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Strength Requirements for Child Restraint Systems: Guidelines and Calculations

This document outlines the strength requirements for Child Restraint Systems (CRS) as mandated by the National Highway Traffic Safety Administration. It details the calculations for force based on mass and acceleration, along with assumptions regarding the mass of children and CRS. Key specifications include peak force values needed for crash testing, stipulations for misuse tests, and appropriate durations for force application. The goal is to ensure adequate protection during vehicle impacts, reinforcing safety standards in child seating systems.

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Strength Requirements for Child Restraint Systems: Guidelines and Calculations

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  1. ANCHORAGE STRENGTH REQUIREMENTS George Mouchahoir Office of Performance Standards National Highway Traffic Safety Administration May, 2002

  2. BASIS FOR STRENGTH REQUIREMENTS • FORCE • DURATION OF FORCE APPLICATION • DISPLACEMENT CRITERIA

  3. STRENGTH CALCULATION • Force = mass X acceleration • System mass (child restraint system (CRS) and child) • Acceleration of vehicle

  4. MASS ASSUMPTIONS • 22.7 kg (50 lb) for child • (Current mass limit of FMVSS No. 213) • 7 kg (15.4 lb) for CRS • System Mass (m) = CRS + child • = 29.7 kg (65.4 lb)

  5. US VEHICLE FLEET CRASH PULSES PEAK VALUES MY99 Saturn SC1

  6. AVERAGE PEAK VEHICLE ACCELERATION

  7. Maximum dynamic force expected to act through the center of gravity (cg) of the CRS is: = [System mass]X[acceleration] = [29.7 kg][(48.4 g)(9.81 m/s2)] = 14,101 N  15 kN (3371 lb) FORCE COMPUTATION

  8. Misuse test: Two lower anchorages of CRS attached only Force of 11 kN will assure that at least a minimum level of protection is provided when the tether is not used to attach CRS to the vehicle in forward direction, and Force of 5 kN in lateral direction MISUSE STRENGTH REQUIREMENTS

  9. For 3 anchorages attached: Pull force as linearly as practicable to 15 kN in 24 s  t  30 s, and maintain at a 15 kN level for 1 second DURATON OF FORCE

  10. Forward force direction – Pull force as linearly as practicable to a full force application of 11 kN in 24 s  t  30 s, and maintain at an 11 kN level, currently, for 10 seconds Lateral direction – Pull force as linearly as practicable to a full force application of 5 kN in 24 s  t  30 s, and maintain at a 5 kN level, currently, for 10 seconds DURATION OF FORCE FOR MISUSE CASE

  11. DISPLACEMENT REQUIREMENTS

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