**7. Compression**

Specimens for uniaxial compression test are made by the 3D printing DMLS technique as shown in **Figure 7**. It was made by the same equipment as EOS M290 and the same material as aluminum alloy, AlSi10Mg. The sample size is designed as diameter is 10 mm and height is 15 mm as shown in **Figure 7**. The figure also shows real specimens made by aluminum alloy. For the compression test, three specimens are ready.

Two specimens are used for the compression test because both samples are almost matched in the stress-strain plot shown in **Figure 8**. Thus, material properties for the compression test with Al alloy, AlSi10Mg, are defined as follows: Young's modulus is 0.316GPa, yield compressive yield strength is 6.35 MPa, and ultimate compressive strength is 179.72 MPa. **Figure 8** shows the crushing 6 steps within a range of 0–0.6, strains and each step is defined as: ① is elastic range,

**121**

**Table 5.**

is shown.

**Applied material**

**Figure 8.**

**8. 4D cube mechanical test**

**Sample type**

**Sample number**

*Measured weights for Type 1 and Type 2 model made by AlSi10Mg alloy.*

*Research of Lightweight Structures for Sandwich Core Model*

② linear, ③ the 1st plateau, ④ valley, ⑤ the 2nd plateau, and ⑥ densification. Thus, Young's modulus is checked in elastic range ①. Linear ② shows increasing loads. Then, 1st plateau shows in ③. In here, loading slowly increase. Valley ④ shows as being abruptly dropped, because belly phenomenon happened in the middle of 15 mm height specimen. It means endurance of applied loading in specimen is over. Then, it shows the 2nd plateau as ⑤ where applied loads slowly decreased. This means applied stress is distributed in specimen. At the end, densification ⑥

*Crushing steps such as ① elastic range, ② linear, ③ 1st plateau, ④ valley, ⑤ 2nd plateau, and ⑥ densification.*

There are two types of model for mechanical testing. The two models are corespaced model defined as Type 1 and core-filled model defined as Type 2. **Figure 2** shows two samples that are made by the 3D printing DMLS skill. Each sample is

AlSi10Mg Type 1 1 20 20 20 1.5 3 5.91

**Length (mm)**

Type 2 1 20 20 20 1.5 3 5.29

Difference 11.72%

**Height (mm)**

2 20 20 20 1.5 3 5.91 Average 20 20 20 1.5 3 5.91

2 20 20 20 1.5 3 5.29 Average 20 20 20 1.5 3 5.29

**Truss diameter (mm)**

**Outer Inner**

**Weight (grams)**

**Width (mm)**

*DOI: http://dx.doi.org/10.5772/intechopen.86852*

**Figure 7.** *Designation and AlSi10Mg specimens for compression test.*

*Research of Lightweight Structures for Sandwich Core Model DOI: http://dx.doi.org/10.5772/intechopen.86852*

#### **Figure 8.**

*Truss and Frames - Recent Advances and New Perspectives*

*Mechanical properties of AlSi10Mg by tension.*

**7. Compression**

are ready.

**Table 4.**

In order to do the tension test for AlSi10Mg, it is defined material properties are as follows: Young's modulus is 71.81GPa, yield strength is 155.52 MPa, and ultimate tensile strength is 348.32 MPa approximately. These are summarized in **Table 4**. When the Young's modulus value is compared in **Table 2**, they almost matched in vertical direction. That is, it is proved that tensile specimen is created in vertical direction by DMLS.

**Material Properties Value** AlSi10Mg Young's modulus (GPa) 71.8

> Yield strength (MPa) 155.5 Ultimate tensile strength (MPa) 348.3 Elongation (%) 8.0

Specimens for uniaxial compression test are made by the 3D printing DMLS technique as shown in **Figure 7**. It was made by the same equipment as EOS M290 and the same material as aluminum alloy, AlSi10Mg. The sample size is designed as diameter is 10 mm and height is 15 mm as shown in **Figure 7**. The figure also shows real specimens made by aluminum alloy. For the compression test, three specimens

Two specimens are used for the compression test because both samples are almost matched in the stress-strain plot shown in **Figure 8**. Thus, material properties for the compression test with Al alloy, AlSi10Mg, are defined as follows: Young's modulus is 0.316GPa, yield compressive yield strength is 6.35 MPa, and ultimate compressive strength is 179.72 MPa. **Figure 8** shows the crushing 6 steps within a range of 0–0.6, strains and each step is defined as: ① is elastic range,

**120**

**Figure 7.**

*Designation and AlSi10Mg specimens for compression test.*

*Crushing steps such as ① elastic range, ② linear, ③ 1st plateau, ④ valley, ⑤ 2nd plateau, and ⑥ densification.*

② linear, ③ the 1st plateau, ④ valley, ⑤ the 2nd plateau, and ⑥ densification. Thus, Young's modulus is checked in elastic range ①. Linear ② shows increasing loads. Then, 1st plateau shows in ③. In here, loading slowly increase. Valley ④ shows as being abruptly dropped, because belly phenomenon happened in the middle of 15 mm height specimen. It means endurance of applied loading in specimen is over. Then, it shows the 2nd plateau as ⑤ where applied loads slowly decreased. This means applied stress is distributed in specimen. At the end, densification ⑥ is shown.

### **8. 4D cube mechanical test**

There are two types of model for mechanical testing. The two models are corespaced model defined as Type 1 and core-filled model defined as Type 2. **Figure 2** shows two samples that are made by the 3D printing DMLS skill. Each sample is


**Table 5.** *Measured weights for Type 1 and Type 2 model made by AlSi10Mg alloy.* designed as width 20 mm, length 20 mm, height 20 mm, inner truss diameter 3 mm, and outer truss radius 1.5 mm. Type 1 is core-spaced model shown in **Figure 2(1)** and Type 2 is core-filled model shown in **Figure 2(2)**.

Before the uniaxial compression test, measured weight for Type 1 is 5.91 grams and Type 2 is 5.29 grams. Difference between Type 1 and Type 2 is about 11.72% in weights. Details are summarized in **Table 5**.

Applied material is Al alloy and powder type shown in **Table 2**. Applied speeding in the UTM machine is defined as 2 mm per minute. Type 1 is core-filled model

**Figure 9.** *Engineering stress as a function of engineering strain from uniaxial compression.*

**123**

**Figure 9**.

*Research of Lightweight Structures for Sandwich Core Model*

**Young's modulus (GPa)**

*Material properties of Type 1, core-filled model, and Type 2, core-spaced model.*

of test 3 and test 4. Type 2 is core-spaced model of test 1 and test 2. Thus, tested result shows engineering stress as a function of engineering strain in **Figure 9**. Based on the compression test, **Figure 9** shows material properties for elastic modulus, compressive yield strength, ultimate compressive strength, compressibility, and so on. **Figure 10** shows setup for uni-axial compression test in UTM for (1) Type 1

**Material properties**

**Ultimate compressive strength (MPa)** **Compressibility (%)**

**Compressive yield strength (MPa)**

Test 4 0.72 2.54 11.47 68 Average 0.82 2.57 12.44 69

Test 2 0.66 2.29 3.08 49 Average 0.69 2.29 3.15 46

1 Test 3 0.92 2.60 13.40 70

2 Test 1 0.71 2.29 3.22 42

Difference 19.7% 12.2% 294.8% 51.6%

For Type 1, the average values of material properties are elastic modulus is 0.82GPa, compressive yield strength is 2.57 MPa, ultimate compressive strength is 12.44 MPa, and percent compressibility is 69%, approximately. For Type 2, the average values of material properties are elastic modulus is 0.69GPa, compressive yield strength is 2.29 MPa, ultimate compressive strength is 3.15 MPa, and compressibility is 46%, approximately. **Table 5** summarizes the material properties of core-filled or core-spaced model. It shows differences between Type 1 for core-filled model and Type 2 for core-spaced model about material properties. For Young's modulus, core-filled model is higher 19.7%, compressive yield strength 12.2%, ultimate compressive strength 294.8%, and compressibility 51.6% than core-spaced

Material properties between core-filled model and core-spaced model are investigated. All models are based on aluminum alloy AlSi10Mg and they are made by the 3D printing DMLS technique. Finally, 4D cube models defined as corefilled as Type 1 and core-spaced as Type 2 are tested by compression. Thus, Type 1 shows a higher Young's modulus, compressive yield strength, compressive ultimate compressive strength, and compressibility. The reason is that Type 1 can endure outer loads with a diagonal truss connected with inside hexagonal truss structure. However, Type 2 can be broken easily because they do not have a diagonal truss supporting. It is simply connected with outer or inner hexagonal structure without a cross truss. Thus, Type 1 shows a general shape of compressive tested line on

However, Type 2 shows an elastic line, yield, plateau, and up down line in **Figure 9** as in test 3 and test 4. Here, the interest is in the up down line. When it is tracked by broken specimens, it is identified as a reason; that is, when specimens are made by the 3D printing DMLS skill, laser melt metal powder at first and then the

*DOI: http://dx.doi.org/10.5772/intechopen.86852*

**number**

**Type Sample** 

and (2) Type 2 model.

**Table 6.**

model as summarized in **Table 6**.

**9. Results**

**Figure 10.** *Uniaxial compression test in UTM for (1) Type 1 and (2) Type 2.*

*Research of Lightweight Structures for Sandwich Core Model DOI: http://dx.doi.org/10.5772/intechopen.86852*


#### **Table 6.**

*Truss and Frames - Recent Advances and New Perspectives*

weights. Details are summarized in **Table 5**.

designed as width 20 mm, length 20 mm, height 20 mm, inner truss diameter 3 mm, and outer truss radius 1.5 mm. Type 1 is core-spaced model shown in

Before the uniaxial compression test, measured weight for Type 1 is 5.91 grams and Type 2 is 5.29 grams. Difference between Type 1 and Type 2 is about 11.72% in

Applied material is Al alloy and powder type shown in **Table 2**. Applied speeding in the UTM machine is defined as 2 mm per minute. Type 1 is core-filled model

**Figure 2(1)** and Type 2 is core-filled model shown in **Figure 2(2)**.

*Engineering stress as a function of engineering strain from uniaxial compression.*

*Uniaxial compression test in UTM for (1) Type 1 and (2) Type 2.*

**122**

**Figure 10.**

**Figure 9.**

*Material properties of Type 1, core-filled model, and Type 2, core-spaced model.*

of test 3 and test 4. Type 2 is core-spaced model of test 1 and test 2. Thus, tested result shows engineering stress as a function of engineering strain in **Figure 9**. Based on the compression test, **Figure 9** shows material properties for elastic modulus, compressive yield strength, ultimate compressive strength, compressibility, and so on. **Figure 10** shows setup for uni-axial compression test in UTM for (1) Type 1 and (2) Type 2 model.

For Type 1, the average values of material properties are elastic modulus is 0.82GPa, compressive yield strength is 2.57 MPa, ultimate compressive strength is 12.44 MPa, and percent compressibility is 69%, approximately. For Type 2, the average values of material properties are elastic modulus is 0.69GPa, compressive yield strength is 2.29 MPa, ultimate compressive strength is 3.15 MPa, and compressibility is 46%, approximately. **Table 5** summarizes the material properties of core-filled or core-spaced model. It shows differences between Type 1 for core-filled model and Type 2 for core-spaced model about material properties. For Young's modulus, core-filled model is higher 19.7%, compressive yield strength 12.2%, ultimate compressive strength 294.8%, and compressibility 51.6% than core-spaced model as summarized in **Table 6**.
