Energy Absorption Of Composites Research Articles

A machine learning-enabled prediction of damage properties for fiber-reinforced polymer composites under out-of-plane loading

For understanding the damage morphology in fiber-reinforced plastics under out-of-plane loading, engineers/ and designers mostly rely on experimental investigations and numerical models, which could be costly in terms of resources and computational requirements. Thus, pragmatic predictive approaches that can offer ready-to-use tools for material optimization have gained traction in recent years. This paper proposes a machine learning model, developed with the use of previous experiments, to predict the damage behaviour of E-glass fiber-reinforced plastics in sandwich structures and laminates. The focus is on quasi-static indentation with different indenter geometries, using acoustic signals for damage monitoring. A total of 10 optimal-performing regression algorithms were employed to develop the prediction models. The developed models based on total energy gave acceptable results for all specimens (R-squared value: 0.9932 – 0.9999), while prediction models using force produced less accurate results (R-squared value: 0.8693) for a sandwich structure subjected to a conical indenter. Results showed that energy absorption of composites provided the most reliable data for the development of predictive models. The load profiles could also be used when the contact area is limited (e.g., for hemispherical and conical indenters). The best-performing model for higher surface areas of the indenter increased was k-NN, thanks to its ability to capture complex and nonlinear relationships between the input features and the target variable. Overall, the developed model could provide more autonomy and control for the material optimisation of composite structures for industrial applications with reduced time and cost constraints.

Quasi-static crush response of lightweight sandwich composite tubes fabricated via newly designed internal thermal expansion technique

Different from conventional unidirectional outward-inward forming methods, this study employs a multidirectional internal expansion shaping approach to fabricate lightweight sandwich composite tubes. Integrating carbon fiber reinforced polymer (CFRP), thermal expansion foam and polymethacrylimide (PMI) foam, the sandwich composite tubes demonstrate adaptability in terms of material properties as validated through several experimental trials. The one-step molding process eliminates the requirements for subsequent structural assembly and bonding, while ensuring adhesion between diverse material components. The sandwich composite tubes exhibit superior impact resistance, showcasing a stable progressive crushing failure. The energy absorption mechanism shifts from single CFRP damage to a multi-material composite energy absorption mode. The specific energy absorption (SEA) value of designed sandwich composite tube is up to 102 J/g. The sandwich composite tubes fabricated in this study hold promising applications in advanced vehicle/aerospace lightweighting and crashworthiness safety.

A novel systematic approach for robust numerical simulation of carbon fiber-reinforced plastic circular tubes: Utilizing machine-learning techniques for calibration and validation

Developing a reliable and robust finite element model of a carbon fiber-reinforced plastic (CFRP) composite structure is investigated by using the LS-DYNA solver and Python. This study tries to provide a systematic numerical approach to cover the principal impediment to adaptation of composite energy absorbers, that is the lack of a reliable predictive method. The proposed procedure aims to further the understanding of advanced composite structures’ behavior during the crash phenomenon by developing an accurate finite element model. To do so, the mechanical properties of the material were extracted from American Society for Testing and Materials (ASTM) standard test methods, followed by experimental investigation of circular CFRP tubes undergoing quasi-static loading. A numerical simulation framework was then utilized to scrutinize the effectiveness of simulation parameters on the crushing mechanism. Finally, a systematic approach based on machine learning techniques was performed to adjust non-physical modeling parameters for further calibration and validation. In this regard, a versatile Python code was developed to automate pre-processing, processing, and post-processing steps. The code also provides a groundwork to perform machine learning techniques. Interestingly, the numerical and experimental results were highly correlated with a correlation coefficient of almost 90%. Additionally, several non-physical numerical parameters were found to be inactive, while some else were identified as effective parameters, and their corresponding effectiveness was quantitatively extracted and discussed for the first time in the literature.

Impact response of composite energy absorbers based on foam-filled metallic and polymeric auxetic frames

In this paper, an innovative concept is proposed, based on the hexachiral auxetic frames filled with foams with enhanced energy absorption capabilities. Numerical assessments of the composite foam-filled auxetic absorbers, of pure foam blocks and unfilled auxetic frames for metallic and polymeric material combinations were accomplished considering a case of localized impact. The energy absorbed by the composite absorbers are found superior to the sum of the energies absorbed by constituent elements tested separately with clear advantages also at the level of the specific energy absorbed per unit mass. The interactions between the two constituents are analyzed and discussed. An experiment considering a 3D-printed polymeric hexachiral frame filled with open-cell soft polyurethane foam under localized impact is conducted to validate the numerical approach. Eventually, a parametric sensitivity study is conducted numerically to illustrate the effects of geometrical parameters on the energy absorption capacity. Overall, the results confirm the potential and the great design flexibility of the concept, provides the guidelines to design advanced energy absorbing system, underlies the importance of the combination between the frame and foam properties and the effect of the main geometrical parameters on the performance.

Influence of polyurea on dynamic response behaviors of cylindrical composite shells under internal explosion load

The dynamic responses of open-ended cylindrical shells with different polyurea layers under explosion load are studied in the current paper. The influences of polyurea thickness and position on the response characteristics of the composite shell are analyzed in detailed. The results indicate that the polyurea layer has significant influence the failure mode and energy absorption of the composite shell. Both polyurea in the interlayer and on the outer layer will decrease the bending moments of the composite shells of equal mass in the initial deformation process, which is easier to make the increase of the deformation heights of metal liner of composite shells with polyurea layers. The polyurea in the interlayer will weaken the constraint of metal liner, delay the fracture of fiber and restrain the bulking phenomenon of metal liner. With increase of polyurea thickness, the bulking phenomenon becomes less obvious and the deformation height of liner decreases non-monotonously. On the contrary, the outer layer polyurea will cause the bulking phenomenon of metal liner more obviously with increase of the polyurea thickness.But the outerlayer polyurea will restrict the deformation of the inner materials and limit the scattering of fiber fragment, improving the safety distance of the explosion vessel. In the whole process of anti-explosion, both polyurea in interlayer and outer layer absorb less than 10% of total energy, but they can significantly change the energy absorption of metal liner and fiber composite.

Mechanical enhancement of aluminum foam via in situ interfacial bonding

Aluminum foam (AF) has extensive application prospects due to its high specific strength and specific energy absorption. However, low compressive strength and plateau stress of AF limit their total energy absorption. This study introduces a combined way of melt foaming and infiltration casting for fabricating bi-continuous interpenetrating porous composites (BIPCs), which formed partial metallurgical bonding interfaces while ensuring three-dimensional mechanical bond constraints. Four types of three-dimensional structures were designed to reinforce AF. Mechanical behavior of AF and the composites under quasi-static compression was analyzed by combining compressive tests and the finite element method (FEM). The results showed that all reinforcements can efficiently improve the energy absorption of composites by preventing the expansion of cracks in aluminum foam. The structure reinforced along the body diagonal and the path of the center lines connecting the three pairs of parallel surfaces of the cube exhibited the best mechanical properties, whose energy absorption, specific energy absorption and specific compressive strength were 9.58, 3.48 and 2.89 times greater than those of AF, respectively. The critical stress of the rods to buckling and stretching failure of the four configurations were calculated. Results showed that large critical stresses tended to appear in the 1/4 and 1/2 round rods, which revealed that the fracture failure easily occurred at the intersection edges of plane surface and curved surface of struts.

Nanocoatings for ballistic applications: A review

Abstract The manufacturing of ballistic impact-resistant (BIR) body armours has evolved over the years with the aim of reducing their weight and enhancing their energy-absorbing capacity upon ballistic impacts. The incorporation of nanoparticles into advanced BIR body armour systems is considered one of the promising techniques. The methods employed in incorporating various nanoparticles in the manufacturing of textile-based body armour systems face a research gap in the optimisation of the associated parameters. This article discusses the mechanism involved in the energy absorption of composites and nanocomposites upon ballistic impact. The current review article highlights the chemical, physical, and mechanical properties of various nanoparticles incorporated into BIR body armour systems. BIR nanocomposites consisting of carbon nanotubes, graphene nanoplatelets, nano-silica, nanoclays, nano-alumina, etc., have been discussed herein. In addition, the significance of various techniques for the dispersion of these nanoparticles was also highlighted. Various methods, such as sol–gel, PVD, CVD, thermal spray, and electroless methods for coating the nanoparticles on the surface of the fibre/fabric were also discussed.

Ballistic Performance, Thermal and Chemical Characterization of Ubim Fiber (Geonoma baculifera) Reinforced Epoxy Matrix Composites.

The search for unexplored natural materials as an alternative to synthetic components has driven the development of novel polymeric composites reinforced with environmentally-friendly materials. Natural lignocellulosic fibers (NLFs) have been highlighted as potential reinforcement in composite materials for engineering applications. In this work, a less known Amazonian fiber, the ubim fiber (Geonoma baculifera), is investigated as a possible reinforcement in epoxy composites and was, for the first time, thermally characterized by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Additionally, its chemical structure was elucidated by Fourier transform infrared spectroscopy (FTIR). Ballistic tests were also performed against the threat of a 7.62 mm high-speed lead projectile. The results were statistically analyzed by the Weibull statistical analysis method. FTIR analysis showed the functional groups normally found for NLFs highly rich in cellulose, hemicellulose, and lignin. The TGA/DTG results showed the onset of thermal degradation for the composites (325~335 °C), which represents better thermal stability than isolated ubim fiber (259 °C), but slightly lower than that of pure epoxy (352 °C). The DSC results of the composites indicate endothermic peaks between 54 and 56 °C, and for the ubim fibers, at 71 °C. Ballistic tests revealed higher energy absorption in composites with lower fiber content due to the more intense action of the brittle fracture mechanisms of the epoxy resin, which tended to dissipate more energy. These failure mechanisms revealed the presence of river marks, cracks, and broken fibers with a detachment interface. These results may contribute to the production of ubim fiber-reinforced composites in engineering applications, such as ballistic armors.

Quasi-static compressive behaviour of epoxy composites reinforced with crumb rubber

Quasi static compressive response of crumb rubber-epoxy composites was examined by varying the crumb rubber composition (0, 10, 20 and 30 vol.%). All the composites, irrespective of the strain rates, depict elastic regions tailed by a wide plateau area that is credited with the densification of rubber particulates. Higher strains to failure of composites were revealed as compared with neat epoxy signifying higher energy absorption ability of constituents. The modulus of elasticity of composites was noted to be lower than neat epoxy specimens, irrespective of the strain rates. Irrespective of strain rates, the strength of all the composites were inferior to neat epoxy specimens. Energy absorption of EC-30 was higher compared to EC-20 and EC-10 and noted to be increased in the range of 6–14% for 0.1 mm/min strain rate while it increases in the range of 5–9% for 0.01 mm/min strain rate, respectively. Rubber-toughening mechanism was credited with the increase in energy absorption of composites. Higher energy absorption of composites was mainly due to higher strain realisation indicating more deformation ability. Fracture features of specimens were analysed by scanning electron microscope.

Mechanical properties of shear thickening fluid filled warp-knitted spacer fabrics

This paper reports the compressive behavior and low-velocity impact behavior of warp-knitted spacer fabrics (WKSFs) filled with shear thickening fluid (STF) when subjected to quasi-static compression and low-velocity impact loadings, respectively. In the steady rheological test, the STF experiences a shear thickening transition at a critical shear rate. Besides, the critical shear rate decreases with the increase of silica mass fraction. The compression curves of WKSFs filled with STF composites were consistent with those of WKSFs, including initial, elastic and compaction stage. As the compression speed increases, the overall compression load values of WKSF and WKSFs filled with STF composite increase. Moreover, the compression load of composite increases with the increase of silica mass fraction. Compared with WKSFs, WKSFs filled with STF composite composites need more work to deform under the same strain. The impact result reveals that STF-filled WKSF would absorb more energy and keep the peak load at a lower level than WKSF under the same impact loadings. In a certain range, the energy absorption of composites becomes more excellent with the increasing silica mass fraction. However, over a certain range, the energy absorption of the composite decreases with the increase of the mass fraction of silica. It was concluded that the STF-filled WKSF composite could be expected as a damping or energy-absorptive material for human body protection.

Implementation of Cement-based nano composite Energy Absorption Damper to improve the damping properties of concrete and monitoring applications

The energy from the moving seismic waves through a building structure is dispersed by means of dampers. Dampers work by converting the kinetic energy into heat energy, dissipating it into the hydraulic fluid. Damper systems are designed and manufactured to protect structural integrity, reduce structural damage, and prevent injury to people by absorbing energy from earthquakes and minimizing structural deformations. The most effective way to achieve good vibration damping is by tailoring the construction materials such as cement with nanomaterials like Silica, Alumina, Graphene, CNTs, etc. This paper focuses on developing a vibration damper, prepared by cement nanocomposite containing MWCNTs and Carbon fibers. The tests, such as the Impact, Flexural, and Compressive strength tests, are conducted to investigate their energy-absorbing capacity, strength, and durability. The microstructural analysis SEM is performed to know the morphology of concrete mix with MWCNTs and Carbon fibers on damping mechanism. Impact test results indicate that the beams without MWCNTs and CFs exhibited an average energy absorption of 248 J, while those with MWCNTs and CFs absorbed an average energy of 262 J which shows almost 15% more energy absorption. Adding nanomaterials in a cement matrix improves concrete’s frictional damping energy consumption ability and increases structures’ energy-absorbing properties, flexural strength, and compressive strength.

Crashworthiness characteristics of composite cylindrical energy absorbers filled with honeycomb and foam under quasi-static load: experimental and analytical study

Crashworthiness characteristics of composite cylindrical energy absorbers filled with honeycomb and foam under quasi-static load: experimental and analytical study

Mechanical properties of carbon fibre reinforced composites modified with star-shaped butyl methacrylate

This article presents the possibility of strength improvement and energy absorption of carbon fibre reinforced polymer composites by matrix modification. In this study, the mechanical properties of bisphenol-A epoxy matrix and carbon fibre reinforced polymer composites were modified with four different wt.% of star-shaped polymer n-butyl methacrylate (P n-BMA) block glycidyl methacrylate (PGMA). The tensile strength of the epoxy with 1 wt.% star-shaped polymer showed 128% increase in comparison to unmodified epoxy samples. Two different wt.% were then used for the modification of carbon fibre-reinforced polymer composite samples. Tensile tests and low-velocity impact tests were conducted for characterising modified samples. Tensile test results performed showed a slight improvement in the tensile strength and modulus of the composite. Low-velocity impact tests showed that addition of 1 wt.% star-shaped polymer additives increase composite energy absorption by 53.85%, compared to pure epoxy composite specimens. Scanning electron microscopy (SEM) analysis of post-impact specimens displays fracture modes and bonding between the matrix and fibre in the composites. These results demonstrate the potential of a novel star-shaped polymer as an additive material for automotive composite parts, where energy absorption is significant.

Study on the Thermal and Impact Resistance Properties of Micro PA66/PU Synergistically Reinforced Multi-Layered Biaxial Weft Knitted Fabric Composites

Abstract In this paper, the influence of micro PA66/PU in multi-layered biaxial weft knitted (MBWK) fabric reinforced composites on thermal and impact resistance was studied. The main objective was to investigate the role of micro PA66/PU in terms of improving material performance. The results showed that the addition of micro PA66/PU improved the thermal stability of the MBWK composite. It is observed that the onset degradation temperatures increased by 1.6°C in thermo-gravimetric analysis (TGA) test and the Tg increased by 2.8°C in the dynamic mechanical analysis (DMA) test. Besides, the impact energy absorption of composites increased by 5.3% after the addition of micro PA66/PU. The addition of micro PA66/PU effectively reduced the impact damage area from the failure morphology after impact. In simple words, the addition of micro PA66/PU effectively improves the comprehensive properties of composites.

Mechanical and thermal properties of glass/epoxy composites filled with silica aerogels

ABSTRACT This paper investigates the effect of silica aerogels on mechanical (flexural and impact), non-destructive and thermal properties of glass/epoxy composites. Silica aerogels were mixed with epoxy at various volume fractions (1% and 3%) and infused with glass fabrics to produce composite laminates. Flexural tests indicated that the addition of aerogels increased the flexural strength of composites at the warp direction. Low impact energy (10–30 J) test results exhibited that impact force and energy absorption of composites were slightly increased . Higher energy (100 J) caused more severe damages and the effect of aerogels was more obvious. The thermogravimetric analysis revealed that addition of aerogels increased the thermostability. Generally, addition 1% of aerogel provides more improvement on mechanical properties and thermal stability compared to addition 3%. Although there is not a linear relationship between aerogel content and thermal conductivity, samples with 3% aerogel exhibited lower thermal conductivity values than other samples.

Crashworthiness performance of green composite energy absorbing structure with embedded sensing device providing cleaner environment for sustainable maintenance

In this study, bio-degradable green composite energy absorbing structure with embedded self–sensing device is proposed as a viable alternative to the conventional synthetic ones without sensing device. The goal of the study is to introduce the promising potentials of integrating a low-cost self sensing device into green composite energy absorbing structure so as to achieve green high performance capabilities. At first, a comparative analysis of the mechanical strength of green composites and their synthetic counterparts is given according to results obtained from previous works. It is shown that by mixing appropriate amount of reinforcing agents with green composites, the mechanical strength is improved significantly and the reinforced green composite material can, therefore, be used to fabricate highly efficient energy absorbers for crashworthiness application. In the latter part of the study, a self–sensing device, made from carbon nanotubes, collects information and tracks the performance of the green energy absorbing structure as well as its extent to environmental friendliness, is proposed. Finally, the synergistic role of the green composite energy absorber with the embedded self–sensing device is presented. The result of the proposed structure promises higher green performance capabilities over their conventional natural and synthetic counterparts without sensing device. It is found that the overall green performance capabilities resulted in increased crashworthiness performance, improved fuel economy, better environmental friendliness, efficient sustainable maintenance and the enhancement of human lives.

Preparation of auxetic warp-knitted spacer fabric impregnated with shear thickening fluid for low-velocity impact resistance

This paper reports the preparation of auxetic warp-knitted spacer fabric impregnated with shear thickening fluid and studied its impact behavior under low-velocity impact loading. The shear thickening fluids have been prepared by mechanically dispersing 12 nm silica particles with weight fraction of 10, 15, 20, and 25% in various carriers (PEG200, PEG400, and PEG600). Rheological results indicate that shear thickening fluid experiences shear thickening transition at a specific shear rate. The critical shear rate reduces, and initial viscosity and maximum viscosity increase with the increase of silica weight fraction. The higher molecular weight of polyethylene glycols can lead to lower critical shear rate. The impact process of composite under impact loading can be divided into three stages. The warp-knitted spacer fabric with different negative Poisson’s ratio has a significant effect on the impact behavior. The warp-knitted spacer fabric with better auxetic performance endows composite better impact resistance, the specific performance is the deformation depth, and energy absorption and peak load increase with the increase of auxetic effect of fabric. The silica weight fraction of shear thickening fluid can increase the energy absorption of composite due to the shear thickening transition of shear thickening fluid. Shear thickening fluid has a synergistic effect with the auxetic warp-knitted spacer fabric on impact resistance of composite. The various carriers have no obvious influence on the overall energy absorption and impact load of composites.

Experimental investigation of impact loading effects on rectangular flat panels of fiber self-compacting cementations composite with expanded steel sheet

Impact loadings essentially differ from static loadings due to a huge amount of the force applied to milliseconds under these loadings. Energy absorption of composites is proper criteria to examine the function against impact loading. Energy absorbers are widely used in the industry. At the same time, due to their unique properties, the use of strong self-compacting composites has been considered by the researchers. High tensile, compressive, and flexural strengths have made these concrete composites more eminent. In a comprehensive experimental work, using four basic mix designs, 64 rectangular composite panels were made with 100 mm2 of area and 30, 45, 60, and 75 mm thickness and tested by impact loading. Compressive, tensile, and flexural strength tests were performed on all the four max designs. Steel fibers with percentages of 0, 0.25, 0.5, and 0.75 with 25 m of length were used to make the concrete composites. A hammer with 180 kg weight and 7500 J power was used as the impact loading with drop hammer test machine (DH-TM). The specimens were dynamically loaded by drop test from a 60 cm height. The use of steel fibers and expanded sheets in combination with each other significantly increases the energy absorption. Moreover, the initial peak force increases, while crushing length and deformation of the specimens reduce.

Development of composite double-hat energy absorber device subjected to traverser loads

This paper introduces a new carbon fiber reinforced plastic (CFRP) structural system in the field of crashworthiness. CFRP hat-shaped and angle-shaped stiffeners were used to develop a double-hat collapsible energy absorption system. Three different design alternatives were investigated. The first alternative is an open-cell design (OC) consisting of two flipped hat stiffeners with four right angles on the edges. The second alternative is a one-in-cell double-hat design (1C), consisting of OC design with additional one inside small hat stiffeners edged with angles. The third alternative is a two-in-cell double-hat design (2C), consisting of OC design with additional two inside small hat stiffeners edged with angles. Three modes of failure were observed, classified as local buckling (mode I), top wall bending (mode II), and brittle collapse that resulted from Euler buckling (mode III). The crashworthiness characteristics were evaluated for the three designs. The 2C double-hat design showed the highest peak load and specific energy absorption (SEA). Accordingly, the core of the 2C design was filled with foam to increase the energy absorption capability and enhance the structure’s stability. Results showed that the SEA of the 2C+ foam design was increased by more than 50% compared to the coreless 2C double-hat design.

Pre-stressed thin tubular composite energy absorbers for improved impact energy absorption

The study proposes pre-stressing techniques as applied to CFRP based composite thin-walled tubes with the intent of increasing energy absorption capacity. The energy computations for the tube with and without pre-stressing are compared using finite element based methodology. The study reveals that the use of pre-stressing in the form of applied internal pressure for the tube induces forces in the direction opposite to that of impact which needs to be overcome when the actual impact happens. The study also demonstrates that the strain energy required for initiating the damage in the thin-walled tubes increases appreciably under the influence of pre-stress.