Pub Date : 2025-10-01DOI: 10.1016/j.dt.2025.06.014
Mingjun Li , Yi Jiang , Miao Chen , Siyi Wang , Lina Yang , Bo Pang
Multi-axle heavy-duty vehicles (MHVs) are essential for military equipment transport due to their safety and stability. However, braking dynamic responses between MHVs and pavement systems still remain underexplored, particularly regarding their complex load transfer mechanisms. This paper develops an enhanced model of a multi-axle heavy-duty vehicle (MHV) coupled with the uneven and flexible pavement. An advanced coupling iterative method is proposed to solve the highly dimensional equations of the MHV-pavement coupled system. The proposed method was validated through experimental tests, with characteristic parameters of vertical accelerations showing relative errors between 0.42% and 11.80%. The coupling effect and influence mechanism of the braking process are investigated by characteristic parameters of the dynamic responses. Additionally, the influences of braking conditions and pavement parameters are analyzed in time and frequency domains in order to reveal the vibration mechanisms of the coupled system. Moreover, this study establishes a theoretical foundation for monitoring pavement health via vehicle-mounted acceleration signals, which is necessary in military transportation.
{"title":"Effects of braking conditions on the dynamic responses of multi-axle heavy-duty vehicles coupled with pavement roughness and flexibility","authors":"Mingjun Li , Yi Jiang , Miao Chen , Siyi Wang , Lina Yang , Bo Pang","doi":"10.1016/j.dt.2025.06.014","DOIUrl":"10.1016/j.dt.2025.06.014","url":null,"abstract":"<div><div>Multi-axle heavy-duty vehicles (MHVs) are essential for military equipment transport due to their safety and stability. However, braking dynamic responses between MHVs and pavement systems still remain underexplored, particularly regarding their complex load transfer mechanisms. This paper develops an enhanced model of a multi-axle heavy-duty vehicle (MHV) coupled with the uneven and flexible pavement. An advanced coupling iterative method is proposed to solve the highly dimensional equations of the MHV-pavement coupled system. The proposed method was validated through experimental tests, with characteristic parameters of vertical accelerations showing relative errors between 0.42% and 11.80%. The coupling effect and influence mechanism of the braking process are investigated by characteristic parameters of the dynamic responses. Additionally, the influences of braking conditions and pavement parameters are analyzed in time and frequency domains in order to reveal the vibration mechanisms of the coupled system. Moreover, this study establishes a theoretical foundation for monitoring pavement health via vehicle-mounted acceleration signals, which is necessary in military transportation.</div></div>","PeriodicalId":58209,"journal":{"name":"Defence Technology(防务技术)","volume":"52 ","pages":"Pages 274-294"},"PeriodicalIF":5.9,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145278364","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-01DOI: 10.1016/j.dt.2025.06.013
Liangliang Shen , Shi Su , Wenhui Zhang , Shilun Shi , Xigao Jian , Tianqi Zhu , Jian Xu
Poly (phthalazinone ether sulfone ketone) (PPESK) is a new-generation high-performance thermoplastic resin that exhibits excellent thermal stability and mechanical properties. However, its damage and failure mechanisms under high-temperature and high-strain-rate coupling conditions remain unclear, significantly limiting the engineering applications of PPESK-based composites in extreme environments such as aerospace. To address this issue, in this study, a temperature-controlled split Hopkinson pressure bar experimental platform was developed for dynamic tensile/compressive loading scenarios. Combined with scanning electron microscopy and molecular dynamics simulations, the thermomechanical behavior and failure mechanisms of PPESK were systematically investigated over the temperature range of 293–473 K. The study revealed a novel "dynamic hysteresis brittle behavior" and its underlying "segmental activation–response lag antagonistic mechanism". The results showed that the strain-rate-induced response lag of polymer chain segments significantly weakened the viscous dissipation capacity activated by thermal energy at elevated temperatures. Although high-strain-rate conditions led to notable enhancement in the dynamic strength of the material (with an increase of 8%–233%, reaching 130%–330% at elevated temperatures), the fracture surface morphology tended to become smoother, and brittle fracture characteristics became more pronounced. Based on these findings, a temperature–strain rate hysteresis antagonistic function was constructed, which effectively captured the competitive relationship between temperature-driven relaxation behavior and strain-rate-induced hysteresis in thermoplastic resins. A multiscale damage evolution constitutive model with temperature–rate coupling was subsequently established and numerically implemented via the VUMAT user subroutine. This study not only unveils the nonlinear damage mechanisms of PPESK under combined service temperatures and dynamic/static loading conditions, but also provides a strong theoretical foundation and engineering guidance for the constitutive modeling and parametric design of thermoplastic resin-based materials.
{"title":"Dynamic hysteresis brittle behavior and temperature–strain rate-coupled damage modeling: A multiscale study of poly(phthalazinone ether sulfone ketone) under extreme service conditions","authors":"Liangliang Shen , Shi Su , Wenhui Zhang , Shilun Shi , Xigao Jian , Tianqi Zhu , Jian Xu","doi":"10.1016/j.dt.2025.06.013","DOIUrl":"10.1016/j.dt.2025.06.013","url":null,"abstract":"<div><div>Poly (phthalazinone ether sulfone ketone) (PPESK) is a new-generation high-performance thermoplastic resin that exhibits excellent thermal stability and mechanical properties. However, its damage and failure mechanisms under high-temperature and high-strain-rate coupling conditions remain unclear, significantly limiting the engineering applications of PPESK-based composites in extreme environments such as aerospace. To address this issue, in this study, a temperature-controlled split Hopkinson pressure bar experimental platform was developed for dynamic tensile/compressive loading scenarios. Combined with scanning electron microscopy and molecular dynamics simulations, the thermomechanical behavior and failure mechanisms of PPESK were systematically investigated over the temperature range of 293–473 K. The study revealed a novel \"dynamic hysteresis brittle behavior\" and its underlying \"segmental activation–response lag antagonistic mechanism\". The results showed that the strain-rate-induced response lag of polymer chain segments significantly weakened the viscous dissipation capacity activated by thermal energy at elevated temperatures. Although high-strain-rate conditions led to notable enhancement in the dynamic strength of the material (with an increase of 8%–233%, reaching 130%–330% at elevated temperatures), the fracture surface morphology tended to become smoother, and brittle fracture characteristics became more pronounced. Based on these findings, a temperature–strain rate hysteresis antagonistic function was constructed, which effectively captured the competitive relationship between temperature-driven relaxation behavior and strain-rate-induced hysteresis in thermoplastic resins. A multiscale damage evolution constitutive model with temperature–rate coupling was subsequently established and numerically implemented via the VUMAT user subroutine. This study not only unveils the nonlinear damage mechanisms of PPESK under combined service temperatures and dynamic/static loading conditions, but also provides a strong theoretical foundation and engineering guidance for the constitutive modeling and parametric design of thermoplastic resin-based materials.</div></div>","PeriodicalId":58209,"journal":{"name":"Defence Technology(防务技术)","volume":"52 ","pages":"Pages 259-273"},"PeriodicalIF":5.9,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145278365","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-01DOI: 10.1016/j.dt.2025.06.008
Zhe Zhang , Zhuowei Sun , Haoming Zou , Xijuan Lv , Ziyang Guo , Shuai Zhao , Qinghai Shu
3-Nitro-1,2,4-triazol-5-one (NTO) is a typical high-energy, low-sensitivity explosive, and accurate concentration monitoring is critical for crystallization process control. In this study, a high-precision quantitative analytical model for NTO concentration in ethanol solutions was developed by integrating real-time ATR-FTIR spectroscopy with chemometric and machine learning techniques. Dynamic spectral data were obtained by designing multi-concentration gradient heating-cooling cycle experiments, abnormal samples were eliminated using the isolation forest algorithm, and the effects of various preprocessing methods on model performance were systematically evaluated. The results show that partial least squares regression (PLSR) exhibits superior generalization ability compared to other models. Vibrational bands corresponding to C=O and –NO2 were identified as key predictors for concentration estimation. This work provides an efficient and reliable solution for real-time concentration monitoring during NTO crystallization and holds significant potential for process analytical applications in energetic material manufacturing.
{"title":"High-precision quantitative analysis of 3-nitro-1,2,4-triazol-5-one (NTO) concentration based on ATR-FTIR spectroscopy and machine learning","authors":"Zhe Zhang , Zhuowei Sun , Haoming Zou , Xijuan Lv , Ziyang Guo , Shuai Zhao , Qinghai Shu","doi":"10.1016/j.dt.2025.06.008","DOIUrl":"10.1016/j.dt.2025.06.008","url":null,"abstract":"<div><div>3-Nitro-1,2,4-triazol-5-one (NTO) is a typical high-energy, low-sensitivity explosive, and accurate concentration monitoring is critical for crystallization process control. In this study, a high-precision quantitative analytical model for NTO concentration in ethanol solutions was developed by integrating real-time ATR-FTIR spectroscopy with chemometric and machine learning techniques. Dynamic spectral data were obtained by designing multi-concentration gradient heating-cooling cycle experiments, abnormal samples were eliminated using the isolation forest algorithm, and the effects of various preprocessing methods on model performance were systematically evaluated. The results show that partial least squares regression (PLSR) exhibits superior generalization ability compared to other models. Vibrational bands corresponding to C=O and –NO<sub>2</sub> were identified as key predictors for concentration estimation. This work provides an efficient and reliable solution for real-time concentration monitoring during NTO crystallization and holds significant potential for process analytical applications in energetic material manufacturing.</div></div>","PeriodicalId":58209,"journal":{"name":"Defence Technology(防务技术)","volume":"52 ","pages":"Pages 131-141"},"PeriodicalIF":5.9,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145278356","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-01DOI: 10.1016/j.dt.2025.06.007
RuiJun Fan , XiaoFeng Wang , ShaoHong Wang , JinYing Wang , He Huang , AiGuo Pi
Low collateral damage weapons achieve controlled personnel injury through the coupling of shock waves and particle swarms, where the particle swarms arise from the high-explosive dispersion of compacted metal particle ring. To investigate the dynamic response of the human target under combined shock waves and particle swarms loading, a physical human surrogate torso model (HSTM) was developed, and the dynamic response test experiment was conducted under the combined loading. The effects of particle size on the loading parameters, the damage patterns of the ballistic plate and HSTM, and the dynamic response parameters of the HSTM with and without protection are mainly analyzed. Our findings revealed that particle swarms can effectively delay the shock wave attenuation, especially the best effect when the particle size was 0.28–0.45 mm. The ballistic plate mainly exhibited dense perforation of the outer fabric and impacted crater damage of ceramic plates, whereas the unprotected HSTM was mainly dominated by high-density and small-size ballistic cavity group damage. The peak values of the dynamic response parameters for the HSTM under combined loading were significantly larger than those under bare charge loading, with multiple peaks observed. Under unprotected conditions, the peak acceleration of skeletons and peak pressure of organs increased with the particle size. Under protected conditions, the particle size, the number of particles hit, and the fit of the ballistic plate to the HSTM together affected the dynamic response parameters of the HSTM.
{"title":"Experimental study on the dynamic response of HSTM under combined shock waves and sub-millimeter particle swarms loading","authors":"RuiJun Fan , XiaoFeng Wang , ShaoHong Wang , JinYing Wang , He Huang , AiGuo Pi","doi":"10.1016/j.dt.2025.06.007","DOIUrl":"10.1016/j.dt.2025.06.007","url":null,"abstract":"<div><div>Low collateral damage weapons achieve controlled personnel injury through the coupling of shock waves and particle swarms, where the particle swarms arise from the high-explosive dispersion of compacted metal particle ring. To investigate the dynamic response of the human target under combined shock waves and particle swarms loading, a physical human surrogate torso model (HSTM) was developed, and the dynamic response test experiment was conducted under the combined loading. The effects of particle size on the loading parameters, the damage patterns of the ballistic plate and HSTM, and the dynamic response parameters of the HSTM with and without protection are mainly analyzed. Our findings revealed that particle swarms can effectively delay the shock wave attenuation, especially the best effect when the particle size was 0.28–0.45 mm. The ballistic plate mainly exhibited dense perforation of the outer fabric and impacted crater damage of ceramic plates, whereas the unprotected HSTM was mainly dominated by high-density and small-size ballistic cavity group damage. The peak values of the dynamic response parameters for the HSTM under combined loading were significantly larger than those under bare charge loading, with multiple peaks observed. Under unprotected conditions, the peak acceleration of skeletons and peak pressure of organs increased with the particle size. Under protected conditions, the particle size, the number of particles hit, and the fit of the ballistic plate to the HSTM together affected the dynamic response parameters of the HSTM.</div></div>","PeriodicalId":58209,"journal":{"name":"Defence Technology(防务技术)","volume":"52 ","pages":"Pages 230-248"},"PeriodicalIF":5.9,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145278362","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-01DOI: 10.1016/j.dt.2025.06.012
Yinan Lyu , Xiaoxia Ma , Xiaoting Ren , Shuping Sun , Lin Shi , Li Yang
Ammonium dinitramide (ADN), as a high-energy oxidizer widely applied in the field of rocket and missile propellants, has a prominent issue of high hygroscopicity due to its strong polarity. The previous coating encapsulation methods have struggled to address the problems of uneven coating and polarity mismatch. This research innovatively introduces perfluorooctanoic acid (PFOA) as a polar transition intermediate layer. Utilizing the polarity of one end of it to adsorb on the surface of ADN through hydrogen bonds, the problem of polarity mismatch is effectively overcome. Meanwhile, the vibrational magnetron sputtering process has been first applied in the energetic field, with a special vibrating abutment enhancing ADN particle fluidity to solve coating non-uniformity, thus preparing prilled ADN@PFOA@PTFE core-dual-shell composites. Performance tests reveal that this composite material possesses excellent hydrophobic and anti-hygroscopic properties. When left at 25 °C and 75% RH for 3 days, moisture absorption was reduced by more than 90% compared to pure ADN. Simultaneously, its thermal stability, heat release performance, and combustion performance have been improved. The research achievements optimize the storage conditions of ADN in the application of rocket and missile propellants, providing solid support and broad development prospects for technological innovation in military fields.
{"title":"Innovative surface modification strategy for ADN: PFOA-interlayered and vibrational magnetron sputtering for constructing anti-hygroscopic composite structures","authors":"Yinan Lyu , Xiaoxia Ma , Xiaoting Ren , Shuping Sun , Lin Shi , Li Yang","doi":"10.1016/j.dt.2025.06.012","DOIUrl":"10.1016/j.dt.2025.06.012","url":null,"abstract":"<div><div>Ammonium dinitramide (ADN), as a high-energy oxidizer widely applied in the field of rocket and missile propellants, has a prominent issue of high hygroscopicity due to its strong polarity. The previous coating encapsulation methods have struggled to address the problems of uneven coating and polarity mismatch. This research innovatively introduces perfluorooctanoic acid (PFOA) as a polar transition intermediate layer. Utilizing the polarity of one end of it to adsorb on the surface of ADN through hydrogen bonds, the problem of polarity mismatch is effectively overcome. Meanwhile, the vibrational magnetron sputtering process has been first applied in the energetic field, with a special vibrating abutment enhancing ADN particle fluidity to solve coating non-uniformity, thus preparing prilled ADN@PFOA@PTFE core-dual-shell composites. Performance tests reveal that this composite material possesses excellent hydrophobic and anti-hygroscopic properties. When left at 25 °C and 75% RH for 3 days, moisture absorption was reduced by more than 90% compared to pure ADN. Simultaneously, its thermal stability, heat release performance, and combustion performance have been improved. The research achievements optimize the storage conditions of ADN in the application of rocket and missile propellants, providing solid support and broad development prospects for technological innovation in military fields.</div></div>","PeriodicalId":58209,"journal":{"name":"Defence Technology(防务技术)","volume":"52 ","pages":"Pages 295-305"},"PeriodicalIF":5.9,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145277813","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-01DOI: 10.1016/j.dt.2025.06.015
Mengli Yin, Haoyang Guo, Erhai An, Kangjie Xie, Zijia Wang, Tengyue Song, Xiong Cao
RDX/Al mixtures are widely utilized in energetic materials, yet their hybrid dust generated during production and application poses potential explosion hazards. Moreover, the synergistic explosion mechanisms remain poorly understood, particularly at varying dust concentrations. This study systematically investigates the effects of different aluminum powder mass percentages and dust concentrations (300 g/m3, 600 g/m3, 900 g/m3) on RDX dust explosion severity, flame propagation behavior, and gaseous products. The results indicate that the maximum explosion pressure peaks at 35% RDX, 65% RDX, and 80% RDX at 300 g/m3, 600 g/m3, and 900 g/m3, respectively. Concurrently, the time for the flame to propagate to the wall (t1) reaches minimum values of 34.8 ms, 25.66 ms, and 23.93 ms. The maximum rate of pressure rise is observed for pure RDX at 900 g/m3. Aluminum powder enhances flame propagation velocity and combustion duration, as validated by the flame propagation system. Overall, the concentrations of carbon oxides (CO+CO2) decrease significantly with increasing aluminum mass percentage. At 20% RDX, the concentrations decreased by 51.64%, 72.31%, and 79.55% compared to pure RDX at 300 g/m3, 600 g/m3, and 900 g/m3, respectively. Notably, N2O concentration only at 300 g/m3 showed such a trend. It rises first and then falls at 35% RDX at 600 g/m3 and 900 g/m3. These findings elucidate the synergistic explosion mechanisms and provide critical guidelines for safe production and handling.
{"title":"Proportional effects of RDX/Al mixtures on dust explosion characteristics, flame behavior, and explosion mechanism","authors":"Mengli Yin, Haoyang Guo, Erhai An, Kangjie Xie, Zijia Wang, Tengyue Song, Xiong Cao","doi":"10.1016/j.dt.2025.06.015","DOIUrl":"10.1016/j.dt.2025.06.015","url":null,"abstract":"<div><div>RDX/Al mixtures are widely utilized in energetic materials, yet their hybrid dust generated during production and application poses potential explosion hazards. Moreover, the synergistic explosion mechanisms remain poorly understood, particularly at varying dust concentrations. This study systematically investigates the effects of different aluminum powder mass percentages and dust concentrations (300 g/m<sup>3</sup>, 600 g/m<sup>3</sup>, 900 g/m<sup>3</sup>) on RDX dust explosion severity, flame propagation behavior, and gaseous products. The results indicate that the maximum explosion pressure peaks at 35% RDX, 65% RDX, and 80% RDX at 300 g/m<sup>3</sup>, 600 g/m<sup>3</sup>, and 900 g/m<sup>3</sup>, respectively. Concurrently, the time for the flame to propagate to the wall (<em>t</em><sub>1</sub>) reaches minimum values of 34.8 ms, 25.66 ms, and 23.93 ms. The maximum rate of pressure rise is observed for pure RDX at 900 g/m<sup>3</sup>. Aluminum powder enhances flame propagation velocity and combustion duration, as validated by the flame propagation system. Overall, the concentrations of carbon oxides (CO+CO<sub>2</sub>) decrease significantly with increasing aluminum mass percentage. At 20% RDX, the concentrations decreased by 51.64%, 72.31%, and 79.55% compared to pure RDX at 300 g/m<sup>3</sup>, 600 g/m<sup>3</sup>, and 900 g/m<sup>3</sup>, respectively. Notably, N<sub>2</sub>O concentration only at 300 g/m<sup>3</sup> showed such a trend. It rises first and then falls at 35% RDX at 600 g/m<sup>3</sup> and 900 g/m<sup>3</sup>. These findings elucidate the synergistic explosion mechanisms and provide critical guidelines for safe production and handling.</div></div>","PeriodicalId":58209,"journal":{"name":"Defence Technology(防务技术)","volume":"52 ","pages":"Pages 71-83"},"PeriodicalIF":5.9,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145277879","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-01DOI: 10.1016/j.dt.2025.06.016
Jie Fu , Qiang Liu , Xiao Liu , Yanqin Zhang
The electric vertical takeoff and landing (eVTOL) aircraft shows great potential for rapid military personnel deployment on the battlefield. However, its susceptibility to control loss, complex crashes, and extremely limited bottom energy-absorbing space demands higher comprehensive crashworthiness of its subfloor thin-walled structures. This study investigated the energy absorption capacity of novel concave polygonal carbon fiber reinforced plastics (CFRP) tubes under multi-angle collisions. Quasi-static compression experiments and finite element simulations were conducted to assess the failure mode and energy absorption. The influences of cross-section shapes, loading conditions, and geometry parameters on crashworthiness metrics were further analyzed. The results revealed that, under the similar weight, concave polygonal tubes exhibited superior energy absorption under axial loads compared to regular polygonal and circular tubes, attributed to the increased number of axial splits. However, both regular and concave polygonal tubes, particularly the latter, demonstrated reduced oblique energy absorption compared to traditional square tubes with the increasing ratio of SEA value decreased from 20%−16%. Notably, this reduction in energy absorption can be compensated for by the implementation of inward and outward crusher plugs, and with them, the concave polygonal tubes demonstrated outstanding overall crashworthiness performance under multiple loading conditions. This concave cross-sectional design methods could serve as a guidance for the development of the eVTOL subfloor.
{"title":"Crashworthiness design of concave polygonal CFRP tubes for eVTOL applications under multi-angle compression loading","authors":"Jie Fu , Qiang Liu , Xiao Liu , Yanqin Zhang","doi":"10.1016/j.dt.2025.06.016","DOIUrl":"10.1016/j.dt.2025.06.016","url":null,"abstract":"<div><div>The electric vertical takeoff and landing (eVTOL) aircraft shows great potential for rapid military personnel deployment on the battlefield. However, its susceptibility to control loss, complex crashes, and extremely limited bottom energy-absorbing space demands higher comprehensive crashworthiness of its subfloor thin-walled structures. This study investigated the energy absorption capacity of novel concave polygonal carbon fiber reinforced plastics (CFRP) tubes under multi-angle collisions. Quasi-static compression experiments and finite element simulations were conducted to assess the failure mode and energy absorption. The influences of cross-section shapes, loading conditions, and geometry parameters on crashworthiness metrics were further analyzed. The results revealed that, under the similar weight, concave polygonal tubes exhibited superior energy absorption under axial loads compared to regular polygonal and circular tubes, attributed to the increased number of axial splits. However, both regular and concave polygonal tubes, particularly the latter, demonstrated reduced oblique energy absorption compared to traditional square tubes with the increasing ratio of SEA value decreased from 20%−16%. Notably, this reduction in energy absorption can be compensated for by the implementation of inward and outward crusher plugs, and with them, the concave polygonal tubes demonstrated outstanding overall crashworthiness performance under multiple loading conditions. This concave cross-sectional design methods could serve as a guidance for the development of the eVTOL subfloor.</div></div>","PeriodicalId":58209,"journal":{"name":"Defence Technology(防务技术)","volume":"52 ","pages":"Pages 100-115"},"PeriodicalIF":5.9,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145278355","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Accurate characterization of three-dimensional burning crack propagation remains pivotal yet challenging for energetic material safety, as conventional diagnostics and models inadequately resolve coupled crack-pressure dynamics in confined explosives. This study combines a novel spherical confinement system (with/without sapphire windows) with synchronized high-speed imaging and 3D reconstruction to overcome optical limitations in opaque explosives. Experimental analysis of centrally ignited HMX-based PBX-1 reveals: (1) burning cracks propagate radially with equatorial acceleration and polar deceleration, (2) systematic formation of 3–4 dominant crack branches across geometries, and (3) pressure evolution exhibiting gradual accumulation (subsurface cracking) followed by exponential growth (surface burn-through), with decay governed by cavity expansion. Building on Hill's framework, we develop a model incorporating cavity volume and fracture toughness criteria, validated against PBX explosive (95% HMX-based) experiments. The model demonstrates improved prediction of pressure trends compared to prior approaches, particularly in resolving laminar-phase accumulation and crack-induced surge transitions. Results establish structural cavity volume as a critical modulator of measured pressure and reveal direction-dependent crack kinematics as fundamental features of constrained combustion. This work provides experimentally validated insights into mechanisms of reaction pressure development and burning cracks pathways during constrained PBX explosive combustion.
{"title":"Three-dimensional burning crack dynamics in constrained spherical explosive: visualization analysis and cavity-coupled pressure modeling","authors":"Chuanyu Pan, Tao Li, Hua Fu, Hailin Shang, Pingchao Hu, Ping Li, Xilong Huang","doi":"10.1016/j.dt.2025.06.011","DOIUrl":"10.1016/j.dt.2025.06.011","url":null,"abstract":"<div><div>Accurate characterization of three-dimensional burning crack propagation remains pivotal yet challenging for energetic material safety, as conventional diagnostics and models inadequately resolve coupled crack-pressure dynamics in confined explosives. This study combines a novel spherical confinement system (with/without sapphire windows) with synchronized high-speed imaging and 3D reconstruction to overcome optical limitations in opaque explosives. Experimental analysis of centrally ignited HMX-based PBX-1 reveals: (1) burning cracks propagate radially with equatorial acceleration and polar deceleration, (2) systematic formation of 3–4 dominant crack branches across geometries, and (3) pressure evolution exhibiting gradual accumulation (subsurface cracking) followed by exponential growth (surface burn-through), with decay governed by cavity expansion. Building on Hill's framework, we develop a model incorporating cavity volume and fracture toughness criteria, validated against PBX explosive (95% HMX-based) experiments. The model demonstrates improved prediction of pressure trends compared to prior approaches, particularly in resolving laminar-phase accumulation and crack-induced surge transitions. Results establish structural cavity volume as a critical modulator of measured pressure and reveal direction-dependent crack kinematics as fundamental features of constrained combustion. This work provides experimentally validated insights into mechanisms of reaction pressure development and burning cracks pathways during constrained PBX explosive combustion.</div></div>","PeriodicalId":58209,"journal":{"name":"Defence Technology(防务技术)","volume":"52 ","pages":"Pages 306-318"},"PeriodicalIF":5.9,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145277814","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-01DOI: 10.1016/j.dt.2025.03.022
Abbas Abbaspour, Behnoud Ganjavi, Mahdi Nematzadeh
Many researchers have focused on the behavior of fiber-reinforced concrete (FRC) in the construction of various defensive structures to resist against impact forces resulting from explosions and projectiles. However, the lack of sufficient research regarding the resistance of functionally graded fiber-reinforced concrete against projectile impacts has resulted in a limited understanding of the performance of this concrete type, which is necessary for the design and construction of structures requiring great resistance against external threats. Here, the performance of functionally graded fiber-reinforced concrete against projectile impacts was investigated experimentally using a (two-stage light) gas gun and a drop weight testing machine. For this objective, 12 mix designs, with which 35 cylindrical specimens and 30 slab specimens were made, were prepared, and the main variables were the magnetite aggregate vol% (55%) replacing natural coarse aggregate, steel fiber vol%, and steel fiber type (3D and 5D). The fibers were added at six vol% of 0%, 0.5%, 0.75%, 1%, 1.25%, and 1.5% in 10 specimen series (three identical specimens per each series) with dimensions of 40 × 40 × 7.5 cm and functional grading (three layers), and the manufactured specimens were subjected to the drop weight impact and projectile penetration tests by the drop weight testing machine and gas gun, respectively, to assess their performance. Parameters under study included the compressive strength, destruction level, and penetration depth. The experimental results demonstrate that using the magnetite aggregate instead of the natural coarse aggregate elevated the compressive strength of the concrete by 61%. In the tests by the drop weight machine, it was observed that by increasing the total vol% of the fibers, especially by increasing the fiber content in the outer layers (impact surface), the cracking resistance and energy absorption increased by around 100%. Note that the fiber geometry had little effect on the energy absorption in the drop weight test. Investigating the optimum specimens showed that using 3D steel fibers at a total fiber content of 1 vol%, consisting of a layered grading of 1.5 vol%, 0 vol%, and 1.5 vol%, improved the penetration depth by 76% and lowered the destruction level by 85%. In addition, incorporating the 5D steel fibers at a total fiber content of 1 vol%, consisting of the layered fiber contents of 1.5%, 0%, and 1.5%, improved the projectile penetration depth by 50% and lowered the damage level by 61% compared with the case of using the 3D fibers.
{"title":"Projectile impact and drop weight resistance of functionally graded fiber-reinforced magnetite aggregate concrete","authors":"Abbas Abbaspour, Behnoud Ganjavi, Mahdi Nematzadeh","doi":"10.1016/j.dt.2025.03.022","DOIUrl":"10.1016/j.dt.2025.03.022","url":null,"abstract":"<div><div>Many researchers have focused on the behavior of fiber-reinforced concrete (FRC) in the construction of various defensive structures to resist against impact forces resulting from explosions and projectiles. However, the lack of sufficient research regarding the resistance of functionally graded fiber-reinforced concrete against projectile impacts has resulted in a limited understanding of the performance of this concrete type, which is necessary for the design and construction of structures requiring great resistance against external threats. Here, the performance of functionally graded fiber-reinforced concrete against projectile impacts was investigated experimentally using a (two-stage light) gas gun and a drop weight testing machine. For this objective, 12 mix designs, with which 35 cylindrical specimens and 30 slab specimens were made, were prepared, and the main variables were the magnetite aggregate vol% (55%) replacing natural coarse aggregate, steel fiber vol%, and steel fiber type (3D and 5D). The fibers were added at six vol% of 0%, 0.5%, 0.75%, 1%, 1.25%, and 1.5% in 10 specimen series (three identical specimens per each series) with dimensions of 40 × 40 × 7.5 cm and functional grading (three layers), and the manufactured specimens were subjected to the drop weight impact and projectile penetration tests by the drop weight testing machine and gas gun, respectively, to assess their performance. Parameters under study included the compressive strength, destruction level, and penetration depth. The experimental results demonstrate that using the magnetite aggregate instead of the natural coarse aggregate elevated the compressive strength of the concrete by 61%. In the tests by the drop weight machine, it was observed that by increasing the total vol% of the fibers, especially by increasing the fiber content in the outer layers (impact surface), the cracking resistance and energy absorption increased by around 100%. Note that the fiber geometry had little effect on the energy absorption in the drop weight test. Investigating the optimum specimens showed that using 3D steel fibers at a total fiber content of 1 vol%, consisting of a layered grading of 1.5 vol%, 0 vol%, and 1.5 vol%, improved the penetration depth by 76% and lowered the destruction level by 85%. In addition, incorporating the 5D steel fibers at a total fiber content of 1 vol%, consisting of the layered fiber contents of 1.5%, 0%, and 1.5%, improved the projectile penetration depth by 50% and lowered the damage level by 61% compared with the case of using the 3D fibers.</div></div>","PeriodicalId":58209,"journal":{"name":"Defence Technology(防务技术)","volume":"52 ","pages":"Pages 1-23"},"PeriodicalIF":5.9,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145277874","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-01DOI: 10.1016/j.dt.2025.06.017
Yi Ren , Yu Nie , Bowen Xue , Yucheng Zhao , Lulu Liu , Chao Lou , Yongxun Li , Wei Chen
The unit cell configuration of lattice structures critically influences their load-bearing and energy absorption performance. In this study, three novel lattice structures were developed by modifying the conventional FBCCZ unit cell through reversing, combining, and turning strategies. The designed lattices were fabricated via laser powder bed fusion (LPBF) using Ti-6Al-4V powder, and the mechanical properties, energy absorption capacity, and deformation behaviors were systematically investigated through quasi-static compression tests and finite element simulations. The results demonstrate that the three modified lattices exhibit superior performance over the conventional FBCCZ structure in terms of fracture strain, specific yield strength, specific ultimate strength, specific energy absorption, and energy absorption efficiency, thereby validating the efficacy of unit cell modifications in enhancing lattice performance. Notably, the CFBCCZ and TFBCCZ lattices significantly outperform both the FBCCZ and RFBCCZ lattice structures in load-bearing and energy absorption. While TFBCCZ shows marginally higher specific elastic modulus and energy absorption efficiency than CFBCCZ, the latter achieves superior energy absorption due to its highest ultimate strength and densification strain. Finite element simulations further reveal that the modified lattices, through optimized redistribution and adjustment of internal nodes and struts, effectively alleviate stress concentration during loading. This structural modification enhances the structural integrity and deformation stability under external loads, enabling a synergistic enhancement of load-bearing capacity and energy absorption performance.
{"title":"Synergistic enhancement of load-bearing and energy-absorbing performance in additively manufactured lattice structures through modifications to conventional unit cells","authors":"Yi Ren , Yu Nie , Bowen Xue , Yucheng Zhao , Lulu Liu , Chao Lou , Yongxun Li , Wei Chen","doi":"10.1016/j.dt.2025.06.017","DOIUrl":"10.1016/j.dt.2025.06.017","url":null,"abstract":"<div><div>The unit cell configuration of lattice structures critically influences their load-bearing and energy absorption performance. In this study, three novel lattice structures were developed by modifying the conventional FBCCZ unit cell through reversing, combining, and turning strategies. The designed lattices were fabricated via laser powder bed fusion (LPBF) using Ti-6Al-4V powder, and the mechanical properties, energy absorption capacity, and deformation behaviors were systematically investigated through quasi-static compression tests and finite element simulations. The results demonstrate that the three modified lattices exhibit superior performance over the conventional FBCCZ structure in terms of fracture strain, specific yield strength, specific ultimate strength, specific energy absorption, and energy absorption efficiency, thereby validating the efficacy of unit cell modifications in enhancing lattice performance. Notably, the CFBCCZ and TFBCCZ lattices significantly outperform both the FBCCZ and RFBCCZ lattice structures in load-bearing and energy absorption. While TFBCCZ shows marginally higher specific elastic modulus and energy absorption efficiency than CFBCCZ, the latter achieves superior energy absorption due to its highest ultimate strength and densification strain. Finite element simulations further reveal that the modified lattices, through optimized redistribution and adjustment of internal nodes and struts, effectively alleviate stress concentration during loading. This structural modification enhances the structural integrity and deformation stability under external loads, enabling a synergistic enhancement of load-bearing capacity and energy absorption performance.</div></div>","PeriodicalId":58209,"journal":{"name":"Defence Technology(防务技术)","volume":"52 ","pages":"Pages 116-130"},"PeriodicalIF":5.9,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145278359","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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