EFFECT OF CURVATURE ON THE IMPACT DAMAGE CHARACTERISTICS AND RESIDUAL STRENGTH OF COMPOSITE
EFFECT OF CURVATURE ON THE IMPACT DAMAGE CHARACTERISTICS AND RESIDUAL STRENGTH OF COMPOSITE PLATES
Damodar R. Ambur and James H. Starnes, Jr.
NASA Langley Research Center
Hampton, VA
Presented at the 39th AIAA/ASME/ASCE/AHS/ASC Structures,
Structural Dynamics, and Materials Conference
AIAA Paper No. 98-1881
Long Beach, California
April 20-23, 1998
AIAA 98-1881 EFFECT OF CURVATURE ON THE IMPACT DAMAGE CHARACTERISTICS AND RESIDUAL
STRENGTH OF COMPOSITE PLATES
Damodar R. Ambur* and James H. Starnes, Jr.
NASA Langley Research Center
Hampton, VA
Abstract
The results of a study of the response and failure characteristics of thin, cylindrically curved, composite plates subjected to low-speed impact damage are presented. The results indicate that the plate radius and the plate thickness are important structural parameters that influence the nonlinear response of a plate for a given amount of impact energy. Analytical and experimental contact-force results are compared for several plates and the results correlate well. The impact-energy levels required to cause damage initiation and barely visible impact damage are a function of the plate radius for a given plate thickness. The impact-energy levels required to initiate impact damage for plates with a certain range of radii are greater than plates with other radii. The contact-force results corresponding to these impact-energy levels follow a similar trend. Residual strength results for plates with barely visible impact damage suggest that the compression-after-impact residual strength is also a function of plate radius. The residual strength of impact-damaged flat plates appears to be lower than the residual strength of the corresponding cylindrically curved plates.
I ntroduction
The effect of low-speed impact damage on the compression strength of laminated composite structures has been studied extensively by many researchers over the past several years. Test data show that the compression strength of composite structures can be
_______________________
* Assistant Head, Structural Mechanics Branch. Associate Fellow, AIAA.
Head, Structural Mechanics Branch. Fellow, AIAA. Copyright ? 1998 by the American Institute of Aeronautics and Astronautics, Inc. No copyright is asserted in the United States under Title 17, U.S. Code. The U.S. Government has a royalty-free license to exercise all rights under the copyright claimed herein for government purposes. All other rights are reserved by the copyright owner.significantly reduced by low-speed impact damage, even if the damage is not detectable by visual inspection. Most of the studies of the effects of low-speed impact damage reported in the literature have focused on thicker flat plates that are typical of those used for wing structures. There is very limited information in the literature that addresses the low-speed impact response of thinner curved composite plates that are typical of fuselage skins. Composite fuselage structures usually have skins that are 16-plies thick or less. It has been shown that these thinner composite skins will experience large deformations when subjected to the transient normal force associated with a low-speed impact event, even for low impact-energy levels.1-4 It has also been shown that structures with curvature and certain combinations of plate dimensions exhibit a nonlinear softening response when impacted with dropped-weight impactors.5-7 A geometrically nonlinear analysis method based on Lagrangian equations of motion and the Rayleigh-Ritz method with assumed mode shapes was developed to predict the nonlinear response of cylindrically curved composite plates, and the results from this analysis have been correlated with experimental results.8 These results indicate that the stiffness of curved composite plates decreases as the dropped-weight impact event progresses. This stiffness reduction suggests that the impact-damage characteristics of curved composite plates can be significantly different from the response of flat composite plates. Since the response of flat composite plates subjected to a low-speed impact event from an airgun-propelled impactor is different from the response of a flat plate subjected to a dropped weight, it is important to identify the differences in the response of a curved composite plate subjected to a low-speed impact event from both an airgun-propelled impactor and from a dropped weight. The effect of any resulting impact damage on the residual strength of a composite plate is usually determined from the results of compression-after-impact tests. Understanding the nature of the
structural responses, damage characteristics, and residual strength of curved composite plates as a function of impactor and structural parameters is essential for designing safe, weight-efficient, and cost-effective curved composite structures.
The present paper presents the results of a study of the effect of low-speed impact events on the response and residual strength of thin, cylindrically curved, quasi-isotropic graphite-epoxy plates with different radii and thicknesses. The influence of curvature on the impact response of the plates and the impact-energy levels necessary to cause damage initiation and barely visible damage are discussed. A barely visible impact damage criterion is identified, and residual-strength results based on this criterion are presented and discussed for 8- and 16-ply-thick, cylindrically curved, quasi-isotropic composite plates.
Test Specimens and Test Procedure
The test specimens studied in this investigation were fabricated from Hercules, Inc. AS4 graphite fibers preimpregnated with Hercules, Inc. 3502 epoxy resin. The specimens were cured using the resin manufacturer?s recommended curing procedure. Typical mechanical properties for the AS4-3502 graphite-epoxy material are presented in Table 1. The nominal ply thickness of the material is 0.005 in. Specimens were fabricated to form 8- and 16-ply-thick flat and curved plates with [45/0/-45/90]
ns
laminates, where n is equal to 1 or 2, respectively. The curved specimens have 15-, 30-, and 60-in. radii. Both the flat and curved specimens are 5-in. wide and 9-in. long.
The specimens were supported with clamped boundary conditions using a test fixture described in Ref. 8, and subjected to a normal impact force by an airgun-propelled impactor or a dropped weight. An instrumented 2.5-lb steel weight with a 0.5-in.-diameter hemispherical tip was used for the dropped-weight impactor. A 0.5-in.-diameter aluminum sphere was used for the airgun-propelled impactor. The dropped-weight impactor was dropped from a prescribed height, and the airgun-propelled impactor was propelled by compressed air with a prescribed speed to impact the specimens with a prescribed impact-energy level.
The impact-energy levels were increased from a low level to determine the impact energy necessary to initiate damage in the specimens, and to cause barely visible damage on the surface of the specimens. The compression-after-impact residual strength of the impact-damaged specimens was determined by testing the specimens in a 120-kip hydraulic test machine. For these tests, the longitudinal, unloaded edges of the specimens were simply supported using knife edge-supports, and the loaded edges were clamped. Electrical resistance strain gages and displacement transducers were used to measure specimen response as the load was applied. A shadow moir? interferometry technique was used to monitor the out-of-plane displacements of the specimens during the tests.
Results and Discussion
Contact force test results are presented in this section for flat and cylindrically curved composite plates that were impacted by dropped weights with impact-energy levels that do not initiate damage in the plates. These results are compared with analytical results for curved plates impacted with dropped weights and airgun-propelled impactors with the same impact-energy levels to identify the differences in the response of the plates for airgun-propelled and dropped-weight impactors. Impact-damage initiation and barely visible impact-damage threshold-energy results are also presented, and the effects of varying plate radius and thickness on these results is discussed. Compression-after-impact residual-strength results are presented for plates with barely visible impact damage, and a criterion based on these results is also presented. The effects of varying plate radius and thickness on these results are discussed. Contact Forces
The maximum values of the contact forces measured by the instrumented dropped-weight test apparatus are shown in Fig. 1 for 16-ply-thick plates with different radii and impacted with 1.5 ft-lb of impact energy. The experimental results are shown in the figure by the open circles and the corresponding analysis results from the analysis of reference 8 are shown by the open squares. The flat plate results are presented in this figure against a plate radius of 200 inches. These results indicate that the value of the contact force decreases significantly for radii between 15 and 60 inches, and then increases to a value that closely corresponds to the flat-plate contact-force result for radii greater than 60 inches. These results suggest that the curved plates have a nonlinear response for radii less than 60 inches. These experimental and analytical contact-force results for dropped weights compare well. Analytical results from the analysis of reference 8 are shown in the figure by the open triangles for the airgun-propelled impactors with 1.5 ft-lb of impact energy level. The magnitudes of these contact forces are significantly greater than the contact forces for the dropped weights, and the radius of the plate has an
insignificant influence on the value of the contact forces. Apparently, the high-speed transient nature of the airgun impact event results in a very local response of the plate which does not affect the value of the contact forces for the plates considered in this study.
I mpact-Damage-Initiation and Barely Visible I mpact-Damage Energies
The differences in the contact-force magnitudes described in the previous section influence the damage characteristics of the plates. The damage-initiation impact-energy levels for curved plates were determined by impacting a given specimen with impact-energy levels that were increased in increments of 0.25 ft-lb until damage initiation occurred. Damage initiation was determined nondestructively using the volumetric scanning approach outlined in Ref. 6. The damage-initiation results for the 16-ply-thick [45/0/-45/90]2s quasi-isotropic plates impacted with dropped weights and airgun-propelled impactors are presented in Fig. 2 for different radii by the open circles and open squares, respectively. The impact energy required to initiate damage is significantly greater for the dropped weights than that of the airgun-propelled impactors. As the plate radius increases to a value of approximately 30 inches, the impact energy required to initiate damage increases, and then decreases for larger radii for both the airgun-propelled and dropped-weight impactors. The dropped-weight impact-energy results are consistent with the trend of the maximum contact-force results presented in Fig. 1, which suggests that a greater impact-energy level is needed for the 30-in.-radius plates to generate the impact force required to initiate damage than for other plates considered in this study. The trend for airgun contact-force results presented in Fig. 1 is not consistent with the nonlinear damage-initiation impact-energy results trend as the plate radius increases. The damage-initiation results presented in Fig. 2 suggest that the damage-initiation mode associated with the much larger contact forces for the airgun-propelled impactors could be different from those of the dropped weights for plates with different radii, and might be responsible for the observed nonlinear trend in the damage-initiation results.
The impact-energy levels required to cause barely visible impact damage on the impacted and opposite or back surfaces of 16-ply-thick plates were determined by increasing the airgun and dropped-weight impact-energy levels until damage was visible on one or both plate surfaces. Typical damage modes for the impacted and back surfaces of 16-ply-thick flat and 15-in.-radius curved plates impacted with dropped weights are shown in Figs. 3 and 4. The impact event causes a dent to form on the impacted surface of the plate at the impact site, and causes the surface ply on the back surface of the plate opposite to the impact location to crack and separate from the plate as shown in the figures. These observations indicate that barely visible impact damage can be detected when the measured dent depth on the impacted surface is approximately 0.05 in. for the 16-ply-thick specimens for both the airgun-propelled and dropped-weight impactors. The dropped-weight impact-energy results presented in Fig. 5 suggest that greater impact-energy levels are needed to develop visible damage in both the 8- and 16-ply-thick curved plates with radii between 15 and 60 in. The measured contact-force results that correspond to these impact-energy levels are shown in Fig. 6. The trends for these contact-force results are similar to those for the impact-energy results. The airgun impact-energy level needed to develop barely visible impact damage is a constant of approximately 9.0 ft-lbs over the range of plate radii considered as indicated in Fig. 5. For the 8-ply-thick plate (0.044-in. thick) the 0.05 in. dent depth does not result in a through penetration. The damage modes for the 16-ply-thick, 15-in.-radius curved plates that were impacted with airgun-propelled and dropped-weight impactors with 8.5 ft-lbs of impact energy are shown in Fig. 7. The damage due to the airgun-propelled impactor is more severe at the impact site than that of the dropped-weight impactor. The airgun-propelled impactor causes all of the plies to fail through the plate thickness, but the dropped-weight impactor only causes extensive delaminations in the plate. The results presented in Fig. 5 suggest that radius is an important structural parameter that must be considered when assessing the damage tolerance of thin, cylindrically curved plates.
Compression-After-Impact Residual Strength
To determine the residual strength of impact-damaged plates, 8- and 16-ply-thick plates were impacted with dropped-weight impact-energy levels that correspond to the 0.05-in.-deep dent-depth barely visible impact-damage criterion that was identified previously. These specimens were then loaded to failure in compression to determine their failure loads. Many of these specimens buckled before they failed. Typical shadow moir?interferometry fringe patterns for the out-of-plane displacement contours associated with the buckling and failure modes of an undamaged 16-ply-thick flat plate are shown in Fig. 8. The contour pattern in Fig. 8(a) indicates that the plate buckled into two-half waves along its length. The plate failed at approximately
11.83 kips, and the plate failed at the plate mid-section across the plate width as shown in Fig. 8(b). These buckling and failure modes are typical for the undamaged flat plates considered in the present study. Typical out-of-plane displacement results for an impact-damaged flat plate are shown in Fig. 9. The displacement contours in Fig. 9(a) indicate that the panel buckled into three half-waves along its length, and the crest of the center buckle coincides with the impact-damage location. This bucking mode shape is different from the mode shape of the undamaged plate, and the difference is caused by the impact damage at the center of the plate. This damage causes the local stiffness of the plate to be reduced, and the damaged region acts like a hinge in the middle of the plate. The failure load for the impact-damaged plate is approximately 11.45 kips, which is approximately 3 percent lower than the failure load of the undamaged plate. The failure location for the damaged plate is at the mid-section of the plate and is through the impact-damage site as shown in Fig. 9(b).
Typical out-of-plane displacement results for an undamaged 15-in.-radius plate loaded in compression are shown in Fig. 10. The curved plate has a buckling mode with three-half waves along the length as shown in Fig. 10(a). Failure of the specimen occurred at a location that is approximately 40 percent along the length of the plate as shown in Fig. 10(b). The recorded failure load is 10.51 kips. The response of a damaged 15-in.-radius plate for an applied compression load is shown in Fig. 11. Local out-of-plane deformations in the vicinity of the impact-damage site are indicated by the moir? fringe pattern as shown in Fig. 11(a), and these deformations are representative of a locally buckled delaminated region. This plate failed at a compression load of 8.98 kips prior to buckling. The failure propagated across the plate at the mid-section as illustrated in Fig. 11(b). The failure load of the damaged 15-in.-radius curved plate is approximately 15 percent less that the failure load of the corresponding damaged flat plate. Residual-strength results for damaged and undamaged 8- and 16-ply-thick cylindrically curved plates are summarized in Fig. 12. These results indicate that the residual strength of these plates is a function of the plate radius. The 15-in.-radius plates have the most severe reduction in residual strength relative to the flat plates. The results for the 16-ply-thick curved plates indicate that the plates with radii between 30.0 and 60.0 inches have higher failure loads than the flat plates, and the plates with radii approaching 15.0 inches have lower failure loads that the flat plates.
Concluding Remarks
The results of a study of the effects of low-speed impact damage on the response of thin, cylindrically curved, graphite-epoxy plates are presented. These results include quasi-isotropic plates with different radii of curvature and different thicknesses, and the results are compared with results for the corresponding flat plates. The results of the study indicate that the contact forces for cylindrically curved plates impacted with a given impact-energy level are a function of the plate radius of curvature and thickness. Test results for an impact-energy level of 1.5 ft-lbs indicate that the magnitude of the maximum contact force developed for the curved plates decreases and then increases as the radius of the plate increases. This contact-force trend is also predicted analytically. This decreasing and then increasing trend for the contact forces associated with dropped-weight impactors is reflected in the impact-energy results for both damage initiation and for the creation of barely visible impact damage. The impact-energy levels for damage initiation in 16-ply-thick plates are different for airgun-propelled and dropped-weight impactors, but the impact-energy levels required to produce barely visible impact damage are not different. The contact forces predicted by analysis for an airgun-propelled impactor with 1.5 ft-lbs of impact energy are much greater than the corresponding forces predicted for a dropped-weight impactor, and are not influenced by the plate radius. Apparently, the response of a plate impacted by an airgun-propelled impactor is localized enough that the plate response is not affected by curvature effects.
The compression-after-impact residual-strength results for flat and curved 8- and 16-ply-thick plates suggest that these results are also a function of the plate radius. The residual strength of flat and 15-in.-radius curved plates with barely visible impact damage is approximately 3 and 15 percent less that the failure load for the corresponding undamaged plates, respectively. These results suggest that radius of curvature is an important structural parameter that must be considered when determining the damage-tolerance characteristics of thin, cylindrically curved, composite plates.
References
1. Ambur, D. R., Starnes, J. H., Jr., and Prasad, C.
B., "Influence of Transverse Shear and Large Deformation Effects on the Low-Speed Impact Response of Laminated Composite Plates," NASA TM-107753, April 1993.
2. Matsuhashi, H., "Nonlinear Analysis of Composite Laminated Plates Subjected to Impact Loading," M. S.
Thesis, September 1992, Department of Aeronautics and Astronautics, Massachusetts Institute of Technology, Cambridge, MA.
3. Byun, C., and Kapania, R. K., "Nonlinear Impact Response of Thin Imperfect Laminated Plates Using a Reduction Method," Composites Engineering , Vol. 2,No. 5-7, 1992, pp. 391-410.
4. Palazotto, A., Perry, R., and Sandhu, R., "Impact Response of Graphite-Epoxy Cylindrical Panels,"AIAA Journal , Vol. 30, No. 7, July 1992, pp. 1827-1832.
5. Kistler, L. S., òExperimental Investigation of the Impact Response of Cylindrically Curved Laminated Composite Plates,ó AIAA-94-1604-CP, April 1994.
6. Ambur, D. R., Starnes, J. H., Jr., òInfluence of Large-Deflection Effects on the Impact Response of Flat and Curved Composite Plates,ó AIAA-95-1205-CP,April 1995.
7. Wardle, B. L., and Lagace, P. A., òImportance of Instability in the Impact Response of Composite Shells,ó AIAA-96-1468-CP, April 1996.
8. Ambur, D. R., and Starnes, J. H., Jr., òNonlinear Response and Damage initiation Characteristics of Composite Curved Plates Subjected to Low-Speed Impact,ó AIAA-97-1058-CP, April 1997.
Table 1. Mechanical properties of AS4-3502 graphite-epoxy unidirectional tape material.
Longitudinal modulus, E1 (Msi) 20.00
Transverse modulus, E 2 (Msi) 1.30In-plane shear modulus, G 12 (Msi)0.87Transverse shear modulus, G 23 (Msi)0.51Transverse shear modulus, G 13 (Msi)0.87Major Poisson's ratio, n 12
0.3
200
400600800
10001200
Maximum contact force, lb
Plate radius, in.
Figure 1. Contact force results for 16-ply-thick, quasi-isotropic plates impacted by dropped weight s and airgun
propelled impactors with 1.5 ft-lbs of impact energy.
0.5
1
1.5
2
2.5
3
Impact energy,ft-lb
Plate radius, in.
Figure 2. Damage-initiation impact energy levels for 16-ply-thick, quasi-isotropic plates impacted by dropped- weight and airgun impactors.
a. Impacted surface
b. Back surface
Figure 3. Photographs of a 16-ply-thick quasi-isotropic flat plates with barely visible impact damage.
a. Impacted surface
b. Back surface
Figure 4. Photographs of a 16-ply-thick quasi-isotropic curved plate with 15-in. radius with barely visible
impact damage.
345678
91011
Impact energy,ft-lb
Plate radius, in.
Figure 5. Dropped-weight and airgun impact-energy levels for barely visible impact damage in 8- and 16-ply-thick
quasi-isotropic plates with different radii.
300
400500
700
800
force,
lb
Plate radius, in.
Figure 6. Maximum contact force magnitudes for dropped-weight impact-energy levels for barely visible impact
damage in 8- and 16-ply-thick quasi-isotropic curved plates with different radii.
a. Airgun impact damage
b. Dropped-weight impact damage Figure 7. Photomicrographs of 16-ply-thick quasi-isotropic 15-in.-radius curved plates subjected to dropped-weight
and airgun impacts with 8.5 ft-lbs of impact energy.
a. Buckled mode shape prior to plate failure
b. Plate failure through the mid-section.
Figure 8. Out-of-plane displacement contours for a compression loaded 16-ply-thick undamaged flat plate.
a. Buckling pattern with three half-waves
b. Failure through the damaged site
Figure 9. Out-of-plane displacement contours for a compression loaded 16-ply-thick flat plate subjected to barely
visible impact damage with a dropped weight.
a. Buckling pattern with three half-waves
b. Off-center panel failure Figure 10. Out-of-plane displacement contours for a compression-loaded 16-ply-thick undamaged 15-in. radius
curved plate.
a. Damage growth with no buckling
b. Failed plate
Figure 11. Out-of-plane displacement contours for a compression loaded 16-ply-thick 15-in. radius curved plate subjected to barely visible impact damage with a dropped weight.
8
91011
1314 Compression failure load,
kip
Plate radius, in.
a. 16-ply-thick curved plates
2
2.5
3
3.5
Compression failure load, kip
Plate radius, in.
b. 8-ply-thick curved plates
Figure 12. Summary of residual strength results for curved plates with different radii.
on the contrary的解析
On the contrary Onthecontrary, I have not yet begun. 正好相反，我还没有开始。 https://www.wendangku.net/doc/ea1426043.html, Onthecontrary, the instructions have been damaged. 反之，则说明已经损坏。 https://www.wendangku.net/doc/ea1426043.html, Onthecontrary, I understand all too well. 恰恰相反，我很清楚 https://www.wendangku.net/doc/ea1426043.html, Onthecontrary, I think this is good. ⑴我反而觉得这是好事。 https://www.wendangku.net/doc/ea1426043.html, Onthecontrary, I have tons of things to do 正相反，我有一大堆事要做 Provided by jukuu Is likely onthecontrary I in works for you 反倒像是我在为你们工作 https://www.wendangku.net/doc/ea1426043.html, Onthecontrary, or to buy the first good. 反之还是先买的好。 https://www.wendangku.net/doc/ea1426043.html, Onthecontrary, it is typically american. 相反，这正是典型的美国风格。 222.35.143.196 Onthecontrary, very exciting.
恰恰相反，非常刺激。 https://www.wendangku.net/doc/ea1426043.html, But onthecontrary, lazy. 却恰恰相反，懒洋洋的。 https://www.wendangku.net/doc/ea1426043.html, Onthecontrary, I hate it! 恰恰相反，我不喜欢！ https://www.wendangku.net/doc/ea1426043.html, Onthecontrary, the club gathers every month. 相反，俱乐部每个月都聚会。 https://www.wendangku.net/doc/ea1426043.html, Onthecontrary, I'm going to work harder. 我反而将更努力工作。 https://www.wendangku.net/doc/ea1426043.html, Onthecontrary, his demeanor is easy and nonchalant. 相反，他的举止轻松而无动于衷。 https://www.wendangku.net/doc/ea1426043.html, Too much nutrition onthecontrary can not be absorbed through skin. 太过营养了反而皮肤吸收不了. https://www.wendangku.net/doc/ea1426043.html, Onthecontrary, I would wish for it no other way. 正相反，我正希望这样 Provided by jukuu Onthecontrary most likely pathological. 反之很有可能是病理性的。 https://www.wendangku.net/doc/ea1426043.html, Onthecontrary, it will appear clumsy. 反之，就会显得粗笨。 https://www.wendangku.net/doc/ea1426043.html,
英语造句
一般过去式 时间状语：yesterday just now (刚刚) the day before three days ag0 a week ago in 1880 last month last year 1. I was in the classroom yesterday. I was not in the classroom yesterday. Were you in the classroom yesterday. 2. They went to see the film the day before. Did they go to see the film the day before. They did go to see the film the day before. 3. The man beat his wife yesterday. The man didn’t beat his wife yesterday. 4. I was a high student three years ago. 5. She became a teacher in 2009. 6. They began to study english a week ago 7. My mother brought a book from Canada last year. 8.My parents build a house to me four years ago . 9.He was husband ago. She was a cooker last mouth. My father was in the Xinjiang half a year ago. 10.My grandfather was a famer six years ago. 11.He burned in 1991
学生造句--Unit 1
●I wonder if it’s because I have been at school for so long that I’ve grown so crazy about going home. ●It is because she wasn’t well that she fell far behind her classmates this semester. ●I can well remember that there was a time when I took it for granted that friends should do everything for me. ●In order to make a difference to society, they spent almost all of their spare time in raising money for the charity. ●It’s no pleasure eating at school any longer because the food is not so tasty as that at home. ●He happened to be hit by a new idea when he was walking along the riverbank. ●I wonder if I can cope with stressful situations in life independently. ●It is because I take things for granted that I make so many mistakes. ●The treasure is so rare that a growing number of people are looking for it. ●He picks on the weak mn in order that we may pay attention to him. ●It’s no pleasure being disturbed whena I settle down to my work. ●I can well remember that when I was a child, I always made mistakes on purpose for fun. ●It’s no pleasure accompany her hanging out on the street on such a rainy day. ●I can well remember that there was a time when I threw my whole self into study in order to live up to my parents’ expectation and enter my dream university. ●I can well remember that she stuck with me all the time and helped me regain my confidence during my tough time five years ago. ●It is because he makes it a priority to study that he always gets good grades. ●I wonder if we should abandon this idea because there is no point in doing so. ●I wonder if it was because I ate ice-cream that I had an upset student this morning. ●It is because she refused to die that she became incredibly successful. ●She is so considerate that many of us turn to her for comfort. ●I can well remember that once I underestimated the power of words and hurt my friend. ●He works extremely hard in order to live up to his expectations. ●I happened to see a butterfly settle on the beautiful flower. ●It’s no pleasure making fun of others. ●It was the first time in the new semester that I had burned the midnight oil to study. ●It’s no pleasure taking everything into account when you long to have the relaxing life. ●I wonder if it was because he abandoned himself to despair that he was killed in a car accident when he was driving. ●Jack is always picking on younger children in order to show off his power. ●It is because he always burns the midnight oil that he oversleeps sometimes. ●I happened to find some pictures to do with my grandfather when I was going through the drawer. ●It was because I didn’t dare look at the failure face to face that I failed again. ●I tell my friend that failure is not scary in order that she can rebound from failure. ●I throw my whole self to study in order to pass the final exam. ●It was the first time that I had made a speech in public and enjoyed the thunder of applause. ●Alice happened to be on the street when a UFO landed right in front of her. ●It was the first time that I had kept myself open and talked sincerely with my parents. ●It was a beautiful sunny day. The weather was so comfortable that I settled myself into the
英语句子结构和造句
高中英语~词性~句子成分~语法构成 第一章节：英语句子中的词性 1.名词：n. 名词是指事物的名称，在句子中主要作主语.宾语.表语.同位语。 2.形容词;adj. 形容词是指对名词进行修饰~限定~描述~的成份，主要作定语.表语.。形容词在汉语中是（的）.其标志是: ous. Al .ful .ive。. 3.动词：vt. 动词是指主语发出的一个动作，一般用来作谓语。 4.副词：adv. 副词是指表示动作发生的地点. 时间. 条件. 方式. 原因. 目的. 结果.伴随让步. 一般用来修饰动词. 形容词。副词在汉语中是（地）.其标志是：ly。 5.代词：pron. 代词是指用来代替名词的词，名词所能担任的作用，代词也同样.代词主要用来作主语. 宾语. 表语. 同位语。 6.介词：prep.介词是指表示动词和名次关系的词，例如：in on at of about with for to。其特征：
介词后的动词要用—ing形式。介词加代词时，代词要用宾格。例如：give up her（him）这种形式是正确的，而give up she（he）这种形式是错误的。 7.冠词：冠词是指修饰名词，表名词泛指或特指。冠词有a an the 。 8.叹词：叹词表示一种语气。例如：OH. Ya 等 9.连词：连词是指连接两个并列的成分，这两个并列的成分可以是两个词也可以是两个句子。例如：and but or so 。 10.数词：数词是指表示数量关系词，一般分为基数词和序数词 第二章节：英语句子成分 主语：动作的发出者，一般放在动词前或句首。由名词. 代词. 数词. 不定时. 动名词. 或从句充当。 谓语：指主语发出来的动作，只能由动词充当，一般紧跟在主语后面。 宾语：指动作的承受着，一般由代词. 名词. 数词. 不定时. 动名词. 或从句充当. 介词后面的成分也叫介词宾语。 定语：只对名词起限定修饰的成分，一般由形容
六级单词解析造句记忆MNO
M A: Has the case been closed yet? B: No, the magistrate still needs to decide the outcome. magistrate n.地方行政官，地方法官，治安官 A: I am unable to read the small print in the book. B: It seems you need to magnify it. magnify vt.１．放大，扩大；２．夸大，夸张 A: That was a terrible storm. B: Indeed, but it is too early to determine the magnitude of the damage. magnitude n.１．重要性，重大；２．巨大，广大 A: A young fair maiden like you shouldn’t be single. B: That is because I am a young fair independent maiden. maiden n.少女，年轻姑娘，未婚女子 a.首次的，初次的 A: You look majestic sitting on that high chair. B: Yes, I am pretending to be the king! majestic a.雄伟的，壮丽的，庄严的，高贵的 A: Please cook me dinner now. B: Yes, your majesty, I’m at your service. majesty n.１．［Ｍ－］陛下（对帝王，王后的尊称）；２．雄伟，壮丽，庄严 A: Doctor, I traveled to Africa and I think I caught malaria. B: Did you take any medicine as a precaution? malaria n.疟疾 A: I hate you! B: Why are you so full of malice? malice n.恶意，怨恨 A: I’m afraid that the test results have come back and your lump is malignant. B: That means it’s serious, doesn’t it, doctor? malignant a.１．恶性的，致命的；２．恶意的，恶毒的 A: I’m going shopping in the mall this afternoon, want to join me? B: No, thanks, I have plans already. mall n.（由许多商店组成的）购物中心 A: That child looks very unhealthy. B: Yes, he does not have enough to eat. He is suffering from malnutrition.
base on的例句
意见应以事实为根据. 3 来自辞典例句 192. The bombers swooped ( down ) onthe air base. 轰炸机 突袭 空军基地. 来自辞典例句 193. He mounted their engines on a rubber base. 他把他们的发动机装在一个橡胶垫座上. 14 来自辞典例句 194. The column stands on a narrow base. 柱子竖立在狭窄的地基上. 14 来自辞典例句 195. When one stretched it, it looked like grey flakes on the carvas base. 你要是把它摊直, 看上去就象好一些灰色的粉片落在帆布底子上. 18 来自辞典例句 196. Economic growth and human well - being depend on the natural resource base that supports all living systems. 经济增长和人类的福利依赖于支持所有生命系统的自然资源. 12 1 来自辞典例句 197. The base was just a smudge onthe untouched hundred - mile coast of Manila Bay. 那基地只是马尼拉湾一百英里长安然无恙的海岸线上一个硝烟滚滚的污点. 6 来自辞典例句 198. You can't base an operation on the presumption that miracles are going to happen. 你不能把行动计划建筑在可能出现奇迹的假想基础上.
英语造句大全
英语造句大全English sentence 在句子中，更好的记忆单词！ 1、(1)、able adj. 能 句子：We are able to live under the sea in the future. (2)、ability n. 能力 句子：Most school care for children of different abilities. (3)、enable v. 使。。。能句子：This pass enables me to travel half-price on trains. 2、(1)、accurate adj. 精确的句子：We must have the accurate calculation. (2)、accurately adv. 精确地 句子：His calculation is accurately. 3、(1)、act v. 扮演 句子：He act the interesting character. （2）、actor n. 演员 句子：He was a famous actor. (3)、actress n. 女演员 句子：She was a famous actress. (4)、active adj. 积极的 句子：He is an active boy. 4、add v. 加 句子：He adds a little sugar in the milk. 5、advantage n. 优势 句子：His advantage is fight. 6、age 年龄n. 句子：His age is 15. 7、amusing 娱人的adj. 句子：This story is amusing. 8、angry 生气的adj. 句子：He is angry. 9、America 美国n.
(完整版)主谓造句
主语+谓语 1. 理解主谓结构 1) The students arrived. The students arrived at the park. 2) They are listening. They are listening to the music. 3) The disaster happened. 2．体会状语的位置 1) Tom always works hard. 2) Sometimes I go to the park at weekends.. 3) The girl cries very often. 4) We seldom come here. The disaster happened to the poor family. 3. 多个状语的排列次序 1) He works. 2) He works hard. 3) He always works hard. 4) He always works hard in the company. 5) He always works hard in the company recently. 6) He always works hard in the company recently because he wants to get promoted. 4. 写作常用不及物动词 1. ache My head aches. I’m aching all over. 2. agree agree with sb. about sth. agree to do sth. 3. apologize to sb. for sth. 4. appear (at the meeting, on the screen) 5. arrive at / in 6. belong to 7. chat with sb. about sth. 8. come (to …) 9. cry 10. dance 11. depend on /upon 12. die 13. fall 14. go to … 15. graduate from 16. … happen 17. laugh 18. listen to... 19. live 20. rise 21. sit 22. smile 23. swim 24. stay (at home / in a hotel) 25. work 26. wait for 汉译英： 1.昨天我去了电影院。 2.我能用英语跟外国人自由交谈。 3.晚上7点我们到达了机场。 4.暑假就要到了。 5.现在很多老人独自居住。 6.老师同意了。 7.刚才发生了一场车祸。 8.课上我们应该认真听讲。9. 我们的态度很重要。 10. 能否成功取决于你的态度。 11. 能取得多大进步取决于你付出多少努力。 12. 这个木桶能盛多少水取决于最短的一块板子的长度。
初中英语造句
【it's time to和it's time for】 ——————这其实是一个句型,只不过后面要跟不同的东西. ——————It's time to跟的是不定式（to do）.也就是说,要跟一个动词,意思是“到做某事的时候了”.如： It's time to go home. It's time to tell him the truth. ——————It's time for 跟的是名词.也就是说,不能跟动词.如： It's time for lunch.(没必要说It's time to have lunch) It's time for class.(没必要说It's time to begin the class.) They can't wait to see you Please ask liming to study tonight. Please ask liming not to play computer games tonight. Don’t make/let me to smoke I can hear/see you dance at the stage You had better go to bed early. You had better not watch tv It’s better to go to bed early It’s best to run in the morning I am enjoy running with music. With 表伴随听音乐 I already finish studying You should keep working. You should keep on studying English Keep calm and carry on 保持冷静继续前行二战开始前英国皇家政府制造的海报名字 I have to go on studying I feel like I am flying I have to stop playing computer games and stop to go home now I forget/remember to finish my homework. I forget/remember cleaning the classroom We keep/percent/stop him from eating more chips I prefer orange to apple I prefer to walk rather than run I used to sing when I was young What’s wrong with you There have nothing to do with you I am so busy studying You are too young to na?ve I am so tired that I have to go to bed early
The Kite Runner-美句摘抄及造句
《The Kite Runner》追风筝的人--------------------------------美句摘抄 1.I can still see Hassan up on that tree, sunlight flickering through the leaves on his almost perfectly round face, a face like a Chinese doll chiseled from hardwood: his flat, broad nose and slanting, narrow eyes like bamboo leaves, eyes that looked, depending on the light, gold, green even sapphire 翻译：我依然能记得哈桑坐在树上的样子，阳光穿过叶子，照着他那浑圆的脸庞。他的脸很像木头刻成的中国娃娃，鼻子大而扁平，双眼眯斜如同竹叶，在不同光线下会显现出金色、绿色，甚至是宝石蓝。 E.g.: A shadow of disquiet flickering over his face. 2.Never told that the mirror, like shooting walnuts at the neighbor's dog, was always my idea. 翻译：从来不提镜子、用胡桃射狗其实都是我的鬼主意。E.g.:His secret died with him, for he never told anyone. 3.We would sit across from each other on a pair of high
翻译加造句
一、翻译 1. The idea of consciously seeking out a special title was new to me., but not without appeal. 让我自己挑选自己最喜欢的书籍这个有意思的想法真的对我具有吸引力。 2.I was plunged into the aching tragedy of the Holocaust, the extraordinary clash of good, represented by the one decent man, and evil. 我陷入到大屠杀悲剧的痛苦之中，一个体面的人所代表的善与恶的猛烈冲击之中。 3.I was astonished by the the great power a novel could contain. I lacked the vocabulary to translate my feelings into words. 我被这部小说所包含的巨大能量感到震惊。我无法用语言来表达我的感情（心情）。 4，make sth. long to short长话短说 5.I learned that summer that reading was not the innocent(简单的) pastime(消遣) I have assumed it to be., not a breezy, instantly forgettable escape in the hammock(吊床)，( though I’ ve enjoyed many of those too ). I discovered that a book, if it arrives at the right moment, in the proper season, will change the course of all that follows. 那年夏天，我懂得了读书不是我认为的简单的娱乐消遣，也不只是躺在吊床上，一阵风吹过就忘记的消遣。我发现如果在适宜的时间、合适的季节读一本书的话，他将能改变一个人以后的人生道路。 二、词组造句 1. on purpose 特意，故意 This is especially true here, and it was ~. (这一点在这里尤其准确，并且他是故意的) 2.think up 虚构，编造，想出 She has thought up a good idea. 她想出了一个好的主意。 His story was thought up. 他的故事是编出来的。 3. in the meantime 与此同时 助记：in advance 事前in the meantime 与此同时in place 适当地... In the meantime, what can you do? 在这期间您能做什么呢？ In the meantime, we may not know how it works, but we know that it works. 在此期间，我们不知道它是如何工作的，但我们知道，它的确在发挥作用。 4.as though 好像，仿佛 It sounds as though you enjoyed Great wall. 这听起来好像你喜欢长城。 5. plunge into 使陷入 He plunged the room into darkness by switching off the light. 他把灯一关，房
改写句子练习2标准答案
The effective sentences:(improve the sentences!) 1.She hopes to spend this holiday either in Shanghai or in Suzhou. 2.Showing/to show sincerity and to keep/keeping promises are the basic requirements of a real friend. 3.I want to know the space of this house and when it was built. I want to know how big this house is and when it was built. I want to know the space of this house and the building time of the house. 4.In the past ten years,Mr.Smith has been a waiter,a tour guide,and taught English. In the past ten years,Mr.Smith has been a waiter,a tour guide,and an English teacher. 5.They are sweeping the floor wearing masks. They are sweeping the floor by wearing masks. wearing masks,They are sweeping the floor. 6.the drivers are told to drive carefully on the radio. the drivers are told on the radio to drive carefully 7.I almost spent two hours on this exercises. I spent almost two hours on this exercises. 8.Checking carefully,a serious mistake was found in the design. Checking carefully,I found a serious mistake in the design.
用以下短语造句
M1 U1 一. 把下列短语填入每个句子的空白处（注意所填短语的形式变化）： add up (to) be concerned about go through set down a series of on purpose in order to according to get along with fall in love (with) join in have got to hide away face to face 1 We’ve chatted online for some time but we have never met ___________. 2 It is nearly 11 o’clock yet he is not back. His mother ____________ him. 3 The Lius ___________ hard times before liberation. 4 ____________ get a good mark I worked very hard before the exam. 5 I think the window was broken ___________ by someone. 6 You should ___________ the language points on the blackboard. They are useful. 7 They met at Tom’s party and later on ____________ with each other. 8 You can find ____________ English reading materials in the school library. 9 I am easy to be with and _____________my classmates pretty well. 10 They __________ in a small village so that they might not be found. 11 Which of the following statements is not right ____________ the above passage? 12 It’s getting dark. I ___________ be off now. 13 More than 1,000 workers ___________ the general strike last week. 14 All her earnings _____________ about 3,000 yuan per month. 二.用以下短语造句： 1.go through 2. no longer/ not… any longer 3. on purpose 4. calm… down 5. happen to 6. set down 7. wonder if 三. 翻译： 1.曾经有段时间，我对学习丧失了兴趣。（there was a time when…） 2. 这是我第一次和她交流。（It is/was the first time that …注意时态） 3.他昨天公园里遇到的是他的一个老朋友。（强调句） 4. 他是在知道真相之后才意识到错怪女儿了。（强调句） M 1 U 2 一. 把下列短语填入每个句子的空白处（注意所填短语的形式变化）： play a …role (in) because of come up such as even if play a …part (in) 1 Dujiangyan(都江堰) is still ___________in irrigation(灌溉) today. 2 That question ___________ at yesterday’s meeting. 3 Karl Marx could speak a few foreign languages, _________Russian and English. 4 You must ask for leave first __________ you have something very important. 5 The media _________ major ________ in influencing people’s opinion s. 6 _________ years of hard work she looked like a woman in her fifties. 二.用以下短语造句： 1.make (good/full) use of 2. play a(n) important role in 3. even if 4. believe it or not 5. such as 6. because of
英语造句
English sentence 1、(1)、able adj. 能 句子：We are able to live under the sea in the future. (2)、ability n. 能力 句子：Most school care for children of different abilities. (3)、enable v. 使。。。能 句子：This pass enables me to travel half-price on trains. 2、(1)、accurate adj. 精确的 句子：We must have the accurate calculation. (2)、accurately adv. 精确地 句子：His calculation is accurately. 3、(1)、act v. 扮演 句子：He act the interesting character.（2）、actor n. 演员 句子：He was a famous actor. (3)、actress n. 女演员 句子：She was a famous actress. (4)、active adj. 积极的 句子：He is an active boy. 4、add v. 加 句子：He adds a little sugar in the milk. 5、advantage n. 优势 句子：His advantage is fight. 6、age 年龄n. 句子：His age is 15. 7、amusing 娱人的adj. 句子：This story is amusing. 8、angry 生气的adj. 句子：He is angry. 9、America 美国n. 句子：He is in America. 10、appear 出现v. He appears in this place. 11. artist 艺术家n. He is an artist. 12. attract 吸引 He attracts the dog. 13. Australia 澳大利亚 He is in Australia. 14.base 基地 She is in the base now. 15.basket 篮子 His basket is nice. 16.beautiful 美丽的 She is very beautiful. 17.begin 开始 He begins writing. 18.black 黑色的 He is black. 19.bright 明亮的 His eyes are bright. 20.good 好的 He is good at basketball. 21.British 英国人 He is British. 22.building 建造物 The building is highest in this city 23.busy 忙的 He is busy now. 24.calculate 计算 He calculates this test well. 25.Canada 加拿大 He borns in Canada. 26.care 照顾 He cared she yesterday. 27.certain 无疑的 They are certain to succeed. 28.change 改变 He changes the system. 29.chemical 化学药品