Thermo-mechanical characterization of polyurea variants

Identifying residual stresses and the distortions in composite structures during the curing process plays a vital role in coming up with necessary compensations in the dimensions of mold or prototypes and having precise and optimized parts for the manufacturing and assembly of composite structures. This paper presents an investigation into process-induced shape deformations in composite parts and structures, as well as a comparison of the analysis results to finalize design parameters with a minimum of deformation. A Latin hypercube sampling (LHS) method was used to generate the required random points of the input variables. These variables were then executed with the Ansys Composite Cure Simulation (ACCS) tool, which is an advanced tool used to find stress and distortion values using a three-step analysis, including Ansys Composite PrepPost, transient thermal analysis, and static structural analysis. The deformation results were further utilized to find an optimum design to manufacture a complex composite structure with the compensated dimensions. The simulation results of the ACCS tool are expected to be used by common optimization techniques to finalize a prototype design so that it can reduce common manufacturing errors like warpage, spring-in, and distortion.

show abstract

“…The same data were further used in the scatter diagram, as shown in Figure 13, to represent the results. [43][44][45][46][47]…”

Section: Parameter Study Resultsmentioning

confidence: 99%

“…Table 4 shows the values of all the simulation results based on all the input design variables. The same data were further used in the scatter diagram, as shown in Figure 13, to represent the results [43][44][45][46][47]. A graphical representation of all simulation results is shown in Figure 14.…”

Section: Parameter Study Resultsmentioning

confidence: 99%

Analysis of Composite Structures in Curing Process for Shape Deformations and Shear Stress: Basis for Advanced Optimization

2021

View full text Add to dashboard Cite

show abstract

“…[ 7 ] A dispersion correction is applied to correct for the time shift of the signal as well as to correct for the dispersive behavior of the aluminum bars. [ 10 ] This correction was done based on the work of Gama et al, which offers a more detailed description of the dispersion correction process. [ 37 ] Dynamic equilibrium was assumed when the compression wave in the sample had traversed the sample three times, with a wave speed in the polycarbonate sample of ~4.5 km/s.…”

Section: Methodsmentioning

confidence: 99%

“…[3][4][5] The split Hopkinson pressure bar (SHPB) technique allows the characterization of the dynamic response high strain rates, ranging nominally from 10 2 to 10 4 s À1 . [6][7][8][9][10] The analysis of the dynamic compressive and tensile behavior of PC was reported by, among others, Prakash [11] and Wang, [4,12] respectively. Both studies showed that PC goes through a significant strain hardening after reaching the yield stress.…”

Section: Introductionmentioning

confidence: 99%

Effect of strain rate on the mechanical properties of polycarbonate processed by compression and injection molding

Ullrich

Singh

McDonald

et al. 2021

Polymer Engineering & Sci

View full text Add to dashboard Cite

The high impact strength of polycarbonate has been studied and exploited for many applications. However, the interaction between processing-induced effects and the strain rate affects the mechanical behavior significantly. In this work, the effects of the processing-induced thermal history, generated by either injection molding or compression molding, were characterized. Polycarbonate samples manufactured with the two processes were experimentally compared using quasi-static and dynamic compression testing. The processing effects are further evaluated by combining a numerical calculation of the temperature history and a constitutive model to predict the yield strength of the glassy polymer. The constitutive modeling approach considers both the effect of the rate-dependent and stress-activated motion of the chain segments, and the strain-hardening effect due to molecular alignment. The results indicate that the thermal history has a significant effect at low strain rates, while its influence is negligible in the dynamic range. The modeling effort allows estimating the yield strength with different accuracy depending on the strain rate values.

show abstract

“…Hence, the transmission of the heat wave from the laser impingement would be negligible by the time it reaches the polyurea, making it an unlikely source for thermal softening. Therefore, the dynamic deformation of polyurea due to the localized adiabatic heating can be described by a balance between the mechanical stress and the heat transfer due to the heat capacity of the material within the plastic deformation (𝜖 p ) regime while suppressing the thermoelastic effect [69,72] 𝜌 p cΔT = ∫ 𝜎d𝜀 p (10) where 𝜌 p is the density of polyurea (1071 kg•m −3 ), c is the specific heat capacity (1150-1400 J•kg −1 •K −1 for temperatures ranging from −40 to 40 °C [73] ), and ΔT is the adiabatic temperature rise. The latter was estimated based on the plastic strain deduced from the bulging height shown in Figure 8 (𝜖 p ≈ 0.9, translating to ∼20 K change).…”

Section: Ductile Failure Of Shock-loaded Polyureamentioning

confidence: 99%

Spectro‐Microscopic Characterization of Elastomers Subjected to Laser‐Induced Shock Waves

Huynh

Gámez

Youssef

2021

Macro Materials & Eng

View full text Add to dashboard Cite

The core of this research is separated into three domains, the ultrahigh strain rate response of elastomeric polymers, laser-induced shock waves , and terahertz time-domain spectroscopy (THz-TDS). Elastomers, e.g., polyurea, constitute an advance class of materials suitable for many applications, specifically in high impact loading scenarios, thus, a laser-induced shock wave (LSW) experimental technique is used to investigate the mechanical response of shock-loaded polyurea. LSW can submit samples to a strain rate exceeding 10 6 s −1 at low strains, enabling determination of material intrinsic failure modes. The large deformation induced during shock loading may alter the macromolecule structure, which can only be detected spectroscopically. Therefore, this research incorporated terahertz bulk spectroscopy to detect and report molecular conformational changes. Microscopy techniques were also used to elucidate changes in the microscale properties, morphology, and topography. The interpretation of the results explicated brittle failure in terms of partial and total spallation and, remarkably, ductile failure leading to plastic deformation, including plastic bulging and adiabatic shearing, not previously associated with LSW technique. Furthermore, spectral changes found in the terahertz regime substantiated the validity of terahertz spectroscopy in elucidating the underlying mechanism associated with the impact mitigating properties of dynamically loaded polyurea.

show abstract

Thermo-mechanical characterization of polyurea variants

Cited by 11 publications

References 37 publications

Analysis of Composite Structures in Curing Process for Shape Deformations and Shear Stress: Basis for Advanced Optimization

Analysis of Composite Structures in Curing Process for Shape Deformations and Shear Stress: Basis for Advanced Optimization

Effect of strain rate on the mechanical properties of polycarbonate processed by compression and injection molding

Spectro‐Microscopic Characterization of Elastomers Subjected to Laser‐Induced Shock Waves

Contact Info

Product

Resources

About