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Effect of laser cutting on mechanical performance of woven glass fiber reinforced plastic composites
激光切割对编织玻璃纤维增强塑料复合材料的力学性能影响

Md Mijanur Rahman a,*, a,*,  ^("a,*, "){ }^{\text {a,*, }} M Muzibur Rahman b b  ^("b "){ }^{\text {b }} a a  ^("a "){ }^{\text {a }} Department of Aeronautical Engineering, Military Institute of Science and Technology (MIST) Mirpur, Dhaka 1216, Bangladesh
航空工程学院，军事科学技术学院（MIST）米尔普尔，达卡 1216，孟加拉国 b b ^(b){ }^{\mathrm{b}} Department of Naval Architecture and Marine Engineering, Military Institute of Science and Technology (MIST) Mirpur, Dhaka 1216, Bangladesh
海军工程与海洋工程系，军事科学技术学院（MIST）米尔普尔，达卡 1216，孟加拉国

A R T I C L E I N F O
文章信息

Article history:  文章历史：

Available online 29 November 2022
2022 年 11 月 29 日在线可用

Keywords:  关键词：

GFRP composites  GFRP 复合材料
Laser cutting  激光切割
Mechanical cutting  机械切割
Mechanical performance  机械性能
SEM observation  射电望远镜观测

Abstract  摘要

The present study is an attempt to investigate the effect of laser cutting on the mechanical performance of woven glass fiber reinforced plastic (GFRP) composites. The composite material is fabricated by combining woven glass fiber cloth and epoxy resin with hardener. Then the GFRP composites are both mechanically cut and laser cut to prepare samples for mechanical performance testing. Prepared samples are tested as per respective ASTM standards to find tensile, flexural and hardness behaviors. Scanning Electron Microscope (SEM) micrographs of the machined surface and tensile fractured surface are analyzed concerning surface integrity and fracture characteristics. Finally, the results of the above tests are compared to find out whether mechanical cutting or laser cutting leads to superior mechanical performance of GFRP. Mechanical performance tests indicate that tensile and flexural properties are superior in mechanically cut samples compared to laser cut samples while microhardness properties remain similar. SEM micrographs show compromised surface integrity due to thermal damage in the case of laser cut samples which is attributed to the loss of tensile and flexural properties while fracture characteristics remain similar. Copyright © 2023 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the Second Global Conference on Recent Advances in Sustainable Materials 2022.
本研究试图调查激光切割对编织玻璃纤维增强塑料（GFRP）复合材料机械性能的影响。该复合材料通过将编织玻璃纤维布和环氧树脂与固化剂结合制成。然后对 GFRP 复合材料进行机械切割和激光切割，以制备机械性能测试样品。制备的样品按照相应的 ASTM 标准进行测试，以确定拉伸、弯曲和硬度行为。对加工表面和拉伸断裂表面的扫描电子显微镜（SEM）图像进行分析，以关注表面完整性和断裂特性。最后，比较上述测试结果，以找出机械切割或激光切割是否导致 GFRP 的机械性能更优。机械性能测试表明，与激光切割样品相比，机械切割样品的拉伸和弯曲性能更优，而显微硬度性能保持相似。 扫描电子显微镜图像显示，激光切割样品由于热损伤而导致表面完整性受损，这归因于拉伸和弯曲性能的丧失，而断裂特性保持相似。版权©2023 Elsevier Ltd。保留所有权利。选择和同行评审由 2022 年第二届全球可持续材料最新进展大会科学委员会负责。

1. Introduction  简介

Fiber-reinforced plastic (FRP) Composites are advanced hybrid functional materials that have gained massive popularity in industrial applications. Glass fiber reinforced plastic (GFRP), a type of FRP composite having glass fibers as the reinforcing element, has received widespread attraction in many applications including aerospace, marine, automobile and sports components due to mainly high strength to weight ratio, sustainability at cryogenic as well as elevated temperature, notable surface finishing, attractive aesthetic view, corrosion resistance and wear resistance [14]. The mechanical performance of FRP depends on the physiomechanical properties of the individual constituents, i.e., fibers, matrix, fillers and their interface [5]. Suitable orientations and composition of glass fibers can produce GFRPs with desired characteristics and functional properties. GFRPs can be fabricated having greater stiffness than aluminum with less relative density than steel. The matrix of the composite decides the maximum operating
纤维增强塑料（FRP）复合材料是先进的混合功能材料，在工业应用中获得了巨大的人气。玻璃纤维增强塑料（GFRP），一种以玻璃纤维为增强元素的 FRP 复合材料，由于主要具有高强度重量比、低温及高温下的可持续性、显著的表面处理、吸引人的美学外观、耐腐蚀性和耐磨性，在航空航天、海洋、汽车和体育部件等许多应用中受到了广泛的关注[14]。FRP 的机械性能取决于单个成分的生理力学特性，即纤维、基体、填料及其界面[5]。合适的玻璃纤维取向和组成可以产生具有所需特性和功能性质的 GFRP。GFRP 可以制成比铝具有更高的刚度，比钢具有更低的相对密度。复合材料的基体决定了最大工作
temperature of the composite material [6]. For high-performance applications in engineering, epoxy resins are most widely used as the matrix material among thermosetting plastics [7]. Many researchers have been investigating the role of inorganic and organic fillers to enhance the mechanical and tribological properties. Micro and Nano fillers like Al 2 O 3 , TiO 2 , SiO 2 , Mg ( OH ) 2 , SiC Al 2 O 3 , TiO 2 , SiO 2 , Mg ( OH ) 2 , SiC Al_(2)O_(3),TiO_(2),SiO_(2),Mg(OH)_(2),SiC\mathrm{Al}_{2} \mathrm{O}_{3}, \mathrm{TiO}_{2}, \mathrm{SiO}_{2}, \mathrm{Mg}(\mathrm{OH})_{2}, \mathrm{SiC}, Carbon Nano Tubes (CNTs) and also various natural fillers have been added by researchers to augment the mechanical properties of GFRPs [8-11].
复合材料温度[6]。在工程的高性能应用中，环氧树脂作为热固性塑料中的基体材料被广泛使用[7]。许多研究人员一直在研究无机和有机填料在增强机械和摩擦学性能中的作用。研究人员已经添加了微纳米填料如 Al 2 O 3 , TiO 2 , SiO 2 , Mg ( OH ) 2 , SiC Al 2 O 3 , TiO 2 , SiO 2 , Mg ( OH ) 2 , SiC Al_(2)O_(3),TiO_(2),SiO_(2),Mg(OH)_(2),SiC\mathrm{Al}_{2} \mathrm{O}_{3}, \mathrm{TiO}_{2}, \mathrm{SiO}_{2}, \mathrm{Mg}(\mathrm{OH})_{2}, \mathrm{SiC} 、碳纳米管（CNTs）以及各种天然填料，以增强 GFRPs 的机械性能[8-11]。
Due to extensive use, the machining of FRP composite is a very important consideration and different processes are needed to be explored to impart high surface quality, good dimensional accuracy and less alteration of mechanical properties. Machining of GFRPs or FRPs in general is a challenging task and different from that of metals due to their low thermal conductivity, heat sensitivity and anisotropic behavior [12]. Laser beam machining being a non-contact and virtually force-free manufacturing method is a preferable alternative means of cutting FRP composites. Laser cutting is a thermal process that focuses a laser beam to melt and vaporize material in a localized area [13].
由于广泛使用，FRP 复合材料的加工非常重要，需要探索不同的工艺来赋予高表面质量、良好的尺寸精度和较少的机械性能变化。GFRP 或 FRP 的加工通常是一项具有挑战性的任务，与金属加工不同，因为它们具有低热导率、热敏感性和各向异性[12]。激光束加工作为一种非接触和几乎无力的制造方法，是切割 FRP 复合材料的一种更可取的替代方法。激光切割是一种热加工过程，通过聚焦激光束在局部区域熔化和蒸发材料[13]。
Several researchers have explored different laser drilling/cutting parameters including laser intensity, cutting speed and gas pressure to achieve minimum surface roughness (Ra), heataffected zone (HAZ), taper angle (TA), and maximum tensile strength (TS) of the laser-drilled glass fiber-reinforced plastic (GFRP) laminate [14]. However, studies on the comparative effect of mechanically cut and laser cut on the mechanical performance of GFRPs or even FRPs in general are very seldom. The closest to our experiment is a research on the evaluation of the cutting process on the tensile and fatigue strength of CFRP composites [15], which found that the static tensile strength and the fatigue strength by laser cutting specimens decreased in comparison with mechanical or water-jet cutting specimen. Moreover, the laser cutting specimen exhibited a linear dependency of the tensile strength on the heat-affected zone (HAZ), indicating that the main effect resulted from the thermal destruction of CFRP within the HAZ.
数位研究人员已探索了不同的激光钻孔/切割参数，包括激光强度、切割速度和气体压力，以实现激光钻孔玻璃纤维增强塑料（GFRP）层压板的最低表面粗糙度（Ra）、热影响区（HAZ）、锥度角（TA）和最大抗拉强度（TS）[14]。然而，关于机械切割和激光切割对 GFRPs 或甚至 FRPs 一般机械性能比较的研究非常罕见。与我们的实验最接近的是一项关于评估切割过程对 CFRP 复合材料拉伸和疲劳强度影响的研究[15]，该研究发现，与机械切割或水射流切割试样相比，激光切割试样的静态抗拉强度和疲劳强度有所降低。此外，激光切割试样表现出抗拉强度与热影响区（HAZ）的线性依赖性，表明主要影响源于 HAZ 内 CFRP 的热破坏。
Summarizing the literature survey depicts that there are a good number of publications on the investigation of mechanical performance of GFRP by adding various fillers and also surface integrity improvement of FRPs in CO 2 CO 2 CO_(2)\mathrm{CO}_{2} laser machining. However, the comparative effect of CO 2 CO 2 CO_(2)\mathrm{CO}_{2} laser cutting and mechanical cutting on the mechanical performance including tensile, flexural and microhardness behavior of GFRP composites remains yet to be explored especially for woven glass fibers. As such, this paper focuses on investigating the effect of laser cutting on the mechanical performance of woven glass fiber reinforced epoxy composites.
总结文献综述表明，关于通过添加各种填料研究 GFRP 机械性能以及 FRPs 在 CO 2 CO 2 CO_(2)\mathrm{CO}_{2} 激光加工中表面完整性改进的出版物数量相当多。然而， CO 2 CO 2 CO_(2)\mathrm{CO}_{2} 激光切割与机械切割对 GFRP 复合材料机械性能（包括拉伸、弯曲和显微硬度行为）的比较效应仍有待探索，尤其是对于编织玻璃纤维。因此，本文重点研究激光切割对编织玻璃纤维增强环氧树脂复合材料机械性能的影响。

2. Materials and methods
2. 材料与方法

2.1. Materials  2.1. 材料

Commercially available 1100 GSM high silica ( SiO 2 ≥ 96 % SiO 2 ≥ 96 % SiO_(2) >= 96%\mathrm{SiO}_{2} \geq 96 \% ) woven Glass fiber cloth was chosen as the reinforcing element for preparing the GFRP composite material. This glass fiber cloth was collected from Jiangnan Company originated in Jiangsu, China. According to the manufacturer of the fiber, the tolerable working temperature of the glass fiber cloth is up to 1100 ∘ C 1100 ∘ C 1100^(@)C1100^{\circ} \mathrm{C} and the melting point is 1700 ∘ C 1700 ∘ C 1700^(@)C1700^{\circ} \mathrm{C}. The glass fiber cloth is 1.2 mm in thickness with a thread count of 20 per cm in WARP and 15 per cm in WEFT. Two layers of glass fibers were cut into 325 mm × 325 mm 325 mm × 325 mm 325mmxx325mm325 \mathrm{~mm} \times 325 \mathrm{~mm} square size and used to prepare one composite slab. Araldite AW 106 IN epoxy resin and HV 953 U hardener were used as the matrix material. The ratio of Resin and Hardener was used as 100 R / 80 H 100 R / 80 H 100R//80H100 \mathrm{R} / 80 \mathrm{H} by weight as per the manufacturer’s recommendation. The specific gravity of resin and hardener are 1.17 and 0.92 respectively, and viscosity (cP) at 25 ∘ C 50 , 000 25 ∘ C 50 , 000 25^(@)C50,00025^{\circ} \mathrm{C} 50,000 and 35,000 respectively.
商用 1100 克/平方米高硅（ SiO 2 ≥ 96 % SiO 2 ≥ 96 % SiO_(2) >= 96%\mathrm{SiO}_{2} \geq 96 \% ）编织玻璃纤维布被选作制备 GFRP 复合材料的增强元素。这种玻璃纤维布来自江苏江南公司，原产于中国。根据纤维制造商，玻璃纤维布的耐受工作温度高达 1100 ∘ C 1100 ∘ C 1100^(@)C1100^{\circ} \mathrm{C} ，熔点为 1700 ∘ C 1700 ∘ C 1700^(@)C1700^{\circ} \mathrm{C} 。玻璃纤维布厚度为 1.2 毫米，经向每厘米 20 根纱线，纬向每厘米 15 根纱线。将两层玻璃纤维裁成 325 mm × 325 mm 325 mm × 325 mm 325mmxx325mm325 \mathrm{~mm} \times 325 \mathrm{~mm} 平方尺寸，用于制备一块复合材料板。使用 Araldite AW 106 IN 环氧树脂和 HV 953 U 硬化剂作为基体材料。树脂和硬化剂的比例按制造商建议的重量比 100 R / 80 H 100 R / 80 H 100R//80H100 \mathrm{R} / 80 \mathrm{H} 使用。树脂和硬化剂的比重分别为 1.17 和 0.92，粘度（cP）分别为 25 ∘ C 50 , 000 25 ∘ C 50 , 000 25^(@)C50,00025^{\circ} \mathrm{C} 50,000 和 35,000。

2.2. Fabrication of GFRP composite
2.2. GFRP 复合材料的制造

The hand layup method was followed to fabricate the GFRP composite material. A transparent plastic release film was placed at the bottom and coated with wax to ease the removal process after fabrication. A mold made of plywood of 325 mm × 325 mm × 10 mm 325 mm × 325 mm × 10 mm 325mmxx325mmxx10mm325 \mathrm{~mm} \times 325 \mathrm{~mm} \times 10 \mathrm{~mm} size was used. At first, one layer of the resin-hardener mixture was applied and spread evenly with a spatula to avoid entrapment of air. Subsequently, two layers of glass fiber separated by one layer of the resin-hardener mixture were applied. Then the topmost layer was again the resinhardener mixture and covered by a transparent plastic release film. Any trapped air was released by using a roller and gently pressing above the release film. The joint components were clamped as soon as the topmost layer of adhesive was applied. Finally, a plywood with a 17 kg dead load was placed above the top layer and the composite was left to cure for 12 h at room temperature. The thickness of the prepared composite slab was 3 mm as per ASTM D3039
手工铺层法用于制造 GFRP 复合材料。在底部放置了一层透明塑料脱模膜，并涂上蜡以简化制造后的去除过程。使用 325 mm × 325 mm × 10 mm 325 mm × 325 mm × 10 mm 325mmxx325mmxx10mm325 \mathrm{~mm} \times 325 \mathrm{~mm} \times 10 \mathrm{~mm} 尺寸的胶合板模具。首先，涂上一层树脂固化剂混合物，并用刮刀均匀涂抹，以避免空气被困。随后，涂上两层玻璃纤维，每层之间夹有一层树脂固化剂混合物。然后最顶层再次是树脂固化剂混合物，并覆盖一层透明塑料脱模膜。通过使用滚筒并在脱模膜上方轻轻按压，释放任何被困的空气。在涂上最顶层粘合剂后，立即夹紧接头组件。最后，在顶层上方放置一块 17 kg 的静载荷胶合板，并将复合材料在室温下养护 12 小时。制备的复合材料板的厚度为 3 毫米，符合 ASTM D3039 标准。
standard [16]. Fig. 1 shows the arrangement of matrix and reinforcement layers of the fabricated glass fiber composite. The composition of the prepared composite sample is presented in Table 1.
标准[16]。图 1 显示了制造玻璃纤维复合材料的矩阵和增强层的排列。制备的复合样品成分在表 1 中给出。

2.3. Mechanical and laser cutting of GFRP composite
2.3. GFRP 复合材料的机械和激光切割

The prepared composite slabs were both mechanically cut and laser cut to prepare the samples for mechanical testing. For mechanical cutting, Bosch GWS 900-100 professional angle grinder with TJWELD 1.2 mm thickness cutting wheel was used.
准备好的复合板既进行了机械切割，也进行了激光切割，以准备进行机械测试的样品。在机械切割中，使用了博世 GWS 900-100 专业角磨机以及 TJWELD 1.2 毫米厚度的切割轮。
For laser cutting, CO 2 CO 2 CO_(2)\mathrm{CO}_{2} laser cutting machine model STJ1530M was employed. The laser power of this machine is 220 w . In our experiment, the laser was used at 80 % 80 % 80%80 \% power ( 176 w ) with a 5 mm / s 5 mm / s 5mm//s5 \mathrm{~mm} / \mathrm{s} speed. It took two runs of the laser to completely cut the 3 mm thickness of the sample. Fig. 2 below shows the Photo of surfaces of mechanically cut and laser cut samples. From Fig. 2(b), it is observed that the laser cut sample has burn spots over the entire thickness along the machined edge of the composite.
激光切割中使用了型号为 STJ1530M 的激光切割机。该机的激光功率为 220 瓦。在我们的实验中，激光以 176 瓦的功率（ 80 % 80 % 80%80 \% ）和 5 mm / s 5 mm / s 5mm//s5 \mathrm{~mm} / \mathrm{s} 的速度使用。激光运行了两次才完全切割了 3 毫米厚的样品。图 2 显示了机械切割和激光切割样品表面的照片。从图 2(b)可以看出，激光切割样品在复合材料的加工边缘沿整个厚度有烧焦斑点。

3. Results and discussion
3. 结果与讨论

3.1. SEM observation of machined surface
3.1. 机械加工表面的 SEM 观察

The machined surface of one sample each from mechanically cut and laser cut composites is examined using Scanning Electron Microscope (SEM) model JSM-7610F. Micrographs of the machined surface are taken in 150x, 300x and 700x magnification at 15 kV setting.
每个机械切割和激光切割复合材料的样品的加工表面使用扫描电子显微镜（SEM）型号 JSM-7610F 进行检查。在 15 kV 设置下，以 150 倍、300 倍和 700 倍放大倍数拍摄加工表面的显微照片。
From Fig. 3, a comparison of surface finishing pattern and quality between mechanically cut and laser cut samples can be observed. Fig. 3(a) shows the surface smoothness and uniformity, good adhesion and uniformly axially aligned fibers in the mechanically cut sample. In contrast, Fig. 3(b) shows burnt and rough surfaces, potholes and coagulation of burnt matrix in the laser-cut sample. This compromised surface integrity has occurred due to thermal damage by the laser beam. During the laser cutting, the composite material melted and subsequently re-hardened. This coagulation process led to irregular geometry and thus the potholes are observed. Also, the glass fibers and their orientation are not visible on the laser cut surface as the fibers got damaged due to melting and subsequent solidification.
从图 3 可以看出，机械切割和激光切割样品的表面加工图案和质量之间的比较。图 3(a)显示了机械切割样品的表面光滑度和均匀性，良好的粘附性和轴向均匀排列的纤维。相比之下，图 3(b)显示了激光切割样品的烧焦和粗糙表面，以及烧焦基质的坑洞和凝固。这种表面完整性受损是由于激光束的热损伤造成的。在激光切割过程中，复合材料熔化并随后重新硬化。这种凝固过程导致了不规则的几何形状，因此观察到了坑洞。此外，由于熔化和随后凝固，玻璃纤维及其方向在激光切割表面上不可见。

3.2. Tensile behaviors  3.2. 拉伸性能

In a tensile test, a sample is subjected to a controlled tension until it reaches failure. The tensile test is performed on flat samples as per ASTM D3039 standard. Samples are cut into 250 mm × 25 mm × 3 mm 250 mm × 25 mm × 3 mm 250mmxx25mmxx3mm250 \mathrm{~mm} \times 25 \mathrm{~mm} \times 3 \mathrm{~mm} sizes with end tabs. The tensile test is performed in the universal testing machine (UTM) PLS100 with a crosshead speed of 5 mm / min 5 mm / min 5mm//min5 \mathrm{~mm} / \mathrm{min}. The flat samples are fixed between the grips of each head of the testing machine. The grip is set up in such a way that the direction of force applied to the sample is coincident with the longitudinal axis of the sample.
在拉伸试验中，样品受到控制拉伸直至破坏。拉伸试验按照 ASTM D3039 标准在平板样品上进行。样品切割成 250 mm × 25 mm × 3 mm 250 mm × 25 mm × 3 mm 250mmxx25mmxx3mm250 \mathrm{~mm} \times 25 \mathrm{~mm} \times 3 \mathrm{~mm} 尺寸，带有端盖。拉伸试验在 PLS100 万能试验机（UTM）上进行，夹头速度为 5 mm / min 5 mm / min 5mm//min5 \mathrm{~mm} / \mathrm{min} 。平板样品固定在试验机每个头的夹具之间。夹具设置得使施加到样品上的力的方向与样品的纵向轴线一致。
At the outset, the load-deflection characteristics are investigated from the standard tensile test of all GFRP samples. The characteristics of both mechanical cutting and laser cutting samples are then expressed in terms of conventional stress-strain curves. Fig. 4 (a) and 4 ( b ) 4 ( b ) 4(b)4(\mathrm{~b}) presents stress-strain relations of the number of samples from mechanical cutting and laser cutting respectively. In Fig. 4©, the average values from both mechanical cutting and laser cutting have been shown comparatively to highlight the differences in stress-strain behavior.
在初始阶段，对所有 GFRP 样品的标准拉伸试验的加载-位移特性进行了研究。然后，机械切割和激光切割样品的特性分别用传统的应力-应变曲线表示。图 4（a）和 4 ( b ) 4 ( b ) 4(b)4(\mathrm{~b}) 分别展示了机械切割和激光切割样品的应力-应变关系。在图 4©中，将机械切割和激光切割的平均值进行了比较，以突出应力-应变行为的差异。
From the said figures, it is evident that the mechanically cut samples reached a higher Ultimate Tensile Strength (UTS) value before failure in comparison to laser cut samples. All the curves
从所述数据中可以看出，与激光切割样品相比，机械切割样品在失效前达到了更高的抗拉强度（UTS）值。所有曲线
Fig. 1. Arrangement of layers in fabricated GFRP composite.
图 1. 制造的 GFRP 复合材料层排列
Table 1  表 1
Composition of the prepared composite sample.
组成制备的复合材料样品。
Material  材料 Weight (gm)  重量（克） Weight (%)  重量（%）
Glass Fiber Cloth  玻璃纤维布 206 45
Epoxy Resin  环氧树脂 138 30
Hardener  硬化剂 111 25
Total  总计 456 100
Material Weight (gm) Weight (%) Glass Fiber Cloth 206 45 Epoxy Resin 138 30 Hardener 111 25 Total 456 100| Material | Weight (gm) | Weight (%) | | :--- | :--- | :--- | | Glass Fiber Cloth | 206 | 45 | | Epoxy Resin | 138 | 30 | | Hardener | 111 | 25 | | Total | 456 | 100 |
show that the relationships among the stress and strain are almost linearly rising, followed by quick fall and fracture after the UTS value is reached indicating a brittle mode of failure.
展示应力与应变之间的关系几乎呈线性上升，达到抗拉强度值后迅速下降并断裂，表明为脆性破坏模式。
Detailed data from the tensile test is analyzed to calculate UTS, yield strength, elastic modulus and tangent modulus (at 2 % 2 % 2%2 \% strain). The average values along with standard deviations are calculated for each data obtained from several repeated tests. Table 2 and Table 3 shows the values of UTS, yield strength, elastic modulus and tangent modulus for mechanically cut and laser cut samples respectively. Fig. 5 shows the comparison of UTS and yield strength with error bars for mechanically cut and laser cut samples. It is observed that both UTS and yield strength decreased by 25.93 % and 26.4 % 26.4 % 26.4%26.4 \% respectively in laser-cut samples compared to mechanical cut samples. Fig. 6 shows the comparison of elastic modulus and tangent modulus (at 2 % 2 % 2%2 \% strain) with error bars for mechanically cut and laser cut samples. It is observed that both elastic modulus and tangent modulus (at 2 % 2 % 2%2 \% strain) decreased by 15.14 % 15.14 % 15.14%15.14 \% and 14.76 % 14.76 % 14.76%14.76 \% respectively in laser-cut samples compared to mechanical cut samples.
详细拉伸测试数据被分析以计算抗拉强度、屈服强度、弹性模量和切线模量（在 0#应变下）。对多次重复测试获得的数据计算平均值和标准偏差。表 2 和表 3 分别显示了机械切割和激光切割样品的抗拉强度、屈服强度、弹性模量和切线模量值。图 5 显示了机械切割和激光切割样品的抗拉强度和屈服强度的比较，并带有误差条。观察到与机械切割样品相比，激光切割样品的抗拉强度和屈服强度分别降低了 25.93%和 26.4 % 26.4 % 26.4%26.4 \% 。图 6 显示了机械切割和激光切割样品的弹性模量和切线模量（在 2 % 2 % 2%2 \% 应变下）的比较，并带有误差条。观察到与机械切割样品相比，激光切割样品的弹性模量和切线模量（在 2 % 2 % 2%2 \% 应变下）分别降低了 15.14 % 15.14 % 15.14%15.14 \% 和 14.76 % 14.76 % 14.76%14.76 \% 。

3.3. SEM observation of tensile fractured surface
3.3. 拉伸断裂表面的 SEM 观察

The tensile fractured surface of one sample each from mechanically cut and laser cut composites have also been studied using Scanning Electron Microscope (SEM) model JSM-7610F. Micrographs of the tensile fractured surface are taken in 150x, 300x and 700x magnification and 15 kV setting. From Fig. 7(a) and 7 (b), it is observed that in both types of machining, the predominant reason for tensile fracture of the composite is matrix/fiber interface debonding, brittle fracture of fibers and fiber pullout. Also, in the laser-cut sample, some areas of weaker adhesion are observed compared to the mechanically cut sample. In general, the nature of tensile fracture is similar in both cases.
该样品的机械切割和激光切割复合材料的拉伸断裂表面也使用扫描电子显微镜（SEM）JSM-7610F 进行了研究。在 150 倍、300 倍和 700 倍放大和 15 kV 设置下拍摄了拉伸断裂表面的显微照片。从图 7(a)和 7(b)可以看出，在两种加工方式中，复合材料拉伸断裂的主要原因都是基体/纤维界面脱粘、纤维脆性断裂和纤维拔出。与机械切割样品相比，激光切割样品中观察到一些粘附较弱的区域。总的来说，两种情况下的拉伸断裂性质相似。

3.4. Flexural behavior  3.4. 弯曲性能

A flexural test has been performed utilizing a three-point loading system applied to a simply supported flat GFRP specimen as per ASTM standard D790. Universal testing machine (UTM) PLS100 with a crosshead speed of 10 mm / min 10 mm / min 10mm//min10 \mathrm{~mm} / \mathrm{min} is employed to perform this test. Samples are cut into 100 mm × 12.7 mm × 3 mm 100 mm × 12.7 mm × 3 mm 100mmxx12.7mmxx3mm100 \mathrm{~mm} \times 12.7 \mathrm{~mm} \times 3 \mathrm{~mm} size. The support span size is 60 mm . The flat samples are placed between the support span. Load is applied to the samples at the center of the support span and the load-deflection characteristics are investigated from the flexural test of the GFRP samples.
弯曲试验已按照 ASTM 标准 D790，在简支平板 GFRP 试样上使用三点加载系统进行。采用跨头速度为 10 mm / min 10 mm / min 10mm//min10 \mathrm{~mm} / \mathrm{min} 的万能试验机（UTM）PLS100 进行此试验。样品切割成 100 mm × 12.7 mm × 3 mm 100 mm × 12.7 mm × 3 mm 100mmxx12.7mmxx3mm100 \mathrm{~mm} \times 12.7 \mathrm{~mm} \times 3 \mathrm{~mm} 尺寸。支撑跨度尺寸为 60 毫米。平板样品放置在支撑跨度之间。在支撑跨度的中心对样品施加载荷，并从 GFRP 样品的弯曲试验中研究载荷-位移特性。
Detailed data from the tensile test is analyzed to calculate Ultimate Flexural Strength (UFS) and Flexural Modulus. The test is performed on five samples and the average values along with standard deviations are calculated for each data. Table 4 and 5 shows the UFS and flexural modulus for mechanically cut and laser cut sam-
详细拉伸测试数据被分析以计算极限弯曲强度（UFS）和弯曲模量。测试在五个样品上进行，并计算了每个数据的平均值和标准偏差。表 4 和 5 显示了机械切割和激光切割样品的 UFS 和弯曲模量。

(a) Mechanically cut sample
(机械切割样品)

(b) Laser cut sample
激光切割样品
Fig. 2. Photographs of mechanically cut and laser cut samples (a) Mechanically cut sample (b) Laser cut sample.
图 2. 机械切割和激光切割样品的图片（a）机械切割样品（b）激光切割样品。
    • Corresponding author.  相应作者。
    E-mail address: mijanur.rahman@ae.mist.ac.bd (M. Mijanur Rahman).
    电子邮件地址：mijanur.rahman@ae.mist.ac.bd（M. Mijanur Rahman）。