Development/properties of boost EPS foam

• Main Author: Png, Melody Ren Xin
• Other Authors: Alfred Tok Iing Yoong
• Format: Final Year Project
• Language: English
• Published: 2019
• Subjects: DRNTU::Engineering::Materials::Non-metallic materials
• Online Access: http://hdl.handle.net/10356/76740
• Institution: Nanyang Technological University

Expanded Polystyrene (EPS) is a common material used to manufacture the inner foam liner of a bicycle helmet due to its outstanding energy absorption characteristic and light-weight property. However, it has been illustrated that the energy absorption ability of current bicycle helmets in the market still has room for improvement. This final year project aims to understand the behaviour of different densities and designs of EPS foam under impact to develop methods to enhance the impact dissipation characteristic of such polymeric foam for bicycle helmet liner applications. Both flat and curved EPS foam samples and ABS panels are manufactured and curved EPS-ABS samples are produced to better represent a bicycle helmet. For flat foam samples, they can be categorised into 4 different types: PF samples (pure EPS foam), MHF samples, (EPS foam with Nomex honeycomb in the middle of the sample), THF (EPS foam with Nomex honeycomb at the top of the sample) and CF samples (corrugated EPS foam). For all 4 types of samples, they can be further categorized into 3 density ranges. For curved foam samples, they can be categorised into 3 types: PC samples (pure EPS curved foam), THC (curved EPS foam with Nomex honeycomb at the top of the sample) and CC samples (corrugated curved EPS foam). Regardless of the different types, all curved foams that are manufactured are within one density range. Proceeding from the manufacturing phase, impact tests were carried out to determine the effect of foam density on its energy absorption ability and the effect of foam designs on both flat and curved foam samples. Peak load, peak acceleration and percentage of absorption energy were analysed in this project. Results were compared between foams of different densities as well as foams of different designs. It can be concluded that an increase in density brings about an increase in energy absorption by the foam. In addition, EPS-honeycomb hybrid structures showed an improvement in impact dissipation characteristics and hence its potential in enhancing energy absorption ability for bicycle helmet foam liner. However, this is not evident with corrugated foams and therefore modifications are needed for it to provide better energy absorption properties. Modifications such as higher corrugated foam weight can be adopted to achieve the desired result.