ARL-TN-0770 ● AUG 2016

US Army Research Laboratory

Modification of General Research Corporation 

(GRC) Dynatup 8200 Drop Tower Rebounding 

Brake System

by David Gray, Robert Kaste, and Bradley Lawrence

Approved for public release; distribution is unlimited.
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ARL-TN-0770 ● AUG 2016

US Army Research Laboratory

Modification of General Research Corporation 

(GRC) Dynatup 8200 Drop Tower Rebounding 

Brake System

by David Gray and Robert Kaste

Weapons and Materials Research Directorate, ARL

Bradley Lawrence

Bennett Aerospace, Cary, NC

Approved for public release; distribution is unlimited.
ii

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1. REPORT DATE (DD-MM-YYYY)

August 2016

2. REPORT TYPE

Technical Note

3. DATES COVERED (From - To)

13 November 2015–3 February 2016

4. TITLE AND SUBTITLE

Modification of General Research Corporation (GRC) Dynatup 8200 Drop 

Tower Rebounding Brake System

5a. CONTRACT NUMBER

5b. GRANT NUMBER

5c. PROGRAM ELEMENT NUMBER

6. AUTHOR(S)

David Gray, Robert Kaste, and Bradley Lawrence

5d. PROJECT NUMBER

5e. TASK NUMBER

5f. WORK UNIT NUMBER

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)

US Army Research Laboratory

ATTN: RDRL-WMM-B

Aberdeen Proving Ground, MD 21005-5069

8. PERFORMING ORGANIZATION REPORT NUMBER

ARL-TN-0770

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR'S ACRONYM(S)

11. SPONSOR/MONITOR'S REPORT NUMBER(S)

12. DISTRIBUTION/AVAILABILITY STATEMENT

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13. SUPPLEMENTARY NOTES

14. ABSTRACT

The Double Column GRC Dynatup 8200 Drop-Weight pneumatic rebound brake system was intended to prevent secondary 

tup impacts on test specimen after the initial strike. Our investigation lead to the discovery of multiple impacts from a single 

test. To achieve a single mass impact of energy on laminate material test panel, we successfully modified the braking system. 

The details of which are explained in this report.

15. SUBJECT TERMS

8200 drop tower, drop weight impact, compression after impact, rebound brake system, secondary impact

16. SECURITY CLASSIFICATION OF:

17. LIMITATION

 OF

 ABSTRACT

UU

18. NUMBER

 OF 

 PAGES

14

19a. NAME OF RESPONSIBLE PERSON

David Gray

a. REPORT

Unclassified

b. ABSTRACT

Unclassified

c. THIS PAGE

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410-306-0852

Standard Form 298 (Rev. 8/98)

Prescribed by ANSI Std. Z39.18
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iii

Contents

List of Figures iv

1. Introduction 1

2. Background of Impact Test 1

3. Conclusion 6

4. References 7

Distribution List 8
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iv

List of Figures

Fig. 1 GRC Dynatup 8200 drop tower.............................................................2

Fig. 2 Original equipment manufactured pneumatic brake actuators ..............2

Fig. 3 IDT Os5 4K high-speed digital camera to capture tup impact period ...3

Fig. 4 Tup impact period sequence stills of generic laminate using old 

pneumatic rebound system.....................................................................4

Fig. 5 New upgraded 3-inch pneumatic cylinders............................................5

Fig. 6 Tup sequenced impact stills from carbon fiber composite laminate 

test material............................................................................................6
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1

1. Introduction

The Double Column GRC Dynatup 8200 Drop-Weight pneumatic rebound brake 

system was intended to prevent secondary tup impacts on test specimens after the 

initial strike. Our investigation discovered multiple impacts from a single test. To 

achieve a single-mass impact of energy on a laminate material test specimen, we 

successfully modified the braking system, the details of which are explained in this 

report.

2. Background of Impact Test

The Dynatup 8200 drop weight test system was designed and manufactured in 1982 

by GRC (Fig. 1). This model has a mass weight range of 7 to 34 lb (3.18 to 

15.42 kg), a maximum drop height of 36 inches (0.91 m), and can produce energy 

impacts (potential energy) up to 96 ft-lb. (120 J). The US Army Research 

Laboratory has performed low-energy (<100 J) impact experiments per ASTM 

D7136/D7136M1 with this system since 2001. The 8200 system was originally 

supplemented with two 1-inch bore/1.5-inch stroke 120-psi pneumatic actuators 

with 0.18-inch ID air supply lines that are used as a rebound brake system (Fig. 2). 

These actuators deploy via a pneumatic valve when a velocity optical sensor is 

tripped from a blade flag attached to the cross head milliseconds before the initial 

tup impact. There is an inherent lag time between initial impact and the actuators 

deploying due to the system’s pneumatic solenoid valve response time. This 

pneumatic system was intended to prevent secondary tup impacts on test specimens

after the initial strike.
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2

Fig. 1 GRC Dynatup 8200 drop tower

Fig. 2 Original equipment manufactured pneumatic brake actuators

Recently, it was suspected that releasing masses greater than 11 lb (5 kg) from 

heights greater than 30 inches (0.76 m) produced an undesirable secondary tup 

impact during the crosshead rebounding period. In test cases where coupons require 

ASTM D7137/D7713M-122 Compressive Residual Strength after Single Impact 

test, the coupons are required to have a single impact from ASTM D7139 test. 

1.5-inch stroke low-volume actuators, retracted 

t t
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3

Having multiple impacts from the drop tower testing can have direct influence on 

the coupon residual strength test. We set up a single Integrated Design Tools (IDT) 

Os5 4K high-speed digital camera with a frame rate of 1000 fps to capture the tup 

impact and rebound period on a generic scrap 0.20-inch-thick laminate (Fig. 3). We 

discovered the current system proved to be insufficient to halt repeated impacts 

from heavier mass assemblies for a single test. The Instron Impulse data collection 

software used by the test frame has a maximum recording time period of 100 ms. 

This misses the recording time period of the second and third impacts that start to 

occur around 500 ms. The nature of the rebound in amplitude and period after the 

initial impact can vary as the reaction is based on the material stiffness. Figure 4 

shows tup impact period sequence stills. 

Fig. 3 IDT Os5 4K high-speed digital camera to capture tup impact period
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4

Fig. 4 Tup impact period sequence stills of generic laminate using old pneumatic rebound 

system
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5

To correct this deficiency, larger 2-inch bore, 3-inch stroke 120-psi pneumatic 

cylinders with 3/8 inch OD/0.245-inch ID airlines were used to upgrade the rebound 

system (Fig. 5). To verify the effectiveness of the new system, the IDT Os5 4K 

camera was used again to capture the tup impact and rebound period at 1000 fps.

Fig. 5 New upgraded 3-inch pneumatic cylinders

3.0-inch stroke high-volume actuators

Retracted 

Position

Extended 

Position
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6

Figure 6 shows sequenced stills from a 0.24-inch-thick carbon fiber composite

material impact test using the updated 3-inch rebound cylinders. With a 26.5-lb

mass (12.02 kg) at 33-inch (0.838-m) drop height, the test yields an impact energy 

of about 74 ft-lb. (100 J). The sequence shows the tup prior to impact, impacting, 

rebounding from the plate, and being stopped by the pneumatic system prior to 

secondary contact.

Fig. 6 Tup sequenced impact stills from carbon fiber composite laminate test material

3. Conclusion

We were able to successfully perform drop-weight standardize testing per ASTM 

D7136/D7136M using a heavier cross head mass assembly dropped from various 

heights with a single impact. Using high-speed photography, verification was made 

that a single impact was achieved on generic laminate material coupons. The GRC 

Dynatup 8200 Drop Weight system was outfitted with 2 large bore, longer stroke 

pneumatic actuators and 3/8-inch OD/0.245-inch ID airlines. This update 

eliminated the secondary rebound impacts that had occurred with the previous 

pneumatic system under the same drop conditions.
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7

4. References

1. ASTM D7136/D7136M. Standard test method for measuring the damage 

resistance of a fiber-reinforced polymer matrix composite to a drop-weight 

impact event. West Conshohocken (PA): ASTM International; 2012.

2. ASTM D7137/D7713M-12. Standard test method for compressive residual 

strength properties of damaged polymer matrix composite plates. West 

Conshohocken (PA): ASTM International; 2012.
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8

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2 DIRECTOR

(PDF) US ARMY RESEARCH LAB

RDRL CIO L

IMAL HRA MAIL & RECORDS

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R KASTE