Enhancement of high-performance structures with sustainable seashell filler-based GFRP composites in static loading

Research on reinforcing airplane structures while reducing their weight by employing sustainable materials is currently challenging. In this study, damage mechanisms, mechanical characteristics, and failure behavior of laminates made of plain-woven glass fiber/epoxy and Glass Fiber Reinforced Polymer (GFRP) with sea shell filler under low-velocity impact static loading conditions are experimentally investigated. The bi-directional GFRP type E-glass laminates with 10 plies and a total thickness of 3.35 mm are created by hand lay-up process using an epoxy matrix. Comparing GFRP with an effective ratio of sea shell filler of 5% under various impact loading, composites are characterized in accordance with ASTM standards to assess the progressive damage and failure of GFRP composite. The findings of the experiment indicate that GFRP with seashell filler composites outperforms GFRP composites in terms of impact strength, outstanding flexural strength, and tensile strength. The findings show that adding seashell filler to GFRP increased the composite’s ability to sustain various impact loads. The sample with seashell infill has a drop weight impact that is 25.26% lower than GFRP. Moreover, the flexural test demonstrated a 59.6% increase in bending over GFRP. Seashell filler outperformed GFRP in the longitudinal strength test by 33.12%, according to the results of the tensile test. Finally, the compression after impact test (CAI) manifested a remarkable increase in transverse strength by 78.23%.


Introduction
In today's aerospace, automobile, and other transportation industry divisions, composite materials in various forms are used due to their highly advantageous mechanical features, such as high stiffness and strength combined with weight reduction, high resistance, and better corrosion resistance. The utility of GFRP(Glass Fibre Reinforced Polymers) composites expanded over the previous decade extensively in aero plane components and subsystems such as wings, spoilers, turboprops, and turbofans. Light alloys have been phased out of aviation components in preference for composites, which are lighter and have reduced maintenance on control surfaces [1,2]. An airplane may sustain various sorts of damage, including deterioration through wear and tear, impact damage, and corrosion. When a composite structure experiences a slow-moving collision, matrix cracking and delamination can occur [3,4]. Such damage lowers compressive strength/stiffness and the structure's integrity and reliability. Foreign objects that cause the impact loading from occurrences like bird strikes, hailstones, shrapnel, runway debris, firearms, and explosion fragments are possibilities to reduce aircraft service life. Such impacts have the potential to embed as well as significantly cause delamination, which would degrade the structural performance, and cause damage to the nose tip. One such real-life aircraft BOEING 777 is shown in (figure 1).
FRP composites are used in a variety of industries, including consumer goods, automotive, aerospace, marine, and the military. They offer numerous benefits for many applications over the usage of conventional materials thanks to their improved material properties. Only 7% of Concorde aircraft were constructed in the and coefficient of thermal expansion of 7%-22% and 3%-17%, respectively, according to DMA/TMA analyses. Additionally, the toughness, toughness modulus, and flexure strength all saw substantial increases of 6%-31%, 11%-37%, and 10%-36%, respectively [15,16].
It's important to note that all research studies reported using chemical or physical means to alter eggshell and seashell particles' sizes or shapes in order to lessen the surface tension between the particles and the polymer matrix. The manipulation of seashell particles to obtain different calcium carbonate crystal structures by precipitation technique and incorporate them into the polymer matrix is unexplored and remains a significant research gap despite the near-optimal eggshell/seashell particle dispersion through polymer matrix achieved by those treatments.
Generally, calcium carbonate (CaCO 3 ) accounts for >4% of the composition in the Earth's crust. It is a common material occurring naturally as chalk, limestone, marble, and calcite. Other than that, CaCO 3 is the main component for shells of marine organisms, clams, snails, pearls, and eggshells. In India, clam species (Meretrix meretrix) are abundantly available in the estuaries along the coast. It is a green material composed of at least 95% of calcium for CaCO 3 production [17][18][19]. The usage of seashells is advantageous since their physical characteristics are quite similar to those of the commonly employed natural aggregates. Finally, employing seashells in the industry helps preserve natural resources and the environment while using materials that are more affordable [20]. Also of its higher temperature stability than other fillers, sea shells could be a filler for biodegradable polymer composites that are especially appealing. The primary components of the marine shell are calcium carbonate (CaCO 3 ) in the forms of calcite and aragonite, as well as a combination of the two, and a number of organic compounds [21,22]. The usage of seashells as fillers in aerospace industries could account to broaden the research in natural fillers for enhancing the mechanical properties of GFRP composites.
Thus, this paper provides an empirical investigation to measure the mechanical and physical properties of GFRP and GFRP with sea shell filler, tensile, flexural, and compression after impact and drop weight tests were performed to assess the properties of composites. A detailed comparison is done to analyze the improved performance of seashell filler in GFRP.

Materials
The specimens in this work investigated are, GFRP weaved roving 400 GSM glass fiber with a density of 2.54 g cm −3 , and GFRP with seashell filler, (0°/90°/0°/90°), 3.35 mm conventional thickness of oriented cross-ply E-glass/epoxy laminated composite. Epoxy resins are extremely compressive materials with great corrosion resistance, high tensile strength, resistance to physical abuse, and outstanding fatigue strength features [23,24]. An Araldite epoxy resin with a molecular mass of 190 g mol −1 and a density of 1.19 g cm −3 is utilized as the polymer matrix. The hardener HY 951 is mixed with it in the mass ratio of 10:1. The materials used for the manufacture of composite, include sea shell powder with random grain sizes between 10 to 12 microns.
The seashell powder is synthesized by ball-milling the collected clam seashells from Elliot's Beach, Chennai, Tamil Nadu, India (12.9989°N, 80.2718°E). Ball milling is processed using an aluminum oxide cup and balls for 100 min and at a rotation speed of 500 rpm at nominal room temperature. A sieve analysis is done using Retsch AS 200 with a vibration amplitude of 0.90 mm for 20 min and with the interval operation set to 20 s to separate the smallest particles [24]. The density of the sea shell is found to be 1.7 g cm −3 with a 92%-99% calcium carbonate content, 5% organic matter, and calcium carbonate particulates approximately 2-10 microns in size.

Composite preparation
The laminate tested in this work involves ten layers of bidirectional E-Glass samples with an average thickness of 3.35 ± 0.05 mm. They are accomplished by utilizing the hand layup technique and an epoxy hardener. (10:1 wt. of epoxy resin) mix and the woven glass fibers of E-type. The addition of the sea shell powder as filler is carried out by the ultrasonication method. Since the application is for aircraft structures, the effectiveness and less amount of weight must be considered for filler addition. Hence filler particle sizes are chosen in a few microns range. Another reason for less weight percentage is to avoid agglomeration and hence reduce voids in the layers of ply which could reduce the strength. It is reported that seashell filler addition increased hardness from 4 wt% and reduced after 12wt % [25]. It is also reported that below 6 wt% crab-shell filler has a maximum impact energy value [26]. Hence, the seashell filler is taken as 5% weight of the composite for this testing. Composite specimens are molded by the compression molding press process technique. The impact is carried out at room temperature on a 100 kN load capacity UTM testing instrument. All samples underwent room-temperature curing for 24 h. Then, specimens are cut according to ASTM standards into a different dimension for the impact test. This standard is usually employed to determine the mechanical properties of reinforced plastics. (figure 2) shows the step-by-step fabrication process of the material.

Characterization of mechanical properties and testing
Tenacity is a crucial characteristic of composite materials that indicates the specimen's ability to absorb energy. The matrix, reinforcement, and interface are indeed the three essentially key phases that make up GFRP composites [27]. Impact damage, which commonly presents as delamination, matrix cracking, and fiber failure, can significantly diminish structural strength and stability [28][29][30]. Due to the unstable resin and inadequate curing methods, voids and porosities are among the most frequent flaws that develop during the composite preparation. Particularly in epoxy zones, air absorption during formulation and the stabilizing agent is the primary cause of these voids and porosities [31][32][33]. Consequently, damage from delamination is referred to as 'macro-damage.' [34]. Composite materials' damage mechanisms must be investigated to gain a better knowledge of their eventual failure and durability [35].

Drop test
All tests were performed in the Faculty of Aeronautical Engineering, Hindustan University, India. According to ASTM D7136, a drop weight impact test was conducted as shown in (figure 3(a)), and equation (1) is used to determine internal energy [36].
The experimental configuration affects the damage response behavior. The damage resistance is measured according to the type and amount of destruction in the specimen. The impactor's mass and drop height identify the drop weight's actual energy, which would be specified prior to the experiment. Several parameters, such as specimen geometry, lay-up, impactor geometry, weight, applied load, impact strength, and material parameters, also significantly affect damage resistance capabilities generated through this test method.

Tensile test
The ability of a material to withstand deformation under gradually applied load circumstances is known as tensile strength. (figure 3(b)) illustrates how a universal Testing Machine (UTM) configuration performs the tensile test. With a specimen size of 250 × 25 × 3 mm, ASTM D3039 tensile testing determines the amount of stress and elongation required to break a composite specimen as well as the force required to use it. A gauge length of 150 mm was marked on each specimen after its thickness and width were measured. This measurement is made in the sample's longitudinal direction.

Flexural 3-point bending test
According to ASTM D790, from being manufactured as glass fiber laminate plates, using universal Testing Machine UTM M-100, test specimens of 150 × 25 × 3 mm is cut to determine the flexural property. The specimens are processed using water jet cutting equipment as illustrated in (figure 3(c)). Bending strength ( ) s is calculated using the formula equation (2) [37].
where L is the length (mm), b is the width (mm), d is the thickness (mm), and F is the load of the specimen (N).

Compression after impact (CAI) tests
Compression after impact test (CAI), is a method for determining the compressive strength of a composite plate after it has been subjected to impact loading [38]. The maximum strength decline occurs under this loading type, whereas the residual compressive strength of affected laminates is used in CAI tests to evaluate damage tolerance performance [39,40]. Evaluating fracture and debonding following an impact event is a convenient as well as established method of evaluating impact damage resistance. According to research, ply blocking or ply clustering increased the CAI strength but had a detrimental impact on damage resistance [41]. The matrix gives the composites their elasticity and atmospheric tolerance while the reinforcing fibers or fabrics grant them additional strength and stiffness. Hence, compressive strength during impact must be evaluated [42]. All samples are placed through drop weight impact testing involving various impact energies (10 J, 15 J, 20 J, and 25 J). As per the ASTM D695 standard, compression after impact (CAI) tests have since been conducted.

Through transmission ultrasonic C-Scan test (TTU) method and scan parameters
TTU is a particularly appealing non-destructive testing technology that has been recognized for its excellent sensitivity to in-service monitoring. TTU is the main technology since that allows for the authentic detection of multiple kinds of damage and its growth through into the materials [43].
A compression probe placed on a manipulator is used in immersion testing, an automatic ultrasonic inspection method, to inspect composite materials while they are submerged in water. Table 1 shows the ultrasonic test parameters in which, the scan parameter in index resolution is 0.3 mm and scan resolution is 0.3 mm. Depending on the geometry of the composite, the manipulator enables the sensor to be tilted at any angle to ensure optimal attenuation.
There are two probes used in the through transmission technique, one on either side of the composite test material. One probe emits a pulse of acoustic energy while the second probe receives it. A decrease in amplitude or signal loss indicates the presence of any defects as the received energy signal is set to a specified level. It is crucial to keep the water path perpendicular to the tested material under inspection during the scanning procedure. It is difficult to inspect composite structures made of superimposed layers. The gain is adjusted so that the signal won't become saturated by using the reference signal from the good region. The sound waves in damaged areas disperse, resulting in less sound energy reaching the receiver transducer than in healthy areas. This method allows a material's anomaly visible.

Volume fraction determination
The theoretical maximum volume fraction of fibers excludes any potential voids in the cured laminate and is based on the notion that all fibers are in the loop. Matrix digestion, according to ASTM 3171, is the accepted  technique for calculating weight fraction. The volume percentage of fibers in a composite laminate is calculated using the weight ratio of the fibers to the resin.

Seashell filler material characterization
To determine the surface morphology and particle size of seashell filler, the collected clam seashells are cleaned multiple times to avoid any dirt inclusion ( figure 4(a)) and ball-milled to a fine powder and sieved to avoid agglomeration ( figure 4(b)).
3.1.1. Laser diffraction particle size analysis The average particle size of clam seashell powder is measured using Horiba Laser Scattering Particle Size Distribution Analyzer LA-950 in the Ceramic Processing Laboratory, Anna University, Chennai, India. The machine is calibrated prior to measurement as follows: The sample is characterized by setting a calcium carbonate refractive index of 1.595 and dispersant as deionized water set as 1.33. Both sample measurement and background time are set as 30 s. The pump speed is set to 1500 rpm with ultrasonic treatment for a total of 2 min. The particle size distribution of the sample is computed from the diffraction measurements using a model based on the Fraunhofer diffraction theory. The resulting analysis is reported as the relative distribution of the volume (%) of seashell powder by size (μm) as plotted in figure 4(c). It can be seen from the plot that D10 and D90 range between 2-20 μm.D50 being the median of particle size distribution, it is found to be 6.97 μm. SEM analysis as shown in figure 4(d) reveals the particle size to range from 2-10 μm.
The chemical composition of the clamshell is determined by x-ray Diffraction(XRD) technique [42]. XRD was conducted using (Cu-Ka) at a scanning rate of 0.06 from 20°to 60°. The peaks at different 2θ values confirm the presence of CaCO 3 according to JCPDS 47-1743. Since there is no lattice strain in the miller indices peak [111], the result depicts that the peak is calcium carbonate. Figure 4(e) illustrates the peaks of XRD for clam seashells with more than 95% of CaCO 3 .The EDAX of the clam seashell in figure 4(f) shows the amount of Ca around 60.28%.
The mechanical analysis is carried out with four rectangular samples for each test and the average of these four specimens is plotted and discussed in detail.

Drop weight impact test
An instrumented impact testing apparatus is used to assess the low-velocity impact (less than 10 m s −1 )response of all composite laminates. 'E' is the energy that the specimen absorbs as a result of the impactor's friction with the specimens and the damage that results from it. The height is calculated as 0.27 m, 0.40 m, 0.54 m, and 0.67 m for the impact energy of 10 J,15 J, 20 J, and 25 J respectively with an impactor mass of 3.835 kg. As the impact energy grew, the damaged area and the depth of the impact damage also increased. Usually, impact failure is initiated as a matrix crack, propagates towards the interface of the laminates, and grows as delamination.
From the observation, all specimens show an almost similar damage pattern at the back face. With delamination clearly seen in GFRP, it is established that, compared to smaller impact energies, the delaminated area significantly increases as impact energy increases. Fiber breakage and delamination is the main energy absorption mechanism in GFRP, and it is observed from the tests that the delamination area was maximum in the middle of the laminate stacked layers. ( figure 5(a)) compares the impact test results between GFRP and GFRP with seashell filler. The former proves 25.36% less than GFRP. Seashell filler presented improved mechanical properties and a good bonding mechanism between the fiber and matrix compared to GFRP. It's good mechanical stability and crystal structure of the sea shell filler improved the impact strength of the specimen.

Flexural 3-point bending test
According to ASTM D790 criteria, 3-point bending is used to perform flexural tests. Each occurrence involves the collection of four samples, and average values are noted. ( figure 5(b)) illustrates the three-point bending test. Plates are calibrated to ATSM D790 following the formation of the glass fiber laminate, for determining flexural properties. According to ASTM standards, the tested results of various combinations of fiber systems are used to determine the flexural parameters of laminated composites. The flexural tests were conducted with a controlled displacement rate of 2 mm min −1 , and ( figure 5(b)) shows the stress versus strain curves for glass fiber reinforced. As long as the first plies don't rupture, the behavior is linear. Once ultimate flexural strength is reached, the GFRP composites keep their energy. Then, as laminate plies begin to break, flexural strength begins to decline. But elasticity modulus and ultimate strength are also rate-dependent (they tend to be higher for higher displacement rates). To investigate and clarify experimentally, the mechanisms of damage growth in GFRP composites subjected to three-point bending. Particularly the relationship between GFRP composite strength, modulus, stiffness, crack propagation, and the orientation angles of bidirectional fibers are considered. ( figure 5(b)) denotes ultimate bending stress for neat material and GFRP with seashell obtained from the flexural tests performed with controlled displacement rates of 2 mm min −1 . It is absorbed from the plots that, as long as the first plies don't rupture, the behavior is linear. The GFRP with sea shell filler composites sustains its energy until they reach its maximum flexural strength (420 MPa). As the laminate plies break after that, the flexural strength starts to decline. The results of the experimental research demonstrate that this composite's mechanical response is highly filler dependent. The flexural strength of GFRP with sea shells increased by 59.6%.

Tensile test
Material will deform longitudinally when it is subjected to tensile loading. The characteristic of deformation can be either elastic or plastic. When a material is subjected to a tensile load, its tensile strength measures how much stress it can bear before failing. The specimen's ultimate tensile strength is represented by the peak of the stressstrain curve. The ASTM D3039 standard sample dimension is (250 × 25 × 3 mm). Tension test of GFRP and Seashell is done following as per standard ASTM D3039M. In ( figure 5(c)), the pertinent stress-strain curve is displayed.
According to the fiber forms, fiber orientation, matrix, section interface, moisture absorption, and agent added to the materials, the tensile strength value of GFRP is typically specified. Investigation of GFRP with seashells has shown that the tensile strength increased by 32.12% due to the structural support of filler. Hence, the use of a limited quantity of sea filler (5% by weight of epoxy) can significantly improve the tensile strength of GFRP by 32.12% and alter the typical broom failure in GFRP with sea shell filler. But, increasing sea shell filler content will adversely affect the improvement in the tensile strength.

Compression-after impact test
Compression-After Impact (CAI) tests are conducted at room temperature as per ASTM-D695. The influence of the impact test in the GFRP sample is greater than in GFRP with seashell filler. The force versus displacement was plotted in ( figure 5(d)) during the CAI test by a data acquisition device. The CAI tests are carried out at 1 mm min −1 speed. The impact energy level affects the damage processes for laminated composite [44]. The back face of the laminate usually sustains the most severe delamination damage, which is gradually smaller as it moves toward the impact face.
The compressive strength of GFRP with seashell filler is greater than that of plain GFRP. It has been revealed from ( figure 5(d)) that the strength of GFRP with seashells improved extensively by 78.23%. Sea shells are highly rich in calcium carbonate (CaCO 3 ) which has good monoisotopic mass properties. Due to the difference in flexural stiffness brought on by the sea shell filler, it was determined that the specimen's impact response and failure modes varied depending on the microstructure of the calcium carbonate (CaCO 3 ) and its post-impact properties( figure 5(e)). However, in the GFRP plate, impact-induced delamination zones in the laminate cause a loss in compressive strength.

Volume fraction determination
The fiber volume fraction (v f ) is computed based on the Rule of Mixtures for the density using the observed density of the composite and the known densities of the fiber and matrix. Equations (3-7) are utilized to calculate the volume fraction [36].
where c r is the composite's density, f r is the fiber's density, m r is the density of the matrix, and f J is the fiber's volume fraction. The weight of fibers (w f ) is determined by dividing the areal weight of the fibers by the area of the ply (layer of fiber) and the rest of the weight is of the resin (w r ) in the laminate. Finally, the volume of fibers v f is [37]; The fiber-to-resin volume ratio, x 5  We can now calculate the theoretical volume of fibers, f r = -One of the crucial factors in determining the mechanical properties of the composite is the fiber volume fraction. We must therefore establish its specific value. The sample is burned for five hours at 520°C in the furnace. The burnt-out remnants are examined for laminate defects once the resin has been completely removed. This process is known as the ignition loss method. It has been noted that the matrix from the composite specimen is completely removed during the burning process. The results from this series of tests are presented, the volume fraction for the GFRP and GFRP with sea shell filler is found to be 50.7% and 52.2%, respectively.

Through transmission ultrasonic(TTU) results of drop weight impact test
The results are analyzed, and the travel duration of the ultrasonic pulse is represented as a displacement along the other axis(x-axis) by C-scan TTU presentation, which receives pulse amplitude displacement along one axis (yaxis). Table 2 shows the damage dimensions on the scan axis and on the index axis for GFRP versus GFRP with seashell filler. From the flaws in laminate specimens, it was feasible to gather evidence of an echo.
The peak rise in signal amplitude studies can identify an ultrasonic C-scan from fiberglass or E-glass that exhibits a high proportion of internal delamination. The ultrasonic energy is transmitted and received using two different probes. The probes are positioned evenly apart on the sample's opposite sides surfaces. Gain is adjusted so that the signal won't get saturated, using the signal from the good region as a reference. Sound waves in damaged areas disperse, resulting in less sound energy reaching the receiver transducer than in a favorable position. This method makes a material's anomaly visible. The growing impact load caused a larger total delamination area, and as the load grows, so does the damage. One of the main design considerations for structures composed of advanced composite laminates is their susceptibility to damage from concentrated out-of-plane impact force. Figure 6 shows the damage pattern of the composite specimen at 25 J. Figure 6(a) is for the GFRP sample, and (b) is for GFRP with sea shell filler on a drop test. It is observed that the damage in GFRP is 26.53 mm and 21.06 mm in scan and index axis respectively for 25 J impact energy while GFRP with seashell filler has 18 mm and 20.3 mm in scan and index axis respectively for surface the same 25 J of impact energy. Thus, the damaged area is 35.16% less for GFRP with seashell fillers compared to plain GFRP. The results of this test technique's attributes can offer the direction intended to assess the material's thickness and stacking order, as well as its damage resistance structure. However, it is essential to know that a composite structure's ability to withstand damage is greatly influenced by a number of variables, including the geometry's thickness, stiffness, mass, support situation, and mainly the filler addition.

SEM test
The microstructure of the composites and the influence of the matrix and fiber on the mechanical properties of E-glass fiber reinforced GFRP with sea shell filler is analyzed by scanning electron microscopy (SEM) shown in ( figure 7).
To examine the change in the microstructure due to the impact test, the samples were taken from the top surface of the area that is damaged. Figures 7(a), (b) indicates that the impact test is responsible for matrix-fiber de-bonding and fiber fracture of GFRP on the surface. The fundamental failure/disintegration of the GFRP composite specimens is shown to be matrix-cracking, fiber pull-out, and fiber-matrix de-bonding, showing interfacial failure. Figures 7(c), (d) obviously demonstrates that the epoxy compound, which appears to wrap and adhere to the fibers, has thoroughly embedded the glass fibers with sea shell filler. A noticeable slight uppermost layer damage can be seen in the matrix right next to the glass fiber, indicating that the fiber sustained the impact with delamination and the matrix rebounded, resulting in strength and more impact sustainability.   Table 3 compares a different range of fillers to enhance the mechanical properties of GFRP composites. It is found that granulated date seed has a high tensile strength of 271 MPa with less density while elasticity modulus is very low (3.95 GPa) compared to clam seashell (35 GPa). Bamboo fiber has very less density while the elasticity modulus and tensile strength are far too low than a seashell. As it is seen from the table all other metal base components are heavier which is a drawback for aerospace applications. Hence seashell filler with 2-10 microns size when added to GFRP composites provides good flexural strength as well as tensile strength with additional features of lightweight and natural filler.
The fillers are capable of absorbing shock to resist a quick collision. The energy-to-break is resisted by the CaCO 3 .When the seashell nanoparticles are introduced, the fiber pullout and fracture length are reduced, as seen from the SEM in figures 7(e), (f).
A strong link between the strong, stiff reinforcement-typically fibers (filaments) or reinforcements with different geometrical shapes, such as particles or platelets-and the weaker, less stiff matrix is what gives composite materials the majority of their advantageous features. Manufacturing flaws are undoubtedly the first sort of damage that might occur. It is rare for a good bond to not form between the fibers and the matrix, though, as long as there is good wetting between the two and there is no porosity. As a result, aside from cracks brought on by resin shrinkage or thermal stresses created during cooling (or a combination of both), thermomechanical loading is typically the cause of fiber-matrix debonding. Such flaws are invisible to the unaided eye and frequently difficult to spot using optical or other types of microscopy.
The seashell filler added to the GFRP composite is 5% weight which is an optimal weight percentage to avoid agglomeration in the synthesis as well as reduce inducing voids in the final ply layering of composites. Hence, all the above results prove that GFRP with 5% seashell filler has enhanced flexural strength and tensile strength which can be a promising natural sustainable strengthening and lightweight filler for aerospace applications.
However, the majority of the research recently used a direct approach and solely calcite crystal structures, reducing the size of calcium carbonate with basic mechanochemical or grinding processes. Untreated or nonprecipitated techniques have the drawback of producing impure, amorphous calcium carbonate particles with no control over crystal structure, size, or shape. It is crucial to look for novel process pathways to improve and boost calcium carbonate's continued success in the future as calcium carbonate made from biogenic waste garners increasing attention. In order to produce an engineered reduced-sized calcium carbonate with stable polymorphic structures and desirable morphologies, further work must be placed into researching, developing, and testing novel procedures such as the indirect, or treated precipitation technique.

Conclusion
In the basic design of aviation components, the damage behavior of laminated composite plates subjected to impact loads is a crucial issue to consider. For the development of avionic products, it is essential to assess the damage-withstanding capabilities of laminated composite plates. This study's main goal is to perform static drop weight tests, three-point bending tests, tensile tests, and compression after impact (CAI) tests to examine how damage develops and how composites containing glass fiber reinforcement and 5% weight of seashell filler fail. In comparison to GFRP composite, GFRP with sea shell composites has better strength for fracture stress. In the GFRP sample, the debonding and tear out of fibers are induced by the extension of a crack, which is spanned by undamaged fibers. Failure of GFRP composites is mainly triggered by isolated buckling or kinking of fibers under impact loading. Fiber crushing and the formation of a crack in the matrix can also be seen in the GFRP composite. In the final analysis, it was determined that adding 5% sea shell filler to GFRP was the best and most efficient way to achieve high flexural strength, stress-withstanding capability in energy absorption, and damage degree of the specimen for airplane constructions. These findings demonstrated the superior resistance of sea shell filler to impact loading. The energy that the entire specimen absorbed during drop weight impact testing increased by 25.26 percent. With fiber content, the composites' flexural strength is increased by 59.26%, which is greater than the improvement. The use of sea shell filler boosted the GFRP's tensile strength by 33.12%. The sea shell has better impact resistance, which was demonstrated by 78.23% in a compressive test.
The stiffness, stress-tolerance, and strain at failure of the GFRP material were all improved by adding 5% weight of seashell filler. With its fascinating morphological and mechanical qualities, this percentage of seashell filler might be a useful one for filler agents. As a result, it can be utilized as a strong filler to reinforce composite materials used in aircraft structures.

Data availability statement
No new data were created or analysed in this study.

Disclosure statement
No potential conflict of interest was reported by the authors.