3D-Printed Energy-Absorbing Polymer Structures for Reducing Injury Risk from Overhead Impacts to Hard Hats

Presenter Information

Andrew Miceli
Grant BevillFollow
Jutima Simsiriwong

Faculty Sponsor

Dr. Grant Bevill, Dr. Jutima Simsiriwong

Faculty Sponsor College

College of Computing, Engineering & Construction

Faculty Sponsor Department

Engineering

Location

SOARS Virtual Conference

Presentation Website

https://unfsoars.domains.unf.edu/2021/posters/3d-printed-energy-absorbing-polymer-structures-for-reducing-injury-risk-from-overhead-impacts-to-hard-hats/

Keywords

SOARS (Conference) (2021 : University of North Florida) – Archives; SOARS (Conference) (2021 : University of North Florida) – Posters; University of North Florida -- Students -- Research – Posters; University of North Florida. Office of Undergraduate Research; University of North Florida. Graduate School; College students – Research -- Florida – Jacksonville – Posters; University of North Florida – Undergraduates -- Research – Posters; University of North Florida. School of Engineering – Research – Posters; Project of Merit Award Winner

Abstract

Project of Merit Winner

Struck-by accidents (i.e., being hit by a falling object) are a leading cause of traumatic brain injuries (TBIs) in the construction industry. While hardhats are the conventional means of head protection in this setting, their overall design has not appreciably changed in decades. In this project, a commercially available hardhat was augmented by creating a compliant cantilever on the superior surface supported by a 3D-printed block (10 x 10 x 50mm, with hexagonal lattice infill) to serve as a sacrificial energy-absorbing structure. The lattices were created using three polymer materials (PLA, ABS, and High-Impact Polystyrene (HIPS)) at four levels of porosity (0%, 32.5%, 56%, and 69.3%). A Hybrid III head/neck assembly was fitted with each hardhat design, and a vertical impact test was conducted using a 1.8-kg steel impactor dropped from 1.83 m. The maximum acceleration and head injury criterion (HIC) were calculated from the impact data for each test. Analysis of variance (ANOVA) revealed that HIC was significantly reduced for all lattices with 56% porosity (p

Comments

Audio Presentation Transcript:

– Hello, my name is Andrew Miceli and my current focus of research delves into material studies and how by utilizing material properties of specific intentional design we can hope to mitigate traumatic brain injuries in the specific field of hard hats. – Hard hats are a device with a main goal of mitigating impacts by reducing the impact to the head of the user and operate best by reducing the load of direct head impacts. – Hard hats have been used for decades with a design changing little to none over these years. The main goal of our research is to optimize this design and see if any features can be added that will further reduce the injuries due to direct head impact from falling objects. – The way we can validate this data is through dynamic equations including the Head Injury Criterion Score “(HIC) abbreviated”. This equation gives us in this design, after the falling object has landed on the hard hat, the likelihood of injury in a score ranging quantitatively and qualitatively from no injury to a traumatic injury with a score associated with these values respectively. Hard hats with no alterations as quantified from previous data gleaned in this same lab reduce the HIC score of direct vertical impacts to the head, but our current design is intending to reduce this score even further. – We have thus created a proof-of-concept design intended to reduce the impact by simulating a sacrificial load point with predetermined geometry that has been studied previously and gives reliable data in their respective studies that reduces overall impact load results. – These proof-of-concept designs have been created and reiterated fluidly using 3D-printing to quickly and efficiently produce these prototype designs. The design we ultimately found to be most optimal for the proof was a block measured 10x10x50mm with a honeycomb design pattern extruded along one surface with its empty volumetric to solid volumetric ratio ranging from 0% to 69.28% loaded into the path of impact from the falling object. – The specific hard hat we used for this study was the MSA V-Gard helmets that have a solid v-ridge along the superior surface of the helmet used as the control helmet in our study as shown at the top of the presentation and in Figure 4 modeled on the Head Form used to capture our data. This v-ridge was cut and removed along two non-Euclidean planes from the front of the helmet up to a point along the helmet that provides a suitable cantilever to test our material properties of the insert and its effect on the load as shown with the insert in Figure 2 and a close-up picture shown in Figure 3. – The three types of 3D-printable material used in this study included: ABS (Acrylonitrile Butadiene Styrene), HIPS (High Impact Polystyrene), and PLA (Polylactic Acid). These three materials are both common in 3D-printing and allow a variety of material properties to be the variables in this study. – The drop tests, simulating a direct impact to the head, was performed by loading a 4lb-steel bar 1.83m above the surface of impact. The head form that receives this impact contains accelerometers that can measure 6-degree orientation acceleration and used during each test. A total of 39 tests were completed. 3 tests per set to create an average for each grouping with the data analyzed shown in Figure 5. – The data was then collected via an acquisition software with the specifics of the software shown under the heading titled Drop Tests. We utilized the accelerometers in the head form to collect most of this data. This data was then subsequently analyzed using a MATLAB script preformatted to determine values such as the maximum HIC value over 15ms of impact as well as the maximum linear acceleration of the head form in the z direction. These two values give us a rough estimate of the injury metrics involving the Traumatic Brain Injury of this impact. – These HIC values and Peak Linear Acceleration values as mentioned in the poster were compared against results from the control helmet with no removal and the data gleaned from this is shown as the Bar graphs again in Figure 5. – ANOVA was performed on this data set and was found that the HIC was significantly reduced for all lattice structures with 56% porosity and for the ABS and HIPS at 69.3% porosity compared to the control or (unmodified helmet). – The ANOVA also showed the maximum acceleration was not significantly changed for most of the inserts. – This data and the research discussed throughout this project therefore shows without a doubt that the inserts reduced the HIC value in these injury metrics thereby reducing the magnitude of the acceleration and functional time period over which the energy was transferred. – These results can be shown clearly if we look at the time period from 0.005s to 0.02s along Figure 6 we can see from the curve that the example shown for the PLA 56% porosity has a lower area under the curve for the acceleration versus time detailing how the HIC score works over this 15ms time interval and is significantly lower than the area under the curve for the Control curve. – All the data presented here can therefore indicate simple and inexpensive modifications can be made to the existing hard hat designs that can reduce the injury risk from overhead impacts. – Finally, I would like to thank Doctors Grant Bevill and Jutima Simsiriwong for allowing me the opportunity to study this research topic and to the UNF Foundation Board for sponsoring our research.

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