Investigation of crack initiation, and mechanical behavior of polypropylene and polymer-based composites under plastic deformation in automotive brake fluid reservoirs

This paper discusses the intensive research on polypropylene, a significant polymeric material, and its extensive application in the automotive industry, particularly in the manufacture of brake fluid reservoirs through a series of laboratory destruction tests and experiments, The paper emphasizes the triaxiality (Triax) (η = σm/σeq) is used as the theoretical framework for evaluating crack initiation and behavior under various stress states and critical factors for the understanding of crack formation intention and the mechanical behavior of polypropylene under mechanical loads. This study present a detailed evaluation of polypropylene behavior under various manufacturing conditions, addressing potential deviations that could affect final product quality. The findings demonstrate the material's robustness and high fracture toughness, thermal stability, and mechanical strength minimize crack initiation, leakage, damage, and other defects during the manufacturing process, ensuring reliable use in reservoir production. The research methodology involved a series of tests and experimental procedures, such as (i) Melt Flow Index (MFI = 0.109 g/10 min, ASTM D1238, 230°C/5 kg); (ii) uniaxial tensile testing (yield strength: 23.0-23.7 MPa, tensile modulus: 2.36-2.48 GPa, fracture strain: 42-68%, ASTM D638, n = 3); (iii) burst pressure testing (mean burst: 2.70 ± 0.10 MPa at Δp = 11 bar/s, minimum requirement: 0.70 MPa, ISO 8033); (iv) air leakage testing (no leakage at 500-700 kPa hold for 60 s); (v) thermal chamber cycling (-40°C to 120°C, 95% RH, 24 h; dimensional change < 0.02 mm); (vi) tilt alarm test (alarm activation at ≤ 0.53° tilt); and (vii) volume capacity verification (within OEM specification) during manufacturing of the brake fluid reservoir. These results confirm the long-term suitability of SABIC 83MF10-polypropylene for safety-critical reservoir applications in modern automotive braking systems. The novel aspects of this study are the demonstration of the mechanical behaviour of polypropylene and the valuable insights provided into the brake fluid reservoir manufacturing process and performance, offering significant implications for automation in the automotive sector.