Interlayer Strength Research Articles

Investigations on ironing parameters in screw extrusion additive manufacturing (SEAM)

Additive Manufacturing (AM) is a novel manufacturing process that enables the physical realization of a given 3D model via layered deposition. Material extrusion (MEX) is one of the most widely used forms of the various AM techniques, in which the screw extrusion-based AM (SEAM) processing offers the most versatile characteristics, in terms of material handling and flow rate capacities. It involves continuous extrusion of the semi-solid material via an extruder screw. Ironing is a common practice in MEX techniques, to maintain z-height and improve the surface morphologies while deposition. Most commercially used nozzles for MEX are thin-walled, such that the ratio of the nozzle width to the diameter (w/d) is close to 1. In this research, investigations on the ironing effect during screw extrusion-based material deposition are explored using a set of wider nozzles (w/d as high as 40). Special emphasis is laid on the deposited surface finish, interlayer strength, and geometrical conformance of the extrusion. The nozzle diameter and the stand-off distance (SOD) are also independently varied. It is found that the best dimensional stability is achieved when the SOD is set between 75 % and 100 % of the nozzle diameter. Ironing improved the surface finish and the interlayer strength in all instances, with an average improvement of 50 % and 200 %, respectively.

Development of novel concave and convex trowels for higher interlayer strength of 3D printed cement paste

Past experimental results have shown that the use of nozzle trowels can enhance the interlayer strength of 3D printed cement paste. In this study, the design is further optimized by introducing concave and convex shapes onto the nozzle trowel design. A technique for accurate simulation of the interlayer stresses with the influence of nozzle trowels is established, and it is found that the nozzle trowels double the maximum shear stress and increase the maximum pressure by about 114 %. Moreover, the concave and convex nozzle trowels with removal of interlayer notch further increase the interlayer strength by 35 %. A theoretical model is also proposed to predict the interface geometry and then validated by the experimental observations on the concave and convex trowels. These findings not only result in 3D printed cement paste with much higher interlayer strength, but also emphasize the importance of nozzle designing with optimal interlayer stresses and interface geometries in the application of 3D concrete printing (3DCP).

A strategy for the improvement of the bonding performance of 3D-printed concrete interlayer interfaces

3D-printed concrete, as an intelligent building technology, has enormous potential in construction. However, the weak bond interfaces between two adjacent layers of concrete are still a well-known problem affecting the mechanical properties of printed structures, with reduced interlayer shear and tensile properties. The reinforcement method of inserting steel bars in vertically printed layers is crucial and requires research and exploration of suitable methods, as well as finding the optimal reinforcement scheme that satisfies the interlayer interface when facing different loads. This study proposes a method of interlayer reinforcement by vertically laying steel fibers between layers, and investigates the effects of steel fiber offset, deployment density, and cross-sectional area on interlayer bonding strength. The strengthening effect of steel fiber on interlayer shear and tensile strength was tested through shear and splitting tests. Microscopic numerical models are used to study the evolution process of interlayer cracking. The correlation between different steel fiber variables and interlayer bonding strength was studied using a Generalized Grey Relational Analysis (GGRA). The results showed that the shear strength and tensile strength of the interlayer interface could be improved by 256.32 % and 353.61 %, respectively, through a reasonable fiber layout scheme. It is recommended to lay steel fibers with small offsets. When the interlayer interface is subjected to shear loads, priority should be given to increasing the cross-sectional area. When the interlayer interface is subjected to tensile loads, the deployment density should be increased first to achieve the best improvement in interlayer strength.

Mechanical property of powder bed fusion printed carbon fiber reinforced polyetheretherketone and enhanced interlayer strength by post‐processing

AbstractAdditive Manufacturing (AM) of carbon fiber reinforced polyetheretherketone (CF/PEEK) composites with excellent performance by Powder Bed Fusion (PBF) has great potential in the applications where high strength and high service temperature are required. However, the reinforcement mechanisms of CF/PEEK composites based on the PBF process are complex and show significant differences from traditional processing methods. In this paper, the mechanical properties of CF/PEEK prepared by PBF were investigated. The results showed that its X‐axis tensile strength and modulus were approximately equal to or a bit lower than the theoretical value with randomly distributed CF, but much lower than the theoretical value with unidirectional distribution of CF in composites. Meanwhile, mechanical strength anisotropy was observed. The composites' Y‐axis tensile strength was slightly lower than X‐axis, and the lowest strength existed in Z‐axis. To improve the weak Z‐axis strength, post‐processing of annealing and solvent‐induced crystallization were carried out, and the Z‐axis tensile strength of post‐processed parts reached 50 MPa, which was 62% higher than untreated samples. Consequently, suitable CF and proper post‐ processing for AM of high strength CF/PEEK were proposed, which would promote the industrial application of this technology.Highlights The effect of CF on mechanical property of CF/PEEK prepared by PBF were studied. The optimal CF for PBF of high strength CF/PEEK were obtained. The post‐processing method for improving the Z‐axis strength were proposed. CF/PEEK with comprehensive mechanical property was successfully prepared by PBF.

Enhanced interlayer strength in 3D-printed PA12 composites via electromagnetic induction post-processing

Weak interlayer strength remains a critical limitation in the application of material extrusion 3D-printed parts. Herein, a non-contact method, electromagnetic induction post-processing, is proposed to address this issue. This method aims to enhance the weak interlayer strength of 3D-printed PA12 samples by introducing Fe3O4 particles for induced heat generation under alternating magnetic fields. The heat generation characteristics, surface morphology, crystallization behavior, and interlayer performance of 3D-printed samples subjected to induction post-processing are systematically investigated. The results indicate that a remarkable improvement in the interlayer strength of 3D-printed PA12 samples can be achieved through induction post-processing. Tensile strength along the Z-direction (perpendicular to the printing plane) exhibits a distinct increase of 218.3 %, while interlayer tear strength can rise by 328.1 %. Improvement in interlayer strength results from heat generation driving interfacial resin diffusion. Additionally, induction post-processing results in localized surface smoothing and a slight reduction in the crystallinity of the 3D-printed sample. Compared to traditional methods like in-oven heat treatment (annealing), induction post-processing offers higher efficiency by circumventing the initial constraints of heat transfer. Furthermore, the concept of selective induction heating (SIH) is proposed to achieve non-contact, localized heating by adjusting the composition of thermoplastics during printing. SIH holds good promise for applications in 3D-printed continuous carbon fiber-reinforced thermoplastic composites, including mold-free forming, complex surface welding, and repair (particularly in narrow and inaccessible areas).

Influences of heat treatment on mechanical properties of SCF/PEEK composites in FDM‐3D printing process with UV laser assistance

AbstractFused deposition modeling (FDM) process with laser assistance can effectively enhance the interfacial strength of short carbon fiber/poly‐ether‐ether‐ketone (SCF/PEEK) composites. However, excessive crystallization of the semi‐crystalline matrix generally results in irregular shrinkage, which seriously deteriorates dimensional accuracy of composite specimens. To overcome this issue, we establish a novel heat treatment technique by the combinations of laser assistance and post‐treatment to improve the interlayer properties and dimensional accuracy simultaneously. It is found that lateral cracks at the interlayer interfaces can be completely eliminated at laser pre‐heating temperature , due to the reduction of temperature gradient and residual stresses. The further increased evidently promotes molecular diffusion and crystallization behaviors, thus increasing the interlaminar shear strength of FDM‐printed specimens. The post‐treatment temperature visibly promotes mutual diffusions of the molecules and formations of the perfect crystals, strengthening the interlayer adhesion of specimens. The proposed combination technique can increase the interlayer strengths of composite specimens by approximately 22.5%, while their warpage deformations are suppressed simultaneously.Highlights Pre‐heated temperature was a threshold for eliminating lateral cracks at interlayer interfaces. Post‐treatment significantly promoted molecular diffusion and crystallization behaviors. A novel technique was established to improve interlayer strength while suppressing warpage. The combination technique could increase the interlayer shear strength by approximately 22.5%.

A quasi-exponential distribution of interfacial voids and its effect on the interlayer strength of 3D printed concrete

In this work, a novel theoretical model of the void length probability distribution in 3D printed concrete is established based on a zigzag analog of the layer interface. A quasi-exponential distribution of void length is predicted and subsequently validated on both the zigzag analog and the actual 3D printed concrete, with different void ratios that determine the descending rate and node intervals that decide the horizontal scaling of the distribution. Moreover, the relationships between the interlayer strength, void ratio, and quantity of voids are also studied based on the theoretical model. It is found that the quantity of voids is symmetric about a void ratio of 0.5, and the decrease in the interlayer strength against the void ratio is non-linear which is approximated well by combined exponential and linear functions. This work is believed to reveal the nature of the interfacial void distributions and significantly advance the understanding of the layer interface in 3D printed concrete. The code for the zigzag analog with the computation of its interlayer strength is publicly available at: https://github.com/Human-HLW/Layer-interface.

Enhanced mechanical properties of continuous carbon fiber reinforced polyether-ether-ketone composites via infrared preheating and high fiber volume fraction

The field of additive manufacturing encounters an innate challenge regarding insufficient interlayer adhesion and anisotropy, which consequently constrains the mechanical properties of printed materials. Continuous fiber-reinforced thermoplastic composite (CFRTP) printing allows ultra-high mechanical properties using a material extrusion (ME) platform but is still significantly affected by the mentioned inherent challenges. The expansion of the usage spectrum for composites manufactured with additive methods depends on overcoming these challenges. Achieving higher fiber volume fractions is a primary method for enhancing the mechanical properties of CFRTP parts. However, it has been proven that high fiber volume fractions can adversely affect mechanical properties due to lower impregnation and reduced interlayer strength. In this study, a high fiber volume fraction of 50 % was utilized, and interlayer strength was further improved by employing an infrared heater to preheat the previous layers. This approach resulted in better interlaminar strength and overall mechanical properties, demonstrating the effectiveness of infrared heating in mitigating the challenges associated with high fiber volume fractions. The infrared heater was positioned in a rotating printing head so it could continuously stay in front of the print path. Mechanical tests showed a flexural strength of 1304 MPa and tensile strength of 995 MPa, with high fiber volume fraction and infrared assistance. As far as we know, these values represent the highest achieved in the literature for CFRTP printing without any post-processing. Optical images and differential scanning calorimeter (DSC) tests were used to investigate the microstructure and thermal properties of the printed samples.

Anisotropic size effect of 3D printed LC3-based engineered cementitious composites (LC3-ECC)

One of the critical factors affecting the development of 3D concrete printing (3DCP) is the challenging issue of in-situ reinforcement. Engineered Cementitious Composites (ECC) are printable self-reinforced materials, and their application in 3DCP technology can facilitate de-steelisation. However, traditional ECC materials pose certain concerns for sustainable environmental development. The integration of Limestone Calcined Clay Cement (LC3) suitable for 3DCP into ECC (LC3-ECC) presents an ideal solution to the aforementioned challenges. Moreover, conducting comprehensive research into its size effects is an essential step from experimentation to engineering application. A thorough exploration of the size effects of 3D printed LC3-ECC in compression, shear, and flexural fracture aspects is conducted to derive size effect laws. The relationship between the anisotropic mechanical properties and size effects has been established. The mold-cast LC3-ECC precisely follows the Bažant size effect law (SEL). The fiber orientation effect enhances bridging efficiency, leading to the fact that the mechanical properties of certain printed LC3-ECC are hardly affected by the size effect. The mechanical performance of some printed LC3-ECC depends on interlayer strength, making its primary reason for size effect not in the Fracture Process Zone (FPZ) energy release, hence closer to the Multifractal Scaling Law (MFSL). LC3-ECC exhibits weak anisotropy in mechanical properties, showing satisfactory stability. However, under flexural fracture behavior, the anisotropic size effect is higher, necessitating careful consideration in structural design.

The Effect of Resin Interleafing on the Wedge Peel Strength of CF/PEEK Manufactured by Laser-Assisted In Situ Consolidation

In this work, a novel approach involving coating fine PEEK powder on prepreg is introduced to improve wedge peel strength and reduce interlaminar voids. CF/PEEK laminates with resin interleaving are in situ consolidated by laser-assisted fiber placement. The morphology of the powdered surface is obtained using an optical profilometer, and the surface roughness and volume of added resin are calculated accordingly. Interface and surface temperature are measured during the layup process. Thermal history indicates that very short bonding time is the dominating factor for voids and limited interlayer strength. Laminate porosity and microscopic features are characterized with an optical microscope. The porosity of resin-interleaved laminates decreases to 3.7%, while the resin content only increases by 4.5% in the meantime. This is because interlayer resin particles rapidly melt under laser heating and quickly fill the voids between layers. The wedge peel strength of resin-interleaved laminates can increase by 30.1% without a repass treatment. This could be attributed to the increase in resin intimate contact and reduction in interlayer voids.

Seismic behavior of precast segmental bridge columns confined by grouted glass fiber reinforced plastic tubes

The application of precast segmental bridge columns (PSBCs) is still restricted in seismicity areas due to concerns such as lower lateral stiffness and column base bearing capacity. To enhance the applicability of PSBCs, this study proposed a novel approach of confining them with grouted GFRP tubes. Four novel and one reference specimens were tested under low cyclic loading to evaluate the effects of energy dissipation (ED) bars ratios, concrete interlayer strength, type of segment concrete, and concrete pouring methods within the outer GFRP tube (OGT) on the seismic behavior. Experimental results reveal that the failure modes of all specimens were triggered by the yielding of ED bars and the break of OGT at the top of ED bars. No crushed concrete at column bases or cracks at the segment joint were observed during the test due to the good confinement of GFRP tubes. All the specimens exhibited stable hysteretic behavior with small residual drift ratios and low strength degradation. Furthermore, finite element models (FEMs) were generated to predict the hysteretic behavior of novel specimens. The effects of some parameters such as OGT thickness, ED bars diameter, and concrete strength were further studied.

Role of fiber-reinforced chip seal interlayers in asphalt pavement bonding strength

ABSTRACT This study investigates the influence of seal coat parameters – rubber-modified asphalt content, fiber content, fiber length, and chip content – on the bonding characteristics of asphalt pavement layers. Employing a full factorial experiment and utilizing direct shear and tensile tests, the research identified the optimal material composition for improving interlayer bonding. The results showed that fiber content notably enhanced shear strength, whereas rubber-modified asphalt content significantly influenced tensile strength. The inclusion of fibers in the seal coat notably increased bonding strengths by up to 45.6% and 61.5% in shear and tensile strengths, respectively, demonstrating considerable performance enhancements at room temperature. In addition, the study explored the economic advantages of fiber-reinforced chip seal treatments, revealing substantial improvements in interlayer strength, particularly under diverse temperature conditions. This research contributes valuable insights into optimizing reinforced bituminous interfaces for asphalt pavements, offering a promising avenue for enhancing pavement durability and performance.

Assessing bio-oil cutback asphalt for prime coat on semi-rigid base asphalt pavement: Lab experiment & indoor test section application

To analyze the potential utilization of bio-oil cutback asphalt (BCA) as an innovative permeable material, this study comprehensively evaluated the road performance of BCA. Infrared spectroscopy and fluorescence microscopy were employed to characterize the components' interaction mechanisms and storage stability within the BCA. The research also involved assessments of interlayer strength, unconfined compressive strength, and dynamic water scouring trials of the base layer. Subsequently, a comprehensive assessment of the road performance of BCA was carried out in conjunction with its application on the indoor test section. The microscopic test results revealed that bio-oil and the penetrant primarily enhanced the asphalt's flow and penetration properties through physical blending. Even after 28 days of storage, no phase separation occurred among the constituents in the BCA. Compared to conventional prime coat materials, the specimens treated with BCA demonstrated notably higher interlayer pull-off and shear strengths at the optimal sprinkling volume. Furthermore, applying BCA to the cement-treated base improved its early strength and erosion resistance. As a result, BCA plays a crucial role in enhancing the structural integrity of asphalt pavements with semi-rigid base layers.

Influence of polyether ether ketone (PEEK) viscosity on interlayer shear strength in screw extrusion additive manufacturing

The excellent properties of polyether ether ketone (PEEK) have made it applicable for high-performance components in aerospace, electrical, chemical, and biomedical industries. Material extrusion (MEX) additive manufacturing (AM) of PEEK using fused filament fabrication (FFF) predominantly uses modified PEEK filament. Fused granulate fabrication (FGF) systems conventionally employ injection moulding and extrusion grades which are not specifically formulated for MEX AM. There is a limited amount of research on the use of these grades for MEX AM using PEEK. This study evaluated different viscosity PEEK grades at various extruder temperatures to optimise interlayer strength and therefore determine the best grades of PEEK for FGF. Compression shear testing (CST) was used to study this property as it represents a mostly shear loading condition i.e., without bending, compared to other conventional shear testing methods, whilst also being easier to fabricate. PEEK crystallinity is corelated to the interlayer strength and was evaluated using differential scanning calorimetry (DSC), Raman spectroscopy and X-ray diffraction (XRD). The highest interlayer strength of 17.70±0.58 MPa and the lowest crystallisation degree of 29.7±1.3% (Raman) was achieved by VESTAKEEP L4000G PEEK, printed at the highest extruder temperature (420°C). This grade had the highest viscosity or the lowest melt volume-flow rate (MVR). In contrast with lower MVR grades, the high MVR grade VESTAKEEP L2000G, achieved a higher increase in bond strength and crystallinity with higher extruder temperatures. At lower MVR, the crystallinity was found to decrease from 33% to 30% with increasing extruder temperatures, along with an increase in melting temperature. This behaviour was attributed to a change in crystalline morphology possibly caused by the long residence time and high processing temperature of FGF.

Investigating the effect of recycled irregular metallic particles embedment on the interlaminar strength of polyamide-based composites

ABSTRACT In this research, for the first time, the effect of embedding irregular and jagged steel particles of recycled milling dendritic chips on the improvement of compressive and interlayer strength of thermoplastic polyamide6 (PA6)-based, 200 g/m2 plain weave E-glass-fabric-reinforced composite laminates was investigated. The goal here is to examine whether the sharp spikes on the particles can penetrate adjoining laminate layers to provide superior interface toughness compared to spherical toughening particles. In-plane compression tests, according to ASTM D695-15 standard, show that through thickness expansion leads to delamination and subsequent failure. Consequently, theoretical considerations suggest that enhancements in interface toughness should lead to an increase in compression strength. For this purpose, steel particles with three size ranges, 300–600 µm, 150–300 µm, and 75–150 µm, were prepared and embedded into the composite laminates using film-stacking and hot-pressing process, in four different volume fractions. The particle distribution, impregnation, and bonding with the PA6 matrix were analyzed using optical and scanning electron microscopy imaging. Overall, results demonstrate a very good mechanical bonding between the particles and the thermoplastic matrix. Some interlocks between the particles and composite laminates were observed which has led to an improvement in the compressive strength of the composite laminate.

Mechanism of hydraulic fracture vertical propagation in deep shale formation based on elastic–plastic model

Deep shale reservoirs exhibit strong plasticity, and the simulation results from previous fracturing simulations based on elastic models may not adequately account for the effects of plastic. Therefore, the research objective is to develop a 3D finite element method (FEM) model of hydraulic fracture vertical propagation in multilayer reservoirs. The model simultaneously considering Drucker-Prager elastic–plastic rock model and bedding plane. To investigate the impact of various parameters on the vertical propagation pattern of fracture, it is crucial to consider factors such as friction angle, yield strength, interlayer strength, and vertical stress. This study quantitatively characterizes the mechanical parameters such as ground stress, matrix strength, and interface strength on hydraulic fracture morphology. Additionally, a new integrated control diagram is established to provide a comprehensive understanding of these effects. The results indicate that rocks with high friction angles and low yield strength are more resistant to cracking, and hydraulic fractures tend to have narrower fractures. Fracturing from high-strength and high-stress zones to lower zones promotes vertical fracture propagation. The high vertical stress plays a crucial role in preventing the fracturing fluid from entering the interface. Moreover, the strength of the formation interface greatly influences the vertical extension of hydraulic fractures. The bedding plane interface with a high cementation level can enhance the possibility of fracture vertical connection with multiple reservoirs. Conversely, breaking through low strength cemented interfaces in the formation can pose challenges for hydraulic fractures. The present simulation conditions determine that the fracture's ability to cross the layer depends on the ratio of interface strength to matrix strength, which should be between 0.25 and 0.5. These findings offer valuable theoretical guidance on the vertical propagation of fractures in deep multilayer fracturing.

Analysis of Interlayer Crack Propagation and Strength Prediction of Steel Bridge Deck Asphalt Pavement Based on Extended Finite Element Method and Cohesive Zone Model (XFEM–CZM) Coupling

The extended finite element method (XFEM) was employed for the computational modeling of internal defects within a bond layer. Furthermore, a cohesive zone model (CZM) was implemented to characterize the behavior of the bond layer in response to interactions at both the bond layer/steel plate and bond layer/asphalt paving layer interfaces. The coupling of XFEM and CZM was used for a comprehensive analysis of crack propagation within the bond layer as well as the assessment of phenomena associated with interfacial debonding and delamination. The feasibility and accuracy of the XFEM–CZM coupling method were verified by comparing it with the virtual crack closure technique (VCCT), CZM, XFEM–VCCT, and experiments. A double cantilever beam experimental model was established to simulate the process of interlayer-type cracks expanding from the inside of the bond layer to the interface between the bond layer and the upper and lower layers, causing debonding. This was undertaken to analyze the damage failure mechanism of interlayer-type cracks in asphalt paving layers of steel bridge decks; to discuss the impacts of the initial crack length, the interface stiffness, the interface strength, and the thickness of the bond layer on the performance of the overall interlayer bond strength; and to carry out the significance analysis. The results showed that the initial crack length, interface stiffness, and bond layer thickness had different effects on the expansion path of interlayer cracks. The interlayer strength decreased with an increase in the initial crack length and interface stiffness, increased with an increase in the interface strength, and decreased with an increase in the thickness of the bond layer. The interface stiffness had the most significant effect on the strength.

The effect of 3D printing fluorene-containing poly (aryl ether ketone)/poly (ether ketone) blends on interlayer strength

The limited diffusion and entanglement of the chains between beads cause pronounced anisotropy in the mechanical properties of 3D printed parts. Therefore, amorphous poly (aryl ether ketone) (aPAEK) containing fluorene groups with high intrinsic strength and good interfacial fusion is synthesized and employed to improve the interlayer adhesion of poly (ether ether ketone) (PEEK) parts. Herein, we designed an aPAEK with high intrinsic strength and good interfacial fusion with PEEK blends. The tensile strength of 30 mol% fluorene groups aPAEK was improved to 75 MPa, and the interlayer strength of 20 wt% blends was increased by 315 % compared to PEEK. Moreover, the selection of an appropriate molecular weight for aPAEK is crucial in maintaining the elevated tensile strength while promoting interlayer diffusion during the printing process. These results highlight a novel strategy for the design and development of blend polymers for interlayer reinforcement in 3D printing applications.

Specified criterion for delamination upon bending of a composite beam

The interlayer strength in polymer fiber composites is characterized mostly by the strength of the matrix, which is much lower than fiber strength. For this reason, the analysis of fracture occurred through delamination is extremely important for assessing the operability of composite structural elements. When designing critical structures, it is necessary to know the interlayer shear strength, for which the method of bending a short beam has been standardized. The shear stresses and the interlayer shear strength in bending theory are traditionally assumed to be independent of the length and width of the beam. However, a large number of experimental studies prove the opposite fact that the geometry of the specimen affects the value of critical stresses. The linear fracture criterion proposed by the authors allows explanation and quantitatively description of the interlayer shear strength dependence on the geometry of the specimen. The influence of the heterogeneity of interlayer shear stresses across the beam on the critical stresses is analyzed. A strict solution of the bending problem showed that taking into account the specified shear stress distribution gives an insignificant correction to the determined value of the interlayer strength, which makes it possible to use a simplest parabolic distribution in height. The results of the analysis are confirmed in three-point bending tests of short composite beams of different widths. The results of fatigue tests of short beams made of carbon fiber reinforced plastic are analyzed. The relationship between tensile fatigue curves of polymer fiber composites and the fatigue curves obtained in cyclic three-point bending test of short beams has been revealed using the proposed linear fracture criterion. The estimation of the strength scale effect on the basis of the energy criterion of delamination with and without taking into account the refined distribution of interlayer shear stresses is presented.

Effect of stacking sequence and interlayer toughening in ＋/−45 laminates

This paper investigates the combined effects of stacking sequence and interlayer toughening on the mechanical response and failure modes of ±45° carbon fiber reinforced laminates, comprising experimental and numerical studies. Two material systems (T800H/3631, T800S/3900) and three stacking sequences (4 double plies, 4 plies, 8 plies) have been analyzed. Digital Image Correlation (DIC) and a high resolution edge camera were utilized to capture the intricate crack patterns in each ply. This paper also addresses the challenge of the nonlinear in-plane shear characterization of the lamina, and proposes an amendment to the existing ASTM standard to obtain the in-situ non-linear response and the lamina shear strength with the consideration of residual stresses. The complex progression of micro-damage, matrix cracks and delamination as well as the final two-piece failure were captured by the enhanced semi-discrete damage modeling (eSD2M) framework. A parametric study was performed to reverse-engineer the most critical parameters such as interlayer strengths and toughnesses. The obtained values reflect the difference in the interlayer composition between the two material systems.