Measuring the Strength and Stability of the Lower LATCH Anchors across a Range of Anchor Spacing

 

Principal InvestigatorAditya Belwadi, PhD, Children’s Hospital of Philadelphia

 

Below is an executive summary of this project. Please note that this summary describes results and interpretation that may not be final. Final interpretation of results will be in the peer-reviewed literature.

 

Project motivation: CRSs are designed to provide two links between the vehicle and the child. The CRS is securely attached to the vehicle seat using the vehicle seat belt or the lower attachments, at the same time that the child is properly secured in the CRS with a separate harness and/or other restraining surface. These two links between the vehicle and the child are critical in reducing injuries or death in the event of a vehicle crash. Lower Anchors and Tethers for Children (LATCH), an installation system created to help standardize and improve the ease in which child restraints are attached to vehicles, has been in the marketplace since the NHTSA-promulgated regulation (Federal Motor Vehicle Safety Standard 225) became fully effective on September 1, 2002. The traditional method of attaching child safety seats with seat belts was prone to misuse such as a loose fit or incorrect routing.

The new LATCH system, which has a user-friendly system of two lower attachments on the safety seats that connect with lower anchors built into the back seats of passenger vehicles, was developed as an alternative method of attaching child safety seats to the vehicle. Vehicle manufacturers are under increased pressure from NHTSA and IIHS to provide the option of using LATCH in the rear center position of vehicles. One possible solution to this request is to allow consumers to “borrow” the inboard lower anchor from each outboard LATCH position to create a “simulated” center LATCH position. However, these borrowed lower anchors are often spaced further apart than the current LATCH standard of 11 inches (280 mm). The proposal looks to evaluate child restraints installed in the rear center seated locations with varying lower LATCH anchor spacing in dynamic loading crash simulations.

Broad objective: The broad long-term objective of the proposed line of research is to gain insight into the strength and stability of the lower LATCH anchors dynamically. Manufacturers, regulators, technicians and eventually caregivers will benefit from the data.

Specific aims: To determine ATD kinetics and kinematics installed in CRSs across a range of lower LATCH anchor spacing and PDOFs

Methods:

Step 1a: Estimation of Lower LATCH Anchor spacing

Step 1b: Sled testing utilizing the Q3 anthropomorphic test dummy

Step 2: Finite Element Simulation utilizing previously developed CChIPS finite element models

Results and Conclusions:

Sled Testing:  36 sled tests were conducted using an instrumented Q3. NHTSA’s 2017 NPRM test bench utilizing the FMVSS 213 test bench were used with one rear facing infant seat, one rear facing convertible, one forward facing with top tether and the same forward facing seat deg, 30 deg and 80 deg) with each condition repeated twice. High-speed crash data, sled acceleration along with ATD kinetics were recorded. Kinetic data – head and chest resultant acceleration, HIC15 and chest deflection were all within IARV values as specified for frontal impact as part of the FMVSS 213 test standard. It was interesting to note reduced HIC15 and head resultant acceleration in higher anchor spacing (19 inches). This number was significant when the PDOF was 80 degrees indicating more stability in the CRS and thus in the ATD for wider anchor spacing.

Finite Element Modeling: In order to further examine the effect of the lower LATCH webbing (single versus double), a design of optimization was carried out with the exact same FE models and the Q3 ATD. 24 simulations were carried out with 0 degrees and 30-degree PDOF’s. There was no significant difference found between single versus double lower LATCH anchor webbing across all conditions.

 

 

 

Comparison of rear-facing infant seats across 11, 15 and 19 inches of lower LATCH anchor spacing.

 

Students: Evan Bisirri, Drexel University; Nhat Duong, Drexel University; Seth Fein, The University of Pennsylvania; Jalaj Maheshwari, The University of Pennsylvania

IAB Mentors: Keith Nagelski, Britax Child Safety Inc.; Eric Dahle, Evenflo Company Inc.; Anthony Rosetto, FCA US LLC; Julie Kleinert, General Motors Holdings LLC; Zine Ben Aoun, General Motors Holdings LLC; Mark La Plante, Graco Children’s Products Inc.; Tim Patrizi, Graco Children’s Products Inc.; Arjun Yetukuri, Lear Corporation; Jon Sumroy, mifold; John Combest, Nissan Motor Company; Hiromasa Tanji, TK Holdings Inc.; Schuyler St. Lawrence, Toyota USA; Barbara Birkenshaw, Volkswagen Group of America; Uwe Meissner, Technical Advisor

 

About This Center

This Center is made possible through a grant from the National Science Foundation (NSF) which unites CHOP, University of Pennsylvania, and The Ohio State University researchers with R&D leaders in the automotive and insurance industries to translate research findings into tangible innovations in safety technology and public education programs.

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