality of defects in composite materials systems under long-term loading International standardisation of candidate test methods Round Robin on compression after impact test

22 Polymers Performance Website Username: PolPerf Password: FPERF

23 Polymers Performance Website