Sobhan Dehghanpour

Scopus Publications

Investigating Strain Rate Effects on the Anisotropic Mechanical Properties of Lignin-Filled Glass/Polypropylene Long-Fiber Thermoplastics Manufactured via Direct Compounded Compression Molding (LFT-D)
Tarun Khapra, Thanh Dat Vo, Reza Beigpour, Sajjad Dehghanpour, W. Altenhof
Polymer Composites, 2026
Fiber‐reinforced composites are employed in various sectors, such as the transportation sector, where they are subjected to various loading conditions, including high loading rates. In this study, the tensile properties of lignin‐filled glass/polypropylene (PP) long‐fiber thermoplastics (LFT) were investigated. These materials were manufactured using a direct compounded compression molding process, and tests were conducted at loading rates ranging from quasi‐static (0.0001 ) to elevated strain rates of up to 200 . The samples were examined in four material orientations, namely, 0°, +45°, −45°, and 90°, to understand their anisotropic behavior with three different percentages of lignin filler (0%, 14%, and 21%). Tensile strength was significantly enhanced at elevated strain rates, stabilizing beyond 100 . For 0% lignin, strength increased from 100 MPa (quasi‐static) to 221 MPa (100 /200 ), with 132% and 98% improvements for 14% and 21% lignin, respectively. While 14% lignin increased stiffness, 21% lignin weakened interfacial bonding, reducing mechanical strength. Strong anisotropy was observed, with the highest tensile strength (221 MPa) in the 0° direction and the lowest (74 MPa) in the 90° direction. SEM analysis revealed increased fiber pullout and matrix‐fiber debonding at higher lignin content, further reducing mechanical performance.
Exploring the effect of lignin as a filler on the mechanical properties and anisotropic nature of Glass/Polypropylene LFTs manufactured via direct compounded compression moulding (LFT-D)
Tarun Khapra, Sajjad Dehghanpour, Reza Beigpour, William Altenhof
Composites Communications, 2025
ABSTRACT Glass Long Fibre Thermoplastics (LFTs) are becoming increasingly popular as lightweight, high-performance recyclable materials. This trend has also led to greater interest in the use of biomaterials, such as bio-fillers like lignin, to help reduce the carbon footprint of these petroleum-based polymer composites. This study investigated the influence of lignin bio-filler on the mechanical properties of glass-reinforced polypropylene (glass/PP) LFTs. Three lignin weight percentages (0%, 14%, and 21%) were evaluated while maintaining 30% glass fibre content. Tensile and shear tests were conducted on samples from both charge and flow regions of compression-moulded plaques, considering 0°, +45°, -45° and 90° material directions. Fracture surface analysis was conducted by utilising a Scanning Electron Microscope (SEM) to understand the failure mechanisms and structural behaviour under mechanical stress. The results indicated a decrease of up to 36% in tensile strength with increasing lignin content in the 0° direction, which was particularly significant at a lignin content of 21%. The 0° direction consistently exhibited higher tensile strength in the range of 70 MPa to 100 MPa than the 90° material directions followed by +45°, -45°. Shear strength remained largely unaffected for 14% lignin content, with an approximately 10% drop for 21% lignin content samples. SEM analysis revealed distinct failure mechanisms across the different material directions (0°, +45°, -45°, and 90°). This study provides essential material characterisation, enabling more accurate numerical and analytical modelling of these materials with a lightweight, low-cost filler.
Influence of fibre content, moisture content, and anisotropy on the mechanical properties of direct compounded compression moulded carbon/PA66 and glass/PA6 composites
Tarun Khapra, Jacob Altenhof, Reza Beigpour, Sajjad Dehghanpour, Pouya Mohammadkhani, Matthew Bondy, William Altenhof
Journal of Thermoplastic Composite Materials, 2025
Long fibre thermoplastic (LFT) materials are employed in a diverse group of engineering applications, and this usage makes it critical to understand how various loading and environmental settings affect the mechanical properties of LFT materials. In this study, the tensile properties of direct-compounded, compression-moulded glass/PA6 with 30% and 45% fibre content and carbon fibre-reinforced thermoplastic (LFT-D) materials were investigated, along with shear properties for glass fibre-reinforced LFTs. Additionally, the tensile and shear properties of glass/PA6 in four different material directions of 0°, 45°, −45°, and 90° were also examined. The results of this study revealed that carbon/PA66(40%) exhibited 67% and 45% higher tensile strength compared to glass/PA6(30%) and glass/PA6(45%), respectively. The behaviour of the glass/PA6 material shifted from brittle to ductile under tension and shear loads when exposed to moisture, regardless of the percentage of fibre content. Notably, the tensile toughness of the glass/PA6 material exhibited a significant increase of up to 230% in specific material configurations from dried to undried samples. The findings of this study will assist in the selection of the optimal LFT material for use in desired loading and environmental conditions and can serve as input for the numerical modelling of these composite materials.
Temperature-Dependent Vibration of Various Types of Sandwich Beams with Porous FGM Layers
Mohsen Rahmani, Sajjad Dehghanpour
International Journal of Structural Stability and Dynamics, 2021
By using a high order sandwich beams theory which is modified by considering the transverse flexibility of the core, free vibration characteristics of two models of sandwich beams are studied in this paper. In type-I, functionally graded layers coat a homogeneous core, and in type-II, an FG core is covered by homogeneous face sheets. To increase the accuracy of the model of the FGM properties, even and uneven porosity distributions are applied, and all materials are considered temperature-dependent. Nonlinear Lagrange strain and thermal stresses of the face sheets and in-plane strain of the core are considered. To obtain the governing equations of motion, Hamilton’s principle is used and a Galerkin method is used to solve them for simply supported and clamped boundary conditions. To verify the results of this study, they are compared with the results of literatures. Also, the effect of variation of temperature, some geometrical parameters and porosities on the frequency are studied.
Stress concentration around of pin-loaded hole in unidirectional multi-layered metallic matrix composite material
Sajjad Dehghanpour, Keivan Hosseini Safari, Farzan Barati, Mohammadmahdi Attar
Journal of Mechanical Science and Technology, 2019
The objective of this study is to examine the stress concentration factor around a pin-loaded hole in a metallic matrix composite material, analytically and numerically. It is assumed that all unidirectional fibers lie in the metallic matrix while the shear stress in fibers is discarded. To generally derive the equilibrium equation for all fibers and the metallic matrix, the previous shear-lag theory had been improved and the extension in the metallic matrix was considered. Afterwards, the equilibrium equation was solved by the eigenvalue method while the displacement field and stress distribution around the pin-loaded hole were computed. Having calculated stress concentration factors and the displacement field in a unidirectional multi-layered composite material, we compared the analytical results with those numerical values from other references. Additionally, the effect of the pin’s diameter, as well as the edge-hole distance on maximum stress concentration factor was investigated. To recapitulate, it is seen that the modified shear-lag theory can simulate the mechanism of the load transfer between metallic matrices.
Experimental and Numerical Study of Lateral Collapse of Square and Rectangular Composite Tubes
Proceedings of the World Congress on Mechanical Chemical and Material Engineering, 2015
Experimental and numerical study of lateral collapse of square and rectangular composite tubes
Proceedings of the World Congress on Mechanical Chemical and Material Engineering, 2015
Experimental and numerical study of the energy absorbed with various thickness of thin rectangular and square sections
Sajjad Dehghanpour, Sobhan Dehghanpour
Applied Mechanics and Materials, 2012
Impact is one of very important subjects which always have been considered in mechanical science. Nature of impact is such that which makes its control a hard task. Therefore it is required to present the transfer of impact to other vulnerable part of a structure, when it is necessary, one of the best method of absorbing energy of impact , is by using Thin-walled tubes these tubes collapses under impact and with absorption of energy, it prevents the damage to other parts. Purpose of recent study is to survey the deformation and energy absorption of tubes with different type of cross section (rectangular or square) and with similar volumes, height, mean cross section, and material under loading. Lateral loading of tubes are quasi-static type and beside as numerical analysis, also experimental experiences has been performed to evaluate the accuracy of the results. Results from the surveys is indicates that in a same conditions which mentioned above, samples with square cross section ,absorb more energy compare to rectangular cross section, and also by increscent in thickness, energy absorption would be more.

RECENT SCHOLAR PUBLICATIONS

Comparative analysis of energy absorption capacity of single and nested metal matrix composite tubes under quasi-static lateral and axial loading
S Dehghanpour, SK HOSSEINI, F Barati, MM Attar
JOURNAL OF SOLID MECHANICS 13 (2), 134-143 , 2021
2021
Citations: 4
Experimental and numerical investigation on geometric parameters of aluminum patches for repairing cracked parts by diffusion method
S Dehghanpour, AR Nezamabadi, MM Attar, F Barati, M Tajdari
JOURNAL OF SOLID MECHANICS 13 (1), 54-67 , 2021
2021
Citations: 4
Repairing cracked aluminum plates by aluminum patch using diffusion method
S Dehghanpour, A Nezamabadi, M Attar, F Barati, M Tajdari
Journal of Mechanical Science and Technology 33 (10), 4735-4743 , 2019
2019
Citations: 8
Experimental and Numerical Study of the Energy Absorbed with Various Thickness of Thin Rectangular and Square Sections
S Dehghanpour, S Dehghanpour
Applied Mechanics and Materials 229, 1120-1124 , 2012
2012

MOST CITED SCHOLAR PUBLICATIONS

Repairing cracked aluminum plates by aluminum patch using diffusion method
S Dehghanpour, A Nezamabadi, M Attar, F Barati, M Tajdari
Journal of Mechanical Science and Technology 33 (10), 4735-4743 , 2019
2019
Citations: 8
Comparative analysis of energy absorption capacity of single and nested metal matrix composite tubes under quasi-static lateral and axial loading
S Dehghanpour, SK HOSSEINI, F Barati, MM Attar
JOURNAL OF SOLID MECHANICS 13 (2), 134-143 , 2021
2021
Citations: 4
Experimental and numerical investigation on geometric parameters of aluminum patches for repairing cracked parts by diffusion method
S Dehghanpour, AR Nezamabadi, MM Attar, F Barati, M Tajdari
JOURNAL OF SOLID MECHANICS 13 (1), 54-67 , 2021
2021
Citations: 4
Experimental and Numerical Study of the Energy Absorbed with Various Thickness of Thin Rectangular and Square Sections
S Dehghanpour, S Dehghanpour
Applied Mechanics and Materials 229, 1120-1124 , 2012
2012