Plastic armour (also known as plastic protection) was a type of vehicle armour originally developed for merchant ships by Edward Terrell of the British Admiralty in 1940. It consisted of small, evenly sized aggregate in a matrix of bitumen, similar to asphalt concrete. It was typically applied as a casting in situ in a layer about 2in (51mm) thick on to existing ship structures made from 1⁄4in-thick (6.4mm) mild steel or formed in equally thick sections on a 1⁄2in-thick (13mm)steel plate for mounting as gun shields and the like. Plastic armour replaced the use of concrete slabs, which although expected to provide protection, were prone to cracking and breaking up when struck by armour-piercing bullets. Plastic armour was effective because the very hard particles would deflect bullets, which would then lodge between the plastic armour and the steel backing plate. Plastic armour could be applied by pouring it into a cavity formed by the steel backing plate and a temporary wooden form. Production of the armour was by road construction firms and was carried out in a similar way to the production of road coverings, the organization of the armouring being carried out by naval officers in key ports.
In August 1939, the British Admiralty had considered the possibility that merchant ships might be attacked by aircraft with machine guns and cannon. No armour plate could be spared to protect the ships' bridges and gun positions, so the Admiralty recommended that ship owners fit concrete paving slabs in layers up to 6 inches (150mm) thick to protect the vulnerable crew. The Admiralty had done no testing with armour-piercing bullets, and when the fighting started in earnest, it became evident that concrete armour was almost useless against German machine-gun fire. As the fighting in the English Channel intensified in August 1940, casualties rose and the prospect of a collapse in morale threatened.[1]
Edward Terrell was a successful barrister and magistrate[2] with a flair for invention; by 1940, he had registered a number of patents relating to pens, ink bottles, and peeling knives.[3] When war came, he volunteered for the Royal Navy Volunteer Reserve and when he was accepted, he was commissioned as a lieutenant in the Special Branch of the Volunteer Reserve, the highest possible rank permitted by fleet orders under the circumstances.[4]
Terrell was brought into the Admiralty to run an information-gathering section, concerned with the manner in which small ships were attacked by aircraft. Terrell collected reports and gathered a library of film showing attacks on ships. When visiting damaged ships, he found bridges and chartrooms riddled with bullet holes and sections of concrete in shattered pieces. He also saw dried blood. These grim scenes made a deep impression on Terrell.[5]
In August 1940, one of Terrell's staff, Lieutenant-Commander Lane, brought to his attention a report by a shipwright, Lieutenant Hindmarsh. The report had been written in July, about events the previous month during the Dunkirk evacuation. A paddle steamer had been hit by shells and bullets, but with remarkably few casualties. A marginal note read:
I noticed that whenever machine-gun bullets struck the deck, there were no ricochets ... The surface of the deck is covered with a cork-filled mastic substance to aid waterproofing.[6]
Terrell found that the worn-out ship had been heavily caulked with Insulphate, a slightly elastic compound of asphalt filled with small bits of cork. Insulphate was a popular solution to the problem of coping with the flexing of a ship that was old or that was now being used in waters rougher than those for which she was originally designed. Lane suggested that the mastic might have protective properties. Terrell agreed and immediately made an appointment to see the manufacturers, Durastic Bituminous Products Ltd.[6] By 17 August 1940, he had samples for testing.[7]
Just two days after receiving his first samples, Terrell tested them at a rifle range at the Road Research Station, Harmondsworth.[7] The results were disappointing; bullets went straight through the soft material and through a mild steel backing plate. Disappointed, some of the scientists witnessing the tests left. William Glanville, head of the station, stayed and the men performed a few more test shots. In the resulting discussions, Terrell suggested replacing the cork with rock to deflect the hard core of an armour-piercing bullet so that it hit the backing plate at an angle, dispersing its energy so that it would not penetrate.
Terrell recalled an old legal case that he had conducted for the Amalgamated Road Stone Corporation. While studying background technicalities, he had visited Penlee Quarry at Newlyn in Cornwall, where he was told that Penlee granite was the hardest available. Terrell, who owned shares in the company, went on to insist that Penlee granite be used for plastic armour, whatever its material qualities.[8]
Terrell had new targets made to his specifications by Durastic Bitumious Products. The new targets, with a variety of sizes of granite chips and proportions of mastic and limestone, were delivered on 20 August. Testing was performed two days later and supplies of granite started to arrive at the Road Research Station for more trials. Terrell’s choice of the Road Research Station for a firing range was convenient, as they had all the necessary experience with dealing with stone and bitumen – though in his memoirs, Terrell insists that the original choice was simply good fortune.
Terrell coined the term "plastic armour" for his invention, partly because it was plastic in the sense of being malleable and ductile while hot, but also because he thought that the term might be confusing to German intelligence, who might assume that the product was made with the synthetic wood plastics then available.[9]
On 27 August, Terrell, Glanville and a Lee drafted a report detailing their efforts and giving a recipe for plastic armour; the entire development cycle had taken just 10 days.[10] The recipe required 55% granite, 38% limestone, and 7% bitumen; it was important that the stone was carefully graded and free from grit. The backing plate was vital; it would usually be 0.25-inch (6.4mm) thick mild steel. Since this was from what vital parts of a ship's superstructure were made, it was possible to cast plastic armour in situ between existing plates and temporary wooden shuttering, usually to a thickness of 4 inches (100mm). Where this was not possible, armoured plates could be factory made. Wooden backing could also be used when nonmagnetic protection was needed near the ship's compass.[11][12] The war had brought road building to a virtual halt, so plenty of suitably qualified workers and machines were available for the task of armouring Britain's ships.
Plastic armour was at first met with resistance from some senior officers. Terrell soon received enthusiastic support from the Admiralty Trade Division, which was responsible for protecting convoys and their ships. To proceed in an orderly manner, the Trade Division needed the approval of the Admiralty's Department of Naval Construction (DNC). Terrell and the chief of the Directorate of Miscellaneous Weapons Development (DMWD), Commander Charles Goodeve, met with representatives of DNC, who rejected plastic armour out of hand. DMWD performed a series of independent tests at the Royal Navy shore establishment HMS Excellent, resulting in a positive report:
There is no doubt that Plastic Armour is very greatly superior to any other non-magnetic material, excluding non-magnetic bullet-proof steel, so far tried ... it is most strongly recommended that the fitting of concrete protection should be discontinued and Plastic Armour fitted in its place.[13]
The report was forwarded to the DNC, but was rejected again.[14] Some within the navy objected to the use of the word armour to describe a mixture derived from road-building materials.[15] The DNC said that it would remove its objections provided the word "armour" was removed from the name of the product. The Trade Division insisted that the term "armour" was important for morale and that at this stage higher authorities decided that the DNC would be bypassed and production would start without their formal approval.[16]
The process and specification was patented secretly under an agreement that the British Crown had full use of the invention. Glanville insisted "in good faith" on his name appearing in the patent; Terrell acquiesced so the armour could be put into use without delay.
Plastic armour was available in large quantities and cost only £12+1⁄2 per ton – compared with heat-treated armoured plate at about £150 per ton and in short supply (though weight-for-weight somewhat more effective than plastic armour).[17] Plastic armour went into full production in October; facilities were soon in place in every major port involving every major road-building contractor in the country. Word spread abroad to Britain's allies. By the end of the war, plastic armour had been fitted to some 10,000 ships. Plastic armour was even used on the fighting ships of the Royal Navy, although in these cases the Department of Naval Construction insisted on referring to it as "plastic protection".[18]
Development and testing continued. Eventually, the bitumen of the original formulation was replaced by less expensive pitch and the Penlee granite was replaced by flint gravel. Elsewhere in the world, people used whatever stone was available.[19]
Terrell invented the Scorpion, a plastic armoured vehicle apparently similar to the Armadillo armoured fighting vehicle.[20][21] Also, a semiportable pillbox or strongpoint made of prefabricated panels of plastic armour was made for the Home Guard and was considered as a means of covering the retreat of the commandos at the end of the raid on Dieppe.[22]
Terrell was appointed to the staff of the First Sea Lord and promoted to the temporary rank of commander.[23]
After the war, Terrell and Glanville received a patent for plastic armour, after the invention was disputed by the manufacturers of Insulphate and applied to the Royal Commission on Awards to Inventors for their work on plastic armour.[24] The court hearing lasted for a full week, with the Crown protesting that plastic armour had been developed in the normal course of the men's work. If this had been the case, it would have reduced the size of the award. The court found in favour of Terrell as sole inventor, granting an award of £9,500 in recognition of the usefulness of the invention and the initiative with which it was developed. Terrell, in turn, passed some of the award on to Glanville.[25][26] (The award was a considerable sum: £9,500 in 1946 is equivalent to £435,000 in 2023.[27])
American production
In August 1943, American experiments on the general problem of protection against shaped charges began, and by October of that year, a plastic armour much lighter than the steel armour required for the same amount of protection was found. This armour, made by the Flintkote Company, was improved through a series of tests and a modified armour of pure quartz gravel in a mastic of pitch and wood flour was designated HCR2. Tests were also conducted to test plastic armour's ability to protect ships from torpedoes with shaped-charge warheads, but this project was abandoned due to the low probability of these weapons becoming a serious threat and protection of armoured fighting vehicles and concrete fortifications became the priorities.
The original plan for tank protection with plastic armour was to produce HCR2-filled steel panels, small in size to reduce the area damaged by a single projectile, which could be fastened to an M4 Sherman in an emergency. To protect against the largest Panzerfaust, 8-12 tons of plastic protection were required for an M4, while an M26 Pershing's greater base armour meant it required only 7.1 tons of additional protection to equal an M4 with 11.7 tons of plastic protection. This was a 34% increase in weight for an M4, but only a 16% increase for an M26, and the panel for the M26's turret was only 10+3⁄4 inches thick compared to 13+3⁄4 inches for the M4. New panels made of welded steel armour, half an inch thick on the sides and three-quarters of an inch thick on the faces, were designed, but their construction was incomplete at the end of World War II. As a result of increasing tank losses to shaped-charge weapons, another type of panel that could enter production in only a few weeks was designed. This new type of panel used 1+1⁄2-inch mild steel instead of armour steel, and had a two-inch plate of 21ST aluminium alloy backing the face plate for reinforcement. One set of this armour was completed and tested just after the end of World War II and was considered quite satisfactory, although less so than the panels made of armour steel.
Related Research Articles
Armour or armor is a covering used to protect an object, individual, or vehicle from physical injury or damage, especially direct contact weapons or projectiles during combat, or from a potentially dangerous environment or activity. Personal armour is used to protect soldiers and war animals. Vehicle armour is used on warships, armoured fighting vehicles, and some combat aircraft, mostly ground attack aircraft.
Composite armour is a type of vehicle armour consisting of layers of different materials such as metals, plastics, ceramics or air. Most composite armours are lighter than their all-metal equivalent, but instead occupy a larger volume for the same resistance to penetration. It is possible to design composite armour stronger, lighter and less voluminous than traditional armour, but the cost is often prohibitively high, restricting its use to especially vulnerable parts of a vehicle. Its primary purpose is to help defeat high-explosive anti-tank (HEAT) projectiles.
A bulletproof vest, also known as a ballistic vest or bullet-resistant vest, is a type of body armour designed to absorb impact and prevent the penetration of firearm projectiles and explosion fragments to the torso. The vest can be either soft—as worn by police officers, security personnel, prison guards, and occasionally private citizens to protect against stabbing attacks or light projectiles—or hard, incorporating metallic or para-aramid components. Soldiers and police tactical units typically wear hard armour, either alone or combined with soft armour, to protect against rifle ammunition or fragmentation. Additional protection includes trauma plates for blunt force and ceramic inserts for high-caliber rounds. Bulletproof vests have evolved over centuries, from early designs like those made for knights and military leaders to modern-day versions. Early ballistic protection used materials like cotton and silk, while contemporary vests employ advanced fibers and ceramic plates. Ongoing research focuses on improving materials and effectiveness against emerging threats.
Protected cruisers, a type of cruising warship of the late 19th century, gained their description because an armored deck offered protection for vital machine-spaces from fragments caused by shells exploding above them. Protected cruisers notably lacked a belt of armour along the sides in-contrast to armored cruisers which carried both deck and belt armour. Protected cruisers were typically lighter in displacement and mounted fewer and/or lighter guns than armored cruisers. By the early 20th-century, with the advent of increasingly lighter yet stronger armour, even smaller vessels could afford some level of both belt and deck armour. In the place of protected cruisers, armored cruisers would evolve into heavy cruisers and light cruisers, the latter especially taking-up many of roles originally envisaged for that of protected cruisers.
The King George V-class battleships were the most modern British battleships in commission during the Second World War. Five ships of this class were built: HMS King George V, HMS Prince of Wales (1941), HMS Duke of York (1941), HMS Anson (1942) and HMS Howe (1942). The names honoured King George V, and his sons, Edward VIII, who had been Prince of Wales, and George VI who was Duke of York before ascending to the throne; the final two ships of the class were named after prominent 18th century admirals of the Royal Navy.
The Renownclass consisted of two battlecruisers built during the First World War for the Royal Navy. They were originally laid down as improved versions of the Revenge-class battleships, but their construction was suspended on the outbreak of war on the grounds they would not be ready in a timely manner. Admiral Lord Fisher, upon becoming First Sea Lord, gained approval to restart their construction as battlecruisers that could be built and enter service quickly. The Director of Naval Construction (DNC), Eustace Tennyson-D'Eyncourt, quickly produced an entirely new design to meet Admiral Lord Fisher's requirements and the builders agreed to deliver the ships in 15 months. They did not quite meet that ambitious goal, but they were delivered a few months after the Battle of Jutland in 1916. They were the world's fastest capital ships upon their commissioning.
HMS Repulse was one of two Renown-class battlecruisers built for the Royal Navy during the First World War. Originally laid down as an improved version of the Revenge-class battleship, her construction was suspended on the outbreak of war because she would not be ready in time. Admiral Lord Fisher, upon becoming First Sea Lord, gained approval for her to resume construction as a battlecruiser that could be built and enter service quickly. The Director of Naval Construction (DNC), Eustace Tennyson-d'Eyncourt, quickly produced an entirely new design to meet Admiral Lord Fisher's requirements and the builders agreed to deliver the ship in 15 months. They did not quite meet that ambitious goal, but the ship was delivered a few months after the Battle of Jutland in 1916. Repulse and her sister ship Renown were the world's fastest capital ships upon completion.
Rolled homogeneous armour (RHA) is a type of vehicle armour made of a single steel composition hot-rolled to improve its material characteristics, as opposed to layered or cemented armour. Its first common application was in tanks. After World War II, it began to fall out of use on main battle tanks and other armoured fighting vehicles intended to see front-line combat as new anti-tank weapon technologies were developed which were capable of relatively easily penetrating rolled homogeneous armour plating even of significant thickness.
Military vehicles are commonly armoured to withstand the impact of shrapnel, bullets, shells, rockets, and missiles, protecting the personnel inside from enemy fire. Such vehicles include armoured fighting vehicles like tanks, aircraft, and ships.
The Malta-class aircraft carrier was a British large aircraft carrier design of World War II. Four ships were ordered in 1943 for the Royal Navy, but changing tactical concepts, based on American experience in the Pacific War, caused repeated changes to the design, which was not completed before the end of the war. All four ships were cancelled in 1945 before they were laid down.
The Admiral-class battlecruisers were to have been a class of four British Royal Navy battlecruisers built near the end of World War I. Their design began as an improved version of the Queen Elizabeth-class battleships, but it was recast as a battlecruiser after Admiral John Jellicoe, commander of the Grand Fleet, pointed out that there was no real need for more battleships, but that a number of German battlecruisers had been laid down that were superior to the bulk of the Grand Fleet's battlecruisers and the design was revised to counter these. The class was to have consisted of HMS Hood, Anson, Howe, and Rodney — all names of famous admirals — but the latter three ships were suspended as the material and labour required to complete them was needed for higher-priority merchantmen and escort vessels. Their designs were updated to incorporate the lessons from the Battle of Jutland, but the Admiralty eventually decided that it was better to begin again with a clean-slate design so they were cancelled in 1919. No more battlecruisers would be built due to the arms limitations agreements of the interbellum.
The Lion class was a class of six fast battleships designed for the Royal Navy (RN) in the late 1930s. They were a larger, improved version of the preceding King George V class, with 16-inch (406 mm) guns. Only two ships were laid down before the Second World War began in September 1939 and a third was ordered during the war, but their construction was suspended shortly afterwards. The design was modified in light of war experience in 1942, but the two ships already begun were scrapped later in the year.
Compound armour was a type of armour used on warships in the 1880s, developed in response to the emergence of armor-piercing shells and the continual need for reliable protection with the increasing size in naval ordnance. Compound armour was a non-alloyed attempt to combine the benefits of two different metals—the hardness of steel with the toughness of iron—that would stand up to intense and repeated punishment in battle. By the end of the decade it had been rendered obsolete by nickel-steel armour. However, the general principle of compound iron was used for case-hardened armour, which replaced nickel-steel in the mid-1890s and is still used today.
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Ceramic armor is armor used by armored vehicles and in personal armor to resist projectile penetration through its high hardness and compressive strength. In its most basic form, it consists of two primary components: A ceramic layer on the outer surface, called the "strike face," backed up by a ductile fiber reinforced plastic composite or metal layer. The role of the ceramic is to (1) fracture the projectile or deform the projectile nose upon impact, (2) erode and slow down the projectile remnant as it penetrates the shattered ceramic layer, and (3) distribute the impact load over a larger area, which can be absorbed by ductile polymer or metallic backings. Ceramics are often used where light weight is important, as they weigh less than metal alloys for a given degree of resistance. The most common materials are alumina, boron carbide, and, to a lesser extent, silicon carbide.
Sir William Henry Glanville CB CBE FRS was a British civil engineer. During World War II he and the Road Research Laboratory were involved in important war work, developing temporary runways, beach analysis, and tank and aircraft design. He also worked on the explosives calculations and scale models used to develop the bouncing bombs used in the Dam Busters Raid.
The Disney bomb, also known as the Disney Swish, officially the 4500 lb Concrete Piercing/Rocket Assisted bomb was a rocket-assisted bunker buster bomb developed during the Second World War by the British Royal Navy to penetrate hardened concrete targets, such as submarine pens, which could resist conventional free-fall bombs.
Edward Terrell (1902–1979) was a British Liberal politician, a successful barrister and magistrate with a flair for invention; by 1940 he had registered a number of patents relating to pens, ink bottles and peeling knives. When war came, he volunteered for the Royal Navy Volunteer Reserve (RNVR) and was commissioned as a lieutenant in the Special Branch of the Volunteer Reserve to run an information section.
The Armadillo was an extemporized improvised armoured fighting vehicle produced in Britain during the invasion crisis of 1940–1941. Based on a number of standard lorry (truck) chassis, it comprised a wooden fighting compartment protected by a layer of gravel and a driver's cab protected by mild steel plates. Armadillos were used by the RAF Regiment to protect aerodromes and by the Home Guard.
Naval armor refers to the various protections schemes employed by warships. The first ironclad warship was created in 1859, and the pace of armour advancement accelerated quickly thereafter. The emergence of battleships around the turn of the 20th century saw ships become increasingly large and well armoured. Vast quantities of heavily armoured ships were used during the World Wars, and were crucial in the outcome. The emergence of guided missiles in the last part of the 20th century has greatly reduced the utility of armor, and most modern warships are now only lightly armored.
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