Crash helmet testing and design specifications Citation for published version (APA): Bosch, van den, H. L. A. (2006). Crash helmet testing and design specifications. Technische Universiteit Eindhoven. https://doi.org/10.6100/IR613094 DOI: 10.6100/IR613094 Document status and date: Published: 01/01/2006 Document Version: Publisher’s PDF, also known as Version of Record (includes final page, issue and volume numbers) Please check the document version of this publication: • A submitted manuscript is the version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. 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Sauren A catalogue record is available from the Library Eindhoven University of Technology ISBN-10: 90-386-2878-1 ISBN-13: 978-90-386-2878-3 Printed by the University Press Facilities, Eindhoven, The Netherlands This research is financially supported by the Dutch Technology Foundation, applied science division of NWO, the technology programme of the Dutch Ministry of Economic Affairs, and the University Research Program of Ford Motor Company. Een vriend zal vrolijk met je mee zingen op de toppen van de bergen, en zwijgzaam naast je lopen als je door een dal gaat. Uit: Een boekje over vriendschap. voor mijn ouders Contents Summary ix List of Symbols and Abbreviations xi 1 Introduction: Crash Helmet Design as Driven by Standards 1 1.1 Crash Helmet Design Then and Now . 1 1.1.1 Effectiveness of Current Day Motorcycle Helmets . 2 1.2 Origin and Outline of the Crash Helmet Standards . 4 1.2.1 Aetiology of Motorcycle Accidents . 6 1.2.2 Head Injury Criteria . 7 1.2.3 Headforms and Biomechanics in Helmet Testing Procedures . 10 1.3 Review of Helmet Shock Absorption Studies . 11 1.3.1 Experimental Studies Based on Standard Drop Tests . 12 1.3.2 Numerical Modelling of Standard Drop Tests . 13 1.3.3 Experimental Studies with Modified Drop Tests . 16 1.4 Problem and Objective . 18 1.4.1 Problem: Limitations of the Current Shock Absorption Tests for Motorcycle Helmets . 18 1.4.2 Objective: Improving Helmet Design by Advanced Shock Absorption Assessment 19 1.4.3 Hypotheses and Research Strategy . 20 2 The Deformable Headform 23 2.1 Introduction . 23 2.2 Design Requirements for the Physical Headform . 24 2.2.1 Anatomical Requirements . 24 2.2.2 Anthropometry . 26 2.2.3 Instrumentation . 27 2.3 Response Requirements . 27 2.3.1 Biofidelity . 27 2.3.2 Repeatability . 28 2.4 Design of the New Headform . 29 2.4.1 Brain and Skull-Brain Interface . 29 2.4.2 Skull . 29 2.5 Testing the New Headform . 30 2.5.1 Anthropometry . 30 v vi CONTENTS 2.5.2 Biofidelity . 31 2.5.3 Repeatability . 34 2.6 Discussion . 34 3 Helmeted Head Drop Test Experiments 37 3.1 Introduction . 37 3.2 Experimental Setup . 37 3.2.1 Drop Test Setup . 37 3.2.2 Headforms . 40 3.2.3 Helmets . 41 3.2.4 Experimental Protocol . 41 3.3 Results: Helmeted Head Drop Test Experiments . 43 3.3.1 Drop Tests Using Conventional Headform . 43 3.3.2 Drop Tests Using Flexible Headform . 50 3.4 Discussion . 54 3.4.1 Research Question 1: Are the Injury Criteria Currently Used in Helmet Certifi- cation Tests Adequate for Predicting Injury Severity? . 54 3.4.2 Research Question 2: How Are Helmet Fit and Headform Flexibility Related to Helmet-head Interaction? . 56 3.5 Conclusions . 59 4 Numerical Modelling of Helmeted Head Drop Tests 61 4.1 Introduction . 61 4.2 Numerical Model of the Flexible Headform . 61 4.2.1 Realization of the Model . 61 4.2.2 Validation of the Model . 63 4.3 Conventional Headform Model . 65 4.4 Helmet Model . 65 4.4.1 Protective Padding Liner . 65 4.4.2 Comfort Padding Liner . 74 4.4.3 Outer Shell . 75 4.4.4 Assembly of the Helmet Model . 75 4.5 Helmeted Head Drop Test Simulations with Conventional Headform . 76 4.5.1 Top Impact . 77 4.5.2 Front Impact . 77 4.5.3 Rear Impact . 78 4.6 Helmeted Head Drop Test Simulations with Flexible Headform . 78 4.6.1 Top Impact . 78 4.6.2 Front Impact . 78 4.6.3 Rear Impact . 79 4.7 Conclusions on Model Validity . 80 CONTENTS vii 5 Helmet Design Sensitivity Analysis Using Simulated Helmet Drop Tests 83 5.1 Introduction . 83 5.2 Effect of Impact Site . 84 5.3 Skin . 85 5.4 Effects of Boundary Conditions . 87 5.5 Effects of Material Parameters. 89 5.5.1 Outer Shell . 89 5.5.2 Protective Padding . 90 5.5.3 Interaction Between Outer Shell and Protective Padding . 92 5.6 Impact Velocity . 92 5.7 Discussion and Conclusions . 93 6 Helmet Design Optimisation 97 6.1 Introduction . 97 6.2 Methodology . 98 6.2.1 Protective Padding Liner Density Optimisation . 98 6.2.2 Variations to the Outer Shell Configuration . 98 6.2.3 Variation of Protective Padding Liner Configuration . 99 6.3 Results . 100 6.3.1 Protective Padding Liner Density Optimisation . 100 6.3.2 Variations to the Outer Shell Configuration . 103 6.3.3 Variation of Protective Padding Liner Configuration . 107 6.4 Discussion and Conclusions . 110 7 Conclusions and Recommendations: Towards a Safer Motorcycle Helmet 113 7.1 Conclusions . 113 7.2 Recommendations for the Flexible Headform . ..