Epoxy Composites Research Articles

Towards fiber-reinforced front-sheets for lightweight PV modules in VIPV

Novel approaches in the field of photovoltaics, such as building or vehicle integration require investigations of lightweight PV module concepts [1]. This research proposes and evaluates a lightweight PV module concept using glass fiber-reinforced polymers (GFRP) based on epoxy composites within the module stack. The usage of GFRP as front material as proposed in this work, reduces weight by 44–74 % compared to conventional glass-back sheet modules. We show results that with the proposed module stack hail impact resistant module can be built with small and large size avoiding any cell cracks after impact. Additionally, modules with GFRP front layer withstand thermal cycling tests with low power losses ranging from −0.9 % to −1.1 % at Pmpp depending on the individual GFRP layer. We also show results of cut susceptibility tests with an increased performance compared to modules with a polymeric front layer. Development topics remain as shown by damp-heat and UV irradiation testing, were an optimization of the module stack still needs to be performed.

Enhancing epoxy composite materials through lime‐treated sugarcane bagasse and glass fiber reinforcement: Morphological, mechanical, and flame‐retardant insights

AbstractThis study investigates the utilization of sugarcane bagasse and glass fiber to reinforce epoxy composites, enhancing both mechanical and fire resistance properties. Initially, bagasse is collected, sun‐dried, and finely ground before being treated with lime water at concentrations of 3%, 5%, and 7% by weight. The treated bagasse is then mixed with epoxy resin and a hardening agent, followed by a curing process. For samples incorporating glass fibers, the fibers are manually integrated and cured similarly. The methodology involved detailed preparation of the bagasse, its treatment, and subsequent integration with epoxy resin. The mixture was processed under controlled conditions to ensure uniformity and quality. Mechanical properties such as tensile strength, flexural strength, compressive strength, and impact resistance were measured. Thermogravimetric analysis (TGA) was employed to assess thermal stability, while fire resistance was evaluated using the limiting oxygen index (LOI) and the 94‐V test method. Results demonstrated significant improvements in both mechanical and thermal properties with the addition of bagasse and glass fibers. The optimal treatment was identified at a 5% lime water concentration, yielding a tensile strength of 295.08 MPa, flexural strength of 371.24 MPa, compressive strength of 255.39 MPa, and Izod impact strength of 157.04 kJ/m2. TGA results showed the highest thermal stability at 5% concentration, with decomposition temperatures peaking at 402.52 °C. Fire resistance was markedly enhanced, achieving an LOI of 29.8% and meeting V2 level standards according to the 94‐V test method. In conclusion, treating sugarcane bagasse with a 5% lime water solution significantly enhances the mechanical and fire‐resistant properties of epoxy composites. The combination of sugarcane bagasse and glass fiber creates a robust material with high thermal stability and fire resistance, making it a viable option for applications requiring these enhanced properties.

Investigating the solid particle erosion behavior of H3BO3 / B2O3 / SiO2 / Al2O3 reinforced glass fibre/epoxy composites and parametric evaluation using artificial intelligence

In this experimental study, the erosion wear behavior of glass fibre-reinforced (GF) composite materials was examined according to ASTM G76–95. Pure/GF reinforced epoxy composite (EP) materials were chosen as the main test sample. Boric Acid (H3BO3), Borax (B2O3), Silicon Dioxide (SiO2), and Aluminium Oxide (Al2O3) were added to the resin as reinforcement at a rate of 15% by weight. The erosion wear rate was investigated with various impingement angles (30°, 60°, and 90°), impact velocities (≈23, 34, and 53 m/s), alumina abrasive particle sizes (≈200 and 400 μm), and fibre directions (0° and 45°). Neural network models were employed effectively to predict the influence of the reinforcements on erosive wear rate. The erosive wear rate indicated that Al2O3 added GF/EP exhibited the most anti-erosive characteristics followed by silicon dioxide GF/EP and pure GF/EP however, the anti-erosive nature of GF/EP deteriorated with the addition of Borax and Boric Acid.

Epoxy resin reinforced with carbonized chicken feathers: An innovative composite material with sustainable potentials

This article explores a novel method for enhancing the mechanical properties of epoxy resin composites by incorporating carbonized chicken feathers as a filler material. The fabrication process involves carbonizing chicken feathers at 600°C and incorporating 5-10 wt% of the fillers into an epoxy matrix. The composites showed enhanced mechanical properties and samples containing 10 wt% filler exhibit the best properties. The performance corresponds to 49% increase in tensile strength, 16% rise in Young’s modulus, 40% improvement in flexural modulus, and 57% in flexural strength. X-ray diffraction and scanning electron microscopy with energy dispersive spectroscopy were employed to characterize the filler. This characterization provides valuable insights into the structure and chemical composition of the pulverized carbonized chicken feathers that contributed to the attained improvement in composites’ properties. Microstructural examination of the developed composite under scanning electron microscope also provides insights into matrix-filler interface and dispersion of the fillers within the composite matrix. The study not only highlights the unique combination of carbonized feathers’ inherent strength and compatibility with the epoxy matrix but also underscores the eco-friendly nature of utilizing agricultural waste. The findings suggest promising applications in industries demanding lightweight, high-strength materials, which can contribute to sustainable engineering solutions.

In situ growth of silver nanoparticles on carbon fiber by plasma–liquid interaction to improve performance of epoxy composites

Grafting nanomaterials on the carbon fiber (CF) surface is considered an effective strategy for enhancing the interfacial properties of CF-reinforced polymer composites (CFRPs). However, the mechanical properties of the CFs are often compromised during treatment. A new method for in situ growing silver nanoparticles (AgNPs) on the CF surface is proposed in this study. The CFs are first immersed in a low-viscosity silver nitrate solution to form a thin liquid film on the surface. Subsequently, using the abundant active particles in the plasma, the silver ions are reduced to silver atoms and grown into AgNPs on the CF surface. The tensile strength of CF@Ag was 38.74% greater than that of untreated CF, potentially due to the reparative action of AgNPs on defects in CF. The CF showed an evident improvement in surface wettability because of the AgNPs. Furthermore, the interfacial properties were noticeably improved, with the interfacial shear strength of CF@Ag increasing to 91.59 MPa, which was about twice that of pristine CF. Thus, the mechanical properties of composites are significantly improved (flexural strength increased by 190.74%). This study presents a non-destructive and convenient method for growing nanoparticles onto CF to establish a robust interface in CFRPs.

Viscoelastic Performance of Bagasse/Glass Fiber Hybrid Epoxy Composites: Effects of Fiber Hybridization on Storage Modulus, Loss Modulus, and Damping Behavior

Abstract This study aimed to investigate the viscoelastic properties of bagasse/glass fiber multilayered hybrid reinforced epoxy composites, focusing on how fiber hybridization affects dynamic mechanical performance. Epoxy composites with various layering sequences, including all-glass (AG), all-bagasse (AB), bagasse-glass-bagasse (BGB), and glass-bagasse-glass (GBG), were fabricated and analyzed using dynamic mechanical analysis (DMA) to measure storage modulus (E'), loss modulus (E''), and damping factor (tan δ). The results showed that hybrid composites (GBG and BGB) experienced a decrease in storage modulus by approximately 25% compared to AG, indicating enhanced polymer molecular chain mobility and improved interfacial adhesion between bagasse fibers and the epoxy matrix. The glass transition temperature (Tg) was slightly lower in hybrid composites, with GBG at 61 °C and BGB at 60 °C, compared to 62 °C for AG. In terms of energy dissipation, AG exhibited the highest loss modulus peak at 62 °C, while AB showed the lowest with a Tg at 53 °C. The damping factor analysis revealed that AB had the highest damping peak (tan δ = 0.9) at 61 °C, although this occurred at a lower temperature than the AG composite (tan δ = 0.7 at 76 °C). These findings suggest that bagasse and glass fiber hybrid composites offer tailored viscoelastic properties, making them suitable for applications in automotive components, aerospace structures, and sports equipment.

Thermal Treatment Effects on Structure and Mechanical Properties of Polybutylene Terephthalate and Epoxy Resin Composites Reinforced with Glass Fiber.

In this study, two types of composites, polybutylene terephthalate (PBT) and epoxy resin (ER), reinforced with 20% of glass fiber (GF) are used as the comparative research objects. Their mechanical properties after thermal aging at 85~145 °C are evaluated by tensile strength and fracture morphology analysis. The results show that the composites have similar aging laws. The tensile strength of GF/PBT and GF/ER decrease gradually with the increase of aging temperature, while their elastic moduli are independent of the thermal treatment temperature. Scanning electron microscopy study of the fracture surface shows that separation of glass fiber from PBT and ER matrix becomes more obvious at higher aging temperature. The fibers on the matrix surface appear clear and smooth, and the whole pulled out GFs can be observed. As a main mechanical strength degradation mechanism, the deterioration of interface adhesion between the matrix and GF is discussed. A large difference in coefficients of thermal expansion of the matrix and GF is a main factor of the mechanical degradation.

Hybridization of thermoplastic/glass fiber reinforced epoxy composites for lightweight structures

Understanding how different hybrid composite designs under flexural, interlaminar shear and fracture is the objective of this study. The hybrid composite was manufactured utilizing the hand-layup process to produce three different laminate arrangements beside the neat composite. The effects of PC integration and position through the hybrid composites were evaluated, and an analysis of the damage mechanisms was performed. The results demonstrated that incorporating the PC sheet resulted in an improvement in overall performance. Additionally, delamination was determined to be the most prevalent type of failure, followed by fiber and matrix breakage and plastic deformation of PC sheet.

An experimental investigation into crashworthiness of filament wound intra-yarn hybrid glass/jute epoxy composites tubes under quasi-static axial and lateral compression

The increasing demand for sustainable materials in the automotive industry has driven the research towards exploration of natural fiber composites for crash structures. This study investigates the quasi-static axial and lateral crushing behavior of hybrid glass/jute fiber epoxy tubes. Intra-yarn hybrid mixing ratios of jute and glass fibers were tested to evaluate the feasibility of using natural fibers as eco-friendly alternatives to traditional synthetic composites. A total of five different configurations were fabricated using filament winding process. The experimental results were analyzed for collapsing behavior, failure modes, and energy absorption characteristics. The hybrid epoxy tubes revealed fiber-matrix fracturing, local buckling, and delamination as three primary failure modes under crushing tests. The hybrid configuration with 25 % jute fiber and 75 % glass fiber demonstrated optimal crashworthiness performance, achieving the highest specific energy absorption (SEA) values of 15.85 J/g under axial loading and 2.96 J/g under lateral loading. The configurations with higher jute content of 50 % and 75 %, showed decreasing SEA and crush force efficiency (CFE) values, with brittle fracturing and delamination as dominant failure modes, indicating a trade-off between weight and energy absorption efficiency. The neat glass fiber configuration maintained nearly consistent CFE values of 0.55 and 0.56, between axial and lateral loadings respectively, demonstrating isotropic behavior in energy absorption. Conversely, the neat jute fiber configuration improved SEA to 12.14 J/g under axial loading but exhibited significant limitations under lateral loading, with SEA decreasing to 0.69 J/g. Visual examination of crushed samples highlighted local buckling in GF configurations and brittle fracturing in hybrid and neat jute fiber configurations. The scanning electron microscope (SEM) analysis provided detailed insights into the microstructural characteristics and failure mechanisms, highlighting the inter-laminar debonding between the jute and glass fibers in hybrid configuration. By evaluating the combined effects of hybridization and loading conditions, the present study contributes to developing eco-friendly and efficient materials for automotive safety, aligning with industry sustainability goals.

Single-layer encapsulation film with CaO absorbent by solution process

A method for preparing a single-layer encapsulation film using an organic-inorganic hybrid precursor solution processing was investigated. The film was created using a commodity epoxy and graphene oxide to ensure cost-effectiveness. Fast curing and annealing techniques, including microwave and intense pulsed light exposure, were employed. Calcium oxide nanoparticles were incorporated as a special moisture absorbent to improve the film's barrier properties. The barrier performance of the single layer encapsulation film was considerably enhanced by post-treatment of these nanoparticles. The characterization of the calcium oxide nanoparticles after post-treatment was performed using transmission electron microscopy with energy-dispersive X-ray spectroscopy, FT-IR, Brunauer-Emmett-Teller test. The composite epoxy encapsulation film, incorporating graphene oxide and post-treated calcium oxide nanoparticles, reduced water permeability approximately 400 times compared to the neat epoxy encapsulation film. This substantial improvement makes it suitable for use in flexible disposable electronics. The enhanced water vapor blocking efficiency is attributed to the combined effect of pathway block by graphene oxide and moisture absorption by calcium oxide.

A phosphorus/fluorine‐containing block copolymer endows epoxy with multifunctionality

AbstractIn order to achieve flame retardant, hydrophobic, and toughened epoxy resins, phosphorus/fluorine‐containing block copolymer (FBCP) was synthesized by reversible addition‐fragmentation chain transfer polymerization, and then the as‐synthesized PMADOPO‐b‐PHFBA block copolymer was used as additive to modify the epoxy resin, accompanying with a random copolymer (FRCP) serving as control group. It showed that due to the regular arrangement of molecular chains, FBPC formed a fibrous‐like structure at the fracture interface of epoxy/PMADOPO‐b‐PHFBA (EP/FBCP) samples, effectively enhancing the toughness of epoxy composite materials. The fracture energy of EP90/FBCP‐10 was higher than that of EP90/FRCP‐10 and was about twice than that of pure EP. The addition of 3 wt% FBCP could enhance the limited oxygen index (LOI) of EP97/FBCP‐3 to 33.2% and reached a V‐1 UL‐94 rating. As the addition of FBCP increased, the LOI gradually increased. When the addition of FBCP was 10%, the LOI and UL‐94 of EP90/FBCP‐10 was 38.2% and V‐0 grade, respectively. Meanwhile, the presence of fluorine element effectively reduced the surface energy of the composite EP material. Compared with pure EP, the water contact angle of EP90/FBCP‐10 was about 101° with an increasing of 20.8%. Furthermore, the flame‐retardant mechanism of EP/FBCP epoxy composites was discussed.

Characterization, impact and wear properties of treated and as-received graphene nanosheets reinforcement in epoxy resin composites

PurposeThis study aims to explore the enhancement of mechanical properties in epoxy resin composites through the incorporation of graphene nanoparticles, focusing on their impact and wear resistance. It investigates the role of graphene, both treated and untreated, as a reinforcing agent in composites, highlighting the significance of nanoparticle dispersion and surfactant treatment in optimizing mechanical performance.Design/methodology/approachEmploying a novel dispersion technique using a drawing brush, this research contrasts with traditional methods by examining the effects of graphene nanoparticle concentrations treated with surfactants – Polyvinylpyrrolidone (PVP) and Sulphonated Naphthalene Formaldehyde (SNF) – on the mechanical properties of epoxy resin composites. The methodology includes conducting a series of impact and wear tests to assess the influence of graphene reinforcement on the composites' performance.FindingsThe findings reveal a marked enhancement in the composites impact resistance and energy absorption capabilities, which escalate with an increase in graphene content. Additionally, the study demonstrates a significant improvement in wear resistance, attributed to the superior mechanical properties, robust interface adhesion and effective dispersion of graphene. The use of surfactants for graphene treatment is identified as a crucial factor in these advancements, offering profound insights into the development of advanced composite materials for diverse industrial uses.Originality/valueThis study introduces a unique dispersion technique for graphene in epoxy composites, setting it apart from conventional methods. By focusing on the critical role of surfactant treatment in enhancing the mechanical properties of graphene-reinforced composites, it provides a novel insight into the optimization of impact and wear resistance.

Analyzing the impact of TiO2 filler on the wear characteristics of flax fiber-reinforced epoxy composite using the Taguchi approach

Purpose This study aims to investigate the impact of titanium oxide (TiO2) filler on the coefficient of friction (COF) and specific wear rate (SWR) in flax fiber reinforced epoxy composites (FFRCs) under abrasive wear conditions utilizing the Taguchi approach. The primary objective is to enhance wear resistance and promote the development of sustainable materials for various applications. Design/methodology/approach Epoxy/flax composites with varying TiO2 filler content (0–8 wt%) are fabricated through the hand layup method. Subsequently, wear testing is conducted following ASTM G99-05 standards. The Taguchi design of experiments (DOE) and analysis of variance (ANOVA) are utilized for statistical analysis. Findings Results indicate a significant improvement in abrasive wear properties with the incorporation of TiO2 filler. The COF is found to be most influenced by the normal load (55.19%), followed by grit size, wt% TiO2 filler and sliding distance. SWR is found to be most influenced by the grit size (42.92%), followed by wt% TiO2, normal load and sliding distance. Notably, the Taguchi model aligns well with experimental results, demonstrating its efficacy in predicting the abrasive wear behavior of FFRCs. Originality/value This research introduces a novel hybrid composite that combines TiO2 filler and flax fibers, showcasing their potential to enhance the tribological properties of epoxy composites. The study offers valuable insights into optimizing abrasive wear test variables in natural fiber-reinforced composites using Taguchi DOE and ANOVA, crucial for improving the performance of sustainable materials in engineering applications.

Combustion synthesis of tunable‐aspect‐ratio β‐Si3N4/BN composite ceramic materials

AbstractHigh thermally conductive β‐Si3N4 is a new type of filler for thermally conductive materials. Tailoring its aspect ratio is crucial to optimize the preparation process and performance of polymer‐based thermal conductive materials. In this work, β‐Si3N4/BN thermally conductive hybrid fillers were prepared by combustion synthesis in a nitrogen atmosphere using low‐cost Si, B2O3 powders as raw materials, and the aspect ratio of β‐Si3N4 crystals were regulated according to the inhibiting growth strategy of second phase BN generated by in situ reaction. With the increase of B2O3, the content of BN increased slightly, while that of β‐Si3N4 decreased slightly. The aspect ratio of β‐Si3N4 decreased from 6.3 ± 1.9 to 1.9 ± 0.6, which might be ascribed to the inhibiting effect of BN sheets on the axial growth of rod‐like β‐Si3N4. Low‐aspect‐ratio β‐Si3N4/BN/epoxy composite exhibited high thermal conductivity of 1.04 W·m‐1·K‐1at the solid content of 50 wt%, which was 372.7% and 30.0% higher than that of neat epoxy and 40 wt% high‐aspect‐ratio β‐Si3N4/epoxy composite, respectively. In addition, β‐Si3N4/BN/epoxy composite also had good mechanical properties.

Influence of nano graphene filler on hardness, impact strength and density of glass epoxy composites

AbstractThis study investigates the effects of graphene reinforcement on the hardness and impact strength of glass epoxy composites. Four different materials were examined: pure epoxy (EP), glass epoxy (GE), glass epoxy with 1 wt.% graphene (GE1), and glass epoxy with 2 wt.% graphene (GE2). The results show that the incorporation of graphene significantly enhances the hardness of the composites. Pure epoxy (EP) exhibited a Shore D hardness of 60 and an impact strength of 0.09 J/m2. The glass epoxy (GE) showed a reduction in hardness to 56 but an increased impact strength of 0.15 J/m2 due to the inclusion of 33 wt.% glass fiber. Further addition of graphene in GE1 and GE2 led to notable improvements in hardness, reaching 68 and 74 Shore D, respectively. However, the impact strength displayed a decrease with the inclusion of graphene, with GE1 and GE2 showing values of 0.13 and 0.11 J/m2, respectively. When transitioning from pure epoxy (EP) to glass epoxy (GE), there is a 6.67% decrease in hardness, while the impact strength increases by 66.67%. Introducing 1 wt.% of graphene to the glass epoxy (GE1) results in a 21.43% increase in hardness but a 13.33% decrease in impact strength. Further adding 2 wt.% of graphene (GE2) leads to an additional 8.82% increase in hardness, though the impact strength decreases by 15.38%. X‐ray diffraction (XRD) analysis has revealed nano graphene presence and distribution, while fractography has revealed its effectiveness in enhancing interfacial adhesion and toughening mechanisms. Furthermore, XRD identifies potential changes in crystallinity or phase composition induced by nano graphene incorporation, further elucidating the composite's structure and properties. The study highlights the novel and significant trade‐offs encountered in optimizing the mechanical properties of epoxy‐based composites by incorporating graphene and glass fiber.

Effect of hollow glass microspheres on transverse properties of carbon fiber reinforced epoxy composites

AbstractHollow glass microsphere (HGM)—based composites are gaining popularity in materials research due to their ability in altering material characteristics drastically. The current study investigates HGMs filled carbon fiber reinforced epoxy (CE) composites on transverse properties, aiming for aerospace and defense applications mainly in composite pressure vessels. Unidirectional laminates of Carbon/Epoxy with varying HGM percentages (0.2, 0.4, 0.6, 0.8, 1.0 wt. %) were wounded onto a flat‐plate mandrel using a 4‐axis filament winder, along with a baseline sample without HGM for comparison. The glass transition temperature (Tg) and thermal stability were analyzed by carrying out dynamic mechanical analysis and thermogravimetric analysis. The fracture mechanism of the samples loaded under tension was investigated using FESEM. Experimental results indicate reduction in density with increase in HGM content, up to 0.4% HGM there is increase in transverse tensile strength of 25% compared to baseline and further increase in HGM content, decrease trend is observed. 30% decrease in transverse compressive strength is observed compared from baseline to 1.0 wt. % of HGM. No significant change was noticed in the thermal stability and Tg on introduction of HGM. Microscopy images of fractured samples revealed effective physical interaction and dispersion of the HGM within the matrix.Highlights Transverse mechanical properties are tested to know the influence of HGM filler on filament wound composites. Density of the composite decreases with increase in HGM content. Thermal stability and Tg shows less change on introduction of HGM in composites.

Sustainable Epoxy Composites with UV Resistance Based on New Kraft Lignin Coatings.

Currently, the composite industry is focusing on more environmentally friendly resources in order to generate a new range of biobased materials. In this manuscript, we present a new work using lignocellulosic wastes from the paper industry to incorporate into biobased epoxy systems. The manufactured materials were composed of kraft lignin, glass fiber, and a sustainable epoxy system, obtaining a 40% biobased content. Using a vacuum infusion process, we fabricated the composites and analyzed their mechanical and UV resistance properties. The findings reveal a significant correlation between the lignin content and flexural modulus and strength, showing an increase of 69% in the flexural modulus and 134% in the flexural strength with the presence of 5% of lignin content. Moreover, it is necessary to highlight that the presence of synthesized lignin inhibits the UV degradation of the biobased epoxy coating. We propose that the use of lignocellulosic-based wastes could improve the mechanical properties and generate UV resistance in the composite materials.

Effect of cobalt ferrite concentration on the EMI shielding effectiveness of cobalt ferrite/graphene based epoxy composites

Effect of cobalt ferrite concentration on the <scp>EMI</scp> shielding effectiveness of cobalt ferrite/graphene based epoxy composites

Enhanced thermal conductivity and mechanical properties of boron nitride@polymethylacrylimide/epoxy composites with self-assembled stable three-dimensional network

Constructing a three-dimensional (3D) network of fillers with high thermal conductivity is considered to be an effective strategy to obtain ideal thermal management materials (TMM). However, 3D filler network is often disrupted by the subsequent processing and forming processes , and it is difficult to incorporate high levels of fillers into lyophilized aerogels, which is a key factor limiting their widespread use. In this work, boron nitride@polymethylacrylimide/epoxy (BN@PMI/EP) composites with a stable 3D BN network were prepared by freeze-drying and hot-pressing. A water-soluble copolymer quaternary ammonium salt has been synthesized by the solution polymerization. BN@PMI aerogel was obtained by the freeze-drying of ammonium salt and BN solution, and thermal imidization. BN@PMI aerogel has a six-membered imine ring structure that can be loaded with a high content of BN, which ensures the stability of the 3D BN network structure and facilitates the subsequent impregnation of EP in vacuum, which is one of the innovations of this work.The stable and complete 3D BN network leads to the enhancement of thermal conductivity, and the out-of-plane and in-plane thermal conductivities of BN@PMI/EP reach 1.21 W·m–1·K–1 and 2.76 W·m–1·K–1 at BN loading of 40% (mass), respectively. Meanwhile, the excellent mechanical properties and results of finite element simulation and actual experiments confirm that BN@PMI/EP is a potential TMM.

Investigating the spall phenomena in glass filler embedded epoxy composites using laser-induced stress wave

Recently, Singh and Kitey (Experimental Mechanics, 60(7), 2020) used laser-induced stress pulse in conjugation with Michelson's interferometer to measure the spall strength of thin polymer layers. In this investigation, the method is expanded to measure the spall strength of spherical and slender glass filler-reinforced epoxy composites. A filler-reinforced epoxy layer of ∼150 μm was deposited onto a glass substrate, and a short-duration and high-magnitude stress pulse developed at the back surface of the substrate. A complex interaction between the mode-converted main compressive wave and slow-moving secondary tensile wave generated a greater magnification tensile area near the layer's free surface, causing a spall. The composite layers experienced a strain rate of ∼107/s, with the secondary wave not distinct from the interferometric data due to filler-induced multiple mode conversions. An equation correlating strain rate, impedance, and fracture toughness with spall strength was used to ascertain the composite layers' spall strength. The findings showed that stiff reinforcements improve epoxy spall strength, with milled fiber composites exhibiting greater spall strength than spherical particle cases, as corroborated by optical micrographs showing fiber-bridging across the spalled zone. The spall strength of epoxy composites with 10 % milled fibers was nearly 2.5 times greater than pure epoxy.