Selective Laser Sintering Parts Research Articles

Influence of Build Orientation and Part Thickness on Tensile Properties of Polyamide 12 Parts Manufactured by Selective Laser Sintering.

The use of additive manufacturing to rapidly test and evaluate solutions to engineering problems has been demonstrated. Selective laser sintering (SLS) is a subset of additive manufacturing that is particularly well suited to producing structural thin wall models and end use parts which can improve the ability to prototype and manufacture certain designs at a substantially lower cost and time compared to current methods. However, a more comprehensive understanding of the material properties of these parts is warranted. The presented research investigates the influence of print orientation and sample thickness on the material properties of printed SLS parts. This novel work involves holding a hatch pattern constant across SLS prints using polyamide 12 material to isolate the anisotropic effects of orientation and thickness. An evaluation of ultimate tensile strength, modulus of elasticity, strain at failure, yield strength, and Poisson's ratio, and scanning electron microscope fractography are conducted. Transverse strain and Poisson's ratio are a key aspect that provide insight into the feasibility of building numerical orthotropic models. These data are used to calculate the degree of anisotropy due to both thickness and orientation. The results support the future use of SLS printing and modeling of thin-walled structures, such as scaled structural ship modeling. The presented data provide guidance on the impact of print orientation and thickness that will aid in manufacturing structural parts with intentionally tuned material properties.

Influence of Particle Size on the Mechanical Performance and Sintering Quality of Peanut Husk Powder/PES Composites Fabricated through Selective Laser Sintering.

This study intends to enhance the mechanical strength of wood-plastic composite selective laser sintering (SLS) parts by using a sustainable composite, peanut husk powder (PHP)/poly ether sulfone (PES) (PHPC). The study aims to address agricultural waste pollution by encouraging the eco-friendly utilization of such waste in SLS technology. To ensure the sintering quality and mechanical properties and prevent deformation and warping during sintering, the thermo-physical properties of PHP and PES powders were analyzed to determine a suitable preheating temperature for PHPC. Single-layer sintering tests were conducted to assess the formability of PHPC specimens with varying PHP particle sizes. The study showed the effects of different PHP particle sizes on the mechanical performance of PHPC parts. The evaluation covered various aspects of PHPC SLS parts, including mechanical strength, density, residual ash content, dimensional accuracy (DA), and surface roughness, with different PHP particle sizes. The mechanical analysis showed that PHPC parts made from PHP particles of ≤0.125 mm were the strongest. Specifically, the density bending strength, residual ash content, tensile, and impact strength were measured as 1.1825 g/cm3, 14.1 MPa, 1.2%, 6.076 MPa, and 2.12 kJ/cm2, respectively. Notably, these parameters showed significant improvement after the wax infiltration treatment. SEM was used to examine the PHP and PES powder particles, PHPC specimen microstructure, and PHPC SLS parts before and after the mechanical tests and waxing. Consequently, SEM analysis wholly confirmed the mechanical test results.

Optimization of Selective Laser Sintering Three-Dimensional Printing of Thermoplastic Polyurethane Elastomer: A Statistical Approach

This research addresses the challenge of determining the optimal parameters for the selective laser sintering (SLS) process using thermoplastic polyurethane elastomer (TPU) flexa black powder to achieve high-quality SLS parts. This study focuses on two key printing process parameters, namely layer thickness and the laser power ratio, and evaluates their impact on four output responses: density, hardness, modulus of elasticity, and time required to produce the parts. The primary impacts and correlations of the input factors on the output responses are evaluated using response surface methodology (RSM). A particular response optimizer is used to find the optimal settings of input variables. Additionally, the rationality of the model is verified through an analysis of variance (ANOVA). The research identifies the optimal combination of process parameters as follows: a 0.11 mm layer thickness and a 1.00 laser power ratio. The corresponding predicted values of the four responses are 152.63 min, 96.96 Shore-A, 2.09 MPa, and 1.12 g/cm3 for printing time, hardness, modulus of elasticity, and density, respectively. These responses demonstrate a compatibility of 66.70% with the objective function. An experimental validation of the predicted values was conducted and the actual values obtained for printing time, hardness, modulus of elasticity, and density at the predicted input process parameters are 159.837 min, 100 Shore-A, 2.17 MPa, and 1.153 g/cm3, respectively. The errors between the predicted and experimental values for each response (time, hardness, modulus of elasticity, and density) were found to be 4.51%, 3.04%, 3.69%, and 2.69%, respectively. These errors are all below 5%, indicating the adequacy of the model. This study also comprehensively describes the influence of process parameters on the responses, which can be helpful for researchers and industry practitioners in setting process parameters of similar SLS operations.

Embedding Components During Laser Sintering

• This paper outlines the process of the embedding of components into ILS prints. • ILS embedding opens the door to direct printing of circuit boards with integrated chips using SLS technology. • Embedding is demonstrated by producing a printed part containing a functional LED. We propose an approach for embedding electronic components during a Selective Laser Sintering (SLS) process. Common SLS processes are incompatible with component embedding because generating voids in the parts developed using this production method is logistically challenging. Here, we use an inverted laser sintering (ILS) process that sidesteps the need for a powder bed, and can therefore trivially generate voids in printed components. We demonstrate this method by embedding an LED inside an SLS part cavity, and then resuming the printing process. The LED is then externally activated, confirming its functionality after several layers are added. This ability could help transform SLS from fabricating passive parts to active systems.

Effects of Laser Power and Hatch Orientation on Final Properties of PA12 Parts Produced by Selective Laser Sintering.

Poly(dodecano-12-lactam) (commercially known as polyamide “PA12”) is one of the most resourceful materials used in the selective laser sintering (SLS) process due to its chemical and physical properties. The present work examined the influence of two SLS parameters, namely, laser power and hatch orientation, on the tensile, structural, thermal, and morphological properties of the fabricated PA12 parts. The main objective was to evaluate the suitable laser power and hatching orientation with respect to obtaining better final properties. PA12 powders and SLS-printed parts were assessed through their particle size distributions, X-ray diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), a scanning electron microscope (SEM), and their tensile properties. The results showed that the significant impact of the laser power while hatching is almost unnoticeable when using a high laser power. A more significant condition of the mechanical properties is the uniformity of the powder bed temperature. Optimum factor levels were achieved at 95% laser power and parallel/perpendicular hatching. Parts produced with the optimized SLS parameters were then subjected to an annealing treatment to induce a relaxation of the residual stress and to enhance the crystallinity. The results showed that annealing the SLS parts at 170 °C for 6 h significantly improved the thermal, structural, and tensile properties of 3D-printed PA12 parts.

Study on selective laser sintering process and investment casting of rice husk/ Co-Polyamide (Co-PA hotmelt adhesive) composite

The current available wood-plastic materials used for selective laser sintering (SLS) investment casting are often poor in fluidity in molten state, which is not easy to flow out the shell mold. This led to a large amount of residual ash in mold after heating and lowered the quality of the sintered parts. In this article, the Co-Polyamide (Co-PA Hotmelt adhesive) and rice husk powders (RH) were proposed as the feedstock of the rice husk (RH)/CO-PA composite (RHPA) for SLS. CO-PA with good fluidity was used as the matrix and RH powder as the additive materials. This paper aims to optimize the SLS processing parameters and determine the optimal ratio of RHPA parts manufactured by SLS. Through this work, an orthogonal experimental method of five factors and four levels was used to determine the optimum SLS parameters for the RHPA SLS test. The scan spacing, scan speed, laser power, layer thickness, and preheating temperature are chosen as main SLS affecting factors of this study. The synthesis weighted scoring methods were used to conclude the optimal combination of SLS parameters of RHPA i.e., scan spacing = 0.15mm, scan speed = 2m/s, laser power =16W, layer thickness = 0.25 mm and the preheating temperature = 74°C. Moreover, the influence of RH content on the mechanical properties, dimensional accuracy, and the residual ash content of RHPA parts was determined. When the ratio of RH powder on RHPA is 10 wt %, the bending strength of the sintered parts will reach 2 MPa. Besides, the residual ash content of RHPA parts after heating step was lower (1.1881%) and the tolerance level is CT5. Thus, the dimensional accuracy in X, Y, and Z directions of 10 wt % RHPA SLS parts is 99.79%, 98.71%, and 97.9%, respectively; and the surface of casting was smooth and clear details.

Life cycle energy and greenhouse gas emissions implications of polyamide 12 recycling from selective laser sintering for an injection‐molded automotive component

AbstractThe selective laser sintering (SLS) process generates waste polymer powders, which can be recycled as feedstock for producing injection‐molded components. Recycling this powder has implications on the life cycle modeling of the SLS product, as well as the subsequent injection‐molded component. This study investigates the life cycle primary energy demand (PED) and global warming potential (GWP) of an automotive fuel‐line clip produced with recycled polyamide 12 (PA12) from an SLS process in comparison to the conventional polyamide 66 (PA66) counterpart, based on real‐world industry data. In addition, the life cycle PED and GWP of an SLS part are examined, with and without recycling PA12 from the SLS process. The results indicate a strong dependence on the approach to evaluate the environmental burden of waste PA12 from the SLS process (cut‐off, mass‐based allocation, economic allocation, and substitution). Compared with the PA66 fuel‐line clip, the recycled PA12 (rPA12) clip reduces the life cycle GWP by up to 26% (cut‐off) or increases by up to 68% (mass‐based allocation). For the SLS part, recycling PA12 powder provides a 42% reduction to its life cycle GWP (mass‐based allocation). Finally, from an expanded two‐part system perspective, the recycling of PA12 from the SLS process provides an 8% reduction in life cycle GWP. Similar trends are shown for the life cycle PED profiles. This study demonstrates the importance of recycling additive manufacturing (AM) wastes within a broader cascading system to improve the environmental performance of AM and the circular economy across industrial systems.

Micromechanical characterization of the material response in a PA12-SLS fabricated lattice structure and its correlation with bulk behavior

Selective laser sintering (SLS) of polymers has made possible the introduction of lattice-based cells as building blocks of polymer parts, allowing to obtain optimal specific properties. The actual mechanical performance of an SLS part is strongly dependent on the printing direction and part shape. Nevertheless, macroscopic testing is not usually possible due to size restrictions of the fabricated part, as it happens, for example, in lattice-based materials. In this case, microscopic tests performed directly on the lattice surface become fundamental. In this work, the mechanical behavior of SLS PA12 under a wide range of strain rates from 10−3 to 103 s−1 and different printing directions is characterized using macroscopic tests on bulk samples and compared with nanoindentation performed directly on the lattice material surface. An excellent correlation was found between the rate-dependent mechanical behavior obtained at the two scales, validating microscopic techniques for characterizing the mechanical response of SLS fabricated PA12 parts.

Effects of various processing parameters on the mechanical properties and dimensional accuracies of Prosopis chilensis/PES composites produced by SLS

PurposeThe range of applications of the currently available biomass selective laser sintering (SLS) parts is limited and low-quality. This study aims to demonstrate the effects of the various processing parameters on the dimensional accuracy, bending strength, tensile strength, density and impact strength of the Prosopis chilensis/polyethersulfone (PES) composites (PCPCs) that were produced by SLS. The various processing parameters are laser power, scan speed, preheating temperature, scan spacing and layer thickness. In addition, the authors’ studied the effects of PCP particle size on the mechanical properties of the PCPCs.Design/methodology/approachThe PCPC specimens were printed using an AFS SLS machine (additive manufacturing). The bending, tensile and impact strengths of the specimens were measured using a universal tensile tester. The dimensional accuracy of the bending specimens was determined by a Vernier caliper. The formability of the PCPC at various mixing ratios of the raw materials was earlier investigated by single-layer sintering experiments (Idriss et al., 2020b). The microstructure and particle distribution of the various PCPC specimens were analyzed by scanning electron microscopy (SEM).FindingsThe mechanical strengths (bending, tensile and impact strengths and density) and the dimensional accuracy of the PCPC SLS parts were directly and inversely proportional, respectively, to the laser power and preheating temperature. Furthermore, the mechanical strengths and dimensional accuracy of the PCPC SLS parts were inversely and directly proportional, respectively, to the scanning speed, scan spacing and layer thickness.Practical implicationsPCPC is an inexpensive, energy-efficient material that can address the drawbacks of the existing SLS parts. It is also eco-friendly because it lowers the pollution and CO2 emissions that are associated with waste disposal and SLS, respectively. The optimization of the processing parameters of SLS in this study produced high-quality PCPC parts with high mechanical strengths and dimensional accuracy that could be used for the manufacture of the roof and wooden floors, construction components and furniture manufacturing.Originality/valueTo the best of the authors’ knowledge, this study is among the first to elucidate the impact of the various SLS processing parameters on the mechanical properties and dimensional accuracy of the sintered parts. Furthermore, novel PCPC parts were produced in this study by SLS.

Selective Laser Sintering Parameter Optimization of Prosopis Chilensis/Polyethersulfone Composite Fabricated by AFS-360 SLS.

The current available selective laser sintering (SLS) materials are often high in cost and limited in variety; the mechanical properties of wood-composite SLS parts are low quality, which restricts the development of SLS technology. This article aims to optimize the SLS processing parameters to enhance the mechanical properties of the Prosopis chilensis powder (PCP)/polyethersulfone (PES) composite (PCPC) part fabricated via SLS. The PCP and PES powder were proposed as the feedstock of the PCPC powder bed for SLS. First, the thermal decomposition and glass transition temperatures (Tg) of PCP and PES powder were estimated to reduce the produced PCPC parts from warping and deformation during SLS. An orthogonal experimental methodology with five factors and four levels was used to optimize the SLS parameters for the PCPC SLS test. The scanning speed, preheating temperature, and laser power are selected as the main affecting factors on this study. The influence of these factors on dimension accuracies, bending and tensile strengths, and surface roughness quality of the produced PCPC parts was studied. The PCPC particle distribution and microstructure were inspected via scanning electron microscopy. Furthermore, the synthesis weighted scoring methods were utilized to determine the optimal SLS processing parameters of the produced PCPC parts. The combined results of tests showed that the optimal SLS parameters were as follows: the scanning speed is 1.8 m/s, preheating temperature is 80°C, and the laser power is 12 W. Thus, the quality of PCPC SLS parts was significantly enhanced when the optimal parameters were utilized in the SLS process. This article provided the main reference values of SLS parameters of the PCPC. To further enhance the surface roughness quality and mechanical strengths, the postprocessing infiltration with wax was introduced; after wax infiltration, the surface roughness and mechanical strengths were significantly improved.

Polymer Brush Induced Electroless Copper Plating on PA12 Surface for Tensile Strength Enhancement of Selective Laser Sintering Part

Polymer Brush Induced Electroless Copper Plating on PA12 Surface for Tensile Strength Enhancement of Selective Laser Sintering Part

SLS Process Parameter Optimization to Improve Surface Quality and Accuracy of Polyamide Parts

The contribution of selective laser sintering (SLS) technique in the 4.0 manufacturing industry is undisputedly significant. SLS part quality exhibits high dependence on SLS process parameters and is a major challenge. Therefore, this research aims to investigate the effect of input parameters (i.e., part orientation, bed temperature, and layer thickness) on the surface roughness and accuracy of laser-sintered polyamide specimens. Response surface methodology (RSM) and ANOVA analysis aided the testing and evaluation. Optimal working conditions for minimum shrinkage were 0.17 mm layer thickness, 177.89°C part bed temperature, and part orientation at 88.91 degrees. The surface quality deteriorated with the increment in part bed temperature and layer thickness, and it shows an inverse trend (or improves) with the part orientation in the prescribed range. The optimal surface roughness was at a layer thickness of 0.11 mm, bed temperature at 174.55°C, and part orientation at 86.5 degrees.

Fabrication of PVDF/BaTiO3/CNT Piezoelectric Energy Harvesters with Bionic Balsa Wood Structures through 3D Printing and Supercritical Carbon Dioxide Foaming.

Piezoelectric energy harvesters have received widespread attention in recent decades due to their inimitable electrical energy conversion methods. However, traditional polymer/piezoceramic materials and 2D thin-film structures have limited output performance, making them difficult to be efficiently applied in the collection of discrete mechanical energy. Here, new ternary composite powders were successfully developed by the ultrasonic coating method, and array structural devices with the construction of micropores were prepared using selective laser sintering (SLS) and supercritical carbon dioxide foaming (Sc-CO2) technologies. Coating carbon nanotubes improved the polarization efficiency of poly(vinylidene fluoride)/barium titanate (PVDF/BaTiO3) composites, which made it easy to perfectly combine the BaTiO3 piezoelectric constant and the flexibility of PVDF, promoting d33 from 0.7 to 2.6 pc/N. In addition, simulations and experiments simultaneously proved that SLS parts with high array densities amplified piezoelectric outputs because of a greater compression deformation in the vertical direction. Meanwhile, under the synergistic effect of SLS and Sc-CO2, 3D bionic balsa wood structure foams were successfully fabricated, which took advantage of the normal space, expanded the stress-strain effect, and improved the piezoelectric output capability. Excitingly, the prepared foam could directly produce 19.3 V and 415 nA piezoelectric output to charge a 1 μF commercial capacitor to 5.03 V within 180 s, which surpassed most of the PVDF piezoelectric energy harvesters reported thus far. This work has an excellent innovative and practical value in enriching the types of piezoelectric materials for SLS 3D printing and the design of 3D piezoelectric structures.

Preparation and selective laser sintering of nylon-12 coated copper powders

PurposeThe purpose of this paper is to prepare metal/polymer composite materials prepared by additive manufacturing (AM) technology.Design/methodology/approachThe effect of sintering parameters including laser power, scanning speed and slice thickness on strength and accuracy of selective laser sintering (SLS) parts were analyzed experimentally. Then, the laser sintering mechanism of nylon-12 coated copper was discussed through analyzing the interfacial reaction of nylon-12 and copper. The SLS parts were infiltrated with epoxy resin to meet the strength requirements of injection molding.FindingsIn this study, mechanical mixed nylon-12/copper and nylon-12 coated copper composite powders were investigated and compared as SLS materials. An effective dissolution–precipitation method was proposed to prepare nylon-12 coated copper powders with better processing and mechanical properties. The bending strength and modulus of fabricated parts after infiltration with epoxy reach 65.3 MPa and 3,200 MPa, respectively.Originality/valueThe composite materials can be used in the manufacture of injection molds with a conformal cooling channel for the production of common plastics in prototype quantities, showing a broad application prospect in rapid tooling.

Improved Sintering Quality and Mechanical Properties of Peanut Husk Powder/Polyether Sulfone Composite for Selective Laser Sintering.

Current wood-plastic materials available for selective laser sintering (SLS) are limited and often suffer from low-quality and mechanical strength. In this study, a new composite of peanut husk powder (PHP)/polyether sulfone (PES) was developed for SLS additive manufacturing (AM). To use the biomass waste materials in AM technology, such as furniture and wood flooring, this composite based on agricultural waste is environmentally friendly, energy efficient, and low in production cost. SLS parts made from PHPC had good mechanical strength and excellent dimensional precision (DP). The thermal decomposition temperature of composite powder components and the glass transition temperatures of PES and various PHPC were determined first to prevent the PHPC parts from warping during sintering. Furthermore, the formability of PHPC powders in various mixing ratios was examined through single-layer sintering; and the density, mechanical strength, surface roughness, and DP of the sintered parts were measured. Particle distribution and microstructure of the powders and the SLS parts (both before and after breakage in mechanical tests) were inspected using scanning electron microscopy. According to the combined results, a ratio of PHP/PES = 10/90 (w/w) resulted in the best forming quality and mechanical strength compared with other ratios and pure PES. The measured density, impact strength, tensile strength, and bending strength for this PHPC are 1.1825 g/cm3, 2.12 kJ/cm2, 6.076 MPa, and 14.1 MPa, respectively. After wax infiltration, these parameters were further improved to 2.0625 g/cm3, 2.96 kJ/cm2, 7.476 MPa, and 15.7 MPa, respectively.

Fabrication of Si3N4–SiC/SiO2 composites using 3D printing and infiltration processing

Si3N4–SiC/SiO2 composites were prepared by employing three-dimensional (3D) printing using selective laser sintering (SLS) and infiltration processing. The process was based on the infiltration of silica sol into porous SLS parts, and silicon carbide and silicon nitride particles were bonded by melted nano-sized silica particles. To optimize the manufacturing process, the phase compositions, microstructures, porosities, and flexural strengths of the Si3N4–SiC/SiO2 composites prepared at different heat-treatment temperatures and infiltration times were compared. Furthermore, the effects of the SiC mass fraction and the addition of Al2O3 and mullite fibers on the properties of the Si3N4–SiC/SiO2 composites were investigated. After repeated infiltration and heat treatment, the flexural strength of the 3D-printed Si3N4–SiC/SiO2 composite increased significantly to 76.48 MPa. Thus, a Si3N4–SiC/SiO2 composite part with a complex structure was successfully manufactured by SLS and infiltration processes.

Effect of Al powder on mechanical properties and microstructure of wood-plastic composites by selective laser sintering

To solve the problem of the low mechanical properties of wood-plastic composites (WPC) by selective laser sintering (SLS), a tiny amount of Al powders were added into WPC as the reinforcement in this work. Both the mechanical properties and the microstructure of SLS parts were investigated. The results showed that the bending properties of parts first increased to 128.08 % and then decreased to 118.1 % with the increase of Al powder content from 0.1 wt% to 2 wt%. The porosity and sintering neck size of fracture had the same change pattern as the mechanical properties of parts. The strengthening mechanism might be that the good thermal conductivity of Al powder would better facilitate the sintering behavior of composite powder and a stronger interface bonding between wood powders and PES matrix can be obtained. However, the mechanical properties of SLS parts with excessive Al powder decreased due to its reflecting lasers.

Prediction of SLS parts properties using reprocessing powder

Purpose Owing to the operating principle of powder bed fusion processes, selective laser sintering (SLS) requires effective management of the mixture ratio of processed material previously exposed to the high temperatures of processing with new virgin material. Therefore, this paper aims to fully understand the effect that the successive reprocessing has in the powder material and to evaluate its influence on the properties of SLS parts produced at different building orientations. Design/methodology/approach Polyamide 12 material with 0%, 30% and 50% of virgin powder and parts produced from them were studied through five consecutive building cycles and their mass, mechanical, thermal and microstructural properties were evaluated. Then, the experimental data was used to validate a theoretical algorithm of prediction capable to define the minimum amount of virgin powder to be added on the processed material to produce parts without significant loss of properties. Findings Material degradation during SLS influences the mass and mechanical properties of the parts, exhibiting an exponential decay property loss until 50% of the initial values. The theoretical algorithms of reprocessing proved the appropriateness to use a mixture of 30% of virgin with 70% of processed material for the most common purposes. Practical implications This paper validates a methodology to define the minimum amount of virgin material capable to fulfil the operational specifications of SLS parts as a function of the number of building cycles, depending on the requirements of the final application. Originality/value The use of theoretical models of prediction allows to describe the degradation effects of SLS materials during the sintering, ensuring the sustainable management of the processed powder and the economic viability of the process.

The influence of process parameters on the performance of nylon 6 selective laser sintering parts

During the selective laser sintering process, the sintering behavior between powders is mainly affected by thermal effect. There are a large number of process parameters influencing the variation of temperature and molten pool, of which the laser density and scanning speed play a crucial role in determining the performance of the parts. In this paper, the effects of laser density and scanning speed on the precision and strength of polyamide 6 selective laser sintering parts were systematically investigated. The results show that with the increase of energy density, the positive dimensional deviation of the parts in three directions increases gradually, and the tensile strength increases at beginning and then decreases. When the laser power and scanning speed were changed, the tensile strength of the parts varied between 5.62 MPa and 58.74 MPa.

Estimation of the compression strength and surface roughness of the as-built SLS components using weibull distribution

Selective laser sintering (SLS) is a process of fabrication of three-dimensional structures by fus- ing powder particles using a guided laser source. The uncertainty in the mechanical properties of the SLS parts fabricated at the same time and with the same process parameters can affect the repeatability of the SLS process. A vast difference in the mechanical properties of the concurrently processed parts can lower the production quality of the batch. Therefore, the param- eters are required to be design based on the most probable outcome of the desired properties. Weibull distribution is one such statistical-based probability distribution method to measure the likelihood of the occurrence of a value of any random variable falling within a particular range of values. Here, the Weibull distribution was used to measure the relative likelihood (90% probability) of the surface roughness and the compressive strength values of the SLS-built polyamide PA2200 components in the given sample space that was obtained from 20 random samples. The results show that the variance in the surface roughness (scan and built plane) and the compressive strength values were in the range of 6–7 μm and around 10 MPa, respectively. Moreover, the surface roughness of the two orthogonal planes with 90% reliability was measured at 14.81 μm (scan plane) and 12.15 μm (built plane). Similarly, the yield strength and the compressive strength with 90% reliability were found 25.87 MPa and 62.64 MPa, respectively.