Jan Spoormaker Spooy rmaker Consulta ncy / D …

1 Spoormaker Consultancy in Reliability & Liability of Plastic ProductsApproaches to Failure analysis of polymeric materialsJan Spoormaker Spoormaker Consultancy / Delft University of TechnologySpooa e Co su a cy / e Ue s y o ec o ogyIf you don't know the fords, don't step in the water!pVeMetContents Spoormaker Consultancy in reliability and liability of plastic productsCo te ts Polymers Typical failure mechanisms of plastics:failure might failure mechanisms of plastics: failure might occur. Failure causes of plastic products: failure has occurred .VeMetPolymerisation of ethylene C2H4oPESpoormaker Consultancy in Reliability & Liability of Plastic Productsyy24 VeMetPolyethelyne C2H4 Spoormaker Consultancy in Reliability & Liability of Plastic Productsyy24lengthunbranchedlengthunbran ched chingbranVeMetbranched Verdeling MolecuulmassaSpoormaker Consultancy in Reliability & Liability of Plastic ProductsVerdeling MolecuulmassaMolecular massoIO-2040-20091130 Chain lengthoMolecular massoChain lengte of PE (CnH2n+2) Spoormaker Consultancy in Reliability & Liability of Plastic Productsg(n2n+2)paraffin(500 g/mol ) glue container(105g/mol) UHMW-PE ( )

2 VeMetAmorphous and semi-crystalline Spoormaker Consultancy in Reliability & Liability of Plastic Productshigh binding energylow binding energytie-moleculehigh binding energylow binding energyVeMetSpoormakerConsultancy in Reliability & Liability of Plastic ProductsBending strength and impact strength as a function of MnVeMetViscosity as a function of molecular massSpoormaker Consultancy in Reliability & Liability of Plastic ProductsyVeMetInjection moulding of thermoplasticsSpoormaker Consultancy in Reliability & Liability of Plastic ProductsjgpAll you need is speed !!!All you need is speed !!!VeMetFailure mechanisms and causesSpoormaker Consultancy in reliability and liability of plastic productsaue eca s sadcausesFailure Mechanisms UVdegradationFailure Causes faulty ribbing UV-degradation creep & stress relaxation environmental stress cracking faulty ribbing difference in stiffnesses high stiffness of mating parts dimensional stability static fatigue grade and polymer selection dynamic fatigue stress concentrations dynamic fatigue wear stress concentrationsVeMetFatigue Spoormaker Consultancy in reliability and liability of plastic productsat gueFailure MechanismsFailure Causes UV-degradation creep & stress relaxation environmental stress cracking faulty ribbing

3 Difference in stiffnesses high stiffness of mating partsenvironmental stress cracking dimensional stability static fatiguehigh stiffness of mating parts grade and polymer selection dynamic fatigue wear stress concentrationsVeMetFatigueSpoormaker Consultancy in Reliability & Liability of Plastic ProductsFatigueDisentanglement in polymers can occurpolymers can occur, resulting in stable crack This is also referred to as static fatigue. gDynamic fatigue is a similar crack growth Paris lawSpoormaker Consultancy in Reliability & Liability of Plastic ProductsygCrack growth per cycleCrack growth per cycleConstant for dynamic loadsSti tit diffStress intensity difference exponent VeMetSpoormaker Consultancy in Reliability & Liability of Plastic ProductsCrack extension crack initiationStable crack extensionunstablecrack extensionThreshholdof initiationof initiationVeMetStatic fatigue Spoormaker Consultancy in Reliability & Liability of Plastic ProductsgCrack growth rateCrack growth rateCac go t ateConstantStress intensityStress intensityexponent VeMetStatic fatigue crack growthSpoormaker Consultancy in

4 Reliability & Liability of Plastic Productsggunstablecrack extensionStable crackwrh rateStable crack extensionrack growwcrack initiationCrPolycarbonate spring Spoormaker Consultancy in reliability and liability of plastic productsoyca bo atesp gFailure Mechanisms UVdegradationFailure Causes faulty ribbing UV-degradation creep & stress relaxation environmental stress cracking faulty ribbing difference in stiffnesses high stiffness of mating parts dimensional stability static fatigue gradeand polymer selection dynamic fatigue stress concentrations dynamic fatigue wear stress concentrationsVeMetPCPC--spring in service positionspring in service positionSpoormaker Consultancy in Reliability & Liability of Plastic ProductsPCPC spring in service positionspring in service positionVeMetPhoto of PC spring in service positionSpoormaker Consultancy in Reliability & Liability of Plastic ProductsPhoto of PC spring in service positionVeMetSpring in unlocked positionSpring in unlocked positionSpoormaker Consultancy in Reliability & Liability of Plastic ProductsSpring in unlocked positionSpring in unlocked positionVeMetPhoto of Spring in unlocked positionSpring in unlocked positionSpoormaker Consultancy in Reliability & Liability of Plastic ProductspgppgpVeMetCrack extensionSpoormaker Consultancy in Reliability & Liability of Plastic ProductsPolycarbonate (PC)

5 Has relatively smooth ymolecular chainsand has a low resistance to stable crack extension. It has, however, a littlarge resistance to crack Consultancy in Reliability & Liability of Plastic ProductsImpact & notch sensitivityECEFA -IVFailed springsSpoormaker Consultancy in Reliability & Liability of Plastic ProductspgVeMetSEM of fracture surface (static fatigue) Spoormaker Consultancy in Reliability & Liability of Plastic Products(g)VeMetSEM of fracture surface (dynamic fatigue) Spoormaker Consultancy in Reliability & Liability of Plastic Products(yg )VeMetMelt Flow Rate (MFR) Spoormaker Consultancy in Reliability & Liability of Plastic ProductsMelt Flow Rate (MFR)MFR - the mass of polymer, in grams, flowing in 10 minutes through a capillary of a specific diameter and length by a pressure applied via prescribed weights for prescribed -IVMolecular mass (Mn) -MFRS poormaker Consultancy in Reliability & Liability of Plastic ProductsRelationship between the Molecular Weight and theRelationship between the Molecular Weight and the MFR for PC (Calibre 300 of DOW Plastics)

6 VeMetRlti MFRI ttthSpoormaker Consultancy in Reliability & Liability of Plastic ProductsRelation MFR-Impact strengthVeMetKid-SitSpoormaker Consultancy in reliability and liability of plastic productsdStFailure Mechanisms UVdegradationFailure Causes faulty ribbing UV-degradation creep & stress relaxation environmental stress cracking faulty ribbing difference in stiffnesses high stiffness of mating parts dimensional stability static fatigue grade and polymer selection dynamic fatigue stress concentrations dynamic fatigue wear stress concentrationsVeMetKid-Sit Spoormaker Consultancy in Reliability & Liability of Plastic stiffness differences Spoormaker Consultancy in Reliability & Liability of Plastic ProductsExtreme high stiffness differences between swivel plate (steel) and the board adjacent to the swivel plate (polymer)VeMetKid-Sit - cracking Spoormaker Consultancy in Reliability & Liability of Plastic Spoormaker Consultancy in Reliability & Liability of Plastic ProductsgSemi-crystalline (final material selection PA6 with 30 % glass fibresAmorphous p(initial material selection)VeMetS-N curve of PA66-30GF (flow direction) Spoormaker Consultancy in Reliability & Liability of Plastic Products()VeMetKid-SitSpoormaker Consultancy in Reliability & Liability of Plastic Extreme high stiffness gdifferences between swivel wheel plate (steel))

7 And the board adjacent to the swivelboard adjacent to the swivel plate (polymer)282 NmswsnaDEI Bending stiffnesss NmbpbDEI Bending stiffness bDsw\Db= 31 VeMetpgImpact factor \ Spoormaker Consultancy in Reliability & Liability of Plastic Productsp\211impacttotFhkF\ totstaticFmgECEFA -IVImpact factor \ Spoormaker Consultancy in Reliability & Liability of Plastic Productsp\211impacttotFhkF\ totstaticFmgh01h 18 kgg m/s2k=22000 \ ktot= 22000 N/m2<o6 VeMetKid-Sit FEM calculation ISpoormaker Consultancy in Reliability & Liability of Plastic high secondarystresses in the VeMetygyregion near the stiffness differenceFEM calculation (filliting) Spoormaker Consultancy in Reliability & Liability of Plastic cu at o(tg)Still veryhighsecondarystressesin the region nearECEFA -IVStill very high secondarystresses in the region near the stiffness difference.

8 Filleting does not helpUV-degradationSpoormaker Consultancy in reliability and liability of plastic productsgFailure Mechanisms UVdegradationFailure Causes faulty ribbing UV-degradation creep & stress relaxation environmental stress cracking faulty ribbing difference in stiffnesses high stiffness of mating parts dimensional stability static fatigue grade and polymer selection dynamic fatigue stress concentrations dynamic fatigue wear stress concentrationsVeMetWeatheringSpoormaker Consultancy in Reliability & Liability of Plastic ProductsWeatheringECEFA -IV WeatheringSpoormaker Consultancy in Reliability & Liability of Plastic Sunlight and spectral sensitivity3. Effect of UV on polymers4.

9 Attack of bonds5. Change in mechanical propertiesECEFA -IV Definition of weatheringSpoormaker Consultancy in Reliability & Liability of Plastic ProductsgWeatheringis the adverse response of a material or dttlit ftitddproduct to climate, often causing unwanted and premature product Factors of Weathering: solar radiation (light energy) temperature water (moisture/dew)ECEFA -IV WeatheringSpoormaker Consultancy in Reliability & Liability of Plastic Sunlight and spectral sensitivity3. Effect of UV on polymers4. Attack of bonds5. Change in mechanical propertiesECEFA -IV Solar radiation spectrum Spoormaker Consultancy in Reliability & Liability of Plastic ProductspECEFA -IVWeatheringSpoormaker Consultancy in Reliability & Liability of Plastic Sunlight and spectral sensitivity3.

10 Effect of UV on polymers4. Attack of bonds5. Change in mechanical propertiesECEFA -IV UV-induced reactionsSpoormaker Consultancy in Reliability & Liability of Plastic ProductsUVinduced reactionsLoss of H-atomLoss of HatomReaction with O2 Reaction with a moleculeReaction with O2 ECEFA -IV Hydrogen peroxide & hydroperoxideSpoormaker Consultancy in Reliability & Liability of Plastic Productsyd oge pe o de & yd ope o deECEFA -IV Degradation reactionsSpoormaker Consultancy in Reliability & Liability of Plastic ProductsgECEFA -IVWeatheringS